Hearing analyzer general plan of the structure. Anatomy: structure and functions of the auditory analyzer

Introduction

Conclusion

Bibliography

Introduction

The society in which we live is an information society, where the main factor of production is knowledge, the main product of production is services, and the characteristic features of society are computerization, as well as a sharp increase in creativity in work. The role of connections with other countries is increasing, and the process of globalization is taking place in all spheres of society.

A key role in communication between states is played by professions related to foreign languages, linguistics, and social sciences. There is an increasing need to study speech recognition systems for automated translation, which will help increase labor productivity in areas of the economy related to intercultural communication. Therefore, it is important to study the physiology and mechanisms of functioning auditory analyzer as a means of perceiving and transmitting speech to the appropriate part of the brain for subsequent processing and synthesis of new speech units.

The auditory analyzer is a combination of mechanical, receptor and nerve structures, whose activity ensures the perception of sound vibrations by humans and animals. WITH anatomical point In terms of vision, the auditory system can be divided into the outer, middle and inner ears, the auditory nerve and the central auditory pathways. From the point of view of the processes that ultimately lead to the perception of hearing, the auditory system is divided into sound-conducting and sound-perceiving.

IN different conditions environment, under the influence of many factors, the sensitivity of the hearing analyzer may change. To study these factors there are various methods hearing research.

auditory analyzer physiology sensitivity

1. The importance of studying human analyzers from the point of view of modern information technologies

Already several decades ago, people made attempts to create speech synthesis and recognition systems in modern information technologies. Of course, all these attempts began with the study of the anatomy and principles of operation of the human speech and auditory organs, in the hope of simulating them using a computer and special electronic devices.

What are the features of the human auditory analyzer? The auditory analyzer captures the shape of the sound wave, the frequency spectrum of pure tones and noises, carries out, within certain limits, the analysis and synthesis of the frequency components of sound stimuli, detects and identifies sounds in a wide range of intensities and frequencies. The auditory analyzer allows you to differentiate sound stimuli and determine the direction of the sound, as well as the distance of its source. The ears sense vibrations in the air and convert them into electrical signals that travel to the brain. As a result of processing by the human brain, these signals turn into images. The creation of such information processing algorithms for computer technology is a scientific problem, the solution of which is necessary to develop the most error-free speech recognition systems.

Many users dictate the text of documents using speech recognition programs. This opportunity is relevant, for example, for doctors conducting an examination (during which their hands are usually busy) and at the same time recording its results. PC users can use speech recognition programs to enter commands, meaning the spoken word will be perceived by the system as a mouse click. The user commands: “Open file”, “Send mail” or “New window”, and the computer performs the corresponding actions. This is especially true for people with disabilities - instead of a mouse and keyboard, they will be able to control the computer using their voice.

Studying the inner ear helps researchers understand the mechanisms by which humans are able to recognize speech, although it is not that simple. Man “spies” on many inventions from nature, and such attempts are also made by specialists in the field of speech synthesis and recognition.

2. Types of human analyzers and their brief characteristics

Analyzers (from the Greek analysis - decomposition, dismemberment) are a system of sensitive nervous formations that analyze and synthesize phenomena in the external and internal environment of the body. The term was introduced into the neurological literature by I.P. Pavlov, according to whose ideas each analyzer consists of specific perceptive formations (receptors, sensory organs) that make up the peripheral part of the analyzer, the corresponding nerves connecting these receptors with different floors of the central nervous system (conductive part), and the brain end, which is represented in higher animals in the cortex of the large cerebral hemispheres.

Depending on the receptor function, analyzers of the external and internal environment are distinguished. The first receptors are directed towards external environment and are adapted to analyze phenomena occurring in the surrounding world. Such analyzers include visual analyzer, hearing analyzer, skin, olfactory, gustatory. Analyzers of the internal environment are afferent nervous devices, the receptor apparatus of which is located in internal organs and are adapted to analyze what is happening in the body itself. Such analyzers also include a motor analyzer (its receptor apparatus is represented by muscle spindles and Golgi receptors), which provides the possibility of precise control of the musculoskeletal system. Another internal analyzer, the vestibular one, closely interacts with the movement analyzer, also plays a significant role in the mechanisms of statokinetic coordination. The human motor analyzer also includes a special section that ensures the transmission of signals from the receptors of the speech organs to the higher levels of the central nervous system. Due to the importance of this section in the activity of the human brain, it is sometimes considered a “speech-motor analyzer.”

The receptor apparatus of each analyzer is adapted to transformation certain type energy in nervous excitement. Thus, sound receptors selectively react to sound stimulation, light - to light, taste - to chemical, skin - to tactile-temperature, etc. The specialization of receptors ensures the analysis of external world phenomena into their individual elements already at the level of the peripheral part of the analyzer.

The biological role of analyzers is that they are specialized tracking systems that inform the body about all events occurring in the environment and within it. From the huge flow of signals continuously entering the brain through external and internal analyzers, that useful information is selected that turns out to be essential in the processes of self-regulation (maintaining an optimal, constant level of functioning of the body) and active behavior of animals in the environment. Experiments show that the complex analytical and synthetic activity of the brain, determined by factors of the external and internal environment, is carried out according to the polyanalyzer principle. This means that the entire complex neurodynamics of cortical processes, which forms the integral activity of the brain, consists of a complex interaction of analyzers. But this concerns a different topic. Let's move directly to the auditory analyzer and look at it in more detail.

3. Auditory analyzer as a means of human perception of sound information

3.1 Physiology of the auditory analyzer

The peripheral section of the auditory analyzer (the auditory analyzer with the organ of balance - the ear (auris)) is a very complex sensory organ. The endings of its nerve are located deep in the ear, due to which they are protected from the action of all kinds of extraneous irritants, but at the same time are easily accessible to sound stimulation. The organ of hearing contains three types of receptors:

a) receptors that perceive sound vibrations(vibrations of air waves), which we perceive as sound;

b) receptors that enable us to determine the position of our body in space;

c) receptors that perceive changes in the direction and speed of movement.

