The brain stem is its meaning. The structure and functions of the trunk

9.1. BRAIN STEM

In the classical textbooks on neurology, the brain stem (truncus cerebri) included all its departments, except hemispheres. In the book "The Human Brain" (1906) L.V. Bluminau (1861-1928) calls the brainstem "all parts of the brain from the visual tubercles to the medulla oblongata, inclusive." A.V. Triumfov (1897-1963) also wrote that "the composition of the brain stem includes the medulla oblongata, the pons with the cerebellum, the cerebral peduncles with the quadrigemina and the visual tubercles." However, in recent decades, only the medulla oblongata, the pons of the brain, and the midbrain have been referred to the brainstem. In the following presentation, we will follow this definition, which has become widespread in practical neurology.

The brain stem is 8-9 cm long and 3-4 cm wide. Its mass is small, but its functional significance is extremely important and diverse, since the viability of the organism depends on the structures located in it.

If the brain stem is presented in a horizontal position, then 3 “floors” are determined on its sagittal section: base, tire, roof.

Base (basis)adjacent to the slope of the occipital bone. It is made up of descending (efferent) pathways (cortical-spinal, cortical-nuclear, cortical-bridge), and in the bridge of the brain there are also ponto-cerebellar connections occupying a transverse position.

Tire (tegmentum)It is customary to call the part of the trunk located between its base and receptacles of cerebrospinal fluid (CSF) - the fourth ventricle, the aqueduct of the brain. It consists of motor and sensory nuclei of cranial nerves, red nuclei, substantia nigra, ascending (afferent) pathways, including spinothalamic pathways, medial and lateral loops and some efferent extrapyramidal pathways, as well as the reticular formation (RF) of the trunk and their connections.

roof brainstem can be conditionally recognized as structures located above the CSF receptacles passing through the brainstem. In this case, it would be possible, although this is not accepted, to include the cerebellum (in the process of ontogenesis it is formed from the same cerebral bladder as the brain bridge, Chapter 7 is devoted to it), the posterior and anterior medullary velum. The plate of the quadrigemina is recognized as the roof of the midbrain.

Brain stem - continued upper division spinal cord, preserving elements of the segmental structure. At the level of the medulla oblongata, the nucleus

The (lower) spinal tract of the trigeminal nerve (the nucleus of the descending root of the fifth cranial nerve) can be considered as a continuation of the posterior horn of the spinal cord, and the nucleus of the hypoglossal (XII cranial) nerve is a continuation of its anterior horn.

As in the spinal cord, the gray matter of the trunk is located in depth. It consists of the reticular formation (RF) and other cellular structures, it also includes the nuclei of the cranial nerves. Among these nuclei are motor, sensory and vegetative. Conventionally, they can be considered as analogs of the anterior, posterior, and lateral horns of the spinal cord, respectively. Both in the motor nuclei of the trunk and in the anterior horns of the spinal cord there are motor peripheral neurons, in the sensory nuclei - the second neurons of the pathways of various types of sensitivity, and in the vegetative nuclei of the trunk, as well as in the lateral horns of the spinal cord - vegetative cells.

cranial nerves of the trunk (Fig. 9.1) can be considered as analogues of the spinal nerves, especially since some of the cranial nerves, like the spinal nerves, are mixed in composition (III, V, VII, IX, X). However, some of the cranial nerves are only motor (XII, XI, VI, IV) or sensory (VIII). The sensitive portions of the mixed cranial nerves and the VIII cranial nerve in their composition have nodes (ganglia) located outside the trunk, which are analogues of the spinal nodes, and like them also contain the bodies of the first sensitive neurons (pseudo-unipolar cells), the dendrites of which go to the periphery, and the axons - to the center, into the substance of the brain stem, where they end at the cells of the sensitive nuclei of the stem.

The motor cranial nerves of the trunk and the motor portions of the mixed cranial nerves consist of axons of motor neurons, the bodies of which are motor nuclei located at different levels of the brain stem. The cells of the motor nuclei of the cranial nerves receive impulses from the motor zone of the cerebral cortex, mainly along the axons of the central motor neurons that make up the cortical-nuclear pathways. These paths, approaching the corresponding motor nuclei, make a partial crossover, in connection with which each motor nucleus of the cranial nerve receives impulses from the cortex of both hemispheres of the brain. The only exceptions to this rule are those cortical-nuclear connections that go to the lower part of the nucleus of the facial nerve and to the nucleus of the hypoglossal nerve; they make an almost complete crossover and thus transmit nerve impulses to the indicated nuclear structures only from the cortex of the opposite hemisphere of the brain.

The reticular formation is also located in the trunk cover (formatio reticularis), related to the so-called non-specific formations of the nervous system.

9.2. RETICULAR FORMATION OF THE BRAIN STEM

The first descriptions of the reticular formation (RF) of the brain stem were made by German morphologists: in 1861 by K. Reichert (Reichert K., 1811-1883) and in 1863 by O. Deiters (Deiters O., 1834-1863); Among domestic researchers, a great contribution to its study was made by V.M. Bekhterev. The RF is a collection of nerve cells and their processes located in the tegmentum of all levels of the trunk between the nuclei of the cranial nerves, the olives, passing here by afferent and efferent pathways. To the reticular formation sometimes

Rice. 9.1.Base of the brain and cranial nerve roots. 1 - pituitary gland; 2 - olfactory nerve; 3 - optic nerve; 4 - oculomotor nerve; 5 - block nerve; 6 - abducens nerve; 7 - motor root of the trigeminal nerve; 8 - sensitive root of the trigeminal nerve; 9 - facial nerve; 10 - intermediate nerve; 11 - vestibulocochlear nerve; 12 - glossopharyngeal nerve; 13 - vagus nerve; 14 - accessory nerve; 15 - hypoglossal nerve, 16 - spinal roots of the accessory nerve; 17 - medulla oblongata; 18 - cerebellum; 19 - trigeminal nerve; 20 - leg of the brain; 21 - optic tract.

some medial structures of the diencephalon are also worn, including the medial nuclei of the thalamus.

RF cells are different in shape and size, the length of axons, they are located mainly diffusely, in some places they form clusters - nuclei that provide integration of impulses coming from nearby cranial nuclei or penetrating here along collaterals from afferent and efferent pathways passing through the trunk. Among the connections of the reticular formation of the brainstem, the most important can be considered the cortico-reticular, spinal-reticular pathways, the connections between the RF of the stem with the formations of the diencephalon and the striopallidar system, and the cerebellar-reticular pathways. The processes of RF cells form afferent and efferent connections between the nuclei of the cranial nerves contained in the trunk tegmentum and the projection pathways that are part of the trunk tegmentum. Through collaterals, RF receives “recharging” impulses from the afferent pathways passing through the brainstem and at the same time performs the functions of an accumulator and an energy generator. The high sensitivity of RF to humoral factors, including hormones, should also be noted. medicines, the molecules of which reach it by the hematogenous route.

Based on the results of studies by G. Magun and D. Moruzzi (Mougoun N., Morruzzi D.), published in 1949, it is generally accepted that in humans the upper parts of the RF of the brain stem have connections with the cerebral cortex and regulate the level of consciousness , attention, motor and mental activity. This part of the Russian Federation is called: ascending non-specific activating system(Fig. 9.2).

Rice. 9.2.Reticular formation of the brainstem, its activating structures and ascending pathways to the cerebral cortex (scheme).

1 - reticular formation of the brain stem and its activating structures; 2 - hypothalamus; 3 - thalamus; 4 - cerebral cortex; 5 - cerebellum; 6 - afferent pathways and their collaterals; 7 - medulla oblongata; 8 - bridge of the brain; 9 - midbrain.

The ascending activating system includes nuclei of the reticular formation, located mainly at the level of the midbrain, to which collaterals from ascending sensory systems approach. Arising in these nuclei nerve impulses along the polysynaptic pathways, passing through the intralaminar nuclei of the thalamus, the subthalamic nuclei to the cerebral cortex, have an activating effect on it. The ascending influences of the nonspecific activating reticular system are of great importance in the regulation of the tone of the cerebral cortex, as well as in the regulation of the processes of sleep and wakefulness.

In cases of damage to the activating structures of the reticular formation, as well as in violation of its connections with the cerebral cortex, a decrease in the level of consciousness, the activity of mental activity, in particular cognitive functions, motor activity, occurs. There may be manifestations of stunning, general and speech hypokinesia, akinetic mutism, stupor, coma, vegetative state.

The Russian Federation includes separate territories that have acquired elements of specialization in the process of evolution - the vasomotor center (its depressor and pressor zones), the respiratory center (expiratory and inspiratory), and the vomiting center. The RF contains structures that affect somatopsychovegetative integration. RF ensures the maintenance of vital reflex functions- respiration and cardiovascular activity, takes part in the formation of such complex motor acts as coughing, sneezing, chewing, vomiting, combined work of the speech motor apparatus, general motor activity.

The ascending and descending influences of the RF on various levels of the nervous system are diverse, which are “tuned” by it to perform one or another specific function. Ensuring the maintenance of a certain tone of the cortex of the cerebral hemispheres, the reticular formation itself experiences a controlling influence on the part of the cortex, thus gaining the opportunity to regulate the activity of its own excitability, as well as influence the nature of the effects of the reticular formation on other brain structures.

The descending influences of the RF on the spinal cord primarily affect the state muscle tone and can be activating or decreasing muscle tone, which is important for the formation of motor acts. Usually, the activation or inhibition of the ascending and descending influences of the RF is carried out in parallel. So, during sleep, which is characterized by inhibition of ascending activating influences, inhibition of descending nonspecific projections also occurs, which is manifested, in particular, by a decrease in muscle tone. The parallelism of influences spreading from the reticular formation along the ascending and descending systems is also noted in coma states caused by various endogenous and exogenous causes, in the origin of which dysfunction of nonspecific brain structures plays a leading role.

At the same time, it should be noted that in pathological conditions the relationship between the functions of ascending and descending influences can also be more complex. So, with epileptic paroxysms, with Davidenkov's hormetonic syndrome, which usually occurs as a result of gross lesions of the brain stem, inhibition of the functions of the cerebral cortex is combined with an increase in muscle tone.

All this testifies to the complexity of the relationship between the functions of various structures of the reticular formation, which can lead both to synchronous ascending and descending influences, and to their disturbances with the opposite direction. At the same time, the RF is only a part of the global integrative system, including the limbic and cortical structures of the limbicoreticular complex, in interaction with which the organization of life and purposeful behavior is carried out.

RF can participate in the formation of pathogenetic processes that are the basis of some clinical syndromes that occur when the primary pathological focus is localized not only in the brainstem, but also in the parts of the brain located above or below it, which is understandable from the point of view of modern ideas about vertically built functional feedback systems. RF communications have a complex vertical organization. It is based on neural circles between cortical, subcortical, stem and spinal structures. These mechanisms are involved in ensuring mental functions and motor acts, and also have a very large impact on the state of the functions of the autonomic nervous system.

It is clear that the features of pathological manifestations associated with impaired RF functions depend on the nature, prevalence, and severity of the pathological process and on which departments of the RF are involved in it. Dysfunction of the limbic-reticular complex, and RF in particular, can be caused by many harmful toxic, infectious influences, degenerative processes in brain structures, disorders of cerebral blood supply, intracranial tumor or brain injury.

9.3. MEDULLA

Medulla (medulla oblongata)- direct continuation of the spinal cord. The conditional border between them is located at the level of the large occipital foramen; it passes through the first spinal roots, or the zone of decussation of the pyramidal tracts. The medulla oblongata has a length of 2.5-3 cm, in shape it looks like an overturned truncated cone; sometimes it is called an onion (bulbus). The lower part of the medulla oblongata is at the level of the edge of the foramen magnum, and the upper, wider, borders on the bridge of the brain. The conditional border between them runs at the level of the middle of the clivus of the occipital bone.

On the ventral surface of the medulla oblongata in the sagittal plane there is a deep longitudinal anterior median fissure (fissura mediana anterior), which is a continuation of the eponymous fissure of the spinal cord. On the sides of it are elevations - pyramids, consisting of corticospinal tracts, including axons of central motor neurons. Behind and lateral to the pyramids on each side of the medulla oblongata is located along the inferior olive (oliva inferior). From the anterolateral sulcus located between the pyramid and the olive (sulcus lateralis anterior) out the roots of the hyoid (XII) nerve. Behind the olives is the posterior lateral sulcus (sulcus lateralis posterior), through which the roots of the accessory, vagus and glossopharyngeal (XI, X and IX) nerves pass from the medulla oblongata.

In the lower part of the dorsal surface of the medulla oblongata, between the posterior median sulcus and the posterior lateral sulci, there are two longitudinal ridges, consisting of the fibers of the tender and wedge-shaped bundles that came here along the posterior cords of the spinal cord. In connection with the deployment of the central canal of the spinal cord into the fourth ventricle of the brain, the ridges formed from the tender and wedge-shaped bundles diverge to the sides and end with thickenings (tuberculi nuclei gracilis et cuneatus), corresponding to the location of the same name (tender and wedge-shaped) nuclei, consisting of the second neurons of the pathways of proprioceptive sensitivity.

Most of the dorsal surface of the medulla oblongata is the lower triangle of the bottom of the fourth cerebral ventricle - the rhomboid fossa, which is limited from below by the lower, and from above - by the upper legs of the cerebellum. If the angles of the rhomboid fossa ABCD, as suggested by L.V. Blumenau (1906), connect AC and BD with straight lines, marking the point of their intersection E, and then draw the bisector of the angle ABD and designate the points of its intersection of the lines AE and AD with the letters H and F and from the point H lower the straight line parallel to the line AD, intersecting the line AB at point G, you can pay attention to the triangles and quadrangle created within the rhomboid fossa, which allow you to imagine how the nuclei of cranial nerves located in the caudal part of the brainstem are projected onto it (Fig. 9.3).

It can be noted that the NVE triangle is occupied by an eminence located above the nucleus of the hypoglossal (XII cranial) nerve, and is designated as the triangle of the nucleus of the hypoglossal nerve (trigonum nervi hypoglossi). Triangle GHB has a recess (fovea inferior, or fovea vagi). Beneath it lies the posterior parasympathetic nucleus of the vagus nerve. Therefore, the triangle GHB is also called the triangle of the vagus nerve. (trigonum nervivagi). The outer part of the rhomboid fossa in the zone of the quadrangle AFHG inscribed in it is occupied by an elevation located above the nuclei of the auditory (VIII cranial) nerve, and therefore it is called the auditory field (area acustica), and its elevated center is designated as the auditory tubercle (tuberculum acustici).

The white matter of the medulla oblongata consists of pathways, some of which pass through it in transit, some are interrupted in the nuclei of the medulla oblongata and the RF that is part of it, or start from these structures. The cortical-spinal (pyramidal) pathways pass through the base of the medulla oblongata, participating in the formation of the pyramids in its composition, and then make an incomplete decussation. The fibers of the cortical-spinal tract that have undergone crossover immediately fall into the composition of the lateral cords of the spinal cord; the fibers of this pathway, which are not involved in the formation of the decussation, are included in the composition of the anterior spinal cord. Both the fibers of the cortical-spinal tract that have crossed to the opposite side and the fibers of the cortical-spinal tract that have remained on their side, as well as other efferent connections descending from various structures of the brain

Rice. 9.3.The geometric scheme of the rhomboid fossa (according to L.V. Blumenau). Explanations in the text.

Rice. 9.4.Location of cranial nerve nuclei in the brainstem (a, b). Motor nuclei - red; sensitive - green.

brain to the spinal cord, are sent to the peripheral motor neurons located in the anterior horns of the spinal cord.

The structure of the medulla oblongata is not identical at its different levels (Fig. 9.4). In this regard, for a more complete and systematic acquaintance with the structure of the medulla oblongata, let us consider the structure of transverse sections made through its caudal, middle and oral sections (Fig. 9.5). In the following presentation, for the same purpose, transverse sections of the pons and midbrain will be described.

The lower part of the medulla oblongata. When studying the transverse section of the caudal part of the medulla oblongata (Fig. 9.6), it is noteworthy that its structure here has a significant similarity with the spinal cord. There are still remains of the horns of the spinal cord, in particular its anterior horns, which, as it were, are cut off from the main mass of the central gray matter by pyramidal fibers that have undergone a decussation and are directed to the lateral funiculi of the spinal cord. The first anterior spinal roots emerge from the outer part of the anterior horns, and axons form the cerebral root of the XI cranial nerve from the cells of the base of the anterior horns. The central part of the gray matter at this level is occupied by the lower part of the reticular formation of the brain stem.

The lateral parts of the cut are mainly occupied by ascending and descending pathways. (tractus spinothalamicus lateralis et medialis, tracti spinocerebellaris dorsalis et ventralis etc.), occupying at this level a position close to that which is characteristic of them in the spinal cord.

Rice. 9.5.Levels of slices of the brain stem.

I - section of the medulla oblongata at its border with the spinal cord; II - section of the medulla oblongata at the level of its middle part; III - section of the medulla oblongata at the level of the upper part; IV - cut at the border of the medulla oblongata and the bridge; V - cut at the level of the middle third of the bridge; VI - cut at the level of the middle third of the bridge; VII - cut at the level of the anterior tubercles of the quadrigemina.

Rice. 9.6.Section of the medulla oblongata at its border with the spinal cord. 1 - gentle bundle; 2 - wedge-shaped bundle; 3 - the core of the tender bundle; 4 - the core of the wedge-shaped bundle; 5 - the nucleus of the descending root of the V nerve; 6 - rear horn; 7 - the nucleus of the XI nerve; 8 - front horn; 9 - posterior spinocerebellar pathway; 10 - intersection of the cortical-spinal (pyramidal) pathways.

Along the outer sections of the posterior horns on the section of the medulla oblongata under consideration, the spinal pathway of the trigeminal nerve descending from the pons of the brain (descending root of the V cranial nerve), surrounded by cells that make up its nucleus, passes. The upper part of the section is occupied by wedge-shaped and tender bundles coming here along the posterior cords of the spinal cord, as well as by the lower parts of the nuclei in which these bundles end.

