Vestibular analyzer, its structure and functional significance. The role of the vestibular system in the regulation and control of motor reactions
Question 1. What is the significance of the vestibular analyzer?
The vestibular analyzer performs the function of regulating the position of the body and its individual parts in space.
Question 2. Why, after rotation, does it seem to a person that the perceived objects continue to move in a circle?
The centers of the vestibular apparatus at the level of the midbrain closely interact with the centers of the oculomotor nerve. This can explain the appearance of the illusion of objects moving in a circle after the rotation stops.
Question 3. In what ways can you train the endurance of the vestibular apparatus?
There are many different ways to train the vestibular system. One of them is sharp turns of the head from side to side with a fixation of the gaze at the end of the turn on the same object, preferably distant. The second way is to rotate around its axis: a) with your head down; b) with the head raised and gaze fixed on one point; c) with eyes closed; d) squatting with eyes closed. The vestibular apparatus trains quite quickly. You need to start with one or two revolutions, increasing the amount daily. Training is carried out several times a day. The third method is somersaults over the head forward and backward.
Question 4. What is muscle feeling?
The skeletal muscles of our body contain special muscle receptors that sense muscle contractions or stretches. Excited when muscles contract or stretch, they send information to the brain about the functional state of the muscular system. Muscular feeling is very important for the orientation of the body in space, for a person to perform coordinated movements. Without muscle feeling, a person cannot perform a single movement. In the work of a car driver, a surgeon, a pianist and people in many other professions, muscle sense plays a big role. The importance of muscle sense especially increases with weakening or loss of vision.
Question 5. Why is it important to mentally imagine it in all details and in the required sequence before performing a complex action?
Before performing a complex action, it is important to mentally imagine it, since when a person imagines a future movement, muscle and tendon receptors determine the required amount of contraction of the muscles that will be involved in performing this action.
Question 6. How do the organs of taste and smell interact?
Taste buds react only to substances dissolved in water, and insoluble substances have no taste. A person distinguishes four types of taste sensations: salty, sour, sweet, bitter. The sense of smell provides the perception of various odors. Olfactory receptors are located in the mucous membrane of the upper part of the nasal cavity. The total area occupied by olfactory receptors in humans is 3-5 cm2. Taste is a complex sensation. The sense of smell and touch are also involved in creating the taste image of food, and the taste zone of the cerebral cortex is located next to the olfactory zone on the inner side of the temporal lobe.
The vestibular apparatus informs the central nervous system about the position of the body in space during movement and in a stationary state, and about balance and its disorders. The position of the head is very important for the activity of the vestibular apparatus: it moves with the body, whether the head moves in relation to the body or the head is motionless, the body moves in relation to it. Moving the head with body movements moves the fluid in the vestibule and semicircular canals.
When the torso and the whole body bends, rotates, or suddenly loses balance, the position of the head necessarily changes. At the same time, in one or the other semicircular canal, the fluid contained in them begins to move. This causes stimulation of the receptors and reflexively changes the tone of the muscles of the limbs, torso, neck and eyes. The contraction of these muscles sets the head in the correct position, and after it the whole body.
Thus, the receptors of the vestibule perceive linear acceleration of movement and the influence of gravity when the position of the head changes. Receptors in the semicircular canals perceive changes in direction of movement. Changes in speed when rotating the body or one head.
Tonic posture reflexes, which occur when the position of the head in space changes, play an important role in maintaining balance. It is excitation from the receptors of the vestibular apparatus, as well as from the receptors of the muscles and tendons of the neck, that causes these reflexes.
Consequently, the vestibular apparatus informs the nervous system about the position of the body and its parts in space, and in response to this information, tonic reflexes help maintain balance both in the dance and in the adopted pose.
So, the vestibular apparatus is important in the spatial orientation of a person, the coordination of his movements at rest and in the process of motor activity. According to I.S.Beritov (1953), thanks to the vestibular apparatus in the human brain, it is possible to form a spatial image of the path traveled. The development of the vestibular apparatus in children and adolescents is currently poorly studied. There are morphological data that a child is born with fairly mature teenage sections of the vestibular apparatus.