The ear is usually divided into three sections: the outer, middle and inner ear.

Outer earconsists of the auricle and outer ear canal. The auricle is built of elastic elastic cartilage, covered with a thin, inactive layer of skin. She is a collector of sound waves; in humans it is motionless and important role does not play, unlike animals; even in its complete absence, no noticeable hearing impairment is observed.

The external auditory canal is a slightly curved canal about 2.5 cm in length. This canal is lined with skin with small hairs and contains special glands, similar to large apocrine glands of the skin, secreting earwax, which, together with the hairs, protects the outer ear from clogging with dust. It consists of an outer section - the cartilaginous external auditory canal and an internal - bony auditory canal, which lies in temporal bone. Its inner end is closed by a thin elastic eardrum, which is a continuation skin external auditory canal and separates it from the middle ear cavity. The outer ear plays only a supporting role in the organ of hearing, participating in the collection and conduction of sounds.

Middle ear, or tympanic cavity (Fig. 1), is located inside the temporal bone between the outer ear canal, from which it is separated by the eardrum, and the inner ear; it is quite small irregular shape a cavity with a capacity of up to 0.75 ml, which communicates with the accessory cavities - the cells of the mastoid process and with the pharyngeal cavity (see below).

Rice. 1. Sectional view of the hearing organ. 1 - geniculate ganglion of the facial nerve; 2 - facial nerve; 3 - hammer; 4 - superior semicircular canal; 5 - posterior semicircular canal; 6 - anvil; 7 - bony part of the external auditory canal; 8 - cartilaginous part of the external auditory canal; 9 - eardrum; 10 - bone part of the auditory tube; 11 - cartilaginous part of the auditory tube; 12 - greater superficial petrosal nerve; 13 - top of the pyramid.

On the medial wall of the tympanic cavity, facing the inner ear, there are two openings: the oval window of the vestibule and the round window of the cochlea; the first is covered by the stirrup plate. The tympanic cavity communicates with the auditory (Eustachian) tube (tuba auditiva) through a small (4 cm long) upper section pharynx - nasopharynx. The hole of the pipe opens on the side wall of the pharynx and in this way communicates with the outside air. Every time the auditory tube opens (which happens with every swallowing movement), the air in the tympanic cavity is renewed. Thanks to her, the pressure on eardrum from the side of the tympanic cavity is always maintained at the level of outside air pressure, and thus, from the outside and inside the eardrum is exposed to the same atmospheric pressure.

This balancing of pressure on both sides of the eardrum is very important, since normal fluctuations are possible only when the pressure of the outside air is equal to the pressure in the cavity of the middle ear. When there is a difference between atmospheric air pressure and the pressure of the tympanic cavity, hearing acuity is impaired. Thus, the auditory tube is a kind of safety valve that equalizes the pressure in the middle ear.

The walls of the tympanic cavity and especially the auditory tube are lined with epithelium, and the mucous tubes are lined with ciliated epithelium; the vibration of its hairs is directed towards the pharynx.

The pharyngeal end of the auditory tube is rich in mucous glands and lymph nodes.

On the lateral side of the cavity is the eardrum. The eardrum (membrana tympani) (Fig. 2) perceives sound vibrations in the air and transmits them to the sound conducting system of the middle ear. It has the shape of a circle or ellipse with a diameter of 9 and 11 mm and consists of elastic connective tissue, the fibers of which are outer surface located radially, and on the inside - circularly; its thickness is only 0.1 mm; it is stretched somewhat obliquely: from top to bottom and from back to front, it is slightly concave inward, since the mentioned muscle stretches from the walls of the tympanic cavity to the handle of the malleus, stretching the eardrum (it pulls the membrane inward). The chain of auditory ossicles serves to transmit air vibrations from the eardrum to the fluid filling the inner ear. The eardrum is not very stretched and does not produce its own tone, but transmits only the sound waves it receives. Due to the fact that vibrations of the eardrum decay very quickly, it is an excellent transmitter of pressure and almost does not distort the shape of the sound wave. On the outside, the eardrum is covered with thinned skin, and on the surface facing the tympanic cavity - with a mucous membrane lined with flat multilayered epithelium.

Between the eardrum and the oval window there is a system of small auditory ossicles that transmit vibrations of the eardrum to the inner ear: the malleus, incus and stapes, connected by joints and ligaments that are driven by two small muscles. The malleus is attached to the inner surface of the eardrum with its handle, and its head is articulated with the incus. The anvil, with one of its processes, is connected to the stirrup, which is located horizontally and with its wide base (plate) inserted into the oval window, tightly adjacent to its membrane.

Rice. 2. Eardrum and auditory ossicles with inside. 1 - head of the hammer; 2 - its upper ligament; 3 - cave of the tympanic cavity; 4 - anvil; 5 - a bunch of it; 6 - drum string; 7 - pyramidal elevation; 8 - stirrup; 9 - hammer handle; 10 - eardrum; 11 - Eustachian tube; 12 - partition between the half-channels for the pipe and for the muscle; 13 - muscle that strains the tympanic membrane; 14 - anterior process of the malleus

deserve a lot of attention muscles of the tympanic cavity. One of them is m. tensor tympani - attached to the neck of the malleus. When it contracts, the articulation between the malleus and the incus is fixed and the tension of the eardrum increases, which occurs with strong sound vibrations. At the same time, the base of the stapes is slightly pressed into the oval window.

The second muscle is m. stapedius (the smallest striated muscle in the human body) - attaches to the head of the stapes. When this muscle contracts, the articulation between the incus and the stapes is pulled downward and limits the movement of the stapes in the oval window.