Middle part of the medulla oblongata (Fig. 9.7). The base of the cut is occupied by powerful pyramids (pyramides). In the tegmentum of the medulla oblongata at this level are the nuclei of the XI, and a little higher - the nuclei of the XII cranial nerves. In the posterior part of the section, there are large nuclei of the tender and wedge-shaped bundles, in which the first neurons of the pathways of deep sensitivity end. The axons of the cells located in these nuclei go forward and medially, bending around in front of the initial segment of the central canal of the spinal cord and the gray matter surrounding it. These axons (fibre arcuatae internae), going from one side and the other, passing through the sagittal plane, completely intersect with each other, thus forming the upper, or sensitive, decussation, also known as the decussation of the loop (decussatio limniscorum). After the intersection, its constituent fibers take an upward direction and form medial loops (lemnisci medialis), which are located behind the pyramids on the sides of the midline.

Rice. 9.7.Section of the medulla oblongata at the level of its middle part.

1 and 2 - the nuclei of the tender and wedge-shaped bundles; 3 - the nucleus of the spinal root of the trigeminal (V) nerve; 4 - intersection of the bulbo-thalamic pathways; 5 - core of the accessory (IX) nerve; b - spinocerebellar pathways; 7 - nucleus of the hyoid (XII) nerve, 8 - spinothalamic path; 9 - pyramidal path; 10 - rear longitudinal beam.

The remaining pathways occupy a position approximately similar to their position in the previous section.

Upper part of the medulla oblongata (Fig. 9.8). Here, the central canal of the spinal cord is expanded into the fourth ventricle, and the cut passes through the lower triangle of the rhomboid fossa that makes up its bottom. The formations, which in the lower part of the medulla oblongata were located above the central canal, are now moved apart and occupy the posterolateral sections of the section. In the lateral part of the tire, a dissected lower olive is visible, the substance of which in the section resembles a folded sac.

The floor of the fourth ventricle is lined with ependymal cells. Under the ependyma layer is the central gray matter, in which, near the midline, on both sides, the nuclei of the XII cranial nerve are located. Outside of each of them is the posterior nucleus of the vagus nerve (nucleus dorsalis nervi vagi), and even more lateral, a transversely dissected bundle of fibers surrounded by cells, known as a single bundle, is visible. Surrounding cells form the nucleus of the solitary pathway (nucleus tractus solitary). Close to it is a small-celled vegetative salivary nucleus

Rice. 9.8.Section of the trunk at the level of the upper part of the medulla oblongata. 1 - medial longitudinal bundle; 2 - the nucleus of the XII nerve; 3 - rhomboid fossa, 4 - nuclei of the vestibular nerve; 5 - posterior nucleus of the X nerve; 6 - the core of the general sensitivity of the X nerve; 7 - the core of a single bundle (gustatory core); 8 - posterior spinocerebellar pathway; 9 - mutual core; 10 - the nucleus of the descending root of the V nerve; 11 - anterior spinal-cerebellar path; 12 - lower olive; 13 - cortical-spinal (pyramidal) path; 14 - medial loop.

(nucleus salivatorius). The lower part of the nucleus of the solitary tract and the salivary nucleus belongs to the glossopharyngeal, and the upper part to the intermediate nerves.

In the depth of the reticular formation in the center of the tegmentum there is a large cell nucleus, which is, as it were, an oral continuation of the nucleus of the XI cranial nerve. This is the motor nucleus, the lower part of which belongs to the IX, and the upper to the X cranial nerves. In this regard, the nucleus is called the mutual or double nucleus. (nucl. ambiguus), the axons of the cells of the lower part of this nucleus make up the cranial part of the accessory nerve.

The nuclei of the tender and wedge-shaped bundles on this section are dissected at the level of their upper pole, their sizes are small here. External arcuate fibers are superimposed on the nucleus of the sphenoid tract, which are a continuation of the posterior spinal cerebellar bundle of Flexig, which are involved in the formation of the inferior cerebellar peduncle. The fibers of the olivocerebellar pathway, coming from the olives, also take part in its formation, most of which previously pass to the opposite side.

Between the olives there are medial loops. Behind them are the medial longitudinal bundles and the operculo-spinal tract, which run from the nuclei of the roof of the midbrain to the spinal cord. Other long pathways pass through the lateral sections of the cut, not interrupted in the medulla oblongata. The dimensions of the reticular formation compared with the levels of the previous

cutting sections continue to grow. The reticular formation is fragmented by nerve fibers crossing it in different directions.

In the highest parts of the medulla oblongata, on the border with the bridge, the width of the IV ventricle reaches a maximum. Due to the fact that the thickness of the lower cerebellar peduncles located on the sides of the rhomboid fossa is already large here, the dimensions of the section of the medulla oblongata at this level are the largest. In addition to the formations of the medulla oblongata already mentioned, a large place is occupied by the lower sections of the cranial nuclei of the bridge, a description of which will be presented when considering this section of the brain stem.

9.4. CRANIAL NERVES OF THE medulla oblongata 9.4.1. Accessory (XI) nerve (n. accessorius)

The accessory nerve has cranial and spinal parts, and therefore it can be said that it occupies, as it were, a transitional position between the spinal and cranial nerves. It could well be called spinal-cranial. Therefore, we begin the description of the cranial nerves with it (Fig. 9.9).

The accessory nerve is motor. His the main long motor nucleus is formed by the cells of the base of the anterior horns of the C II-C V segments of the spinal cord. The axons of the cells of the spinal nucleus of the XI cranial nerve emerge from the indicated segments of the spinal cord between the anterior and posterior spinal roots and at its lateral surface, gradually uniting, forming spinal root of accessory nerve which accepts the

Rice. 9.9.Accessory (XI) nerve and its connections.

1 - spinal roots of the accessory nerve; 2 - cranial roots of the accessory nerve; 3 - accessory nerve trunk; 4 - jugular opening; 5 - the inner part of the accessory nerve; b - the lower node of the vagus nerve; 7 - external branch of the accessory nerve; 8 - sternocleidomastoid muscle; 9 - trapezius muscle. Motor nerve structures are marked in red; blue - sensitive vegetative, green - parasympathetic, purple - afferent vegetative.

walking direction and enters the cavity of the posterior cranial fossa through the foramen magnum of axons. In the posterior cranial fossa, the cerebral (cranial) root, consisting of neurons located in the lower part of the double (mutual) nucleus, joins the spinal root next to the neurons of the vagus nerve (X cranial nerve). The cerebral root of the XI cranial nerve can be considered as part of the motor portion of the X cranial nerve, since it actually has a common motor nucleus and common functions with it.

The XI cranial nerve, formed after the fusion of the cerebral and spinal roots, emerges from the posterolateral sulcus of the medulla oblongata below the X cranial nerve root. The trunk of the XI cranial nerve, formed after this, exits the cranial cavity through the jugular foramen (foramen jugularis). After that fibers of the cranial part of the trunk of the XI cranial nerve join the X cranial nerve, and the rest spinal part, called external branch of accessory nerve down the neck and innervates the sternocleidomastoid muscle (m. sternocleidomastoideus) and the upper part of the trapezius muscle (m. trapezium).

Damage to the spinal nucleus or trunk of the XI cranial nerve and its branches at any level leads to the development of peripheral paralysis or paresis of these muscles. Over time, their atrophy occurs, leading to asymmetry, detected during external examination, while the shoulder on the side of the lesion is lowered, the lower angle of the scapula moves away from the spine. The scapula is displaced outwards and upwards ("pterygoid" scapula). Difficulty "shoulder shrug" and the ability to raise the arm above the horizontal level. Due to the excessive "sagging" of the shoulder on the side of the lesion, the arm appears to be longer. If the patient is asked to stretch his arms in front of him so that the palms touch each other, and the fingers are extended, then the ends of the fingers on the side of the lesion come forward.

Paresis or paralysis of the sternocleidomastoid muscle leads to the fact that when the head is turned on the affected side, this muscle is poorly contoured. A decrease in her strength can be detected by resisting turning the head in the direction opposite to the lesion, and slightly upward. A decrease in the strength of the trapezius muscle is clearly revealed if the examiner puts his hands on the patient's shoulders and resists their active lifting. With bilateral damage to the XI cranial nerve or its spinal nucleus, there is a tendency for the head to hang down on the chest. Damage to the XI cranial nerve is usually accompanied by deep, aching, difficult to localize pain in the arm on the side of the lesion, which is associated with hyperextension joint bag And ligamentous apparatus shoulder joint due to paralysis or paresis of the trapezius muscle.

Disorder of function of the XI cranial nerve may be the result of damage to peripheral motor neurons in patients with tick-borne encephalitis, poliomyelitis, or amyotrophic lateral sclerosis. The defeat of this nerve on both sides leads to the development of a symptom of a hanging head, which may also be due to a disorder in the function of the neuromuscular synapses in myasthenia gravis. Damage to the accessory nerve is possible with craniovertebral anomalies, in particular with Arnold-Chiari syndrome, as well as with injuries and tumors of the same localization. When the cells of the spinal nucleus of the accessory nerve are irritated in the muscles innervated by it, fascicular twitches and nodding movements are possible.

The peripheral neurons that make up the spinal nucleus of the XI cranial nerve receive impulses along the cortical-spinal and cortical-nuclear pathways, as well as along the extrapyramidal tegmental-spinal, vestibulo-spinal pathways and along the medial longitudinal bundle, on both sides, but mainly on the opposite side. sides. In this regard, a change in the impulse coming from the side of the central neurons to the peripheral motor neurons of the spinal nuclei of the XI cranial nerve can cause spastic paresis of the striated muscles innervated by this nerve, more pronounced on the side opposite to the pathological process. It is assumed that a change in the nerve impulses arriving at the peripheral neurons of the spinal nucleus XI of the cranial nerve can cause hyperkinesis by the type of spastic torticollis. It is believed that the cause of this form of hyperkinesis may be irritation of the spinal root of the accessory nerve.

9.4.2. Hypoglossal (XII) nerve (n. hypoglossus)

The hypoglossal nerve is motor (Fig. 9.10). Its nucleus is located in the medulla oblongata top part the nucleus is located under the bottom of the rhomboid fossa, and the lower one descends along the central canal to the level of the beginning of the intersection of the pyramidal tracts. The nucleus of the XII cranial nerve consists of large multipolar cells and a large number of fibers located between them, by which it is divided into 3 more or less separate cell groups. The axons of the cells of the nucleus of the XII cranial nerve gather into bundles that penetrate the medulla oblongata and emerge from its anterior lateral groove between the inferior olive and the pyramid. In the future, they leave the cranial cavity through a special hole in the bone - the hypoglossal nerve canal (canalis nervi hypoglossi), located above the lateral edge of the large occipital foramen, forming a single trunk.

Coming out of the cranial cavity, the XII cranial nerve passes between the jugular vein and the internal carotid artery, forms a hyoid arch, or loop (ansa cervicalis), passing here in close proximity to the branches of the spinal nerves coming from the three upper cervical segments of the spinal cord and innervating the muscles, attached to the hyoid bone. Later, the hypoglossal nerve turns forward and divides into lingual branches (rr. linguales), innervating tongue muscles: sublingual-lingual (m. hypoglossus) awl-lingual (m. styloglossus) and chin-lingual (m. genioglossus), as well as the longitudinal and transverse muscles of the tongue (m. longitudinalis and m. transversus linguae).

With the defeat of the XII cranial nerve, peripheral paralysis or paresis of the same half of the tongue occurs (Fig. 9.11), at the same time, the tongue in the oral cavity shifts to the healthy side, and when protruding from the mouth, it deviates towards the pathological process (the tongue “points to the focus”). This happens due to the fact that m. genioglossus the healthy side pushes the homolateral half of the tongue forward, while its paralyzed half lags behind and the tongue turns in its direction. The muscles of the paralyzed side of the tongue atrophy over time, become thinner, while the relief of the tongue on the side of the lesion changes - it becomes folded, "geographical".

Rice. 9.10.Hypoglossal (XII) nerve and its connections.

1 - the nucleus of the hypoglossal nerve; 2 - sublingual canal; 3 - meningeal branch; 4 - connecting branch to the upper cervical sympathetic node; 5 - connecting branch to the lower node of the vagus (X) nerve; b - upper cervical sympathetic node; 7 - the lower node of the vagus nerve; 8 - connecting branches to the first two spinal nodes; 9 - internal carotid artery; 10 - internal jugular vein; 11 - awl-lingual muscle; 12 - vertical muscle of the tongue; 13 - upper longitudinal muscle of the tongue; 14 - transverse muscle of the tongue; 15 - lower longitudinal muscle of the tongue; 16 - genio-lingual muscle; 17 - chin-hyoid muscle; 18 - hyoid-lingual muscle; 19 - thyroid muscle; 20 - sternohyoid muscle; 21 - sternothyroid muscle; 22 - upper abdomen of the scapular-hyoid muscle; 23 - lower belly of the scapular-hyoid muscle; 24 - neck loop; 25 - lower spine of the neck loop; 26 - upper spine of the neck loop. Branches extending from the medulla oblongata are marked in red, branches from the cervical spinal cord are marked in purple.

Rice. 9.11.The defeat of the left hypoglossal nerve of the peripheral type.

Unilateral paralysis of the tongue has almost no effect on the acts of chewing, swallowing, speech. At the same time, signs of paresis of the muscles that fix the larynx are possible. When swallowing in such cases, a noticeable displacement of the larynx to the side.

In the case of bilateral damage to the nuclei or trunks of the XII cranial nerve, complete paralysis of the muscles of the tongue (glossoplegia) may occur, then it turns out to be sharply thinned and motionless lying on the diaphragm of the mouth. There comes a speech disorder in the form of anartria. With bilateral paresis of the muscles of the tongue, articulation is disturbed by the type of dysarthria. During the conversation, it seems that the patient's mouth is full. The pronunciation of consonant sounds is especially significantly impaired. Glossoplegia also leads to difficulty in eating, as it is difficult for the patient to move the food bolus into the throat.

If peripheral paresis or paralysis of the tongue is the result of a gradually progressive damage to the nucleus of the XII cranial nerve, it is characteristic appearance in language on the side of the pathological process fibrillar and fascicular twitches. Damage to the nuclei of the XII cranial nerve is usually accompanied by peripheral (flaccid) paresis of the circular muscle of the mouth (m. orbicularis oris), in which the lips become thinner, wrinkles appear on them, converging to the oral fissure ("purse-string mouth"), it is difficult for the patient to whistle, blow out the candle. This phenomenon is explained by the fact that the bodies of peripheral motor neurons, the axons of which pass as part of the VII (facial) cranial nerve to the circular muscle of the mouth, are located in the nucleus of the XII cranial nerve.

If the lower part of the motor cortex is affected hemisphere or corticonuclear pathways,

carrying impulses from the cortex, in particular to the nucleus of the XII cranial nerve, then (since the cortical-nuclear fibers approaching this nucleus make an almost complete decussation) on the side opposite to the pathological process, there is a central paresis of the muscles of the tongue (Fig. 9.12). When protruding from the mouth, the tongue is turned in the direction opposite to the pathological focus

Rice. 9.12.Lesion of the left hypoglossal nerve in the central type.

in the brain, there is no atrophy of the tongue and there are no fibrillar twitches in it. Central paresis of the tongue is usually combined with central paresis of the facial nerve and manifestations of central hemiparesis on the same side.

The decrease in the strength of the muscles of the tongue that occurs during their paresis can be checked if the examiner asks the patient to press the tip of the tongue on the inner surface of his cheek, while he himself resists this movement by pressing on the outer surface of the patient's cheek.

Signs of bilateral damage to the nuclei and trunks of the XII cranial nerve are usually combined with manifestations of dysfunction of other cranial nerves of the bulbar group, and then a clinical picture of a more complete bulbar syndrome occurs; violation of the functions of the cortical-nuclear pathways leading to the motor nuclei of these nerves is manifested by a pseudobulbar syndrome, which is a manifestation of central paresis or paralysis of the muscles innervated by them.

9.4.3. Vagus (X) nerve (n. vagus)

Nervus vagus is mixed (Fig. 9.13). It contains motor, sensory and autonomic (parasympathetic) fibers. In accordance with this, in the cranial nerve X system there are 3 main cores, located in the tegmentum of the medulla oblongata. Motor core - double(nucl. ambiguus), its upper part belongs to the IX cranial nerve, and the lower part to the X cranial nerve and to the cerebral part of the XI cranial nerve. sensitive core(nucl. sensorium) also common to IX and X cranial nerves. In addition, the X nerve system has its own nucleus - posterior nucleus of the vagus nerve(nucl. dorsalis nervi vagi), located under the bottom of the IV ventricle, outside of the upper nucleus of the hypoglossal nerve. It comprises small vegetative cells and is directly related to the innervation of the majority internal organs and that's why sometimes it is called visceral.

The X cranial nerve leaves the posterolateral sulcus of the medulla oblongata and goes to the jugular foramen, through which, together with the IX and XI cranial nerves, it leaves the cranial cavity. In the zone of the jugular foramen on the trunk of the X cranial nerve are located top knot (ganglion superius) and 1 cm lower, already outside the cranial cavity - bottom knot (ganglion inferius). Both of these nodes are analogues of the spinal nodes and part of the sensitive portion of the X cranial nerve. They contain the bodies of the first neurons of the sensory pathways, their axons are sent to the medulla oblongata to the mentioned sensory nucleus, and the dendrites to the periphery.

Below the jugular foramen, in section X of the cranial nerve, located between these nodes, fibers of the accessory nerve join its motor portion, which make up its cerebral root and are axons of peripheral motor neurons that make up the double nucleus.

The motor and sensory portions of the X cranial nerve provide innervation to the striated muscles of the upper parts of the digestive and respiratory systems: soft palate, pharynx, larynx, epiglottis. Of the branches of the X cranial nerve, extending from it at the base of the skull and on the neck, the largest are the following.

Rice. 9.13.The vagus nerve (X) and its connections.

