Lateral spinothalamic pathway diagram. Spinothalamic tract lateral

The axons of T-cells located in the posterior horns of the spinal cord, passing to its opposite side as part of the anterior commissure of the spinal cord, form several afferent pathways, the main of which are two ascending spinal cord pathways that provide pain impulses. One of them in the process of phylogenesis develops earlier, the other later, the first in this connection is called the paleospinothalamic, the second - the neospinothalamic way. The neospinothalamic pathway (it also includes the neotrigeminothalamic pathway, consisting of part of the axons of the cells of the nucleus of the spinal cord of the trigeminal nerve) is monosynaptic, consisting of relatively thick myelin fibers with a certain somatotopic organization. In the lateral funiculus of the spinal cord, it occupies a lateral position and carries out a rapid transmission of phasic discriminatory information about the onset of the action of a painful stimulus, about the exact place of its impact, about its nature, intensity and duration. This information, which is quickly transmitted along the neospinothalamic pathway to the lateral nuclei of the thalamus and further to the somatosensory cortex, provides the possibility of a person's instant motor response to the impact of a painful stimulus, aimed at stopping further damaging effects on tissues. Nerve structures, which are involved in the conduction of pain impulses along the neospinothalamic pathway, as well as impulses going along the posterior cords of the spinal cord and the medial loop to the lateral nuclei of the thalamus and further to the somatosensory cortex, constitute the so-called sensory-discriminatory system. The impulses that entered the thalamus along the neospinothalamic pathways, after switching here to the neurons of the cells that make up the ventral posterolateral and posteromedial nuclei of the thalamus, reach the projection zone general types sensitivity - postcentral gyrus. Here, as well as in the adjacent associative zones of the cortex parietal lobe the formation of simple and complex sensations is carried out, adequate to those affecting the peripheral receptor apparatus factors, in particular pain sensations, adequate to the place and intensity of irritation of peripheral pain receptors. In the cortex, a detailed analysis of spatio-temporal and complex characteristics information entering her projection area, which performs (according to Pavlov I.P.) the role of the cortical end of the analyzer of general types of sensitivity. The paleospinothalamic pathway is polysynaptic, extralemniscal. In the spinal cord, it is located medial to the neospinothalamic tract. It consists of spinoreticular, spinomesencephalic and trigeminoreticulomesencephalic pathways, consisting of thin nerve fibers that conduct impulses relatively slowly; at the same time, they lack the somatotopic principle of organizing bundles of nerve fibers. The spinoreticular part of the paleospinothalamic pathway ends in the nuclei of the reticular formation of the caudal brainstem. The axons of neurons located in these nuclei form the reticulothalamic pathway, which reaches the intralaminar nuclei of the thalamus (median center, paracentral and fascicular nuclei), as well as the hypothalamus and limbic structures. The fibers of the spinomesencephalic part of the paleospinothalamic tract reach the roof of the midbrain (lamellae of the quadrigemina), as well as the central gray matter, where the switching of nerve impulses to the next neurons occurs. The axons of these neurons terminate in the medial nuclei of the thalamus and in the nuclei of the hypothalamus. The impulses that came to the brain along the polysynaptic paleospinothalamic pathway to the medial and intralaminar nuclei of the thalamus are then sent along the axons of neurons whose bodies are located in these nuclei to the limbic structures. hemispheres and to some nuclei (paraventricular, medial, preoptic) of the posterior hypothalamus. Under the influence of these impulses, a stubborn, painful, indistinctly localized and differentiated feeling of pain arises, as well as accompanying negative emotional manifestations, vegetative and motivational reactions. The affective reactions that arise in such cases may, to some extent, provoke the activation of the antinociceptive system. Connections of the paleospinothalamic pathway with the limbic-reticular complex provide motivational-affective reactions to nociceptive impulses coming through it. The connections of the somatosensory cortex with the temporal cortex and the amygdala play a significant role in the formation of sensory memory, which provides an assessment pain sensation comparing it with previously acquired life experience. There is an opinion that, in addition to neospinothalamic and paleospinothalamic pathways, propriospinal cord and proprioreticular structures, which make up numerous chains of short-axon intercalary neurons, are involved in the conduction of pain impulses. On the way to the cells of the reticular formation of the brain stem, they are adjacent to the gray matter of the spinal cord. The impulses passing through them reach the cells of the reticular formation of the trunk and cause a feeling of difficult localization dull pain, and also participate in the formation of autonomic, endocrine and affective reactions caused by pain.