Just like in adults, children experience the phenomenon of motion sickness, which can occur when transporting children in cars, trains, airplanes, etc. An effective remedy against this is the medicine Aeron. The pharmacological action of aeron is aimed at reducing the excitability of vestibular receptors. Special training is important in reducing the excitability of the vestibular apparatus.
Literature
1. Neiman L.V., Bogomilsky M.R. Anatomy, physiology and pathology of the organs of hearing and speech: Textbook. for students higher ped. textbook institutions / Ed. V.I. Seliverstova. M.: VLADOS, 2001. -224 p.
2. Shvetsov A.G. Anatomy, physiology and pathology of the organs of hearing, vision and speech: Textbook. – Veliky Novgorod, 2006. – 68 p.
3. Mamontov S.G. Biology: Textbook. – M.: Bustard, 2008. -543s.
4. Kurepina M.M. Human anatomy: textbook. For university students. – M.: Humanitarian Publishing House. VLADOS Center, 2005. -383 p.
Questions at the beginning of the paragraph.
Question 1. How do the balance organs function?
The orientation of the body in space is carried out by the vestibular apparatus. It is located deep in the pyramid of the temporal bone, next to the cochlea of the inner ear.
The vestibular apparatus consists of two sacs and three semicircular canals. The channels are located in three mutually perpendicular directions. This corresponds to three dimensions of space (height, length, width) and allows one to determine the position and movement of a body in space.
The receptors of the vestibular apparatus are hair cells. They are located in the walls of the sacs and semicircular canals. The sacs are filled with a thick liquid containing small crystals of calcium salts. If the head is in an upright position, the pressure is applied to the hairs of the cells located at the bottom of the sac. If the position of the head changes, the pressure shifts to its side walls.
The semicircular canals, like the sacs, are closed reservoirs of fluid. During rotational movements of the body, the fluid in a certain tubule either lags behind in movement or continues to move by inertia, leading to deflection of sensitive hairs and stimulation of receptors.
From the receptors of the vestibular apparatus, nerve impulses go to the central nervous system. At the level of the midbrain, the centers of the vestibular analyzer form close connections with the centers of the oculomotor nerve. This, in particular, explains the illusion of objects moving in a circle after we stop rotating. The vestibular centers are closely connected with the cerebellum and hypothalamus, which is why, when motion sickness occurs, a person loses coordination of movement and nausea occurs. The vestibular analyzer ends in the cerebral cortex. Its participation in the implementation of conscious movements allows you to control the body in space.
Question 2. Why are muscle sensation and skin sensitivity inseparable in the sense of touch?
In the walls of muscles and tendons there are receptors that record the stretch and degree of muscle contraction. They constantly send nerve impulses to the brain corresponding to the position of the muscle. Therefore, muscle sensation and skin sensitivity are inseparable in the sense of touch.
Question 3. How do taste and smell analyzers work?
Olfactory receptors are located on the mucous membrane of the middle and superior turbinates. These are cells with cilia. Each olfactory cell is capable of detecting a substance of a certain composition. When interacting with it, it sends nerve impulses to the brain.
In the mucous membrane of the tongue there are small elevations - taste buds, which have a mushroom-shaped, leaf-shaped shape. Each papilla communicates with the oral cavity through a small hole - sometimes. It leads into a small chamber, at the bottom of which taste buds are located. They are hair cells, the hairs of which are immersed in a liquid that fills the chamber.
When food is in the mouth, it dissolves in saliva, and this solution enters the cavity of the chamber, affecting the cilia. If a receptor cell reacts to a given substance, it is excited, and information in the form of nerve impulses enters the brain.
Question 4. How is the falsity of illusory perceptions established?
False perceptions are called illusions. In addition to physical, their causes can also be psychological. So, we usually overestimate the upper part of the figure: it seems larger. To verify this, open a page in the book where there is the number eight. Both of her mugs seem the same. Turn the font page down and you'll see that the top circle of the 8 (now at the bottom) appears smaller. Illusory perceptions are revealed by practice.
Questions at the end of the paragraph.
Question 1. What is the significance of the vestibular analyzer?
The vestibular analyzer controls the position of our body in space.
Question 2. Why, after rotation, does it seem to a person that the perceived objects continue to move in a circle?
The centers of the vestibular apparatus at the level of the midbrain closely interact with the centers of the oculomotor nerve. This can explain the appearance of the illusion of objects moving in a circle after the rotation stops.