1 - the core of a single path; 2 - the nucleus of the spinal tract of the trigeminal nerve; 3 - double core; 4 - posterior nucleus of the vagus nerve; 5 - spinal roots of the accessory nerve; 6 - meningeal branch (into the subtentorial space); 7 - ear branch (to the posterior surface of the auricle and external auditory canal); 8 - upper cervical sympathetic node; 9 - pharyngeal plexus; 10 - muscle that raises the palatine curtain; 11 - tongue muscle; 12 - palatopharyngeal muscle;

13 - palatine-lingual muscle; 14 - tubal-pharyngeal muscle; 15 - upper constrictor of the pharynx; 16 - sensitive branches to the mucous membrane of the lower part of the pharynx; 17 - upper laryngeal nerve; 18 - sternocleidomastoid muscle; 19 - trapezius muscle; 20 - lower laryngeal nerve; 21 - lower constrictor of the pharynx; 22 - cricoid muscle; 23 - arytenoid muscles; 24 - thyroid arytenoid muscle; 25 - lateral cricoarytenoid muscle; 26 - posterior cricoarytenoid muscle; 27 - esophagus; 28 - right subclavian artery; 29 - recurrent laryngeal nerve; 30 - thoracic cardiac nerves; 31 - cardiac plexus; 32 - left vagus nerve; 33 - aortic arch; 34 - diaphragm; 35 - esophageal plexus; 36 - celiac plexus; 37 - liver; 38 - gallbladder; 39 - right kidney; 40 - small intestine; 41 - left kidney; 42 - pancreas; 43 - spleen; 44 - stomach. Motor nerve structures are marked in red; blue - sensitive; green - parasympathetic.

Meningeal branch (r. meningeus)- sensitive, participates in the innervation of predominantly solid meninges posterior cranial fossa.

ear branch (r. auricularis, Arnold's nerve) - sensitive, innervates the posterior wall of the external auditory canal and the posterior surface of the auricle.

superior laryngeal nerve (n. laringeus superior) innervates the muscles of the soft palate, constrictors of the pharynx and the cricothyroid muscle, participates in the sensitive innervation of the larynx and epiglottis. With neuralgia of the superior laryngeal nerve, attacks of excruciating pain from several seconds to a minute are characteristic, localized in the larynx, sometimes accompanied by a cough. On palpation on the lateral surface of the larynx under the thyroid cartilage is noted pain point(trigger zone), the pressure on which can cause an attack.

recurrent laryngeal nerve (n. laringeus recurrents)- right recurrent nerve wraps around the subclavian artery from front to back, left - aortic arch. Then both nerves rise between the trachea and esophagus, participate in their innervation and reach the larynx.

The terminal branches of the recurrent nerves are called lower laryngeal nerves they anastomose with the superior laryngeal nerves. Neuropathy of the recurrent laryngeal and lower laryngeal nerves is manifested by paralysis of the vocal cords, other muscles of the larynx, except for the cricothyroid muscle. As a result, if the branch of the X cranial nerve and its branch - the recurrent laryngeal nerve, as well as its continuation - the lower laryngeal nerve - are damaged, the sonority of the voice may be disturbed - dysphonia in the form of hoarseness without dysphagia (Ortner symptom) due to paresis or paralysis of the vocal cord on the side of the pathological process, detected during laryngoscopy.

Damage to both recurrent laryngeal nerves causes aphonia and respiratory stridor. Such dysphonia (or aphonia) may be the result of an aortic aneurysm, mediastinal tumor, surgery on the neck or mediastinum, but often the cause of recurrent laryngeal nerve neuropathy cannot be established.

After the departure of these branches, the remaining, consisting mainly of parasympathetic fibers, part of the vagus nerve, located between the internal, then the common carotid arteries on the one hand and the jugular vein on the other, penetrates the chest. Passing through the chest

X cranial nerve gives off bronchial and thoracic cardiac branches and then through esophageal opening diaphragm enters the abdominal cavity. Here the X cranial nerve divides into the anterior and posterior vagus trunks (truncus vagalis anteror et truncus vagalis posterior); their numerous branches (gastric, celiac, renal and other branches) provide sensory and parasympathetic innervation (innervation of smooth muscles, digestive glands, urinary system, etc.).

With damage to the vagus nerve in the proximal section, the soft palate droops on the side of the pathological process; it turns out to be motionless or tenses less than on the healthy side. The palatine curtain during phonation shifts to the healthy side. Usually on the affected side of cranial nerve X uvula (uvula) deviated to the healthy side, reduced or absent pharyngeal and palatine reflexes. They are checked on both sides with a spatula, a spoon or a sheet of paper rolled into a tube, with which the examiner touches the back of the pharynx or the soft palate.

Bilateral decrease in the functions of the vagus nerves can cause manifestations of bulbar syndrome, in particular, a speech disorder in the form of aphonia and dysphagia - a violation of swallowing, choking on liquid food - a consequence of paresis of the soft palate, palatine curtain, epiglottis, pharynx. The weakening of the swallowing reflex leads to the accumulation of saliva and food debris in the oral cavity. Paresis of the pharynx and a decrease in the cough reflex contribute to obstruction of the upper respiratory tract, followed by bronchial occlusion, which leads to respiratory failure and the development of obstructive pneumonia.

Irritation of the parasympathetic portion of the vagus nerves can lead to bradycardia, broncho- and esophagospasm, pylorospasm, increased peristalsis, vomiting, increased secretion of glands digestive tract, and over time to the possible development of peptic ulcer of the stomach and duodenum. Damage to these nerves leads to respiratory disorders, tachycardia, inhibition of secretion of the glandular apparatus of the digestive tract etc. A pronounced bilateral disorder of the parasympathetic innervation of the internal organs can lead to the death of the patient due to impaired breathing and cardiac activity.

The cause of damage to the X cranial nerve can be syringobulbia, amyotrophic lateral sclerosis, intoxication (alcohol, diphtheria, lead poisoning, arsenic), nerve compression is possible in oncological pathology, aortic aneurysm, etc.

9.4.4. Glossopharyngeal (IX) nerve (n. glossopharyngeus)

The glossopharyngeal nerve is mixed. It contains motor, sensory, including taste, and autonomic parasympathetic fibers.

In accordance with this, the IX cranial nerve system includes those located in the medulla oblongata nucleus: motor (nucl. ambiguus) And core of general types of sensitivity (nucl. sensorius)- common to IX and X cranial nerves, as well as core of taste sensation - single path core (nucl. solitarius) And parasympathetic secretory nucleus - inferior salivary nucleus (nucl. salvatorius), common to IX cranial and intermediate nerves.

The IX cranial nerve emerges from the posterolateral sulcus of the medulla oblongata, located behind the inferior olive, and goes to the jugular foramen, after passing through which it leaves the cranial cavity (Fig. 9.14).

The motor portion of the IX cranial nerve innervates only one muscle - the stylopharyngeal (m. Stylopharyngeus), which raises the pharynx.

The bodies of the first sensory neurons, providing conduction of impulses of general types and taste sensitivity, are located in analogues of the spinal ganglia - in upper(ganglion superius) And lower(ganglion inferius) nodes near the jugular foramen. The dendrites of these neurons

begin in the posterior third of the tongue, soft palate, pharynx, pharynx, anterior surface of the epiglottis, as well as in the auditory (Eustachian) tube and tympanic cavity, participating in providing general types of sensitivity in them, and in the posterior third of the tongue also taste sensitivity. The axons of the same pseudo-unipolar cells as part of the cranial nerve root IX penetrate the medulla oblongata, then those that conduct impulses of general types of sensitivity approach the corresponding nucleus; and those through which impulses of taste sensitivity are transmitted, to the lower part of the nucleus of the solitary pathway.

In these nuclei, sensitive impulses are switched to second neurons, whose axons pass to the opposite side, participating in the formation of the medial loop, and end in the thalamic nuclei, where are third neurons. Axons of the third neurons of the sensory pathways of the IX cranial nerve system pass through the medial sensory loop, posterior femur of the internal capsule, corona radiata, and end in the lower part of the cortex of the postcentral gyrus (fibers transmitting impulses of general types of sensitivity) and in the crust around the islet (fibers that conduct impulses of taste sensitivity, their unilateral damage does not lead to a disorder of taste sensitivity).

It should be noted that the impulses that arise in the receptor apparatus in the zone of sensitive innervation of the vagus, trigeminal and intermediate nerves also pass from the sensory nuclei of the trunk to the projection zones of the cortex, similar to the one considered above.

Parasympathetic salivary fibers which are axons of cells laid down in the lower part of the salivary nucleus, located in the lateral part of the tegmentum of the medulla oblongata, through the branch glossopharyngeal nerve - tympanic nerve And small stony nerve - reach the ear parasympathetic node (gangl. oticum). Postganglionic parasympathetic fibers exit from here, which pass through the anastomosis into the branch of the trigeminal nerve (n. auriculotemporalis) And innervate the parotid gland, providing its secretory function.

With damage to the glossopharyngeal nerve there are difficulties in swallowing, a violation of the sensitivity of general types (pain, temperature, tactile) of the soft palate, pharynx, upper pharynx, anterior surface of the epiglottis, posterior third of the tongue. Due to the disorder of proprioceptive sensitivity in the tongue, the sensation of its position in the oral cavity can be disturbed, which makes it difficult to chew and swallow solid food. In the back third of the tongue, the perception of taste sensations is disturbed, mainly the sensation of bitter and salty. In addition to the glossopharyngeal nerve, the perception of taste is provided by the system of the intermediate nerve and its branch - the tympanic string. (chorda tympani).

Rice. 9.14.Glossopharyngeal (IX) nerve.

1 - the core of a single path; 2 - double core; 3 - lower salivary nucleus; 4 - jugular opening; 5 - upper node of the glossopharyngeal nerve; 6 - lower node of the glossopharyngeal nerve; 7 - connecting branch with the ear branch of the vagus nerve; 8 - the lower node of the vagus nerve; 9 - upper cervical sympathetic node; 10 - bodies of the carotid sinus; 11 - carotid sinus and its plexus; 12 - common carotid artery; 13 - sinus branch; 14 - tympanic nerve; 15 - facial nerve; 16 - knee-tympanic nerve; 17 - large stony nerve; 18 - pterygopalatine node; 19 - ear knot; 20 - parotid gland; 21 - small stony nerve; 22 - auditory tube; 23 - deep stony nerve; 24 - internal carotid artery;

25 - carotid-tympanic nerves; 26 - styloid muscle; 27 - connecting branch with the facial nerve; 28 - stylo-pharyngeal muscle; 29 - sympathetic plexus; 30 - motor branches of the vagus nerve; 31 - pharyngeal plexus; 32 - branches to the muscles and mucous membrane of the pharynx and soft palate; 33 - sensitive branches to the soft palate and tonsils; 34 - gustatory and sensitive branches to the posterior third of the tongue. Motor nerve structures are marked in red; blue - sensitive; green - parasympathetic; purple - sympathetic.

With a decrease in the functions of the IX cranial nerve, the patient sometimes complains of some dryness in the mouth, but this symptom is unstable and unreliable, since the decrease and even cessation of the function of one parotid gland can be compensated by other salivary glands.

Irritation by the pathological process of the IX cranial nerve can cause pain in the pharynx, posterior pharyngeal wall, tongue, as well as in the auditory tube and tympanic cavity. These sensations may be permanent or paroxysmal in nature. In the latter case, the patient may develop neuralgia of the IX cranial nerve.

It should be noted that a certain anatomical and functional commonality of the IX and X cranial nerves usually leads to a combination of their lesions and to the practical simultaneity of checking their functions during a neurological examination. So, when checking the palatine and pharyngeal reflexes, it must be borne in mind that their decrease may be due to damage to both the X and IX cranial nerves (the afferent part of the reflex arc passes along the sensitive portion of the IX and X cranial nerves, the efferent part - along the motor portion of the X cranial nerve, and the closure of the reflex arc occurs in the medulla oblongata).

9.5. TASTE AND ITS DISORDERS

Specialized gustatory receptors are located in the taste annular and fungiform papillae of the tongue and are chemoreceptors, as they react to chemicals dissolved in water, which is the main part of saliva. Separate chemoreceptors are located in the mucous membrane of the soft and hard palate, at the top of the epiglottis.

It should be borne in mind that taste stimuli of different nature are perceived by specific receptors located in the mucous membrane of the tongue mostly like this: bitter - in the posterior third of the tongue salty - in the posterior third of the tongue and in its lateral zones, sour - in the lateral sections of the upper surface of the tongue and on its sides, sweet - in the anterior parts of the tongue. The middle part of the back of the tongue and its lower surface are practically devoid of taste buds.

The state of taste sensitivity is checked separately for each of the four main flavors (sour, sweet, bitter, salty). When checking taste sensitivity, drops of a solution containing

presenting a taste stimulus 1, while making sure that the drop does not spread over the tongue. After applying each drop, the patient should point to one of the pre-written words that reflect his taste sensations: “bitter”, “salty”, “sour” and “sweet”, and then rinse his mouth thoroughly. The examination may reveal: taste disorders - dysgeusia, lack of taste sensation ageusia, decreased taste sensitivity hypogeusia, perversions of taste parageusia, the presence of a metallic taste, often occurring when taking certain medications, - phantageusia.

Violation of taste sensitivity may indicate damage to the glossopharyngeal nerve or the intermediate nerve of Vrisberg, which is part of the facial nerve. For the detection of a topical neurological diagnosis, the detection of taste disorders can be essential. For the defeat of the IX cranial nerve, a disorder of perception of bitter and salty, detected in the posterior third of the tongue, is more characteristic.

Disorders are of undoubted importance for neurological topical diagnosis. certain types taste sensitivity in a certain area of ​​​​the tongue on the one hand, since sensory disorders on both sides may be due to inhibition of the receptor apparatus due to diffuse pathology of the mucous membrane of the tongue and walls oral cavity. A decrease in the brightness, clarity of taste sensations may occur in older people due to progressive atrophy of part of the taste buds and a decrease in saliva secretion, which occur with aging and are provoked by wearing dentures, especially the upper jaw, prolonged smoking, prolonged being in a state of depression. A taste disorder is a possible consequence of dry mouth due to a violation of salivation, for example, in Sjogren's disease.

Hypogeusia is often noted with tongue lining, tonsillitis, glossitis (in cases of hypovitaminosis A, pellagra, with prolonged antibiotic treatment, with radiation therapy). Ageusia can be in patients with endocrinopathy (hypothyroidism, diabetes mellitus, etc.), with familial dysautonomia (Riley-Day syndrome). With Addison's disease, a significant exacerbation of taste (hypergeusia) is possible. Manifestations of dysgeusia can be the result of taking many drugs: tetracycline, d-penicillamine, ethambutol, antifungal drugs, levodopa, lithium carbonate, cytotoxic agents.

9.6. SYNDROMES INCLUDING SIGNS OF IMPAIRMENT OF THE MEMBRANE AND ITS CRANIAL NERVES

Dandy Walker Syndrome - congenital malformation of the caudal brain stem and cerebellar vermis, leading to incomplete opening of the median (Magendie) and lateral (Lushka) apertures of the IV ventricle of the brain. It is manifested by signs of hydrocephalus, and often hydromyelia. The last circumstance

1 To test taste sensitivity, you can use solutions of sugar, salt, citric acid, quinine.

The property, in accordance with the hydrodynamic theory of Gardner, can cause the development of syringomyelia, syringobulbia. Severe Dandy-Walker syndrome is characterized by manifestations of functional insufficiency of the medulla oblongata and cerebellum, symptoms of intracranial hypertension. The diagnosis is clarified by methods that visualize the brain tissue - CT and MRI, while signs of hydrocephalus are revealed and, in particular, a pronounced expansion of the IV cerebral ventricle, MRI can reveal deformation of these brain structures. Described in 1921 by the American neurosurgeons W. Dandy (1886-1946) and A. Walker (born in 1907).

Laruelle syndrome characterized by signs of intracranial hypertension, in particular paroxysmal intense diffuse headache, contracture of the neck muscles, tonic convulsions, respiratory and cardiovascular disorders. Possible destruction of the edges of the foramen magnum (symptom of Babchin). Described in tumors of subtentorial localization by the Belgian neuropathologist M. Laruelle.

Arnold-Chiari-Solovtsev anomaly (see chapter 24).

Oscillopsia- the illusion of vibrations of motionless objects. Oscillopsia in combination with vertical nystagmus, instability and vestibular vertigo is observed with craniovertebral anomalies, in particular with Arnold-Chiari syndrome.

Symptom Ortner- hoarseness of voice, sometimes aphonia as a result of paresis or paralysis of the vocal cords, caused by damage to the recurrent laryngeal nerves. The cause may be their compression by a tumor of the mediastinum, as well as a hypertrophied heart or left pulmonary artery with mitral valve stenosis. Described in 1897 by the Austrian doctor N. Ortner (1865-1935).

Lermitte-Monnier syndrome (Tsokanakis symptom) - a swallowing disorder caused by spasms of the muscles of the pharynx and esophagus that occur when the vagus nerves are irritated by a pathological process at the base of the skull or in the tissues of the neck and mediastinum. It occurs, in particular, with a tumor of the mediastinum. Described by the French neuropathologists J. Lhermitte (1887-1959), Monier and the Greek physician Tsocanakis.

Glossopharyngeal neuralgia (Sicard-Robineau syndrome) - acute paroxysmal pain that begins in the root of the tongue or in the tonsil and spreads to the palatine curtain, pharynx, radiating to the ear, lower jaw, and neck. Attacks of pain can be provoked by tongue movements, swallowing, especially when taking hot or cold food. The pain attack lasts up to 2 minutes. There are essential and symptomatic forms of neuralgia. The cause of the disease can be a kink (angulation) and compression of the hypoglossal nerve at the site of its contact with the posterior inferior edge of the stylopharyngeal muscle or compression of the nerve root by the compacted vertebral or inferior cerebellar arteries, as well as inflammatory and blastomatous processes or aneurysms in the posterior cranial fossa. Described by the French neurologist R. Sicard (1872-1949), the French morphologist M. Robineau

(1870-1960).