The spinal cord is composed

Gray matter (consists of the bodies of neurons and their processes)

White matter (consists of axons covered with myelin sheath)

Gray matter forms three pillars

Front

Rear (horns).

side horn present only in the breast lumbar spinal cord.

Anterior horn contains nerve cells to which they fit motor fibers anterior roots of the spinal cord.

rear horn narrower and longer includes neurons to which the sensory fibers of the posterior roots approach.

side horn consists of neurons, consisting of the vegetative part of the NS.

In the middle of the gray matter is a narrow central canal of the spinal cord, it runs along the entire length of the spinal cord.

Central channel is a remnant of the cavity of the primary neural tube, so at the top it communicates with the fourth ventricle of the forebrain, at the bottom it ends with a slight expansion of the ventricle.

With age, the central canal narrows, overgrows and ceases to be a continuous canal.

white matter The spinal cord consists of the anterior, lateral and posterior cords and is formed by longitudinally running nerve fibers combined into bundles, the so-called conduction pathways.

3 types of pathways.

Fibers that connect parts of the spinal cord at different levels.

Motor (descending) fibers coming from the brain to the dorsal to connect with the cells that give rise to the anterior motor roots.

Sensory (ascending fibers) which are partly a continuation of the fibers of the posterior roots and partly processes of spinal cord cells and ascend upward to the brain.

Main pathways

ǀ ascending pathways – the main ascending systems pass through the dorsal cords of the spinal cord, and represent the axons of afferent neurons in the spinal ganglia:

A) thin Gaulle's bundle

B) the wedge-shaped bundle of Burdach, they are formed by the axons of sensory neurons, in the spinal ganglia and end in the area medulla oblongata, in the cores of Gaulle or Burdakh, therefore they are called the Gaull tractor or the Burdakh tractor.

In the medulla oblongata there are second neurons, the axons of which cross in the brain stem, forming medial loop.

The axons of the second neurons are sent to the diencephalon, where they form synapses with the third neurons, the processes of which are sent to the postcentral gyrus, in this way impulses are transmitted from the muscles, ligaments, tendons.

Divided into two paths: lateral, ventral.

The fibers of the nuclei lying in the posterior horns of the spinal cord and running along the lateral funiculus form the lateral spinothalamic pathway. Conducts pain, temperature sensitivity.

The axons of the neurons that form this path (tract) pass to the opposite side, enter the white matter, opposite to the lateral cord, and in it rise up through the entire spinal cord, through the floor of the brain

Third-order neurons carry impulses to the cerebral cortex.

2. The spinal cerebellar tract, they pass as part of the lateral cords and connect the spinal cord with the cerebellar cortex. Ways of Flexig and Gowers.

ǀǀ Descending paths.

The nerve fibers that go through these pathways are divided into

A) corticospinal tract- formed by the axons of the pyramidal cells of the cerebral cortex, so it is often called the pyramidal tract. The main motor pathway for the regulation of voluntary movements

B) rubrospinal path compares subcortical centers with spinal cord

B) vestibulospinal, reticulospinal pathways- this medulla oblongata originate 2 paths, vestibulospinal, it starts from the vestibular nuclei, reticulospinal starts from the accumulation of nerve cells, the fibers from these paths end on the neurons of the medial part of the anterior horns of the spinal cord.

Each spinal reflex has its own level

For example - the center of the knee jerk is at the level of the second fourth lumbar segment. The centers of the spinal muscles are at the level of 8-12 lumbar segment. Motor centers of the diaphragm - 3-4 cervical segments.

Cerebellum(cerebellum) closely connected with the medulla oblongata, pons and midbrain, it is located posterior to these formations, filling most of the posterior cranial fossa. The mass of the cerebellum is about 150 g. Its largest transverse size is 10-12 cm, the longitudinal one in the region of the vermis is up to 4 cm, and in the region of the hemispheres it is up to 6 cm.