Inner ear.The inner ear is the most important and most complex part of the hearing system, called the labyrinth. The labyrinth of the inner ear is located deep in the pyramid of the temporal bone, as if in a bone case between the middle ear and the internal auditory canal. The size of the bony ear labyrinth along its long axis does not exceed 2 cm. It is separated from the middle ear by the oval and round windows. The opening of the internal auditory canal on the surface of the pyramid of the temporal bone, through which the auditory nerve exits the labyrinth, is closed by a thin bone plate with small holes for the auditory nerve fibers to exit the inner ear. Inside the bone labyrinth there is a closed connective tissue membranous labyrinth, which exactly repeats the shape of the bone labyrinth, but is somewhat smaller in size. The narrow space between the bony and membranous labyrinths is filled with a fluid similar in composition to lymph and called perilimph. The entire internal cavity of the membranous labyrinth is also filled with a fluid called endolymph. The membranous labyrinth is connected in many places to the walls of the bony labyrinth by dense cords running through the perilymphatic space. Thanks to this arrangement, the membranous labyrinth is suspended inside the bony labyrinth, just as the brain is suspended (inside cranium on their meninges.

The labyrinth (Fig. 3 and 4) consists of three sections: the vestibule of the labyrinth, the semicircular canals and the cochlea.

Rice. 3. Diagram of the relationship of the membranous labyrinth to the bony labyrinth. 1 - duct connecting the utricle with the sac; 2 - superior membranous ampulla; 3 - endolymphatic duct; 4 - endolymphatic sac; 5 - translymphatic space; 6 - pyramid of the temporal bone: 7 - apex of the membranous cochlear duct; 8 - communication between both staircases (helicotrema); 9 - cochlear membranous passage; 10 - staircase vestibule; 11 - drum ladder; 12 - bag; 13 - connecting stroke; 14 - perilymphatic duct; 15 - round window of the cochlea; 16 - oval window of the vestibule; 17 - tympanic cavity; 18 - blind end of the cochlear duct; 19 - posterior membranous ampulla; 20 - utricle; 21 - semicircular canal; 22 - upper semicircular course

Rice. 4. Transverse section through the cochlea. 1 - staircase vestibule; 2 - Reissner's membrane; 3 - integumentary membrane; 4 - cochlear canal, in which the organ of Corti is located (between the integumentary and main membranes); 5 and 16 - auditory cells with cilia; 6 - supporting cells; 7 - spiral ligament; 8 and 14 - bone snails; 9 - supporting cell; 10 and 15 - special supporting cells (the so-called Corti cells - pillars); 11 - scala tympani; 12 - main membrane; 13 - nerve cells of the spiral cochlear ganglion

The membranous vestibule (vestibulum) is a small oval cavity that occupies the middle part of the labyrinth and consists of two vesicles-sacs connected to each other by a narrow tubule; one of them, the posterior one, the so-called utricle (utriculus), communicates with the membranous semicircular canals by five openings, and the anterior sac (sacculus) communicates with the membranous cochlea. Each of the sacs of the vestibule apparatus is filled with endolymph. The walls of the sacs are lined with flat epithelium, with the exception of one area - the so-called spot (macula), where there is a cylindrical epithelium containing supporting and hair cells bearing on their surface thin processes facing the cavity of the sac. Higher animals have small lime crystals (otoliths), glued into one lump together with the hairs of neuroepithelial cells, in which the nerve fibers of the vestibular nerve (ramus vestibularis - branch of the auditory nerve) end.

Behind the vestibule there are three mutually perpendicular semicircular canals (canales semicirculares) - one in the horizontal plane and two in the vertical. The semicircular canals are very narrow tubes filled with endolymph. Each of the canals forms an extension at one of its ends - an ampulla, where the endings of the vestibular nerve are located, distributed in the cells of the sensitive epithelium, concentrated in the so-called auditory crest (crista acustica). The cells of the sensitive epithelium of the auditory comb are very similar to those present in the speck - on the surface facing the cavity of the ampulla, they bear hairs that are glued together and form a kind of brush (cupula). The free surface of the brush reaches the opposite (upper) wall of the canal, leaving an insignificant lumen of its cavity free, preventing the movement of endolymph.

In front of the vestibule is the cochlea, which is a membranous, spirally convoluted canal, also located inside the bone. The cochlear spiral in humans makes 2 3/4revolution around the central bone axis and ends blind. The bony axis of the cochlea with its apex faces the middle ear, and its base closes the internal auditory canal.

Into the cavity of the spiral canal of the cochlea along its entire length, a spiral bone plate also extends and protrudes from the bony axis - a septum that divides the spiral cavity of the cochlea into two passages: the upper one, communicating with the vestibule of the labyrinth, the so-called staircase of the vestibule (scala vestibuli), and the lower one, abutting one end into the membrane of the round window of the tympanic cavity and therefore called the scala tympani (scala tympani). These passages are called staircases because, curling in a spiral, they resemble a staircase with an obliquely rising strip, but without steps. At the end of the cochlea, both passages are connected by a hole about 0.03 mm in diameter.

This longitudinal bone plate blocking the cavity of the cochlea, extending from the concave wall, does not reach the opposite side, and its continuation is a connective tissue membranous spiral plate, called the main membrane, or the main membrane (membrana basilaris), which is already closely adjacent to the convex opposite wall along the the entire length of the common cavity of the cochlea.