Tympanic plexus syndrome (Reichert's syndrome) - attacks of acute pain in the depths of the external auditory canal, often radiating to the behind-the-ear region, to the temple, sometimes to the homolateral half of the face. Unlike neuralgia of the glossopharyngeal nerve, there are no pains in the tongue, tonsils, palate, changes in salivation. In addition, the occurrence of pain is not associated with movement

tongue movements and swallowing. Usually accompanied by edema and hyperemia in the area of ​​the external auditory canal. There are essential and symptomatic forms of the disease. The syndrome was described by irritation of the tympanic plexus in 1933 by the American surgeon F. Reichert (born in 1894).

Syndrome of the blockade of the cerebellar cistern - stiff neck muscles (extensors of the head), sharp pain in the occipital region, diffuse arching headache and other signs of occlusive hydrocephalus (see Chapter 20), bulbar symptoms are possible, in particular respiratory distress, congestion in the fundus and other signs of intracranial hypertension . Described in 1925 by Lange and Kindler.

Jugular foramen syndrome (Vernet syndrome, Sicard-Collet syndrome) - a combination of signs of damage to the IX, X and XI cranial nerves emerging from the cranial cavity through the jugular foramen. It occurs due to a fracture of the base of the skull, passing through the jugular foramen of the occipital bone, or the presence of a tumor in the area of ​​the jugular foramen, often metastatic.

Described in 1918 by French doctors: neuropathologists M. Vernet (1887-1974), J. Sicard (1872-1929) and otorhinolaryngologist F. Collet (1870-1966).

Retroparotitis syndrome (Villaret syndrome) - a combination of signs of unilateral lesions of the IX, X, XI and XII cranial nerves and the cervical sympathetic trunk, which leads to a combination of manifestations of the Sicard-Colle syndrome and Horner's syndrome. Usually indicates an extracranial location of the pathological process, more often in the retroparotid space (tumor, lymphadenitis of the parotid region). Described in 1922 by the French neurologist M. Villaret (1887-1944).

Serjean's syndrome- a combination of signs of damage to the vagus nerve or its branch - the upper laryngeal nerve with Horner's syndrome in the pathological process (tumor, tuberculosis focus, etc.) in the upper lobe of the lung. Described by the French therapist F. Sergent (1867-1943).

Arnold's nerve syndrome - reflex cough caused by irritation of the external auditory canal and the lower back of the tympanic membrane - the zone innervated by the ear branch of the vagus nerve, also known as Arnold's nerve.

The nerve is named after the German anatomist F. Arnold (1803-1890).

Angle-Sterling Syndrome - congenital or acquired elongation or curvature of the horns of the hyoid bone, fibrosis of the stylohyoid fold, causing irritation of the X-XII cranial nerves on the same side. There may be attacks of contraction of the muscles of the larynx, suffocation, a feeling of “turning over” the tongue, difficulty in phonation and swallowing, head rotation. With the styloid-pharyngeal type of this syndrome, pain occurs in the throat (in the tonsillar fossa and tonsil), radiating to the ear and to the hyoid bone. With the styloid-carotid type of the syndrome, pain usually occurs in the forehead, orbit, in the eyeball and from here radiates to the temple and crown. Described by the American dentist E. Angle (1855-1930) and the Polish neuropathologist W. Sterling (born in 1877).

Retroolivar syndrome (McKenzie syndrome) - a combination of hoarseness (dysphonia), swallowing disorders (dysphagia), hypotrophy and paresis of the tongue, in which fibrillar twitches are possible. Occurs when the double (related to the systems of IX and X cranial nerves) and hypoglossal (XII) motor nuclei or the axons of their constituent motor neurons, which form the corresponding cranial nerves in the medulla, are damaged in the medulla oblongata.

those of their exit from the medulla oblongata in the anterior lateral groove between the lower olive and the pyramid. Described by the English doctor S. McKenzie (1844-1909).

Jackson Syndrome - alternating syndrome, in which the pathological focus is located on one side of the medulla oblongata, while the root of the hyoid (XII cranial) nerve and the fibers of the cortical-spinal pathway passing to the other side at the border of the medulla oblongata and spinal cord are affected. It is characterized by the development of peripheral paresis or paralysis of half of the tongue on the side of the pathological focus, while central hemiparesis or hemiplegia occurs on the opposite side. Described in 1864 by the English neurologist J. Jackson (1835-1911).

Medial medullary syndrome (Dejerine's syndrome) - alternating syndrome, in which on the side of the pathological focus develops peripheral paralysis of half of the tongue, and on the opposite side - central hemiparesis or hemiplegia in combination with a violation of deep, vibration and a decrease in tactile sensitivity. It usually occurs in connection with the occlusion of the short branches of the basilar artery and the upper part of the anterior spinal artery, which feed the paramedian region of the medulla oblongata. Described by the French neurologist J.J. Dejerine (1849-1917).

Dorsolateral medulla oblongata syndrome (Wallenberg-Zakharchenko syndrome, inferior posterior cerebellar artery syndrome) - alternating syndrome resulting from ischemia in the basin of the inferior posterior cerebellar artery. It is manifested by dizziness, nausea, vomiting, hiccups, dysarthria, hoarseness, swallowing disorder, decreased pharyngeal reflex, while on the side of the lesion there are hypesthesia on the face, a decrease in the corneal reflex, paresis of the soft palate and pharyngeal muscles, hemiataxia, Horner's syndrome, nystagmus when looking towards the lesion. On the opposite side, a decrease in pain and temperature sensitivity according to the hemitype is revealed. Described in 1885 by the German doctor A. Wallenberg (1862-1949), and in 1911 domestic doctor M.A. Zakharchenko (1879-1953).

Avellis syndrome - an alternating syndrome that occurs in connection with the lesion of the medulla oblongata at the level of the location of the double nucleus, related to the IX and X cranial nerves. With Avellis syndrome, paralysis or paresis of the palatine curtain, vocal cord, and esophageal muscles develops on the side of the pathological focus. Dysphonia and dysphagia appear, and on the opposite side - central hemiparesis, sometimes hemihypesthesia. Described in 1891 by the German otorhinolaryngologist G. Avellis (1864-1916).

Schmidt syndrome- an alternating syndrome, in which damage to the medulla oblongata leads to the development of peripheral paralysis of the soft palate, pharynx, vocal cord, sternocleidomastoid muscle and the upper part of the trapezius muscle on the side of the pathological focus (a consequence of damage to the IX, X, XI cranial nerves ), and on the opposite side - central hemiparesis, sometimes - hemihypesthesia. Described in 1892 by the German doctor A. Schmidt (1865-1918).

Sestan-Chene Syndrome - alternating syndrome that occurs when the medulla oblongata is damaged at the level of the double nucleus. It is manifested by paralysis or paresis of the muscles innervated by the IX and X cranial nerves, cerebellar insufficiency and signs of Horner's syndrome on the side of the pathological focus, and on the opposite side - conduction disorders (central hemiparesis, hemihypesthesia). Described in 1903 by French neuropathologists E. Cestan (1872-1933) and L. Chenais (1872-1950).

Babinski-Najotte syndrome - alternating syndrome, in which on the side of the pathological focus there is a lesion of the inferior cerebellar peduncle, the olivocerebellar tract and sympathetic fibers, as well as the pyramidal, spinothalamic tracts, and the medial loop. On the side of the lesion, cerebellar disorders (hemiataxia, hemiasynergia, leteropulsia), Horner's syndrome are noted, on the opposite side - central hemiplegia (hemiparesis) in combination with hemianesthesia (hemihypesthesia). Described in 1902 by the French neurologists J. Babinski (1857-1932) and J. Nageotte (1866-1948).

Wollstein syndrome - alternating syndrome, in which the upper part of the double nucleus and the spinothalamic pathway are affected in the tegmentum of the medulla oblongata. On the side of the pathological focus, paresis of the vocal cord is detected, and on the opposite side, a violation of pain and temperature sensitivity. Described by the German doctor K. Wollestein.

Tapia syndrome- an alternating syndrome caused by a lesion of the medulla oblongata, in which on the side of the pathological focus there is a lesion of the nuclei or roots of the XI and XII cranial nerves (peripheral paralysis of the sternocleidomastoid and trapezius muscles, as well as half of the tongue), and on the opposite side - central hemiparesis . Described in 1905 in thrombosis of the inferior posterior cerebellar artery by the Spanish otorhinolaryngologist A. Tapia (1875-1950).

Grenove's syndrome - alternating syndrome, in which on one side of the medulla oblongata, the lower nucleus of the trigeminal nerve and the spinothalamic pathway suffer. Homolaterally manifests itself as a disorder of pain and temperature sensitivity according to the segmental type on the face, contralaterally - a violation of pain and temperature sensitivity according to the conduction type on the trunk and extremities. Described by the German doctor A. Groenouw (1862-1945).

Pyramid Syndrome - an isolated lesion of the pyramids located on the ventral side of the medulla oblongata, through which approximately 1 million axons pass, which make up the cortical-spinal tract proper, leads to the development of a central, predominantly distal tetraparesis, with more significant paresis of the hands. Muscle tone in such cases is low, pyramidal pathological signs may be absent. The syndrome is a possible sign of a tumor (usually a meningioma), a clivus of the base of the skull (Blumenbach's clivus).

9.7. BULVAR AND PSEUDOBULBAR SYNDROMES

Bulbar syndrome, or bulbar paralysis, - combined lesion of the bulbar group of cranial nerves: glossopharyngeal, vagus, accessory and hypoglossal. Occurs when the function of their nuclei, roots, trunks is impaired. It is manifested by bulbar dysarthria or anarthria, in particular, a nasal tone of speech (nazolalia) or loss of sonority of the voice (aphonia), swallowing disorder (dysphonia). Possible atrophy, fibrillar and fascicular twitching in the tongue, "purse-string mouth", manifestations of flaccid paresis of the sternocleidomastoid and trapezius muscles. Usually palatal, pharyngeal and cough reflexes fade. The resulting respiratory and cardiovascular disorders are especially dangerous.

Bulbar dysarthria - a speech disorder caused by flaccid paresis or paralysis of the muscles that provide it (muscles of the tongue, lips, soft palate, pharynx, larynx, muscles that lift the lower jaw, respiratory muscles). The voice is weak, muffled, exhausted. Vowels and voiced consonants are stunned. The timbre of speech is changed according to the type of open nasality, the articulation of consonant sounds is blurred. Simplified articulation of fricative consonants (d, b, t, p). Selective disorders in the pronunciation of the mentioned sounds are possible due to the variability in the degree of flaccid paresis of individual muscles of the speech motor apparatus. Speech is slow, quickly tires the patient, he is aware of speech defects, but it is impossible to overcome them. Bulbar dysarthria is one of the manifestations of the bulbar syndrome.

Brissot syndromecharacterized by the fact that a patient with bulbar syndrome periodically, more often at night, has general trembling, blanching of the skin, cold sweat, respiratory and circulatory disorders, accompanied by a state of anxiety, vital fear. Probably, it is a consequence of dysfunction of the reticular formation at the level of the brain stem. Described by the French neurologist E. Brissaud (1852-1909).

Pseudobulbar syndrome or pseudobulbar palsy - combined dysfunction of the bulbar group of cranial nerves, due to bilateral damage to the cortical-nuclear pathways leading to their nuclei. The clinical picture at the same time resembles the manifestations of the bulbar syndrome, but the paresis is of a central nature (the tone of the paretic or paralyzed muscles is increased, there is no malnutrition, fibrillar and fascicular twitches), and the pharyngeal, palatine, cough, mandibular reflexes are increased. In addition, the severity of reflexes of oral automatism is characteristic, uncontrolled emotional reactions - violent crying, less often - violent laughter.

Pseudobulbar dysarthria - a speech disorder caused by central paresis or paralysis of the muscles that provide it (pseudobulbar syndrome). The voice is weak, hoarse, hoarse; the pace of speech is slow, its timbre is nasal, especially when pronouncing consonants with a complex articulation pattern (r, l, w, w, h, c) and back vowels (e, i). Stop consonants and "r" are usually replaced by fricative consonants, the pronunciation of which is simplified. The articulation of hard consonants is disturbed to a greater extent than soft ones. The ends of words often do not agree. The patient is aware of articulation defects, actively tries to overcome them, but this only increases the tone of the muscles that provide speech, and the increase in the manifestations of dysarthria. Pseudobulbar dysarthria is one of the manifestations of pseudobulbar syndrome.

Reflexes of oral automatism - a group of phylogenetically ancient proprioceptive reflexes, the V and VII cranial nerves and their nuclei, as well as the cells of the nucleus of the XII cranial nerve, the axons of which innervate the circular muscle of the mouth, take part in the formation of their reflex arcs. They are physiological in children under the age of 2-3 years. Later, the subcortical nodes and the cerebral cortex exert an inhibitory effect on them. With the defeat of these brain structures, as well as their connections with the marked nuclei of the cranial nerves, reflexes of oral automatism appear. They are caused by irritation of the oral part of the face and are manifested by pulling the lips forward - by sucking or kissing movement. These reflexes are characteristic, in particular, for the clinical picture of pseudobulbar syndrome.

Rice. 9.15.Proboscis reflex.

Proboscis reflex (oral ankylosing spondylitis) - involuntary protrusion of the lips in response to light tapping with a hammer on upper lip or by the finger of the subject placed on the lips (Fig. 9.15). Described by the domestic neurologist V.M. Bekhterev (1857-1927).

Sucking reflex (Oppenheim sucking reflex) - the appearance of sucking movements in response to stroke irritation of the lips. Described by the German neurologist H. Oppengeim (1859-1919).

Wurp-Toulouse reflex (Wurp labial reflex) - involuntary stretching of the lips, reminiscent of

satelnoe movement that occurs in response to the stroke irritation of the upper lip or its percussion. This is one of the reflexes of oral automatism. Described by French doctors S. Vurpas and E. Toulouse.

Oral Oppenheim reflex - chewing, and sometimes swallowing movements (except for the sucking reflex) in response to stroke irritation of the lips. Refers to the reflexes of oral automatism. Described by the German neurologist H. Oppenheim.

Escherich's reflex- a sharp stretching of the lips and their freezing in this position with the formation of a "goat's muzzle" in response to irritation of the mucous membrane of the lips or oral cavity. Refers to the reflexes of oral automatism. Described by the German doctor E. Escherich (1857-1911).

Bulldog reflex (Yanishevsky reflex) - tonic closure of the jaws in response to irritation with a spatula of the lips, hard palate, gums. Refers to the reflexes of oral automatism. It usually manifests itself with damage to the frontal lobes of the brain. Described by the domestic neuropathologist A.E. Yanishevsky (born in 1873).

Nasolabial reflex (nasolabial reflex of Astvatsaturov) - contraction of the circular muscle of the mouth and protrusion of the lips in response to tapping with a hammer on the back or tip of the nose. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist M.I. Astvatsaturov (1877-1936).

Oral Henneberg reflex - contraction of the circular muscle of the mouth in response to irritation with a spatula of the hard palate. Described by the German psychoneurologist R. Genneberg (1868-1962).

Distant oral reflex of Karchikyan-Rastvorov - protrusion of the lips when approaching the lips of the hammer or some other object. Refers to the symptoms of oral automatism. Russian neuropathologists I.S. Karchikyan (1890-1965) and I.I. solutions.

Bogolepov's distant-oral reflex. After evoking the proboscis reflex, the approach of the hammer to the mouth leads to the fact that it opens and freezes in the “ready to eat” position. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist N.K. Bogolepov (1900-1980).

Babkin's distal chin reflex - contraction of the muscles of the chin when approaching the face of the hammer. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist P.S. Babkin.

labiochin reflex - contraction of the muscles of the chin with irritation of the lips. It is a sign of oral automatism.

Rybalkin's mandibular reflex - intense closing of the parted mouth when hitting with a hammer on a spatula placed across the lower jaw on her teeth. May be positive in bilateral corticonuclear pathways. Described by the domestic doctor Ya.V. Rybalkin (1854-

1909).

Clonus of the lower jaw (symptom of Dana) - clonus of the lower jaw when tapping with a hammer on the chin or on a spatula placed on the teeth of the lower jaw of a patient whose mouth is ajar. It can be detected with bilateral damage to the cortical-nuclear pathways. Described American

doctor Ch.L. Dana (1852-1935).

Guillain's nasopharyngeal reflex - closing the eyes when tapping with a hammer on the back of the nose. Can be called when pseudobulbar syndrome. Described by the French neurologist G. Guillein (1876-1961).

Palmar-chin reflex (Marinescu-Radovici reflex) - later exteroceptive skin reflex (in comparison with oral reflexes). The reflex arc closes in the striatum. Inhibition of the reflex is provided by the cerebral cortex. It is caused by stroke irritation of the skin of the palm in the area of ​​​​the eminence of the thumb, while on the same side there is a contraction of the chin muscle. Normally caused in children under 4 years of age. In adults, it can be caused by cortical pathology and damage to the cortical-subcortical, cortical-nuclear connections, in particular with pseudobulbar syndrome. Described by the Romanian neurologist G. Marinesku (1863-1938) and the French doctor I.G. Radovici (born in 1868).

Violent crying and laughter - spontaneously arising, not amenable to volitional suppression and not having adequate reasons, facial expressions inherent in crying or laughter, not conducive to resolving internal emotional stress. One of the signs of pseudobulbar syndrome.

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brain stem

The brain stem includes the medulla oblongata, pons, midbrain, diencephalon, and cerebellum. The brain stem performs the following functions:

1) organizes reflexes that ensure the preparation and implementation of various forms of behavior; 2) performs a conductive function: paths connecting the structures of the central nervous system pass through the brainstem in an ascending and descending direction; 3) when organizing behavior, it ensures the interaction of its structures with each other, with the spinal cord, basal ganglia and cerebral cortex, i.e., provides an associative function.