Body cerebellum (corpus cerebelli) make up the central narrow part - the worm (vermis cerebelli) and two large convex lateral parts - hemispheres (hemispheri cerebelli).

Numerous cracks(fissurae cerebelli) different depths divide the surface of the hemispheres and the cerebellar vermis into shares(lobi cerebelli),slices(lobuli cerebelli) and leaflets(folia cerebelli). Many fissures greatly increase the surface of the cerebellum. Deep fissures divide the body of the cerebellum into 3 share: front(lobus cerebelli anterior),back(lobus cerebelli posterior) and Klochkovo- nodular(lobus flocculonodularis). In turn, each of the lobes is divided into sheets by slits passing through the worm and hemispheres (Fig. 218).

Gray matter cerebellum is concentrated mainly on its surface in the form of a three-layer bark(cortex cerebelli)(Fig. 219). Under the cortex is white matter, in the depths of which are paired subcortical nuclei of gray matter.

The cortex covers both the free surface of the gyri of the cerebellum and the surface located deep in the fissures. It consists of 3 layers: light outer - molecular (stratum moleculare), layer of piriform neurons (stratum neuronorum piriformium) and dark inner - grainy (stratum granulosum). Pear-shaped neurons are efferent cells of the cortex, while cells of the molecular and granular layers are intercalary and associative neurons.

Rice. 218. Cerebellum:

a - top view: 1 - hemisphere; 2 - worm;

b - bottom view: 1 - lobules within the posterior lobe; 2 - leaflets within the lobule; 3 - cavity of the IV ventricle; 4 - superior cerebellar peduncle; 5 - middle cerebellar peduncle; 6 - lower cerebellar peduncle; 7 - scrap; 8 - knot; 9 - worm. The anterior lobe of the cerebellum is red, the posterior lobe is green, the tuft-nodular lobe is blue;

c - section of the cerebellum at the level of the upper legs: 1 - cerebellar cortex; 2 - gaps separating the bark; 3 - worm; 4 - cork-like nucleus; 5 - dentate nucleus; 6 - spherical nucleus; 7 - the core of the tent; 8 - cavity of the IV ventricle; 9 - leg of the brain

Rice. 219. The structure of the cerebellar cortex (diagram):

1 - molecular layer; 2 - layer of pear-shaped neurons; 3 - granular layer; 4 - white matter; 5 - glial cell with a sultan (Bergmann's fiber); 6 - large nerve cell-grain (Golgi cell); 7 - basket nerve cell; 8 - small neurocytes of grain; 9 - ganglionic nerve cell (Purkinje cells); 10 - astrocyte

The subcortical nuclei of the cerebellum are accumulations of gray matter of various shapes and sizes. Of these, the largest is dentate nucleus(nucl. dentatus). The axons of the pear-shaped cells of the hemispheres of the cerebellum and the vermis approach the dentate nucleus. The processes of the cells of the dentate nucleus make up the bulk of the fibers superior cerebellar peduncle(pedunculus cerebellaris superior).

corky nucleus(nucl.emboliformis) located in the white matter of the hemisphere, medial to the dentate nucleus.

The most medial position among the subcortical nuclei of the cerebellum, above the tent of the IV ventricle, is tent core(nucl. fastigii).

Between the cork-like core and the core of the tent is located globular nucleus(nucl. globosus).

white matter The cerebellum consists of intra- and extra-cerebellar fibers.

A group of intracerebellar fibers is formed by processes of cells of the cerebellar cortex. Among them, there are associative fibers that connect different parts of the cerebellar cortex; commission-

ral fibers connecting parts of the cortex of opposite hemispheres; short projection fibers - processes of pear-shaped cells to the subcortical nuclei of the cerebellum.

Extracerebellar fibers include long projection efferent and afferent fibers, through which the cerebellum is connected to other parts of the brain. These fibers form 3 pairs of cerebellar peduncles, of which the lower and middle ones consist mainly of afferent, and the upper ones consist of efferent fibers formed in the subcortical nuclei of the cerebellum. As part of the lower legs, the posterior spinal cerebellar path, fibers from the vestibular nuclei to the core of the tent and fibers from the olive enter the cerebellum - olivocerebellar pathway(tr. olivocerebellaris). In addition, this includes the efferent pathway from the tent nucleus to the lateral vestibular nucleus.