Question 3. In what ways can you train the endurance of the vestibular apparatus?
There are many different ways to train the vestibular system. One of them is sharp turns of the head from side to side with a fixation of the gaze at the end of the turn on the same object, preferably distant. The second way is to rotate around its axis: a) with your head down; b) with the head raised and gaze fixed on one point; c) with eyes closed; d) squatting with eyes closed. The vestibular apparatus trains quite quickly. You need to start with one or two revolutions, increasing the amount daily. Training is carried out several times a day. The third method is somersaults over the head forward and backward.
Question 4. What is muscle feeling?
The basis of muscle feeling is the work of special muscle receptors, which are located in the skeletal muscles of our body. Excited when muscles contract or stretch, they send information to the brain about the functional state of the muscular system. Muscular feeling is very important for the orientation of the body in space, for a person to perform coordinated movements.
Question 5. Why is it important to mentally imagine it in all details and in the required sequence before performing a complex action?
Before performing a complex action, it is important to mentally imagine it, since when a person imagines a future movement, muscle and tendon receptors determine the required amount of contraction of the muscles that will be involved in performing this action.
Question 6. How do the organs of taste and smell interact?
Taste is a complex sensation. The sense of smell and touch are also involved in creating the taste image of food, and the taste zone of the cerebral cortex is located next to the olfactory zone on the inner side of the temporal lobe.
A study of the functional state of the vestibular analyzer in a person is carried out either for the purpose of diagnosing painful processes in the non-auditory part of the labyrinth, or to determine the suitability of a given person for a particular profession. To assess the functional state of the vestibular analyzer, both uniformly accelerated (positive acceleration) and uniformly slowed down (negative acceleration) rotational movements are used as an adequate stimulus. Along with this, methods of combining a stimulus to the receptors of the vestibular analyzer are used, as well as determining its resistance to the cumulative effects of an adequate stimulus. Methodological approaches to adequatometry in clinical practice differ in their objectives from studies conducted during professional selection. During professional selection, a labyrinthologist determines the individual ability of the person under study to respond to significant in magnitude and duration of action of an adequate stimulus, impact on the vestibular analyzer. In clinical practice, this methodological technique is also quite acceptable when the task is to identify hidden damage to the vestibular analyzer.
In this case, the intensity of irritation of the vestibular analyzer should be slightly less than during professional examination of healthy individuals, so as not to cause an exacerbation of the pathological process. The sensory, somatic and autonomic components of vestibular reactions are subject to quantitative assessment. Those that can be objectively recorded and quantified have the greatest diagnostic value. Therefore, when using rotational tests, nystagmus, deviation of the limbs and torso, blood pressure, and changes in the galvanic skin reflex are studied. (Yu.G. Grigoriev, 1970) Everyone knows that there is a connection between the vestibular analyzer and the external muscles of the eyes.
The role of individual labyrinthine receptors in orienting the eyes and head in space was studied by the Hungarian researcher Szentagothai. Head movements cause simultaneous irritation of various receptors. Their interaction is characterized as follows. During head movements, impulses from the semicircular canals reflexively move the eyes to a new position corresponding to the new position of the head; At the same time, the maculae hold the eyes in a certain position. Let's imagine the interaction of reflexes from the vestibular analyzer for a simple and often encountered in life case of turning the head. Let's assume that the head of a person with frontally located eyes passively or actively turns in any direction around the naso-occipital axis of 25 degrees. in 0.4 sec. and maintains this position.
In this case, a short-term ampulofugal current occurs in both vertical semicircular canals on the side facing downward, and as a result, the superior rectus and oblique muscles of the eye of the same side and the inferior rectus and oblique muscles of the opposite side occur. In humans, this corresponds to the rotation of both eyes around the optical axes in the direction opposite to the rotation of the head. At the end of the turn, the eyes remain in their position as long as the head maintains this position in space. This “compensatory eye position” is maintained reflexively by impulses from the macula. Thus, one should imagine the interaction of vestibular receptors when placing the head in space.