Medulla brain stem cerebellum physiological

Features of the functional organization. The human medulla oblongata is about 25 mm long. It is a continuation of the spinal cord. Structurally, in terms of the variety and structure of the nuclei, the medulla oblongata is more complex than the spinal cord. Unlike the spinal cord, it does not have a metameric, repeatable structure; the gray matter in it is located not in the center, but with nuclei to the periphery.

In the medulla oblongata there are olives associated with the spinal cord, the extrapyramidal system and the cerebellum - these are thin and wedge-shaped nuclei of proprioceptive sensitivity (the nuclei of Gaulle and Burdach). Here are the intersections of the descending pyramidal paths and the ascending paths formed by the thin and wedge-shaped bundles (Gaulle and Burdakh), the reticular formation.

The medulla oblongata, due to its nuclear formations and the reticular formation, is involved in the implementation of autonomic, somatic, gustatory, auditory, and vestibular reflexes. A feature of the medulla oblongata is that its nuclei, being excited sequentially, ensure the execution of complex reflexes that require the sequential inclusion of different muscle groups, which is observed, for example, when swallowing.

The nuclei of the following cranial nerves are located in the medulla oblongata:

a pair of VIII cranial nerves - the vestibulocochlear nerve consists of the cochlear and vestibular parts. The cochlear nucleus lies in the medulla oblongata;

pair IX -- glossopharyngeal nerve (p. glossopharyngeus); its core is formed by 3 parts - motor, sensory and vegetative. The motor part is involved in the innervation of the muscles of the pharynx and oral cavity, the sensitive part receives information from the taste receptors of the posterior third of the tongue; autonomic innervates the salivary glands;

pair X - the vagus nerve (n.vagus) has 3 nuclei: the autonomic innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; sensitive receives information from the receptors of the alveoli of the lungs and other internal organs, and motor (the so-called mutual) provides a sequence of contraction of the muscles of the pharynx, larynx when swallowing;

pair XI -- accessory nerve (n.accessorius); its nucleus is partially located in the medulla oblongata;

pair XII - the hypoglossal nerve (n.hypoglossus) is the motor nerve of the tongue, its core is mostly located in the medulla oblongata.

Touch functions. The medulla oblongata regulates a number of sensory functions: reception skin sensitivity faces - in the sensory nucleus of the trigeminal nerve; primary analysis of taste reception - in the nucleus of the glossopharyngeal nerve; reception of auditory stimuli - in the nucleus of the cochlear nerve; reception of vestibular stimuli - in the upper vestibular nucleus. In the posterior superior sections of the medulla oblongata, there are paths of skin, deep, visceral sensitivity, some of which switch here to the second neuron (thin and sphenoid nuclei). At the level of the medulla oblongata, the enumerated sensory functions implement the primary analysis of the strength and quality of the stimulus, then the processed information is transmitted to the subcortical structures to determine the biological significance of this stimulus.

conductor functions. All ascending and descending pathways of the spinal cord pass through the medulla oblongata: spinal-thalamic, corticospinal, rubrospinal. The vestibulospinal, olivospinal and reticulospinal tracts originate in it, providing tone and coordination of muscle reactions. In the medulla, the paths from the cerebral cortex end - the corticoreticular paths. Here ends the ascending pathways of proprioceptive sensitivity from the spinal cord: thin and wedge-shaped. Brain formations such as the pons, midbrain, cerebellum, thalamus, hypothalamus, and cerebral cortex have bilateral connections with the medulla oblongata. The presence of these connections indicates the participation of the medulla oblongata in the regulation of skeletal muscle tone, autonomic and higher integrative functions, and the analysis of sensory stimuli.

reflex functions. Numerous reflexes of the medulla oblongata are divided into vital and non-vital, but such a representation is rather arbitrary. The respiratory and vasomotor centers of the medulla oblongata can be attributed to vital centers, since a number of cardiac and respiratory reflexes are closed in them.

The medulla oblongata organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, tearing, closing of the eyelids. These reflexes are realized due to the fact that information about irritation of the receptors of the mucous membrane of the eye, oral cavity, larynx, nasopharynx through the sensitive branches of the trigeminal and glossopharyngeal nerves enters the nuclei of the medulla oblongata, from here comes the command to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result, one or another protective reflex is realized. In the same way, due to the sequential inclusion of muscle groups of the head, neck, chest and diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

In addition, the medulla oblongata organizes postural reflexes. These reflexes are formed by afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, the processed information for assessing the need for a change in posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscle systems, segments of the spinal cord should take part in a change in posture, therefore, from the neurons of the medial and lateral nuclei, along the vestibulospinal pathway, the signal arrives at the anterior horns of the corresponding segments of the spinal cord, innervating the muscles, whose participation in changing the posture in necessary at the moment.

Posture change is carried out due to static and statokinetic reflexes. Static reflexes regulate the tone of skeletal muscles in order to maintain a certain position of the body. Statokinetic reflexes medulla oblongata provide a redistribution of the tone of the muscles of the body to organize a posture corresponding to the moment of rectilinear or rotational movement.

Most of the autonomic reflexes of the medulla oblongata are realized through the nucleus of the vagus nerve which receive information about the state of activity of the heart, blood vessels, digestive tract, lungs, digestive glands, etc. In response to this information, the nuclei organize the motor and secretory reactions of these organs.

Excitation of the nuclei of the vagus nerve causes an increase in the contraction of the smooth muscles of the stomach, intestines, gallbladder and, at the same time, relaxation of the sphincters of these organs. At the same time, the work of the heart slows down and weakens, the lumen of the bronchi narrows.

The activity of the nuclei of the vagus nerve is also manifested in increased secretion of the bronchial, gastric, intestinal glands, in the excitation of the pancreas, secretory cells of the liver.

Located in the medulla oblongata salivation center, the parasympathetic part of which provides an increase in general secretion, and the sympathetic part - protein secretion salivary glands.

The respiratory and vasomotor centers are located in the structure of the reticular formation of the medulla oblongata. The peculiarity of these centers is that their neurons are able to be excited reflexively and under the influence of chemical stimuli.

respiratory center localized in the medial part of the reticular formation of each symmetrical half of the medulla oblongata and is divided into two parts, inhalation and exhalation.

In the reticular formation of the medulla oblongata, another vital center is represented - vasomotor center(regulation of vascular tone). It functions in conjunction with the overlying structures of the brain and, above all, with the hypothalamus. Excitation of the vasomotor center always changes the rhythm of breathing, the tone of the bronchi, intestinal muscles, bladder, ciliary muscle, etc. This is due to the fact that the reticular formation of the medulla oblongata has synaptic connections with the hypothalamus and other centers.

In the middle sections of the reticular formation there are neurons that form the reticulospinal pathway, which has an inhibitory effect on the motor neurons of the spinal cord. At the bottom of the IV ventricle, the neurons of the "blue spot" are located. Their mediator is norepinephrine. These neurons cause activation of the reticulospinal pathway during REM sleep, which leads to inhibition of spinal reflexes and a decrease in muscle tone.

Damage symptoms. Damage to the left or right half of the medulla oblongata above the intersection of the ascending pathways of proprioceptive sensitivity causes disturbances in the sensitivity and work of the muscles of the face and head on the side of the injury. At the same time, on the opposite side relative to the side of the injury, there are violations of skin sensitivity and motor paralysis of the trunk and limbs. This is due to the fact that the ascending and descending pathways from the spinal cord and into the spinal cord intersect, and the nuclei of the cranial nerves innervate their half of the head, i.e., the cranial nerves do not intersect.

Bridge

The bridge (pons cerebri, pons Varolii) is located above the medulla oblongata and performs sensory, conductive, motor, integrative reflex functions.

The structure of the bridge includes the nuclei of the facial, trigeminal, abducens, vestibulocochlear nerve (vestibular and cochlear nuclei), the nuclei of the vestibular part of the vestibulocochlear nerve (vestibular nerve): lateral (Deiters) and superior (Bekhterev). The reticular formation of the bridge is closely related to the reticular formation of the middle and medulla oblongata.

An important structure of the bridge is the middle cerebellar peduncle. It is she who provides functional compensatory and morphological connections of the cerebral cortex with the cerebellar hemispheres.

The sensory functions of the bridge are provided by the nuclei of the vestibulocochlear, trigeminal nerves. The cochlear part of the vestibulocochlear nerve ends in the brain in the cochlear nuclei; the vestibular part of the vestibulocochlear nerve is in the triangular nucleus, Deiters' nucleus, Bekhterev's nucleus. Here is the primary analysis of vestibular stimuli of their strength and direction.

The sensory nucleus of the trigeminal nerve receives signals from receptors in the skin of the face, the anterior scalp, mucous membranes of the nose and mouth, teeth, and the conjunctiva of the eyeball. The facial nerve (p. Facialis) innervates everything facial muscles faces. The abducens nerve (n. abducens) innervates the rectus lateral muscle, which abducts the eyeball outwards.

The motor portion of the trigeminal nucleus (n. trigeminus) innervates the masticatory muscles, the muscle that stretches the eardrum, and the muscle that pulls the palatine curtain.

The conductive function of the bridge. Provided with longitudinal and transverse fibers. Transversely located fibers form the upper and lower layers, and between them pass the pyramidal paths coming from the cerebral cortex. Between the transverse fibers are neuronal clusters - the nuclei of the bridge. From their neurons, transverse fibers begin, which go to the opposite side of the bridge, forming the middle cerebellar peduncle and ending in its cortex.

In the tire of the bridge there are longitudinally running bundles of fibers of the medial loop (lemniscus medialis). They are crossed by transversely running fibers of the trapezoid body (corpus trapezoideum), which are axons of the cochlear part of the vestibulocochlear nerve of the opposite side, which end in the nucleus of the superior olive (oliva superior). From this nucleus, the paths of the lateral loop (lemniscus lateralis) go to the posterior quadrigemina of the midbrain and to the medial geniculate bodies of the diencephalon.

The anterior and posterior nuclei of the trapezoid body and the lateral loop are localized in the tegmentum of the brain. These nuclei, together with the superior olive, provide the primary analysis of information from the organ of hearing and then transmit information to the posterior colliculus of the quadrigemina.

The tegmentum also contains a long medial and tectospinal tract.

The intrinsic neurons of the pons structure form its reticular formation, the nuclei of the facial and abducens nerves, the motor portion of the nucleus, and the middle sensory nucleus of the trigeminal nerve.

The reticular formation of the bridge is a continuation of the reticular formation of the medulla oblongata and the beginning of the same midbrain system. The axons of the neurons of the reticular formation of the bridge go to the cerebellum, to the spinal cord (reticulospinal pathway). The latter activate the neurons of the spinal cord.

The pontine reticular formation affects the cerebral cortex, causing it to awaken or sleep. In the reticular formation of the bridge there are two groups of nuclei that belong to a common respiratory center. One center activates the inhalation center of the medulla oblongata, the other activates the exhalation center. The neurons of the respiratory center located in the bridge adapt the work respiratory cells medulla oblongata in accordance with the changing state of the organism.

midbrain

The midbrain (mesencephalon) is represented by the quadrigemina and the legs of the brain. The largest nuclei of the midbrain are the red nucleus, the substantia nigra and the nuclei of the cranial (oculomotor and trochlear) nerves, as well as the nuclei of the reticular formation.

Touch functions. They are realized due to the receipt of visual, auditory information.

conductor function. It consists in the fact that all ascending paths pass through it to the overlying thalamus (medial loop, spinothalamic path), cerebrum and cerebellum. Descending paths go through the midbrain to the medulla oblongata and spinal cord. This is the pyramidal path, cortical-bridge fibers, rubroreticulospinal path.

motor function. It is implemented due to the nucleus of the trochlear nerve (n. trochlearis), the nuclei of the oculomotor nerve (n. oculomotorius), the red nucleus (nucleus ruber), the black substance (substantia nigra).

Red nuclei are located in the upper part of the legs of the brain. They are connected with the cerebral cortex (paths descending from the cortex), the subcortical nuclei, the cerebellum, and the spinal cord (the red nuclear-spinal path). The basal ganglia of the brain, the cerebellum have their endings in the red nuclei. Violation of the connections of the red nuclei with the reticular formation of the medulla oblongata leads to decerebrate rigidity. This condition is characterized by a strong tension in the extensor muscles of the limbs, neck, and back. The main cause of decerebrate rigidity is the pronounced activating effect of the lateral vestibular nucleus (Deiters' nucleus) on the extensor motor neurons. This influence is maximal in the absence of inhibitory influences of the red nucleus and overlying structures, as well as the cerebellum. When the brain is transected below the nucleus of the lateral vestibular nerve, the decerebrate rigidity disappears.

Red nuclei, receiving information from the motor zone of the cerebral cortex, subcortical nuclei and the cerebellum about the upcoming movement and the state of the musculoskeletal system, send corrective impulses to the motor neurons of the spinal cord along the rubrospinal tract and thereby regulate muscle tone, preparing its level for the emerging voluntary movement .

Another functionally important core of the midbrain - the substantia nigra - is located in the legs of the brain, regulates the acts of chewing, swallowing (their sequence), provides accurate movements of the fingers of the hand, for example, when writing. The neurons of this nucleus are able to synthesize the mediator dopamine, which is supplied by axonal transport to the basal ganglia of the brain. The defeat of the substantia nigra leads to a violation of the plastic tone of the muscles. Fine regulation of plastic tone when playing the violin, writing, performing graphic works is provided by the black substance. At the same time, when a certain posture is held for a long time, plastic changes occur in the muscles due to a change in their colloidal properties, which ensures the lowest energy costs. The regulation of this process is carried out by the cells of the substantia nigra.

The neurons of the nuclei of the oculomotor and trochlear nerves regulate the movement of the eye up, down, out, towards the nose and down to the corner of the nose. The neurons of the accessory nucleus of the oculomotor nerve (Yakubovich's nucleus) regulate the lumen of the pupil and the curvature of the lens.

reflex functions. Functionally independent structures of the midbrain are the tubercles of the quadrigemina. The upper ones are the primary subcortical centers of the visual analyzer (together with the lateral geniculate bodies of the diencephalon), the lower ones are the auditory (together with the medial geniculate bodies of the diencephalon). In them, the primary switching of visual and auditory information occurs. From the tubercles of the quadrigemina, the axons of their neurons go to the reticular formation of the trunk, the motor neurons of the spinal cord. Neurons of the quadrigemina can be polymodal and detector. In the latter case, they react only to one sign of irritation, for example, a change of light and darkness, the direction of movement of the light source, etc. The main function of the tubercles of the quadrigemina is to organize the reaction of alertness and the so-called start reflexes to sudden, not yet recognized, visual or sound signals. Activation of the midbrain in these cases through the hypothalamus leads to an increase in muscle tone, increased heart rate; there is a preparation for avoidance, for a defensive reaction.

The quadrigemina organizes orienting visual and auditory reflexes.

In humans, the quadrigeminal reflex is a watchdog. In cases of increased excitability of the quadrigemina, with a sudden sound or light irritation, a person starts shuddering, sometimes jumping to his feet, screaming, moving away from the stimulus as quickly as possible, sometimes unrestrained flight.

In violation of the quadrigeminal reflex, a person cannot quickly switch from one type of movement to another. Therefore, the quadrigemina take part in the organization of voluntary movements.

Reticular formation of the brain stem

The reticular formation (formatio reticularis; RF) of the brain is represented by a network of neurons with numerous diffuse connections between themselves and with almost all structures of the central nervous system. The RF is located in the thickness of the gray matter of the medulla oblongata, middle, diencephalon and is initially associated with the RF of the spinal cord. In this regard, it is advisable to consider it as a single system. The network connections of RF neurons with each other allowed Deiters to call it the reticular formation of the brain.

RF has direct and feedback connections with the cerebral cortex, basal ganglia, diencephalon, cerebellum, middle, medulla and spinal cord.

The main function of the RF is to regulate the level of activity of the cerebral cortex, cerebellum, thalamus, and spinal cord.

On the one hand, the generalized nature of RF influence on many brain structures gave grounds to consider it a nonspecific system. However, studies with brainstem RF stimulation have shown that it can selectively have an activating or inhibitory effect on various forms of behavior, on sensory, motor, and visceral systems of the brain. The network structure provides high reliability of RF functioning, resistance to damaging effects, since local damage is always compensated for by the remaining network elements. On the other hand, the high reliability of RF functioning is ensured by the fact that irritation of any of its parts is reflected in the activity of the entire RF of the given structure due to the diffuseness of connections.

Most RF neurons have long dendrites and a short axon. There are giant neurons with long axons that form pathways from RF to other areas of the brain, such as downstream, reticulospinal, and rubrospinal. The axons of RF neurons form a large number of collaterals and synapses that terminate in neurons. various departments brain. The axons of RF neurons, going to the cerebral cortex, end here on the dendrites of layers I and II.

The activity of RF neurons is different and, in principle, similar to the activity of neurons in other brain structures, but among RF neurons there are those that have a stable rhythmic activity that does not depend on incoming signals.

At the same time, in the RF of the midbrain and pons, there are neurons that are “silent” at rest, i.e., they do not generate impulses, but are excited when visual or auditory receptors are stimulated. These are the so-called specific neurons, providing a quick response to sudden, unidentified signals. A significant number of RF neurons are polysensory.

In the RF of the medulla oblongata, midbrain and pons converge signals of different sensory. The neurons of the bridge receive signals mainly from somatosensory systems. Signals from the visual and auditory sensory systems mainly come to RF neurons in the midbrain.

The RF controls the transmission of sensory information passing through the nuclei of the thalamus, due to the fact that with intense external stimulation, the neurons of the nonspecific nuclei of the thalamus are inhibited, thereby removing their inhibitory effect from the relay nuclei of the same thalamus and facilitating the transmission of sensory information to the cerebral cortex.

In the RF of the bridge, medulla oblongata, midbrain, there are neurons that respond to pain stimuli coming from muscles or internal organs, which creates a general diffuse discomfort, not always clearly localized, pain sensation"dull pain".

Repetition of any type of stimulation leads to a decrease in the impulse activity of RF neurons, i.e., the processes of adaptation (addiction) are also inherent in RF neurons of the brainstem.