The middle cerebellar peduncles form the transverse fibers of the pons, which connect the nuclei of the pons to the cerebellar cortex.

As part of the upper cerebellar peduncles, the anterior spinal cerebellar pathways enter the cerebellum, outgrowths of the cells of the dentate nucleus, which, after decussation, end in the red nucleus of the midbrain.

IV ventricle

IV ventricle(ventriculus quartus) formed by the medulla oblongata, pons and cerebellum. It distinguishes the bottom, side walls and roof. The floor of the IV ventricle is rhomboid fossa(fossa rhomboidea), which is a diamond-shaped area of ​​\u200b\u200bthe posterior surface of the bridge and the medulla oblongata limited by the upper and lower cerebellar legs (see Fig. 215, b). The upper corner of the rhomboid fossa passes into the aqueduct of the midbrain, and the lower corner into the central canal of the spinal cord. The lateral angles of the rhomboid fossa pass into lateral pockets(recessus lateralis) IV ventricle. Median sulcus(sul medianus) divides the rhomboid fossa into two symmetrical halves. As noted above, the medulla oblongata and the pons contain nuclei cranial nerves. The topography of their projections on the rhomboid fossa is of practical importance (Fig. 220).

The lateral walls of the IV ventricle are represented by 3 pairs of cerebellar peduncles. Roof of the IV ventricle(tegmen ventriculi quarti) form the superior medullary velum, the substance of the cerebellum and the inferior medullary velum (Fig. 221).

Rice. 220. Projection of the nuclei of cranial nerves localized in the brainstem to the rhomboid fossa:

1 - median furrow; 2 - facial tubercle; 3 - cerebellar legs. Roman numerals indicate cranial nerve numbers; motor nuclei and fibers are highlighted in red, sensitive in blue, autonomous (parasympathetic) in purple

Upper medullary velum(velum medullare superius) is a thin triangular plate of white matter, which is located between both upper cerebellar peduncles.

Inferior medullary velum(velum medullare inferius) formed by a thin epithelial lamina rear wall primary brain bladder. This plate is complemented vascular base of the fourth ventricle(tela choroidea ventriculi quarti).

There is a hole in the middle line of the lower medullary sail - median aperture of the fourth ventricle(apertura mediana ventriculi

Rice. 221. Antero-superior and posterior-inferior parts of the roof of the IV ventricle, dorsal view. Cerebellum removed:

1 - bridle of the upper medullary sail; 2 - upper brain sail; 3 - superior cerebellar peduncle; 4 - IV ventricle; 5 - middle cerebellar peduncle; 6 - scrap; 7 - choroid plexus of the IV ventricle; 8 - lower brain sail; 9 - median aperture of the IV ventricle; 10 - medulla oblongata; 11 - tubercle of a thin nucleus; 12 - tubercle of the sphenoid nucleus; 13 - shred leg; 14 - tongue of the anterior lobe of the cerebellum; 15 - block nerve; 16 - lower colliculus (midbrain)

quarter). From lateral pockets open lateral apertures of the IV ventricle(aperturae laterales ventriculi quarti). These openings connect the cavity of the IV ventricle and the subarachnoid space of the brain. Besides tela choroidea ventriculi quarti, in the cavity of the fourth ventricle choroid plexus(plexus choroideus ventriculi quarti), which, in the form of highly convoluted vessels, passes into the side pockets and exits through the lateral apertures of the IV ventricle in the region of the cerebellopontine angle.

• Sensitivity (sensibilitas) - the ability of the body to perceive various stimuli emanating from the external and internal environment, and respond to them. Ch. is based on the processes of reception, biological significance which lies in the perception of acting on the organ ...
• Core(s)1 c.s.c. (nucleus, PNA) - an accumulation of gray matter in a certain area of ​​the central nervous system, which ensures the performance of certain functions. Basal nuclei (n. basales, PNA; synonym: basal ganglia - obsolete, I. subcortical) & ...

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