Another membrane (Reisner’s) extends from the edge of the bone plate at an angle above the main one, which limits a small middle passage between the first two passages (scales). This passage is called the cochlear canal (ductus cochlearis) and communicates with the vestibule sac; it is the organ of hearing in the proper sense of the word. The canal of the cochlea in a cross section has the shape of a triangle and, in turn, is divided (but not completely) into two floors by a third membrane - the integumentary membrane (membrana tectoria), which apparently plays a large role in the process of perception of sensations. In the lower floor of this last canal, on the main membrane in the form of a protrusion of the neuroepithelium, there is a very complex device, the actual perceptive apparatus of the auditory analyzer - the spiral (organon spirale Cortii) (Fig. 5), washed together with the main membrane by the intralabyrinthine fluid and playing in relation to to hearing the same role as the retina in relation to vision.

Rice. 5. Microscopic structure of the organ of Corti. 1 - main membrane; 2 - cover membrane; 3 - auditory cells; 4 - auditory ganglion cells

The spiral organ consists of numerous diverse supporting and epithelial cells located on the main membrane. The elongated cells are arranged in two rows and are called pillars of Corti. The cells of both rows are slightly inclined towards each other and form up to 4000 arcs of Corti throughout the cochlea. In this case, a so-called internal tunnel is formed in the cochlear canal, filled with intercellular substance. On the inner surface of the Corti columns there is a number of cylindrical epithelial cells, on the free surface of which there are 15-20 hairs - these are sensitive, perceptive, so-called hair cells. Thin and long fibers - auditory hairs, sticking together, form delicate brushes on each such cell. Adjacent to the outer side of these auditory cells are the supporting Deiters cells. Thus, the hair cells are anchored to the main membrane. Thin nerve fibers without pulp approach them and form an extremely delicate fibrillar network in them. The auditory nerve (its branch - ramus cochlearis) penetrates the middle of the cochlea and runs along its axis, giving off numerous branches. Here, each pulpy nerve fiber loses its myelin and becomes a nerve cell, which, like the cells of the spiral ganglia, has a connective tissue sheath and glial meningeal cells. The whole amount of these nerve cells as a whole and forms a spiral ganglion (ganglion spirale), occupying the entire periphery of the cochlear axis. From this nerve ganglion, nerve fibers are already sent to the perceptive apparatus - the spiral organ.

The main membrane itself, on which the spiral organ is located, consists of the thinnest, dense and tightly stretched fibers (“strings”) (about 30,000), which, starting from the base of the cochlea (about oval window), gradually lengthen towards its upper curl, reaching from 50 to 500 ?(more precisely, from 0.04125 to 0.495 mm), i.e. short near the oval window, they become increasingly longer towards the apex of the cochlea, increasing by about 10-12 times. The length of the main membrane from the base to the apex of the cochlea is approximately 33.5 mm.

Helmholtz, who created the theory of hearing at the end of the last century, compared the main membrane of the cochlea with its fibers of different lengths with musical instrument- a harp, only in this living harp a huge number of “strings” are stretched.

The perceiving apparatus of auditory stimuli is the spiral (Corti) organ of the cochlea. The vestibule and semicircular canals play the role of balance organs. True, the perception of the position and movement of the body in space depends on the joint function of many senses: vision, touch, muscle sense, etc., i.e. reflex activity necessary to maintain balance is provided by impulses in various organs. But the main role in this belongs to the vestibule and semicircular canals.

3.2 Sensitivity of the hearing analyzer

The human ear perceives air vibrations from 16 to 20,000 Hz as sound. The upper limit of perceived sounds depends on age: the older the person, the lower it is; Often older people cannot hear high tones, such as the sound made by a cricket. In many animals the upper limit lies higher; in dogs, for example, it is possible to form a whole series conditioned reflexes to sounds inaudible to humans.

With fluctuations up to 300 Hz and above 3000 Hz, the sensitivity decreases sharply: for example, at 20 Hz, as well as at 20,000 Hz. With age, the sensitivity of the auditory analyzer, as a rule, decreases significantly, but mainly to high-frequency sounds, while to low-frequency sounds (up to 1000 vibrations per second) it remains almost unchanged until old age.

This means that to improve the quality of speech recognition, computer systems can exclude from analysis frequencies that lie outside the range of 300-3000 Hz or even outside the range of 300-2400 Hz.

In conditions of complete silence, hearing sensitivity increases. If a tone of a certain pitch and constant intensity begins to sound, then, due to adaptation to it, the sensation of loudness decreases, first quickly, and then more and more slowly. However, although to a lesser extent, sensitivity to sounds that are more or less close in vibration frequency to the sounding tone decreases. However, adaptation usually does not extend to the entire range of perceived sounds. After the sound stops, due to adaptation to silence, the previous level of sensitivity is restored within 10-15 seconds.

Adaptation partly depends on the peripheral part of the analyzer, namely on changes in both the amplifying function of the sound apparatus and the excitability of the hair cells of the organ of Corti. The central section of the analyzer also takes part in the phenomena of adaptation, as evidenced by the fact that when sound affects only one ear, shifts in sensitivity are observed in both ears.

Sensitivity also changes with the simultaneous action of two tones of different heights. In the latter case, a weak sound is drowned out by a stronger one, mainly because the focus of excitation, which arises in the cortex under the influence of a strong sound, reduces, due to negative induction, the excitability of other parts of the cortical section of the same analyzer.

Prolonged exposure to strong sounds can cause prohibitive inhibition of cortical cells. As a result, the sensitivity of the auditory analyzer sharply decreases. This condition persists for some time after the irritation has stopped.

Conclusion

The complex structure of the auditory analyzer system is determined by a multi-stage algorithm for signal transmission to the temporal region of the brain. The outer and middle ears transmit sound vibrations to the cochlea, located in the inner ear. Sensitive hairs located in the cochlea convert vibrations into electrical signals that travel along nerves to the auditory area of ​​the brain.