The RF of the brainstem is directly related to the regulation of muscle tone, since the RF of the brainstem receives signals from the visual and vestibular analyzers and the cerebellum. From the RF to the motor neurons of the spinal cord and nuclei of the cranial nerves, signals are received that organize the position of the head, torso, etc.

Reticular pathways, which facilitate the activity of the motor systems of the spinal cord, originate from all departments of the Russian Federation. Pathways from the pons inhibit the activity of the motor neurons of the spinal cord that innervate the flexor muscles and activate the motor neurons of the extensor muscles. Pathways coming from the RF of the medulla oblongata cause opposite effects. Irritation of the RF leads to tremor, increased muscle tone. After the cessation of stimulation, the effect caused by it persists for a long time, apparently due to the circulation of excitation in the network of neurons.

RF of the brainstem is involved in the transmission of information from the cerebral cortex, spinal cord to the cerebellum and, conversely, from the cerebellum to the same systems. The function of these connections is to prepare and implement motor skills associated with addiction, orienting reactions, pain reactions, organization of walking, eye movements.

The regulation of the vegetative activity of the RF organism is described in section 4.3; here we note that this regulation is most clearly manifested in the functioning of the respiratory and cardiovascular centers. In the regulation of vegetative functions, the so-called starting neurons RF. They give rise to the circulation of excitation within a group of neurons, providing the tone of regulated autonomic systems.

RF influences can be broadly divided into downward and upward. In turn, each of these influences has an inhibitory and exciting effect.

The ascending influences of RF on the cerebral cortex increase its tone, regulate the excitability of its neurons without changing the specificity of responses to adequate stimuli. RF affects the functional state of all sensory areas of the brain, therefore, it is important in the integration of sensory information from different analyzers.

RF is directly related to the regulation of the wakefulness-sleep cycle. Stimulation of some structures of the RF leads to the development of sleep, stimulation of others causes awakening. G. Magun and D. Moruzzi put forward the concept that all types of signals coming from peripheral receptors reach the medulla oblongata and the pons via the RF collaterals, where they switch to neurons that give ascending pathways to the thalamus and then to the cerebral cortex.

Excitation of the RF of the medulla oblongata or pons causes synchronization of the activity of the cerebral cortex, the appearance of slow rhythms in its electrical parameters, and sleep inhibition.

Excitation of the midbrain RF causes the opposite effect of awakening: desynchronization of the electrical activity of the cortex, the appearance of fast low-amplitude V-like rhythms in the electroencephalogram.

G. Bremer (1935) showed that if the brain is cut between the anterior and posterior tubercles of the quadrigemina, then the animal stops responding to all types of signals; if the transection is made between the medulla oblongata and the midbrain (while the RF retains its connection with the forebrain), then the animal reacts to light, sound, and other signals. Therefore, maintaining an active analyzing state of the brain is possible while maintaining communication with the forebrain.

The reaction of activation of the cerebral cortex is observed with RF stimulation of the medulla oblongata, midbrain, diencephalon. At the same time, irritation of some nuclei of the thalamus leads to the appearance of limited local areas of excitation, and not to its general excitation, as happens with stimulation of other parts of the RF.

RF of the brainstem can have not only an excitatory, but also an inhibitory effect on the activity of the cerebral cortex.

The descending influences of the RF of the brainstem on the regulatory activity of the spinal cord were established by I.M. Sechenov (1862). He showed that when the midbrain is irritated by salt crystals in a frog, paw withdrawal reflexes arise slowly, require stronger stimulation, or do not appear at all, i.e., they are inhibited.

G. Megun (1945-1950), applying local irritations to the RF of the medulla oblongata, found that when some points are stimulated, the reflexes of the flexion of the forepaw, knee, and corneal are sluggish. When stimulated by the RF at other points of the medulla oblongata, these same reflexes were evoked more easily, were stronger, i.e., their implementation was facilitated. According to Magun, inhibitory influences on the reflexes of the spinal cord can only be exerted by the RF of the medulla oblongata, while facilitating influences are regulated by the entire RF of the stem and spinal cord.

diencephalon

The diencephalon (diencephalon) integrates sensory, motor and vegetative reactions necessary for the holistic activity of the body. The main formations of the diencephalon are the thalamus, the hypothalamus, which consists of the fornix and epiphysis, and the thalamic region, which includes the thalamus, epithalamus, and metathalamus.

thalamus

Thalamus (thalamus, optic tubercle) is a structure in which the processing and integration of almost all signals going to the cerebral cortex from the spinal cord, midbrain, cerebellum, and basal ganglia of the brain takes place.

Morphofunctional organization. In the nuclei of the thalamus, the information coming from the extero-, proprioreceptors and interoceptors is switched and thalamocortical pathways begin.

Given that the geniculate bodies of the thalamus are the subcortical centers of vision and hearing, and the frenulum node and the anterior visual nucleus are involved in the analysis of olfactory signals, it can be argued that the thalamic thalamus as a whole is a subcortical “station” for all types of sensitivity. Here, the stimuli of the external and internal environment are integrated, after which they enter the cerebral cortex.

The visual hillock is the center of the organization and realization of instincts, drives, emotions. The ability to receive information about the state of many body systems allows the thalamus to participate in the regulation and determination of the functional state of the body as a whole (this is confirmed by the presence of about 120 multifunctional nuclei in the thalamus). The nuclei form peculiar complexes that can be divided according to the projection into the cortex into 3 groups: the anterior one projects the axons of its neurons into the cingulate gyrus of the cerebral cortex; medial - in the frontal lobe of the cortex; lateral - in the parietal, temporal, occipital lobes of the cortex. The function of the nuclei is also determined from the projections. Such a division is not absolute, since one part of the fibers from the nuclei of the thalamus goes to strictly limited cortical formations, the other to different areas of the cerebral cortex.

The nuclei of the thalamus are functionally divided into specific, nonspecific and associative, according to the nature of the incoming and outgoing pathways.

TO specific nuclei include the anterior ventral, medial, ventrolateral, postlateral, postmedial, lateral, and medial geniculate bodies. The latter belong to the subcortical centers of vision and hearing, respectively.

The basic functional unit of specific thalamic nuclei are "relay" neurons, which have few dendrites and a long axon; their function is to switch information going to the cerebral cortex from skin, muscle and other receptors.

From specific nuclei, information about the nature of sensory stimuli enters strictly defined areas of III-IV layers of the cerebral cortex (somatotopic localization). Violation of the function of specific nuclei leads to the loss of specific types of sensitivity, since the nuclei of the thalamus, like the cerebral cortex, have somatotopic localization. Individual neurons of specific nuclei of the thalamus are excited by receptors of only their own type. Signals from the receptors of the skin, eyes, ear, and muscular system go to the specific nuclei of the thalamus. Signals from the interoreceptors of the projection zones of the vagus and celiac nerves, the hypothalamus also converge here.

The lateral geniculate body has direct efferent connections with the occipital lobe of the cerebral cortex and afferent connections with the retina and anterior colliculi. The neurons of the lateral geniculate bodies react differently to color stimuli, turning on and off the light, i.e., they can perform a detector function.

The medial geniculate body (MC) receives afferent impulses from the lateral loop and from the inferior tubercles of the quadrigeminae. The efferent pathways from the medial geniculate bodies go to the temporal zone of the cerebral cortex, reaching there the primary auditory cortex. MKT has a clear tonotopicity. Consequently, already at the level of the thalamus, the spatial distribution of the sensitivity of all sensory systems of the body, including sensory transmissions from the interoreceptors of blood vessels, organs of the abdominal and chest cavities, is ensured.

Associative nuclei thalamus are represented by the anterior mediodorsal, lateral dorsal nuclei and pillow. The anterior nucleus is connected with the limbic cortex (cingulate gyrus), the mediodorsal - with the frontal lobe of the cortex, the lateral dorsal - with the parietal, the pillow - with the associative zones of the parietal and temporal lobes of the cerebral cortex.

The main cellular structures of these nuclei are multipolar, bipolar three-pronged neurons, i.e., neurons capable of performing polysensory functions. A number of neurons change activity only with simultaneous complex stimulation. Convergence of excitations of different modalities occurs on polysensory neurons, an integrated signal is formed, which is then transmitted to the associative cortex of the brain. The neurons of the pillow are mainly associated with the associative zones of the parietal and temporal lobes of the cerebral cortex, the neurons of the lateral nucleus - with the parietal, the neurons of the medial nucleus - with the frontal lobe of the cerebral cortex.

Non-specific nuclei thalamus are represented by the median center, paracentral nucleus, central medial and lateral, submedial, ventral anterior, parafascicular complexes, reticular nucleus, periventricular and central gray mass. The neurons of these nuclei form their connections according to the reticular type. Their axons rise to the cerebral cortex and contact with all its layers, forming not local, but diffuse connections. Connections from the RF of the brain stem, hypothalamus, limbic system, basal ganglia, and specific nuclei of the thalamus come to nonspecific nuclei.

Excitation of nonspecific nuclei causes the generation of specific spindle-shaped electrical activity in the cortex, indicating the development of a sleepy state. Violation of the function of nonspecific nuclei makes it difficult for spindle-shaped activity to appear, i.e., the development of a sleepy state.

The complex structure of the thalamus, the presence of interconnected specific, nonspecific and associative nuclei in it, allows it to organize such motor reactions as sucking, chewing, swallowing, and laughing. Motor reactions are integrated in the thalamus with autonomic processes that provide these movements.

The convergence of sensory stimuli to the thalamus causes the emergence of so-called thalamic intractable pains that occur during pathological processes in the thalamus itself.

Cerebellum

The cerebellum (cerebellum, small brain) is one of the integrative structures of the brain, which is involved in the coordination and regulation of voluntary, involuntary movements, in the regulation of autonomic and behavioral functions.

Features of the morphofunctional organization and connection of the cerebellum. The implementation of these functions is provided by the following morphological features of the cerebellum:

1) the cerebellar cortex is built quite uniformly, has stereotypical connections, which creates conditions for fast processing information;

2) the main neural element of the cortex, the Purkinje cell, has a large number of inputs and forms the only axon output from the cerebellum, the collaterals of which end at its nuclear structures;

3) almost all types of sensory stimuli are projected onto Purkinje cells: proprioceptive, skin, visual, auditory, vestibular, etc.;

4) exits from the cerebellum provide its connections with the cerebral cortex, with stem formations and the spinal cord.

The cerebellum is anatomically and functionally divided into old, ancient and new parts.

TO old part of the cerebellum(archicerebellum) - vestibular cerebellum - refers to the flocculent-floccular lobe. This part has the most pronounced connections with the vestibular analyzer, which explains the importance of the cerebellum in the regulation of balance.

Ancient part of the cerebellum(paleocerebellum) - the spinal cerebellum - consists of sections of the vermis and pyramid of the cerebellum, uvula, parietal division and receives information mainly from the proprioceptive systems of muscles, tendons, periosteum, and joint membranes.

New cerebellum(neocerebellum) includes the cortex of the cerebellar hemispheres and sections of the worm; it receives information from the cortex, mainly via the fronto-cerebellopontine pathway, from visual and auditory receptor systems, which indicates its participation in the analysis of visual and auditory signals and the organization of the reaction to them.

The cerebellar cortex has a specific structure that is not repeated anywhere in the central nervous system. The upper (I) layer of the cerebellar cortex is a molecular layer, consists of parallel fibers, branchings of dendrites and axons of II and III layers. In the lower part of the molecular layer, basket and stellate cells are found, which provide interaction between Purkinje cells.

The middle (II) layer of the cortex is formed by Purkinje cells lined up in one row and having the most powerful dendritic system in the CNS. On the dendritic field of one Purkinje cell, there can be up to 60,000 synapses. Therefore, these cells perform the task of collecting, processing and transmitting information. The axons of Purkinje cells are the only way in which the cerebellar cortex transmits information to its nuclei and the nuclei of the brain structure.

Under the II layer of the cortex (under the Purkinje cells), there is a granular (III) layer, consisting of granule cells, the number of which reaches 10 billion. The axons of these cells rise up, divide in a T-shape on the surface of the cortex, forming contact paths with Purkinje cells. Here are the Golgi cells.

Information leaves the cerebellum through the upper and lower legs. Through the upper legs, the signals go to the thalamus, the pons, the red nucleus, the nuclei of the brain stem, and the reticular formation of the midbrain. Through the lower legs of the cerebellum, the signals go to the medulla oblongata to its vestibular nuclei, olives, and the reticular formation. The middle cerebellar peduncle connects the new cerebellum with the frontal lobe of the brain.

The impulse activity of neurons is recorded in the layer of Purkinje cells and the granular layer, and the frequency of generation of impulses of these cells ranges from 20 to 200 per second. The cells of the cerebellar nuclei generate impulses much less frequently - 1-3 impulses per second.

Stimulation of the upper layer of the cerebellar cortex leads to prolonged (up to 200 ms) inhibition of Purkinje cell activity. Their same inhibition occurs with light and sound signals. The total changes in the electrical activity of the cerebellar cortex on irritation of the sensory nerve of any muscle look like a positive oscillation (inhibition of cortical activity, hyperpolarization of Purkinje cells), which occurs after 15–20 ms and lasts 20–30 ms, after which a wave of excitation occurs, lasting up to 500 ms (depolarization of Purkinje cells).

Signals from skin receptors, muscles, articular membranes, and periosteum enter the cerebellar cortex through the so-called spinal cerebellar tracts: along the posterior (dorsal) and anterior (ventral) tracts. These paths to the cerebellum pass through the inferior olive of the medulla oblongata. From the olive cells come the so-called climbing fibers that branch on the dendrites of the Purkinje cells.

The nuclei of the bridge send afferent pathways to the cerebellum, forming mossy fibers that terminate on the granule cells of layer III of the cerebellar cortex. Between the cerebellum and the bluish part of the midbrain there is an afferent connection with the help of adrenergic fibers. These fibers are capable of diffusely ejecting norepinephrine into the intercellular space of the cerebellar cortex, thereby humorally changing the state of excitability of its cells.

Axons of cells of the third layer of the cerebellar cortex cause inhibition of Purkinje cells and granule cells of their own layer.

Purkinje cells, in turn, inhibit the activity of neurons in the cerebellar nuclei. The nuclei of the cerebellum have a high tonic activity and regulate the tone of a number of motor centers of the intermediate, middle, medulla oblongata, and spinal cord.

The subcortical system of the cerebellum consists of three functionally different nuclear formations: the tent nucleus, the corky, spherical, and dentate nuclei.

The tent nucleus receives input from the medial cerebellar cortex and is connected to the Deiters nucleus and RF of the medulla and midbrain. From here, the signals travel along the reticulospinal pathway to the motor neurons of the spinal cord.

The intermediate cortex of the cerebellum projects to the cork and globular nuclei. From them, connections go to the midbrain to the red nucleus, then to the spinal cord along the rubrospinal path. The second path from the intermediate nucleus goes to the thalamus and further to the motor cortex.

The dentate nucleus, receiving information from the lateral zone of the cerebellar cortex, is connected with the thalamus, and through it - with the motor zone of the cerebral cortex.

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The composition of the white matter of the brain. The structure and functions of the trunk. Anatomical features of the cerebellum. Big brain functions. Vertical and horizontal organization of the cortex. Analytical and synthetic activity of the cerebral cortex. limbic system of the brain.

Medulla. The medulla oblongata starts from the spinal cord, keeping its shape. Their border is the level of the lower edge of the first cervical vertebra. With its upper expanded end, it passes into the pons. The border between them is a transverse groove at the lower edge of the pons. On its front surface, on both sides of the longitudinal slit, two rollers stretch, called pyramids.

The fibers of the lower section of the right pyramid pass to the left side, and the left - to the right. This fiber transition is called cross pyramids. Thanks to the decussation, the cortex of the right hemisphere controls the functions of the left side of the body and the left limbs, and, conversely, the left - right side and right limbs.

On the dorsal surface of the medulla oblongata is visible diamond pit- the bottom of the fourth cerebral ventricle, on which are the nuclei of eight pairs of twelve nerves extending from the brain.

Sections of the medulla oblongata show white and gray matter. In the lower section, the gray matter still retains the appearance of a butterfly, and in the upper section it is in the form of separate sections (nuclei) located along the back surface. These are the centers of respiration, regulation of cardiac activity, vasomotor, metabolism, sucking, swallowing and others.

White matter consists of centripetal and centrifugal pathways.

Like the spinal cord, with which it is similar in structure, the medulla oblongata performs two functions: reflex and conduction. It is associated with body position reflexes and changes in the tone of the neck and trunk muscles.

Pons. The bridge of Varolii is a roller-shaped, white formation transversely lying above the medulla oblongata.

The main mass of the pons is white matter, formed by nerve fibers of the transverse direction. The gray matter is distributed in the thickness of the white in separate nuclei. These are accumulations of neuron bodies with outgoing processes.

The white matter of the bridge is the pathways. They connect the cerebral cortex with peripheral organs.

Cerebellum. The cerebellum is located in the skull, below and behind the cerebral hemispheres, above the medulla oblongata and the pons. By the age of 10, his weight increases 6 times and is 129-133 G with an adult weight of just over 150 g.

The cerebellum has two hemisphere. They are covered with a thin layer of gray matter. In the white matter there are nuclei of the gray matter: serrated, spherical and others. The cerebellum is connected to other parts of the brain by three pairs of peduncles. The strongest, middle cerebellar peduncles connect it to the pons. The anterior peduncles connect the cerebellum to the quadrigemina. The posterior legs (rope bodies) connect the cerebellum to the medulla oblongata. Centripetal fibers from the spinal cord enter the cerebellum along these legs and vestibular apparatus.

Functionally, the cerebellum is involved in every motor act - it provides a certain tension to muscle groups and eliminates unnecessary and unnecessary movements. It has some effect on blood circulation, respiration, metabolism, etc.