Changes in the functional state of the vestibular analyzer are reflected in the assessment of space through visual sensations, since throughout life a person develops the ability to combine the normal position of the eyes with a certain position of the head. Overstimulation of the vestibular analyzer, especially with increased excitability, causes a characteristic sensation of dizziness. The reason for this pathological sensation is the aftereffect of strong excitation of the vestibular analyzer, which is perceived as rotation in the direction opposite to the actual rotation. It is also associated with a short-term disturbance of blood circulation in the brain. Thanks to the close connections of the vestibular nerve pathways and centers with the autonomic system, irritation of the vestibular apparatus is accompanied by various autonomic reflexes: increased and slowed heartbeats, narrowing and dilation of blood vessels, increased and decreased blood pressure, increased peristalsis, vomiting , increased sweating (Lomov, 1970).
There are a number of professions in which the functions of the vestibular analyzer are constantly affected by various long-term and intense impacts, which leads to an increase in the body’s resistance to these impacts (pilots, ballet and circus performers). Significant loads affect the vestibular analyzer during space flights. In a state of weightlessness, there is no irritation of the vestibular apparatus, which can lead to disruption of physiological functions and deterioration of well-being. The vestibular analyzer is of great importance in physical education and sports (gymnastics, acrobatics, alpine skiing, diving, figure skating, etc.).
Systematic sports training increases the stability of the vestibular analyzer in swimming; the irritants of this analyzer are the accelerations that occur when turning the head during inhalation and exhalation, as well as the unusual position of the athlete’s body. In figure skating, the stimuli are rotational exercises and changing positions during rotation. Sports games with their fast movements, sharp stops and turns, and jumps place increased demands on the vestibular analyzer. The vestibular analyzer belongs to the area of subconscious (subsensory) perceiving mechanisms. “We constantly use,” writes academician A.A. Ukhtomsky, “excellent coordination and orientation of our body according to the indications of proprioception and labyrinths, while sensations from this area reach our consciousness only in emergency cases, in unusual positions or in diseases.” (A.A. Ukhtomsky, 1945) the large participation of vegetative reactions during irritation only emphasizes its role in the subsensory sphere of nervous activity. At the same time, there is a close connection between the vestibular analyzer and the internal organs.
With any (adequate or inadequate) irritation of this analyzer, along with motor incoordination, certain vegetative reactions are observed, and with prolonged or especially strong irritation, reflex disorders of breathing, blood circulation and digestion occur. With some impacts of the working environment on a person (noise, vibration, ultrasound), as well as in some professions (driving) and sports exercises, changes occur in the state of the vestibular analyzer. To assess them, subjects are examined for rotational or elevator reactions that occur during rapid ascents or descents. The vestibular analyzer is the second most important afferent source of regulation of postural tone and body position.
In this regard, it is surpassed only by proprioception (kinesthesia). The stability of the functions of the vestibular analyzer increases very significantly with comprehensive training, especially the use of special exercises associated with changing the position of the body in space. (M.R. Mogendovich and I.B. Temkin, 1971)
Developed under the influence of gravity on earth. The impulses of the vestibular apparatus are used in the body to maintain body balance, to regulate and maintain posture, and to spatially organize human movements.
General plan of the organization
The vestibular sensory system consists of the following sections:
- the peripheral section includes two formations containing mechanoreceptors of the vestibular system - the vestibule (saccule and uterus) and semicircular canals;
- the conductive section begins from the fibers of the bipolar cell (the first neuron) of the vestibular node, located in the bone; other processes of these neurons form the vestibular nerve and, together with the auditory nerve as part of the 8th pair of cranial nerves, enter the; in the vestibular nuclei of the medulla oblongata there are second ones, impulses from which enter the third neurons in the diencephalon;
- The cortical section is represented by fourth neurons, some of which are represented in the projection (primary) field of the vestibular system in the temporal region of the cortex, and the other part is located in close proximity to the pyramidal neurons of the motor area of the cortex and in the postcentral gyrus. The exact localization of the cortical part of the vestibular sensory system in humans has not currently been established.
Functioning of the vestibular apparatus
The peripheral part of the vestibular sensory system is located in. The canals and cavities in the temporal bone form the bony labyrinth of the vestibular apparatus, which is partially filled with the membranous labyrinth. Between the bony and membranous labyrinths there is a fluid - perilymph, and inside the membranous labyrinth - endolymph.
