The olfactory analyzer plays an essential role in the life of animals and humans, informing the body about the state of the environment, monitoring the quality of food and inhaled air.
The first receptor neurons of the pathway of the olfactory analyzer (tractus olfactorius) are bipolar cells embedded in the mucous membrane of the olfactory region of the nasal cavity (the region of the superior nasal concha and the corresponding part of the nasal septum).
Their short peripheral processes end with a thickening - an olfactory club, carrying on its free surface a different number of cilia-like outgrowths (olfactory hairs), significantly increasing the surface of interaction with molecules of odorous substances and transforming the energy of chemical stimulation into a nerve impulse.
The central processes (axons) unite with each other to form 15-20 olfactory filaments, which together make up the olfactory nerve. The olfactory filaments penetrate into the cranial cavity through the ethmoid plate of the ethmoid bone and approach the olfactory bulb, where the second neurons are located. The axons of the second neurons are part of the olfactory tract, the olfactory triangle and the anterior perforated substance of its own and opposite sides, the podosolous gyrus and the transparent septum. Here are the bodies of third neurons. Their axons follow to the cortical end of the olfactory analyzer - the hook of the parahipocampal gyrus and the ammonic horn, where the bodies of the fourth neurons are located (Fig. 34).
Pathways for skin sensitivity
Skin sensitivity includes feelings of pain, temperature, touch, pressure, etc.
Pathway of pain and temperature sensitivity
The beginning of the path is the skin receptor, the end is the cells of the fourth layer of the cortex of the postcentral gyrus.
The crossed path, the cross - segment by segment in the spinal cord. Pain and temperature signals are carried along the lateral spinal-thalamic tract (tractus spinothalamicus lateralis).
Rice. 34. Pathway of the olfactory analyzer
(Yu.A. Orlovsky, 2008).
The body of the first neuron is the pseudo-unipolar nerve cell of the spinal ganglion. The dendrite goes to the periphery as part of the spinal nerve and ends with a specific receptor. The axon of the first neuron passes through back spine to the nuclei of the posterior horn of the spinal cord. Here are located the second neurons (in the own nuclei of the posterior horn). The axon of the second neuron passes to the opposite side and rises in the lateral cord of the spinal cord as part of the lateral spinothalamic tract to the oblong, where it is involved in the formation of the medial loop. The fibers of the latter follow through the bridge, the legs of the brain, to the lateral nuclei of the optic hillock, where the third neurons of the pathway of pain and temperature sensitivity are located. The axon of the third neuron passes through the inner capsule and ends on the cells of the cortex of the postcentral gyrus (thalamocortical tract). This is the fourth neuron of the pathway of pain and temperature sensitivity (Fig. 35).
Olfactory tract enters the brain in front of the junction between the midbrain and the large brain; there the path is divided into two paths, as shown in the figure. One goes medially to the medial olfactory region of the brainstem, while the other runs laterally to the lateral olfactory region. The medial olfactory region is a very old olfactory system, while the lateral region is the entrance to (1) the less old and (2) the new olfactory system.
Very old olfactory system - the medial olfactory region. The medial olfactory region consists of a group of diencephalon nuclei located immediately in front of the hypothalamus. The most prominent are the nuclei of the septum, which represent the nuclei of the diencephalon that deliver information to the hypothalamus and other primitive parts of the limbic system of the brain. This area of the brain is mainly associated with innate behavior.
Meaning medial olfactory region can be understood by imagining what will happen to the animal after bilateral removal of the lateral olfactory areas, provided the medial system is preserved. It turns out that in this case, such simple reactions as licking lips, salivation and others remain practically unchanged. food reactions smell, or primitive emotional behavior associated with smell.
On the contrary, removal of the lateral regions eliminates more complex conditioned olfactory reflexes.
Less old olfactory system- the lateral olfactory region. The lateral olfactory region consists mainly of the piriform cortex and the piriform cortex, as well as the cortical regions of the amygdala. From these areas, signaling pathways go to almost all parts of the limbic system, especially to less primitive parts, such as the hippocampus. It is the most important structure for teaching the body to distinguish between pleasant and unpleasant foods based on life experience.
It is believed that it is this lateral olfactory region and its extensive connections with the limbic behavioral system are responsible for the absolute withdrawal (aversion) of food, which in the past has caused nausea and vomiting.
An important feature lateral olfactory region is that many signaling pathways from it also go directly to the sections of the old cortex large brain(paleocortex) in the anteromedial region of the temporal lobe. This is the only area of the cortex where sensory signals arrive without a switch in the thalamus.