A disorder in the activity of the cerebellum in humans leads to a violation of the coordination of movements and the distribution of muscle tone between individual muscle groups of the limbs, to a decrease in tone. At the same time, the movements become awkward and uncalculated. A person gets tired quickly, walks with legs wide apart, continuously sways, stumbles and falls. Subsequently, the movement disorder is restored, but not completely. This recovery is explained by the participation of the cerebral cortex in the coordination of movements.

Midbrain. The midbrain is made up of legs of the brain, quadrigemina and a channel called sylvian aqueduct. It is located above the pons.

In the upper pair of tubercles of the quadrigemina, intermediate centers of orienting reflexes of vision are laid, and in the lower pair - of hearing.

The anterior surface of the midbrain is represented by two voluminous bundles - the legs of the brain. These are pathways to the cerebral hemispheres. Inside the midbrain there are small accumulations of gray matter - the nuclei of the trochlear and oculomotor nerves.

Intermediate brain. Above the midbrain lies the diencephalon. It consists of two thalamus And hypothalamic region. Between the visual tubercles there is a cavity of the third ventricle of the brain.

Visual tubercles- a paired formation, visible on the longitudinal and transverse sections of the hemispheres. All centripetal impulses of the body's receptors, except for auditory ones, enter the visual tubercles, where they pass to a new neuron and are sent to the cerebral cortex. The defeat of the visual tubercles causes a complete or partial loss of sensitivity, headaches, sleep disorders, paralysis and decreased vision.

Hypodermic region presented gray mound, funnel And pituitary gland- lower cerebral appendage. Anterior to the hypothalamus, the optic nerves cross.

The formation and differentiation of various nuclei of the hypothalamic region is completed non-simultaneously. By the age of 7, cell differentiation ends, and during puberty, the connections of the hypothalamic region with other parts of the brain and body systems grow rapidly.

The hypothalamic area is functionally connected with the regulation of the metabolism of proteins, fats, salts and water. It is in charge of the work of internal organs (peristalsis of the intestines, contraction of the uterus in women, bladder, vessel walls), sweating, carbohydrate metabolism, regulation of heat transfer in the body, regulation of sleep and wakefulness.

Net formation of the brain. Mesh or reticular brain formation is a set of structural elements located in the central parts of the brain stem.

The neurons of the reticular formation differ in their structure from all other neurons. Their dendrites branch weakly, while axons, on the contrary, come into contact with a huge number of nerve cells. The nerve fibers of the formation go in a variety of directions. And when viewed under a microscope, they look like a grid, which is the basis of the name mesh formation.

The cells of the mesh formation have different sizes and shapes. Its large-celled neurons are arranged so that their dendrites and lateral processes of axons (collaterals) branch in a plane perpendicular to the longitudinal axis of the brain stem.

In places, the cells of the reticular formation are scattered in the brain stem, and sometimes they are grouped into nuclei (for example, the nucleus in the pons operculum). The cells of the formation are located along the entire length of the brain stem and occupy a central position from the medulla oblongata to the visual tubercles inclusive.

The reticular formation is connected with all parts of the central nervous system, including the cerebral cortex.

The reticular formation is considered an "energy generator" that regulates the processes taking place in other parts of the central nervous system, including the cerebral cortex.

All complex reflex acts that require the participation of many muscles in different combinations (articulation of sounds, breathing, vomiting, sneezing, etc.) are coordinated in a mesh formation. In this case, she herself is a complex reflex center, ensuring the relative safety of the automatism of breathing and cardiac activity.

The reticular formation has a general non-specific activating effect on the entire cerebral cortex. This is ensured by the presence of ascending pathways from the formation to all lobes of the cerebral hemispheres. Two bringing systems pass through the brainstem to the cortex: one is specific (sensitive pathways from all types of receptors); the other is non-specific, formed by a mesh formation. The first system ends in the cell bodies of the fourth layer of the cortex, and the second - on the dendrites of all layers of the cerebral cortex. The interaction of both systems determines the final reaction of the neurons of the cerebral cortex.

The functional mutual influence of the reticular formation with the cerebral cortex does not pass without the participation of humoral regulation, which provides analysis and synthesis of nerve impulses entering the cortex along the bringing (ascending) paths.

One of the departments, including the oblong, bridge (varoli) and middle, is called the brain stem. It has a length of 7 cm. Representing one of the parts of the base of the brain, the trunk contains the nuclei of the cranial nerves, as well as nuclear formations responsible for the functioning of vital centers (the vascular system, the respiratory center, etc.).

The localization of the trunk is such that it bypasses the ascending and descending rays, thus connecting the cerebral cortex, in other words, the brain and spinal cord. Unlike the latter, the trunk does not have metamerism, showing the nuclear system of formations.

The components of the stem are:

• midbrain

It is formed by the left and right leg brain (ventral direction), quadrigemina (dorsonal direction). This brain section has common borders with the diencephalon and passes into the bridge and cerebellum. The III and IV pairs of cranial nerves depart from the midbrain.

• Pons

It is the middle part of the trunk, characterized by a thickening. V-VIII pairs of nerves of the skull depart from the bridge. The transverse section of the bridge allows you to find the base, the tire, elements of the ventricular system, the quadrigemina (otherwise, the roof of the midbrain) and the so-called roof of the IV ventricle.

• Medulla

It resembles an onion in shape, it is separated from the bridge by a transverse furrow. From this part of the brain diverge IX to XII pairs of nerves and one of the nuclei of the VII pair.

The mesh substance, which is formed by individual nerve cells and their nuclei, the connection of which is carried out through nerve fibers, is called the reticular formation of the trunk.

The reticular formation is found both in the medulla oblongata and in the intermediate, middle and central parts of the brain. Formation cells are necessary to ensure the conductive function and activate the functions of the cerebral cortex. Passing through the cells of the reticular formation, nerve impulses experience their strengthening or relaxing effect. Thus, the reticular formation demonstrates a stimulating or inhibitory effect in relation to impulses.

The reticular formation is also called the "activating system", which is associated with the tone of impulses passing through the cells of the formation to the cerebral cortex.

The structural features of the reticular formation are such that they are characterized by 2 types of neurons:

1. Dendrites are longer and have few branches;
2. Axons characterized by good, more often - T-shaped branching.

The branches of these neurons form a mesh, or reticulum. In other words, the name of the reticular formation is due to the structure of this brain structure.

Reticular formations are associated with the structures of the CNS. Here it is necessary to distinguish between 2 types of nerve conduction:

1. Afferent (information is carried from the periphery to the center) output;
2. Efferent (information comes from the center to the periphery) output.

In the first case, the entrances penetrate the reticular formation according to the following schemes:

• Pain and temperature move along the spinal reticular pathways;
• Impulses move from the sensory and other areas of the cerebral cortex along the cortico-reticular pathways, entering the nuclei, where the projection onto the cerebellum is carried out;
• Impulsation is carried out from the cerebellar nucleus along the cerebellar-corticular path.

Efferent outputs from the reticular formation can be projected into the following departments:

• Spinal cord (movement is made along the reticulospinal path);
• (the movement goes along the ascending paths, which are initially located in the nuclei of the bridge and the medulla oblongata);
• Cerebellum (the path begins in the paramedial and lateral reticular nuclei, the nuclei of the pontine tegmentum).

Functions

The trunk contains nuclei III - XII pairs of cranial nerves. The functions of the latter are sensitive, somatic (motor), parasympathetic (vegetative). Let us consider in more detail the features of each of the pairs of cranial nerves:

1. The nuclei of the oculomotor nerve, or the III pair of cranial nerves, are located in the midbrain. They provide the following functions:

• Contraction of the upper, lower, internal rectus and inferior oblique muscles, as well as the muscles that lift the eyelid - the possibility of oculomotor reflexes;
• The parasympathetic nucleus innervates the sphincter of the pupil and the ciliary muscle, that is, it makes possible the constriction and accommodation reflexes of the eye.

1. The midbrain also contains the fourth pair of cranial nerves - the nucleus of the trochlear nerve. Its task is to innervate the superior oblique muscle, which ensures the rotation of the eyeball.
2. Bridge localization has the V pair of nerves - the trigeminal nerve. Here are the following cores:

• The motor nucleus located in the bridge, whose task is to innervate the masticatory muscles, ensure the motor activity of the lower jaw in 5 directions - up, down, to the sides, forward, tension of the soft palate and eardrum.
• Sensory nuclei (their location is the mid-cerebral, cerebral and spinal space) are necessary to receive impulses (pain, tactile, temperature, proprioceptive and visceral) from the mucous membranes, skin, organs of the head and face. The same nuclei are a component of the conductive section of the corresponding analyzers, and therefore participate in chewing, sneezing, and swallowing reflexes.

1. The next, VI pair, the nucleus of the abducens nerve is located in the bridge and contributes to the contraction of the external rectus muscle of the eye. This is how the eyes move.
2. VII pair - nuclei, also localized in the bridge:

• The functions of the motor nucleus are the contraction of the mimic and accessory muscles, as well as the stirrup muscle, due to which the regulation of sound fluctuations in the middle ear is carried out;
• The sensory nucleus of the solitary tract is necessary for the innervation of the taste buds located in the anterior 2/3 of the tongue. It also participates in the analysis of taste sensations and motor, secretory reflexes of digestion;
• The parasympathetic nucleus provides secretory activity of the sublingual, submandibular salivary glands, as well as the function of the lacrimal gland.

1. The VIII pair of cranial nerves is represented by the vestibulocochlear nerve and is located in the medulla oblongata:

• The vestibular nuclei are necessary for the innervation of the receptors of the vestibular apparatus, they are involved in static and statokinetic (provide balance, posture regulation), vestibulo-ocular, vestibulo-vegetative reflexes. The vestibular nuclei are also an element of the conduction department of the vestibular analyzer.
• Cochlear nuclei innervate auditory receptors, and also take part in the auditory orienting reflex; are part of the conductive department of the auditory analyzer.

1. IX pair - nuclei of the glossopharyngeal nerve, the location of which is the medulla oblongata:

• The motor nucleus is necessary for the swallowing reflex - the nucleus is responsible for raising the larynx and pharynx, lowering the soft palate and epiglottis.
• The task of the sensitive nucleus of the solitary tract is to obtain data (taste, pain, tactile, interoceptive, temperature) from the pharyngeal mucosa, the back of the tongue, the caratid body and the tympanic cavity. This core is part of the analyzers involved in the processes of swallowing, chewing, digestion (secretory and motor), vascular reflexes;
• The parasympathetic nucleus makes possible the lower salivation due to the innervation of the parotid salivary gland.

1. X pair of cranial nerves, localized in the medulla oblongata - these are the nuclei of the vagus nerve:

• The motor, otherwise double, nucleus takes part in swallowing, sneezing, coughing and vomiting reflexes, and also provides voice power. This action is due to the ability of the double nucleus to contract the muscles of the pharynx, palate, larynx and upper esophagus;
• The sensory nucleus of the solitary pathway acts as an afferent link in chewing, swallowing, visceral and respiratory reflexes. These functions are provided by the innervation of the mucous membranes of the root of the tongue and palate, the respiratory tract, and the thoracic and abdominal cavities. The nucleus is a component of the conductive analyzer that recognizes taste, tactile, pain, interoceptive and temperature impulses.
• The parasympathetic nucleus provides pulmonary and bronchial, digestive, cardiac reflexes, as it innervates the smooth muscles of the heart, cervical gland, chest and abdominal cavity.

1. The spinal and medulla oblongata contains the XI pair of nerves - the motor nucleus of the accessory nerves, which sends impulses to the trapezius and sternocleidomastoid muscles. This, in turn, provides contraction of these muscles. This ability gives a person the opportunity to tilt his head and at the same time turn his face in the opposite direction, bring the shoulder blades together, lift up.
2. XII pair, the motor nucleus of the hypoglossal nerve, is located in the medulla oblongata. The function of the nucleus is to provide chewing, sucking and swallowing reflexes, as well as participation in the creation of speech sounds, which is possible due to the innervation of the muscles of the tongue.

The brain stem performs sensory and reflex (somatic and autonomic) functions, the implementation of which is impossible without the participation of the nuclei of the cranial nerves.

chain reflexes

Chain reflexes of the brain stem are provided by the accumulation of the action of several pairs of cranial nuclei at once. The most significant chain reflexes will be considered below.

• oculomotor reflexes

Thanks to them, it is possible to coordinate the direction of the gaze in one direction or another. The paths of movement of the impulse are the vestibulo-cochlear and trigeminal nerves, as well as the motor nuclei of the abducens, lateral, and oculomotor nerves. Their activity is coordinated by such departments as the reticular cells of the stem, as well as the cerebral cortex and the cerebellum.

• chewing act

This reflex is possible due to the muscles that provoke the movement of the lower jaw. An afferent-type impulse comes from the mucosal receptors and proprioceptors of the masticatory apparatus, passing through the trigeminal nerve. The masticatory center is localized in the medulla oblongata (reticular formation) and the area of ​​the bridge and provokes the movement of muscle motor neurons. Due to the excitation of the latter, lowering and raising the lower jaw is possible.

• swallowing act

The purpose of the swallowing reflex is to move food from the mouth to the stomach. The movement of food becomes possible due to receptor excitation of the lingual root, and then - the soft palate, after - the pharynx and, finally, the esophagus. Impulses enter the swallowing center. The latter is located in the bridge and the medulla oblongata. As part of this center, the nucleus of the trunk, spinal cord (its cervical and thoracic regions). This center has a functional connection with the respiratory center.

• cough reflex

It is a protective reflex, the occurrence of which is associated with irritation of the receptors of the trachea, as well as the bronchi, larynx. The impulse moves along the vagus nerve, stopping in the cough center and excites it. The latter is localized in the medulla oblongata and is associated with the spinal motor center of the respiratory muscles. The formation of a cough is carried out in 3, strictly following each other, stages:

1. Deep breath;
2. Contractile movement of the expiratory muscles with a closed glottis and narrowed bronchi. This, in turn, contributes to a sharp increase in pulmonary pressure;
3. Active exhalation, produced in parallel with the opening of the glottis. This results in the creation air flow that is sent through the mouth. The soft palate is tense.
4. sneeze reflex

Protective reflex due to irritation of the branches of the trigeminal nerve located in the nasal mucosa. The mechanism of occurrence of the sneeze reflex is similar to the stages of development of the cough reflex, and the center of sneezing is also located in the medulla oblongata. The only difference is that when sneezing at the 3rd stage of reflex development, the air flow is directed not through the mouth, but through the nose.

Deviations from the norm

The nature of the pathologies of the brain stem is due to the localization and etiology of deviations in the activity of its systems. Deviations are manifested by oculomotor pathologies, sleep disturbance, alternating syndromes (partial or absolute paralysis,), decerebrate rigidity (increased tone of the extensor muscles with relaxation of the flexor muscles).

When the pathology is localized in the midbrain, the following symptoms are found:

• Weber's syndrome, in which oculomotor disorders are diagnosed, combined with paresis of the muscles of the tongue, face. Violations are accompanied by omission of the eyelid, the development of strabismus, doubling of objects;
• Vascular lesions, in which there is a disorder of temperature and pain sensitivity;
• The development of akinetic-rigid syndrome (increased muscle tone in combination with slowness of movement) or decerebrate rigidity.

With the defeat of the bridge area, the following picture is observed:

• alternating syndromes;
• Pseudobulbar syndrome - impaired speech, loss of voice, impaired swallowing caused by problems with the innervation of the muscles of the tongue, pharynx, soft palate.
• Miyyar-Gubler syndrome - paresis, paralysis of the muscles of the face;
• Fauville syndrome - damage to the abducent and facial nerves;
• With vascular disorders in the area of ​​​​the bridge, mutism, stupor (lack of body response to stimuli, with the exception of severe pain) are possible.

Damage to the medulla oblongata of the brain stem leads to the appearance of such signs as:

• Bulbar paralysis, which is characterized by the same symptoms as for pseudobulbar syndrome;
• Decreased sensitivity of the limbs;
• Bernard-Horner syndrome, which is characterized by drooping of the eyelid (ptosis), pathological constriction of the pupil (miosis), weakening of the pupil's reaction to light, retraction of the eyeball, impaired activity of the sweat glands on the affected part of the face (dyshidrosis).

Pathologies of blood flow in the region of the brain stem (ischemic stroke) as a result of vascular damage, less often - hemorrhages, the cause of which is a persistent increase in blood pressure.

Ischemic stroke can be caused by atherosclerosis, hypertension, rheumatism. Patients with diabetes mellitus are at risk. Stroke is the most common cause of death or disability in patients, as the death of brain cells occurs during the course of the disease.

A separate group of pathologies of the trunk, the etiology of which is associated with neuroinfection. The latter can be primary (poliomyelitis and similar diseases) and secondary (occur with tuberculosis, syphilis, severe forms of influenza). Common symptoms for these pathologies are oculomotor disorders, paralysis of the muscles of the tongue, pharynx, damage to the facial nerve and, as a result, paralysis of one side of the face.

The etiology of brainstem pathologies can be caused by craniocerebral injuries (including birth injuries) and neoplasms. The clinical picture is loss of consciousness, confusion of thoughts, disturbances in the activity of the respiratory and cardiac systems, coma is possible.

Depending on the type and location of the tumor, the clinical picture may vary. For example, gliomas that affect the midbrain can cause hydrocephalus. Symptoms such as severe headache, nausea and vomiting, oculomotor pathologies are diagnosed. Headache often has a paroxysmal character. Arising sharply, such pain is short-lived. In the intervals between attacks, the person feels healthy.

Most brain stem tumors are malignant. Tumor growth is rapid - from several months to 2 years. benign tumor can grow slowly, not manifesting itself until 15-20 years from the moment of appearance.

Video

Medulla(medulla oblongata) is a continuation of the spinal cord and in back has a very similar shape and structure. They stretch along it from the spinal cord anterior median fissure, posterior median sulcus, and anterior and posterior lateral sulci, inside is central channel. As the ventral and dorsal roots of the spinal nerves depart from the spinal cord, so the roots of the IX-XII cranial nerves depart from the medulla oblongata (Fig. 123). Furrows and nerve roots divide the medulla oblongata into three bundles of cords: anterior, lateral and posterior.