When considering the functioning of an auditory analyzer for further application of knowledge when creating speech recognition programs, one should also take into account the sensitivity limits of the hearing organ. The frequency range of sound vibrations perceived by humans is 16-20,000 Hz. However, the frequency range of speech is already 300-4000 Hz. Speech remains intelligible when the frequency range is further narrowed to 300-2400 Hz. This fact can be used in speech recognition systems to reduce the influence of interference.

Bibliography

1.P.A. Baranov, A.V. Vorontsov, S.V. Shevchenko. Social studies: a complete reference book. Moscow 2013

2.Great Soviet Encyclopedia, 3rd edition (1969-1978), volume 23.

.A.V. Frolov, G.V. Frolov. Speech synthesis and recognition. Modern solutions.

.Dushkov B.A., Korolev A.V., Smirnov B.A. encyclopedic Dictionary: Labor psychology, management, engineering psychology and ergonomics. Moscow, 2005

.Kucherov A.G. Anatomy, physiology and methods of studying the organ of hearing and balance. Moscow, 2002

.Stankov A.G. Human anatomy. Moscow, 1959

7.http://ioi-911. ucoz.ru/publ/1-1-0-47

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Hearing analyzer (auditory sensory system) is the second most important distant human analyzer. Hearing plays a vital role in humans in connection with the emergence of articulate speech. Acoustic (sound) signals are air vibrations with different frequencies and strengths. They stimulate the auditory receptors located in the cochlea of ​​the inner ear. The receptors activate the first auditory neurons, after which sensory information is transmitted to the auditory area of ​​the cerebral cortex (temporal region) through a series of sequential structures.

The organ of hearing (ear) is a peripheral section of the auditory analyzer in which auditory receptors are located. The structure and functions of the ear are presented in table. 12.2, fig. 12.10.

Table 12.2.

Structure and functions of the ear

Ear part	Structure	Functions
Outer ear	Auricle, external auditory canal, eardrum	Protective (sulfur release). Captures and transmits sounds. Sound waves vibrate the eardrum, which vibrates the auditory ossicles.
Middle ear	An air-filled cavity containing the auditory ossicles (hammer, incus, stapes) and the Eustachian (auditory) tube	The auditory ossicles conduct and amplify sound vibrations 50 times. The Eustachian tube, connected to the nasopharynx, equalizes pressure on the eardrum
Inner ear	Organ of hearing: oval and round windows, cochlea with a cavity filled with fluid, and organ of Corti - sound-receiving apparatus	Auditory receptors located in the organ of Corti convert sound signals into nerve impulses that are transmitted to the auditory nerve and then to the auditory zone of the cerebral cortex
	Organ of balance ( vestibular apparatus): three semicircular canals, otolithic apparatus	Perceives the position of the body in space and transmits impulses to the medulla oblongata, then to the vestibular zone of the cerebral cortex; response impulses help maintain body balance

Rice. 12.10. Organs hearing And equilibrium. The outer, middle and inner ear, as well as the auditory and vestibular branches of the vestibular nerve (VIII pair of cranial nerves) extending from the receptor elements of the organ of hearing (organ of Corti) and balance (crests and spots).

The mechanism of sound transmission and perception. Sound vibrations are picked up by the auricle and transmitted through the external auditory canal to the eardrum, which begins to vibrate in accordance with the frequency of the sound waves. Vibrations of the eardrum are transmitted to the chain of ossicles of the middle ear and, with their participation, to the membrane of the oval window. Vibrations of the membrane of the vestibule window are transmitted to the perilymph and endolymph, which causes vibrations of the main membrane along with the organ of Corti located on it. In this case, the hair cells touch the integumentary (tectorial) membrane with their hairs, and due to mechanical irritation, excitation arises in them, which is transmitted further to the fibers of the vestibulocochlear nerve (Fig. 12.11).

Rice. 12.11. Membranous channel And spiral (Corti) organ. The cochlear canal is divided into the scala tympani and vestibular canal and the membranous canal (middle scala), in which the organ of Corti is located. The membranous canal is separated from the scala tympani by a basilar membrane. It contains peripheral processes of neurons of the spiral ganglion, forming synaptic contacts with outer and inner hair cells.

Location and structure of receptor cells of the organ of Corti. On the main membrane there are two types of receptor hair cells: internal and external, separated from each other by the arches of Corti.

The inner hair cells are arranged in a single row; their total number along the entire length of the membranous canal reaches 3,500. The outer hair cells are arranged in 3-4 rows; their total number is 12,000-20,000. Each hair cell has an elongated shape; one of its poles is fixed on the main membrane, the second is located in the cavity of the membranous canal of the cochlea. There are hairs at the end of this pole, or stereocilia. Their number on each internal cell is 30-40 and they are very short - 4-5 microns; on each outer cell the number of hairs reaches 65-120, they are thinner and longer. The hairs of the receptor cells are washed by the endolymph and come into contact with the integumentary (tectorial) membrane, which is located above the hair cells along the entire course of the membranous canal.

The mechanism of auditory reception. When exposed to sound, the main membrane begins to vibrate, the longest hairs of the receptor cells (stereocilia) touch the integumentary membrane and tilt slightly. Deviation of the hair by several degrees leads to tension in the thinnest vertical filaments (microfilaments) connecting the tops of neighboring hairs of a given cell. This tension, purely mechanically, opens from 1 to 5 ion channels in the stereocilium membrane. A potassium ion current begins to flow through the open channel into the hair. The tension force of the thread required to open one channel is negligible, about 2·10 -13 newton. What seems even more surprising is that the weakest sounds felt by humans stretch the vertical filaments connecting the tops of neighboring stereocilia to a distance half the diameter of a hydrogen atom.

The fact that the electrical response of the auditory receptor reaches a maximum after only 100-500 μs (microseconds) means that the membrane ion channels open directly from the mechanical stimulus without the participation of intracellular second messengers. This distinguishes mechanoreceptors from much slower-acting photoreceptors.