New way... A new olfactory pathway has now been discovered that passes through the thalamus, its dorsomedial nucleus and then to the posterolateral quadrant of the orbitofrontal cortex. According to experimental studies on monkeys, this new system probably participates in the deliberate analysis of odor.
Based on the foregoing, it is obvious that there is:
(1) a very old olfactory system providing basic olfactory reflexes;
(2) a less old system responsible for the automatic, but to a certain extent, acquired selection of food fit for consumption and the elimination of toxic and unhealthy substances; (3) a new system that, like most other cortical sensory systems, is used for conscious perception and analysis of olfactory information.
Centrifugal control olfactory bulb activity from the central nervous system... Many nerve fibers emanating from the olfactory parts of the brain go in the opposite direction as part of the olfactory tract to the olfactory bulb (i.e., centrifugally - from the brain to the periphery). They end in a large number small granular cells located among the mitral and bundle cells in the olfactory bulb.
Granular cells send inhibitory signals to mitral and bundle cells. It is believed that this inhibitory feedback may be a way of enhancing a person's specific ability to distinguish one odor from another.
Table of contents of the subject "Paths.":1. Pathways. Pathway of the visual analyzer. The pathway of sight.
2. The nuclei of the pathway of the visual analyzer. The nucleus of vision. Signs of damage to the optic tract.
3. The pathway of the auditory analyzer. Conductive path of hearing.
4. The nuclei of the auditory analyzer. Signs of damage to the auditory tract.
5. Pathway of the vestibular (statokinetic) analyzer. The nucleus of the vestibular analyzer. Signs of damage to the pathway of the vestibular analyzer.
6.
7. The nuclei of the conducting pathway of smell. Signs of impairment of the sense of smell.
8. Pathway of the taste analyzer. The pathway of taste (gustatory sensitivity).
9. The cores of the pathway of taste (gustatory sensitivity). Signs of taste impairment.
It is distinguished by a significant complexity of the structure and an abundance of connections with various structures of the brain. further, with the formation of the final brain, the development of the cortex and the transformation of the final brain into the higher section of the central nervous system, new higher centers appear in it for all types of sensitivity.However, the brain retains many polyfunctional structures related to the olfactory analyzer and at the same time performing other functions in certain situations
Pathway of the olfactory analyzer- a system of sequentially located neurons that form complex reflex circuits. thanks to which it becomes possible holding impulses from the periphery (from the olfactory receptor cells) to the cortical and subcortical olfactory centers.
In the mucous membrane of the upper nasal passage (in the region of the superior nasal concha and the corresponding section of the nasal septum), in the so-called olfactory regions, the first neurons of the olfactory pathway are laid, called receptor or olfactory cells. Receptor olfactory cells are scattered in the olfactory region and therefore the olfactory nerves do not have nerve nodes unlike other sensory nerves
Short peripheral processes of olfactory cells - dendrites - end in thickenings - olfactory clubs protruding above the surface olfactory area... Each club carries 10-12 olfactory hairs. Olfactory hairs interacting with molecules of odorous substances, transform the energy of chemical irritation into nerve impulse.
The central processes (axons) of olfactory cells are collected in 15-20 stems - olfactory nerves.
Olfactory nerves pass through the holes of the ethmoid bone into the cranial cavity, where they are immersed in the olfactory bulb and come into contact with the dendrites of the cells of the olfactory bulb.
From the neurons of the olfactory bulb, the pathway of the olfactory analyzer begins. The axons of the second neurons follow in the olfactory tract towards the olfactory triangle.
The bodies of the first neurons(bipolar olfactory cells) are located in the nasal mucosa (Fig. 8) within its olfactory zone (the region of the superior turbinates and the nasal septum at their level). The ends (branches) of the dendrites of these neurons act as receptors, and their axons are grouped into 15-20 olfactory nerves, nn. olfactorii... These nerves through lamina cribrosa ossis ethmoidalis pass into the cranial cavity and reach the olfactory bulbs, bulbi olfactorii in which are located bodies of second neurons... The axons of the latter are formed into the olfactory tracts, tractuum olfactorii, in which medial and lateral stripes are distinguished.
A. Fibers medial stripes fit the bodies of third neurons located in the following structures:
1) the olfactory triangle, trigonum olfactorium;
2) anterior perforated substance, substantia perforata anterior;
3) a transparent partition, septum pellucidum.
One part of the axons of the third neurons of these structures passes over corpus callosum and reaches the cortical nucleus of the analyzer, which is the parahippocampal gyrus, gyrus parahippocampalis, (Brodmann's field).