The vestibule apparatus is designed to analyze the effect of gravity upon changes in the position of the body in space and accelerations of rectilinear motion. The membranous labyrinth of the vestibule is divided into 2 cavities - the sac and the utricle, containing otolithic devices. The mechanoreceptors of the otolith devices are hair cells. They are glued together by a gelatinous mass that forms an otolithic membrane on top of the hairs, in which there are crystals of calcium carbonate - otoliths (Fig. 1-B). In the uterus, the otolithic membrane is located in the horizontal plane, and in the sac it is bent and located in the frontal and sagittal planes. When the position of the head and body changes, as well as during vertical or horizontal accelerations, the otolith membranes move freely under the influence of gravity in all three planes, pulling, compressing or bending the mechanoreceptor hairs. The greater the deformation of the hairs, the higher the frequency of afferent impulses in the fibers of the vestibular nerve.
The semicircular canal apparatus is used to analyze the action of centrifugal force during rotational movements. Its adequate value is angular acceleration. The three arcs of the semicircular canals are located in three mutually perpendicular planes: anterior - in the frontal plane, lateral - in the horizontal, posterior - in the sagittal. At one end of each channel there is an extension - an ampoule. The hairs of the sensitive cells located in it are glued together into a ridge - the ampullary cupula. It is a pendulum that can deviate as a result of the difference in endolymph pressure on the opposite surfaces of the cupula (Fig. 1-D). During rotational movements, as a result of inertia, the endolymph lags behind the movement of the bone part and puts pressure on one of the surfaces of the cupula. Deflection of the cupula bends the hairs of the receptor cells and causes the appearance of nerve impulses in the vestibular nerve. The greatest changes in the position of the cupula occur in the semicircular canal, the position of which corresponds to the plane of rotation.
It has now been shown that rotations or tilts in one direction increase afferent impulses, and in the other direction - decrease them. This makes it possible to distinguish between the direction of linear or rotational movement.
The influence of vestibular system irritations on other body functions
The vestibular sensory system is connected to many centers of the spinal cord and brain and causes a number of vestibulo-somatic and vestibulo-vegetative.
Vestibular irritations cause adjustment reflexes, changes in muscle tone, elevator reflexes, as well as special eye movements aimed at preserving the image on the retina. - nystagmus (movement of the eyeballs with a speed of rotation, but in the opposite direction, then a rapid return to the starting position and a new opposite rotation).
In addition to the main analytical function, which is important for controlling a person’s posture and movements, the vestibular sensory system has a variety of side effects on many functions of the body, which arise as a result of the irradiation of excitation to others with low stability of the vestibular apparatus. Its irritation leads to a decrease in the excitability of the visual and cutaneous sensory systems, and a deterioration in the accuracy of movements. Vestibular irritations lead to impaired coordination of movements and gait, changes in heart rate and blood pressure, an increase in motor time and a decrease in the frequency of movements, a deterioration in the sense of time, changes in mental functions - attention, operational thinking, emotional manifestations. In severe cases, dizziness, nausea, vomiting occur. . Increasing the stability of the vestibular system is achieved to a greater extent by active rotations of a person than by passive ones.
Functional connections. When the vestibular analyzer is excited, somatic reactions occur, which are carried out thanks to vestibulospinal connections with the participation of the vestibuloreticular and vestibulorubrospinal tracts. In this case, a redistribution of the tone of the skeletal muscles and reflex reactions necessary to maintain the balance of the body in space occur. Reflexes that provide this function are divided into two groups - static and statokinetic.
Thanks to the connections of the vestibular nuclei with the autonomic nervous system, vestibulo-vegetative reactions of the cardiovascular system, gastrointestinal tract and other organs appear. They can manifest themselves in changes in heart rate, vascular tone, blood pressure, increased motility of the stomach and intestines, increased salivation, nausea, vomiting, etc.
In conditions of weightlessness (in space), a type of afferent impulse occurs from the vestibular apparatus, which never occurs on Earth. In conditions of weightlessness (when a person's vestibular influences are turned off), a loss of understanding of the direction of the gravitational vertical and the spatial position of the body occurs. Walking and running skills are lost. The state of the nervous system worsens, increased irritability and mood instability occur.
However, getting used to the conditions of weightlessness during space flights occurs quickly. It should be borne in mind that astronauts undergo an intense training course, which explains their low susceptibility to the influence of weightlessness conditions.