Depolarization of the presynaptic ending of the hair cell leads to the release of a neurotransmitter (glutamate or aspartate) into the synaptic cleft. By acting on the postsynaptic membrane of the afferent fiber, the mediator causes the generation of excitation of the postsynaptic potential and further generation of impulses propagating in the nerve centers.

The opening of just a few ion channels in the membrane of one stereocilium is clearly not enough to generate a receptor potential of sufficient magnitude. An important mechanism for amplifying the sensory signal at the receptor level of the auditory system is the mechanical interaction of all stereocilia (about 100) of each hair cell. It turned out that all stereocilia of one receptor are interconnected into a bundle by thin transverse filaments. Therefore, when one or more of the longer hairs bends, they pull all the other hairs with them. As a result, the ion channels of all hairs open, providing a sufficient magnitude of the receptor potential.

Binaural hearing. Humans and animals have spatial hearing, i.e. the ability to determine the position of a sound source in space. This property is based on the presence of two symmetrical halves of the auditory analyzer (binaural hearing).

The acuity of binaural hearing in humans is very high: he is able to determine the location of a sound source with an accuracy of about 1 angular degree. The physiological basis for this is the ability of the neural structures of the auditory analyzer to evaluate interaural (interaural) differences in sound stimuli by the time of their arrival at each ear and by their intensity. If the sound source is away from midline head, the sound wave arrives at one ear somewhat earlier and with greater force than at the other. Assessing the distance of a sound from the body is associated with a weakening of the sound and a change in its timbre.

The receptive part of the auditory analyzer is the ear, the conductive part is the auditory nerve, and the central part is the auditory zone of the cerebral cortex. The hearing organ consists of three sections: the outer, middle and inner ear. The ear includes not only the organ of hearing itself, with the help of which auditory sensations are perceived, but also the organ of balance, due to which the body is held in a certain position.

The outer ear consists of the pinna and the external auditory canal. The shell is formed by cartilage covered on both sides by skin. With the help of a shell, a person catches the direction of sound. Muscles that move auricle, are rudimentary in humans. The external auditory canal looks like a tube 30 mm long, lined with skin, in which there are special glands that secrete earwax. In the depths, the ear canal is covered with a thin oval-shaped eardrum. On the side of the middle ear, in the middle of the eardrum, the handle of the hammer is strengthened. The membrane is elastic; when struck by sound waves, it repeats these vibrations without distortion.

The middle ear is represented by the tympanic cavity, which communicates with the nasopharynx through the auditory (Eustachian) tube; It is delimited from the outer ear by the eardrum. The components of this department are: hammer, anvil And stapes. With its handle, the malleus fuses with the eardrum, while the anvil is articulated with both the malleus and the stirrup, which covers the oval hole leading to the inner ear. In the wall separating the middle ear from the inner ear, in addition to the oval window, there is also a round window covered with a membrane.
Structure of the hearing organ:
1 - auricle, 2 - external auditory canal,
3 - eardrum, 4 - middle ear cavity, 5 - auditory tube, 6 - cochlea, 7 - semicircular canals, 8 - anvil, 9 - hammer, 10 - stapes

The inner ear, or labyrinth, is located deep in the temporal bone and has double walls: membranous labyrinth as if inserted into bone, repeating its shape. The gap-like space between them is filled clear liquid - perilymph, cavity of the membranous labyrinth - endolymph. Labyrinth presented the threshold anterior to it is the cochlea, posteriorly - semicircular canals. The cochlea communicates with the middle ear cavity through a round window covered by a membrane, and the vestibule communicates through the oval window.

The organ of hearing is the cochlea, its remaining parts make up the organs of balance. The cochlea is a spirally twisted canal of 2 3/4 turns, separated by a thin membranous septum. This membrane is spirally curled and is called basic. It consists of fibrous tissue, which includes about 24 thousand special fibers (auditory strings) of different lengths and located transversely along the entire course of the cochlea: the longest are at its apex, and the shortest at the base. Overhanging these fibers are auditory hair cells - receptors. This is the peripheral end of the auditory analyzer, or organ of Corti. The hairs of the receptor cells face the cavity of the cochlea - the endolymph, and the auditory nerve originates from the cells themselves.

Perception of sound stimuli. Sound waves passing through the external auditory canal cause vibrations in the eardrum and are transmitted to the auditory ossicles, and from them to the membrane of the oval window leading to the vestibule of the cochlea. The resulting vibration sets in motion the perilymph and endolymph of the inner ear and is perceived by the fibers of the main membrane, which carries the cells of the organ of Corti. High-pitched sounds with a high vibration frequency are perceived by short fibers located at the base of the cochlea and transmitted to the hairs of the cells of the organ of Corti. In this case, not all cells are excited, but only those located on fibers of a certain length. Consequently, the primary analysis of sound signals begins already in the organ of Corti, from which excitation along the fibers of the auditory nerve is transmitted to the auditory center of the cerebral cortex in the temporal lobe, where their qualitative assessment occurs.

Vestibular apparatus. The vestibular apparatus plays an important role in determining the position of the body in space, its movement and speed of movement. It is located in the inner ear and consists of vestibule and three semicircular canals, located in three mutually perpendicular planes. The semicircular canals are filled with endolymph. In the endolymph of the vestibule there are two sacs - round And oval with special lime stones - statolites, adjacent to the hair receptor cells of the sacs.

In normal body position, the statoliths irritate the hairs of the lower cells with their pressure; when the body position changes, the statoliths also move and irritate other cells with their pressure; the received impulses are transmitted to the cerebral cortex. In response to irritation of the vestibular receptors associated with the cerebellum and the motor zone of the cerebral hemispheres, muscle tone and body position in space reflexively change. Three semicircular canals extend from the oval sac, which initially have extensions - ampoules, in which hair cells - receptors are located. Since the channels are located in three mutually perpendicular planes, the endolymph in them, when the body position changes, irritates certain receptors, and the excitation is transmitted to the corresponding parts of the brain. The body reflexively responds necessary change body position.