The second part of the axons of the third neurons from the olfactory triangle reaches the subcortical centers of smell, which are the mastoid bodies, corpora mammilaria, in which the bodies of 4 neurons are located. From them, the NI is directed through the fornix of the brain to the aforementioned cortical nucleus of the analyzer.
The third part of the axons of third neurons reaches the structures of the limbic system, the autonomic centers of the reticular formation, the salivary nuclei of the facial and glossopharyngeal nerves, dorsal nucleus vagus nerve... These connections explain the phenomenon of nausea, dizziness and even vomiting when certain odors are perceived.
B. Fibers lateral stripes pass under the corpus callosum and approach the third neurons within the amygdala, the axons of which reach the aforementioned cortical nucleus of the analyzer.
Partially olfactory function is performed by structures trigeminal nerve... NI from receptors outside the olfactory zone are conducted along its fibers, which contributes to the perception of pungent odors that enhance the depth of breathing.
Function olfactory analyzer - perception of smells. Due to the connections of the analyzer's structures with the formations of the limbic system and the brain stem, it also provides certain emotional and behavioral reactions to odors that cause appetite, salivation, vomiting, and nausea.
Rice. 8. Pathways of the olfactory analyzer. 1 - cellulae neurosensoriae olfactoriae; 2 - concha nasalis superior; 3 - nn. olfactorii; 4 - bulbus olfactorius; 5 - tractus olfactorius; 6 - corpus callosum; 7 - fornix; 8 - corpora mammillare; 9 - gyrus parahippocampalis; 10 - uncus; 11 –trigonum olfactorium.
BNA, JNA) part of the olfactory brain in the form of a thin cord located on the lower surface of the frontal lobe of the cerebral hemisphere between the olfactory bulb and the olfactory triangle.
1. Small medical encyclopedia. - M .: Medical encyclopedia... 1991-96 2. First health care... - M .: Great Russian Encyclopedia. 1994 3. encyclopedic Dictionary medical terms... - M .: Soviet encyclopedia. - 1982-1984.
See what the "Olfactory tract" is in other dictionaries:
- (tractus olfactorius, PNA, BNA, JNA) part of the olfactory brain in the form of a thin cord located on the lower surface of the frontal lobe of the cerebral hemisphere between the olfactory bulb and the olfactory triangle ... Comprehensive Medical Dictionary
Schemes ... Wikipedia
Scheme of the olfactory brain The olfactory brain (lat. Rhinencephalon) is a set of a number of structures of the telencephalon associated with the sense of smell ... Wikipedia
Olfactory brain- - the area of the brain responsible for the neuropsychology of smell perception: the olfactory bulb, the olfactory tract, the pear-shaped zone, parts of the pear-shaped cortex and the amygdala complex ... Encyclopedic Dictionary of Psychology and Pedagogy
SMELLING BRAIN- The area of the brain responsible for the perception of smells. It includes the olfactory bulb, the olfactory tract, the pear-shaped region, parts of the pear-shaped cortex and parts of the amygdala complex ... Explanatory Dictionary of Psychology
- (tractus olfactomesencephalicus; L. Edinger, 1855 1918, German neuropathologist; A. Wallenberg, 1862 1949, German neuropathologist) a bundle of nerve fibers connecting the olfactory tract and the olfactory triangle with the nuclei of the hypothalamus, mastoid bodies, ... ... Comprehensive Medical Dictionary
Brain structures that were associated with olfactory analyzer... The olfactory brain includes the olfactory bulb, the olfactory tract, the olfactory triangle, the anterior perforated substance, ... ... Medical terms
olfactory brain- (rhinencephalon) the most ancient part of the cerebral hemispheres, is divided into peripheral and central departments... The peripheral section is located on the lower surface of the frontal lobe and includes the olfactory tract with the olfactory bulb, ... ... Glossary of terms and concepts in human anatomy
SMELLING BRAIN- (rhinencephalori) structures of the brain, which in the early stages of evolution were associated with the olfactory analyzer. The olfactory brain includes the olfactory bulb, the olfactory tract, the olfactory triangle, the anterior ... ... Explanatory Dictionary of Medicine
Cranial nerves- The olfactory nerve (n. Olfactorius) (I pair) refers to the nerves of special sensitivity. It starts from the olfactory receptors of the nasal mucosa in the superior turbinate. Represents 15 20 thin nerve filaments, ... ... Human Anatomy Atlas
Brain- (encephalon) (Fig. 258) is located in the cavity cerebral skull. Average weight the brain of an adult is approximately 1350 g. It has an ovoid shape due to the protruding frontal and occipital poles. On the outer convex upper lateral ... ... Human Anatomy Atlas
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