Anterior cords lie on both sides of the anterior median fissure. They are formed by convex white strands - pyramids, which consist of fibers of the descending cortical-spinal tract that is still common here. The pyramids taper downwards, since about 2/3 of their fibers gradually move to the opposite side, forming pyramid cross and below - lateral corticospinal tract(Atl., 79). A smaller part of the fibers remains on the same side, continuing into the anterior cords of the spinal cord in the form anterior corticospinal tract.

The lateral pyramids come to the surface of the hypoglossal nerve (XII), the roots of which are located corresponding to the ventral roots of the spinal cord.

Lateral cords occupy the lateral surfaces of the medulla oblongata. Their ventral part is made up of olives, the dorsal part is the lower cerebellar peduncles. olives have an oval shape and consist of nerve cells. On a transverse section (Atl., 79) they are like a folded sac, open medially. Olives have rich connections to the cerebellum and are functionally related to keeping the body upright. Inferior cerebellar peduncles- massive fibrous strands. Diverging upwards to the sides, they limit from the sides the lower corner of the bottom of the fourth ventricle - a rhomboid fossa (Atl., 81).

From the lateral funiculi of the medulla oblongata, the roots of the accessory (XI), vagus (X) and glossopharyngeal (IX) cranial nerves emerge in succession, located respectively to the dorsal roots of the spinal cord (Atl., 77).

Posterior cords are on both sides of the posterior median sulcus and consist of thin and wedge-shaped bundles rising here from the spinal cord (Fig. 124). The first of them thickens here into a thin one, and the second into sphenoid tubercle. Thickenings are formed by nuclei - clusters of intercalary neurons, on which the fibers of the bundles end. cell fibers thin and wedge-shaped nuclei go in two directions: under the name outer arcuate fibers- along the periphery of the medulla oblongata into the composition of the lower legs of the cerebellum of the opposite side; others, called internal arcuate fibers, cross in front of the central channel, between the olives, and form medial loop, which takes an upward direction (Atl., 78, 79 and 82).

The anterior, expanded part of the medulla oblongata, with its dorsal surface, is involved in the formation of the bottom of the posterior part of the fourth ventricle - rhomboid fossa.

All formations located between the fossa and the pyramids belong to tire. Outside of the medial loop, in the tire, is located especially powerfully developed in the medulla oblongata reticular formation(Atl., 78), which is a continuation of a similar substance of the spinal cord. Previously, it was believed that this formation had only the function of an apparatus of local significance, that is, it connected various neurons of the medulla oblongata, in particular intercalary and effector neurons, lying in the region of the bottom of the fourth ventricle of the nuclei of cranial nerves (IX-XII, etc.). Recently, the reticular formation has been given a wider meaning. In particular, the reticular formation of the trunk is associated with the regulation of the excitability of the higher-lying parts of the brain that are related to their combined (integrative) activity. The reticular formation of the trunk also affects the change in the excitability of the spinal cord. In the reticular formation there are vital centers: regulation of the cardiovascular system, respiration and protective respiratory reflexes, centers of activity of the digestive tract, etc.

The reticular7 formation of the trunk is closely connected with various analyzers and not only affects their activity, but is itself subject to influences from these systems.

Of the cranial nerves, the nuclei of which are located in the medulla oblongata, of particular importance is the vagus (X), which innervates the respiratory, digestive, circulatory and other systems. Damage to the medulla oblongata, which is closely associated with the basic vital functions of the body, leads to death.

In addition to cellular structures, the tire contains medial longitudinal bundle, red nuclear-spinal, anterior spinal-cerebellar and vestibulo-spinal, spinal-tubercular and other ascending and descending paths. Thus, the medulla oblongata also serves to a large extent as the conductor section of the brain.

Bridge(pons) is located above the medulla oblongata in the form of a transverse white shaft (Fig. 123).

At the lateral end of the groove separating the medulla oblongata and the pons, there are roots of the vestibulocochlear (VIII) nerve, consisting of fibers emanating from the receptor cells of the cochlea and the vestibule, and the roots of the facial with the intermediate (VII) nerve. In the medial part of the groove between the bridge and the pyramid, the roots of the abducens nerve (VI) depart.

In front, the bridge is sharply delimited from the legs of the brain, and laterally connected to the cerebellum through middle cerebellar peduncles.

On the border between the bridge and the middle legs of the cerebellum, the sensory and motor roots of the trigeminal nerve (V) come to the surface.

A longitudinal groove runs along the median line of the bridge, in which lies main artery brain. On a transverse section in the bridge, the ventral part protruding on the lower surface of the brain is distinguished - bridge base and dorsal - tire lying deep. The surface of the base on both sides of the longitudinal furrow is convex due to the cortical-spinal tract, and is transversely striated with fibers of the cells of the base of the bridge (Atl., 80). These transverse fibers, continuing to the sides, penetrate the cerebellum, forming its middle legs. They conduct impulses received by cells nuclei bases of the bridge from the cerebral cortex. Thus, phylogenetically new structures are located at the base of the pons: base nuclei associated with the cerebral cortex, and cortical-spinal tracts. Phylogenetically, the old tegmentum of the pons serves as a direct upward continuation of the tegmentum of the medulla oblongata, together with the anterior part of which it enters into the formation of the floor of the fourth ventricle. In the tegmentum pons extends from the medulla oblongata reticular formation, in which they lie cranial nerve nuclei(V-VIII) (Atl., 80), the fiber layer of the medial loop and other phylogenetically old pathways that start below. From vestibular nerve nuclei(part VIII nerve) originates here medial longitudinal bundle, carrying impulses that ensure that the body maintains equilibrium. This is where it starts and trigeminal loop from the switching nuclei of the trigeminal nerve, conducting impulses of skin sensitivity from the face.

On the border between the tire and the base lies the intersection of the fibers of one of cochlear nerve nuclei(part of VIII nerve) - trapezoidal body, the continuation of which is the lateral loop - the path that carries the auditory impulses.

Cerebellum located behind the bridge and the medulla oblongata (Atl., 77, A). The cerebellum consists of a middle, unpaired, phylogenetically old part - the worm - and paired hemispheres, characteristic only of mammals. Cerebellar hemispheres develop in parallel with the cerebral cortex and reach a significant size in humans. Worm on the lower side is immersed deep between the hemispheres; its upper surface passes into hemispheres gradually.

The gray matter lies superficially in the cerebellum, forming its cortex, in which the cells are arranged in two layers. The first layer, outer, molecular, wide, consists of stellate and basket cells; in the depths of it lies a number of very large cells of a peculiar form - ganglionic. The second layer is granular, formed by numerous granular cells, between which there are single, larger stellate cells. ganglion cells send their neurites to the cerebellar nuclei. The bark of the hemispheres and the worm is indented grooves, which divide it into convolutions, grouped into slices separated by permanent, deeper grooves. A somewhat isolated slice - scrap- adjacent to the middle legs of the cerebellum (Fig. 124). This is the only phylogenetically ancient part of the cerebellar hemispheres, which, together with the knot of the vermis, is already associated in lower vertebrates with the organ of balance, or the vestibular apparatus.

White matter lies in the cerebellum under the cortex. In the worm, it is represented by a thin layer, the shape of which, on the sagittal section, the ancient anatomists called the tree of life, since they found in it a resemblance to the toothed leaf of the arborvitae, or "tree of life" (so named for its constantly green color).

In the thickness of the white matter there are clusters of nerve cells that form four pairs of cerebellar nuclei (Fig. 125). In the region of the worm lies tent core; lateral to it, already in the hemispheres, are globular and corky nuclei and then the largest dentate nucleus. On the cells of the latter, the fibers of the ganglion cells of the cortex of the cerebellar hemispheres terminate. The fibers of the ganglion cells of the cortex of the worm and the shred also terminate on other nuclei.

The pathways of the cerebellum, connecting it with other parts of the central nervous system, are folded into three pairs of legs (Atl., 81). Lower and upper legs exist at all stages of phylogenesis; middle ones appear only in mammals in connection with the development of a powerful bridge and the cerebral cortex.

Inferior cerebellar peduncles contain posterior dorsal tract, outdoor arcuate fibers, emanating from the thin and wedge-shaped nuclei, fibers of olive cells and other, mainly afferent paths, the fibers of which terminate on the cells of the cortex of the worm (Atl., 93). Thus, the vermis, the phylogenetically oldest part of the cerebellum, receives mainly proprioceptive impulses from the entire body. In addition, ascending and descending pathways pass in the lower legs, connecting the vestibular nuclei with the cerebellum.

Middle peduncles of the cerebellum- the most massive, connect a bridge with it. They cover the medulla oblongata from the sides and enter the hemispheres of the cerebellum in the deep horizontal slot running along its posterior edge. In the middle legs to the neurons of the cortex of the cerebellar hemispheres pass transverse fibers foundations of the bridge (Atl., 88). On the cells of the base of the bridge, the fibers of the cerebral cortex terminate. This path is called cortical-bridge. Through the latter, the influence of the cerebral cortex on the activity of the cerebellum is carried out.

superior cerebellar peduncle, developing from the isthmus of the rhomboid brain, lie most dorsally and close to the midline. In the form of white strands, they go from the cerebellum to the midbrain, where they are located along the legs of the brain, closely adjoining them. The upper legs of the cerebellum consist mainly of fibers emanating from its nuclei, and serve as the main pathways that conduct impulses from the cerebellum (Atl., 88; Fig. 125) to the red nucleus, optic tubercle, hypothalamus, etc.

The cerebellum, receiving impulses from the muscular-articular receptors of the body, the vestibular nuclei and from the cerebral cortex, etc., participates in the coordination of all motor acts, including voluntary movements, and affects muscle tone.

The old formation - the cerebellar vermis - is associated with the movements of the axial structures of the body - the trunk, neck and head; phylogenetically young hemispheres - with the work of paired parts of the body - limbs. This explains the exceptional development of the human cerebellar hemispheres. The works of Russian physiologists established the importance of the cerebellum as an important center of the autonomic nervous system.

fourth ventricle originates from the cavity of the rhomboid bladder of the embryo, therefore it is limited by the medulla oblongata and the bridge, which form the bottom - the rhomboid fossa, and the cerebellum, which is part of the roof of the ventricle (Atl., 81). The transition of the central canal into the cavity of the fourth ventricle occurs as a result of the opening of the canal from the dorsal side. This leads to the fact that the left and right parts of the alar plate diverge to the sides and are located lateral to the main plate, together with which they form the bottom of the fourth ventricle. Due to a similar course of development, the nuclei of the cranial nerves are laid in the rhomboid fossa as follows. The middle position is occupied by those developed from the main plate motor nuclei whose neurons are homologous to the motor neurons of the anterior horns of the spinal cord. The most lateral place belongs to switching cores, the so-called sensory or sensitive, developed from the wing plate; they are formed by intercalary neurons and are homologues of the dorsal horns of the spinal cord. Between the motor and switching nuclei of the structures characteristic of the head that originated from the visceral apparatus, for example, the motor nuclei of the V and VII cranial nerves, are laid. In the region of the border furrow are located nuclei of the autonomic nervous system homologous to the lateral horns of the spinal cord.

The rhomboid fossa has a shape corresponding to its name. From below and from the sides, it is limited by the lower legs of the cerebellum, from above - by its upper legs. The lateral angles of the fossa are elongated lateral pockets.

Rhomboid fossa lined with ependyma, under which are located the nuclei of cranial nerves from V to XII surrounded by the reticular formation.

On the border of the anterior and middle third of the rhomboid fossa, in its small depression, lies trigeminal motor nucleus(V). Lateral motor lies superior sensory nucleus this nerve. Up from it, on the sides of the water pipe wall, stretches nucleus of the mesencephalic tract trigeminal nerve, and down, along the medulla oblongata and posterior horns of the cervical part of the spinal cord, - spinal tract nucleus this nerve.

Not far from the middle of the rhomboid fossa lies the motor abducens nucleus(VI). Motor facial nerve nucleus(VII) is located in the cover of the bridge deeper and outward. The lateral pocket of the rhomboid fossa is occupied for a large extent vestibular nuclei and dorsal cochlear nucleus. The narrowed posterior end of the rhomboid fossa contains motor nucleus of the hypoglossal nerve. Laterally located vagus triangle, which contains its autonomous dorsal nucleus, which has a two-way connection with the internals. The nuclei of the remaining nerves lying at the bottom of the fourth ventricle are somewhat deeper and are not found on the surface. This is, for example, the ventral cochlear nucleus VIII nerve, double core X and IX nerves single path core, sensitive nuclei VII, IX and X nerves.

In the switching nuclei, afferent fibers terminate, which come as part of the cranial nerves from the skin of the face (V), the organ of taste (VII, IX), the organs of hearing and balance (VIII), the respiratory tract, lungs, heart, blood vessels, digestive tract (X). From the cells of the motor nuclei in the composition of the cranial nerves, fibers pass to the muscles of the face (V, VII nerves), heart, respiratory tract and almost all digestive organs (X), tongue (XII). At the bottom of the rhomboid fossa, reflex arcs are closed, along which the regulation of breathing, digestion, blood circulation, body position, etc. is carried out.

Roof fourth ventricle is formed in front of the anterior brain sail, which is a plate of white matter stretched between both upper legs of the cerebellum and its worm. Behind the roof consists of a thin epithelial plate. This is an underdeveloped wall of the brain bladder, called rear brain sail(Fig. 124). The choroid of the brain is firmly connected with the latter, which protrudes into the ventricle during development and forms in it choroid plexus. The posterior medullary velum is attached on the sides to the lower legs of the cerebellum, and from above to the cerebellum; from touching the latter, it is easily torn, as a result of which the cavity of the ventricle is opened. In the rear sail are three small holes, through which the cerebrospinal fluid of the cavities of the brain passes into the intrathecal spaces of the brain. From the anterior cerebral sail, the roots of the thinnest of the cranial nerves appear on the surface of the brain - the trochlear (IV nerve) (Fig. 126), which, having rounded the brain stem, reaches its base.

midbrain consists of the legs of the brain and the roof of the midbrain, separated by a narrow canal - aqueduct of the brain, which communicates with the fourth ventricle from below, and from above with the third (Fig. 126).

Legs of the brain(pedunculi cerebri) occupy the anterior part of the midbrain and are located above the bridge. Between them, the roots of the oculomotor nerve (III) appear on the surface. The legs are composed of bases and operculum, which are separated by highly pigmented cells of the substantia nigra (Atl., 82).

IN base of legs are included pyramidal path, consisting of cortical-spinal heading across the bridge to the spinal cord, and cortical-nuclear, the fibers of which reach the neurons of the motor nuclei of the cranial nerves located in the region of the fourth ventricle and under the water supply, as well as cortical-bridge path, ending at the cells of the base of the bridge. Since the base of the legs consists of descending tracts of the cerebral cortex, this part of the midbrain is as phylogenetically new as the base of the pons or pyramid of the medulla oblongata.

Leg cover, continuing the tegmentum of the pons and medulla oblongata, consists of phylogenetically ancient structures. Its upper surface serves as the bottom of the aqueduct of the brain. In the tire are located nuclei of the trochlear and oculomotor nerves. These nuclei develop in embryogenesis from the main plate, which lies under the borderline groove, consist of motor neurons and are homologous to the anterior horns of the spinal cord. The nuclei with roots extending from them thus represent the metameric apparatus of the midbrain. Under the gray matter surrounding the plumbing, there is a phylogenetically old path - medial longitudinal bundle. Starting from the nuclei of the nerve of the vestibule, it carries impulses to the nuclei of the III, IV, V and XI cranial nerves. Participates in setting the eyes and head in motion when the balance apparatus is irritated. In the region of the nuclei of the III nerve lies its parasympathetic nucleus; it develops at the site of the border furrow and consists of intercalary neurons of the autonomic nervous system. Lateral to the aqueduct along the entire midbrain stretches nucleus of the mesencephalic tract trigeminal nerve. It receives proprioceptive sensitivity from the muscles of mastication and the muscles of the eyeball.

At the level of the inferior colliculus, cross fibers of the upper legs of the cerebellum, after which they partially end in massive cell clusters lying in front - red nuclei, and partially continue to the visual tubercle of the interstitial brain. In the red nucleus, fibers from the cerebral hemispheres also terminate. From the red nuclei there are ascending paths, in particular, to the thalamus. The main downward path of the red nuclei is red nuclear-spinal. Its fibers, which immediately cross out of the nucleus, are directed along the tires of the brain stem and lateral funiculus of the spinal cord to the cells of the anterior horns. In lower mammals, this path transmits to them, and then to the musculature of the body, impulses switched in the red nucleus, mainly from the cerebellum. But in higher mammals, the red nuclei function in a strong dependence on the cerebral cortex, the influence of which on motor reactions is transmitted to the red nuclear-spinal tract. As a result, the red nuclei are an important link in the extrapyramidal system.

Lateral to the red nucleus in the tire is located medial loop. Between it and the gray matter surrounding the plumbing lie nerve cells and fibers reticular formation(continuation of the reticular formation of the bridge and the medulla oblongata) and pass the ascending and descending paths.

quadrigemina, or midbrain roof(tectum mesencephali), makes up its back (Fig. 127); the quadrigemina is divided by grooves perpendicular to each other into upper and lower hillocks.

Superior colliculus contains centers of orienting reflexes to visual stimuli. Through the handles extending forward, the mounds are connected to the lateral geniculate bodies of the interstitial brain. By handles of the superior colliculus part of the fibers fits them visual pathway.

inferior colliculus serves as the center of orienting reflexes to auditory stimuli. From the mounds forward and outwards go handles, ending at the medial geniculate bodies. Hillocks take part of the fibers lateral loop, the remaining fibers of the latter are in the composition handles of the inferior colliculus to the medial geniculate body.

Originates from the roof of the midbrain tecto-spinal tract. Its fibers after cross in the tegmentum of the midbrain they go to the motor nuclei of the brain and to the cells of the anterior horns of the spinal cord.

The path conducts efferent impulses in response to visual and auditory stimuli.