Hearing hygiene. Earwax accumulates in the external auditory canal and traps dust and microorganisms, so it is necessary to regularly wash your ears with warm soapy water; Under no circumstances should you remove sulfur with hard objects. Overwork nervous system and hearing strain can cause sharp sounds and noises. Prolonged noise is especially harmful, causing hearing loss and even deafness. Loud noise reduces labor productivity by up to 40-60%. To combat noise in industrial environments, walls and ceilings are lined with special materials that absorb sound, and individual noise-reducing headphones are used. Motors and machines are installed on foundations that muffle the noise from the shaking of the mechanisms.

The auditory analyzer is a set of mechanical, receptor and neural structures that perceive and analyze sound vibrations. The peripheral section of the auditory analyzer is represented by the auditory organ, consisting of the outer, middle and inner ear. The outer ear consists of the pinna and the external auditory canal. The auricle of a newborn is flattened, its cartilage is soft, the skin is thin, and the earlobe is small. The auricle grows most rapidly during the first two years and after 10 years. It grows in length faster than in width. The eardrum separates the outer ear from the middle ear. The middle ear consists of the tympanic cavity, the auditory ossicles and the auditory tube.

The tympanic cavity in a newborn is the same in size as in an adult. In the middle ear there are three auditory ossicles: the malleus, the incus and the inner ear, or labyrinth, has double walls: the membranous labyrinth is inserted into the bone labyrinth. The bony labyrinth consists of the vestibule, cochlea and three semicircular canals. The cochlear duct divides the cochlea into two parts, or scalae. The inner ear of a newborn is well developed, its size is close to that of an adult. The basal parts of the receptor cells contact the nerve fibers, which pass through the basement membrane and then exit into the spiral lamina canal. Next they go to the neurons of the spiral ganglion, which lies in the bony cochlea, where the conductive section of the auditory analyzer begins. The axons of the neurons of the spiral ganglion form fibers of the auditory nerve, which enters the brain between the inferior cerebellar peduncles and the pons and is directed into the pontine tegmentum, where the first crossover of the fibers takes place and the lateral lemniscus is formed. Some of its fibers end on the cells of the inferior colliculus, where the primary auditory center is located. Other fibers of the lateral lemniscus, as part of the handle of the inferior colliculus, approach the medial geniculate body. The processes of the cells of the latter form the auditory radiation, ending in the cortex of the superior temporal gyrus (cortical section of the auditory analyzer).

The organ of Corti is a peripheral part of the auditory analyzer. Age characteristics

The organ of Corti, located on the basilar membrane, contains receptors that convert mechanical vibrations into electrical potentials that excite the auditory nerve fibers. When exposed to sound, the main membrane begins to vibrate, the hairs of the receptor cells are deformed, which causes the generation of electrical potentials that reach the auditory nerve fibers through synapses. The frequency of these potentials corresponds to the frequency of sounds, and the amplitude depends on the intensity of the sound. As a result of the occurrence of electrical potentials, the auditory nerve fibers are excited, which are characterized by spontaneous activity even in silence (100 impulses/s). During sound, the frequency of impulses in the fibers increases throughout the entire duration of the stimulus. For each nerve fiber there is an optimal sound frequency that gives the highest discharge frequency and minimum response threshold. When the spiral organ is damaged, high tones fall out at the base, and low tones fall out at the apex. The destruction of the middle curl leads to the loss of tones in the middle frequency range. There are two mechanisms for pitch discrimination: spatial and temporal encoding. Spatial coding is based on the unequal location of excited receptor cells on the main membrane. At low and medium tones, time coding is also carried out. A person perceives sounds with a frequency of 16 to 20 O O O Hz. This range corresponds to 10-11 octaves. The limits of hearing depend on age: the older a person is, the more often he does not hear high tones. Sound frequency discrimination is characterized by the minimum difference in frequency of two sounds that a person perceives. A person can notice a difference of 1-2 Hz. Absolute hearing sensitivity is the minimum strength of sound heard by a person in half the cases of its sound. In the region from 1000 to 4000 Hz, human hearing has maximum sensitivity. Speech fields also lie in this zone. The upper limit of audibility occurs when an increase in the intensity of a sound of a constant frequency causes an unpleasant feeling of pressure and pain in the ear. The unit of sound loudness is bel. In everyday life, decibels are usually used as a unit of loudness, i.e. 0.1 bel. The maximum volume level when sound causes pain is 130-140 dB above the threshold of audibility. The auditory analyzer has two symmetrical halves (binaural hearing), i.e. Humans are characterized by spatial hearing - the ability to determine the position of a sound source in space. The acuity of such hearing is great. A person can determine the location of a sound source with an accuracy of 1°.

Hearing in ontogenesis

Despite the early development of the auditory analyzer, the hearing organ in a newborn is not yet fully formed. He has relative deafness, which is associated with the structural features of the ear. The newborn reacts to loud sounds by shuddering, stopping crying, and changing breathing. Children's hearing becomes quite clear by the end of the 2nd - beginning of the 3rd month. At the 2nd month of life, the child differentiates qualitatively different sounds, at 3-4 months he distinguishes pitches ranging from 1 to 4 octaves, at 4-5 months sounds become conditioned stimuli, although conditioned food and defensive reflexes to sound stimuli are developed already from 3 months. -5 weeks of age. By 1-2 years, children differentiate sounds, the difference between which is 1 tone, and by 4 years - even 3/4 and 1/2 tones. Hearing acuity is determined by the lowest sound intensity that can cause a sound sensation (hearing threshold). For an adult, the hearing threshold is in the range of 10-12 dB, for children 6-9 years old - 17-24 dB, 10-12 years old - 14-19 dB. The greatest acuity of sound is achieved by middle and high school age.

Question 87. Prevention of Myopiaormyopia, astigmatism, hearing loss. Myopia is a visual impairment in which a person has difficulty seeing objects that are far away and can see close objects well. The disease is very common, affecting one third of the entire world population. Myopia usually appears at the age of 7-15 years, and can worsen or remain at the same level without changes throughout life.

Prevention of myopia: Proper lighting will reduce eye strain, so you should take care of the proper organization of the workplace and a desk lamp. It is not recommended to work under a fluorescent lamp. Compliance with the regime of visual stress, alternating them with physical activity. Proper, balanced nutrition should contain a complex of essential vitamins and minerals: zinc, magnesium, vitamin A, etc. Strengthening the body through hardening, physical activity, massage, contrast shower. Monitor the child's correct posture. These simple precautions can minimize the likelihood of decreased distance vision, that is, the development of myopia. It is important to take all this into account for parents whose child has a hereditary tendency to the disease.

Childhood astigmatism is an optical defect when two optical foci exist simultaneously in the eye, and neither of them is where it should be. This is due to the fact that the cornea refracts rays more strongly along one axis than along the other.

Prevention.

Often children simply do not notice that their vision is decreasing. This means that even if there are no complaints, it is better to show the child to an ophthalmologist once a year. Then the disease will be detected in time, and treatment will begin. Eye exercises for astigmatism are quite useful. Thus, R.S. Agarwal advises making large turns 100 times, moving the gaze along the lines of small print on the vision table, combining them with blinking on each line.

Hearing loss is a hearing loss of varying severity, in which speech perception is difficult, but is possible when certain conditions are created (the speaker or speaker is brought closer to the ear, the use of sound amplifying equipment). When pathology of hearing and speech is combined (deaf-mute), children are not able to perceive and reproduce speech. Prevention of hearing loss and deafness in children is the most important way to solve the problem of hearing loss. A leading role in the prevention of hereditary forms of hearing loss. All pregnant women should undergo examination to detect kidney and liver diseases, diabetes mellitus and other diseases. It is necessary to limit the prescription of ototoxic antibiotics to pregnant women and children, especially younger ones childhood. From the very first days of a child’s life, prevention of acquired forms of hearing loss should be combined with prevention of diseases of the hearing system, especially infectious-viral etiology. If the first signs of hearing impairment are detected, the child should be consulted by an otolaryngologist.

Auditory system is a sound analyzer. It distinguishes between sound-conducting and sound-receiving devices (Fig. 1). The sound-conducting apparatus includes the outer ear, middle ear, labyrinthine windows, membranous formations and fluid media of the inner ear; sound-perceiving - hair cells, auditory nerve, neural formations of the brain stem and hearing centers (Fig. 2).

Rice. 1. Schematic structure of the ear (peripheral structure of the auditory analyzer): 1 - outer ear; 2 - middle ear; 3 - inner ear

Rice. 2. Diagram of sound-conducting and sound-receiving devices: 1 - outer ear; 2 - middle ear; 3 - inner ear; 4 - pathways; 5 - cortical center

The sound-conducting apparatus ensures the conduction of acoustic signals to sensitive receptor cells, the sound-perceiving apparatus transforms sound energy into nervous stimulation and conducts it to the central sections of the auditory analyzer.

The external ear (amis externa) includes the pinna (auricula) and the external auditory canal (meatus acusticus extemus).

The auricle is an irregularly shaped oval formation near the beginning of the external auditory canal. Its basis is elastic cartilage covered with skin. There is no cartilage in the lower part of the shell, which is called the lobulus auriculae. Instead, there is a layer of fiber under the skin.

In the auricle there are a number of elevations and pits (Fig. 3). Its free, roller-shaped edge is called a helix (helix). The curl starts from the posterior edge of the lobe, stretches along the entire perimeter of the concha and ends above the entrance to the external auditory canal. This part of the auricle is called the helix (cms helicis). In the upper posterior part of the helix, an oval thickening is defined, which is called the duck tubercle (tubercuhtm auriculae).

Rice. 3. The main anatomical formations of the auricle: 1 - helix; 2 - leg of the corneal helix; 3 - stem of the helix; 4 - anterior notch; 5 - supratragus tubercle; 6 - tragus; 7 - external auditory canal; 8 - intertragus notch; 9 - antitragus: 10 - lobe (earring); 11 - posterior ear groove; 12 - antihelix; 13 - auricle; 14 - scaphoid fossa; 15 - ear tubercle; 16 - triangular fossa

There is also a second roller - antihelix (anthelix). Between the helix and the antihelix there is a triangular fossa (fossa triangularis). The antihelix ends above the earlobe with an elevation called the antitragus. In front of the antitragus there is a dense cartilaginous formation - the tragus. It partially protects the ear canal from the penetration of foreign bodies into it. The deep fossa, located between the tragus, antihelix and antitragus, makes up the actual concha of the ear (concha auriculae). The muscles of the auricle are rudimentary and have no practical significance.

The auricle passes into the external auditory canal (meatus (icusticus exterrms). The outer part of the canal (approximately 1/3 of its length) consists of cartilage, inner part(2/3 of the length) - bone. The membranous-cartilaginous part of the external auditory canal is mobile, the skin contains hair, sebaceous and sulfur glands. Hair protects the ear from the penetration of insects and foreign bodies into it; sulfur and #ir lubricate and cleanse the ear canal from scales and foreign particles. The skin of the bony part of the external meatus is thin, devoid of hair/glands, and fits tightly to the temporal bone.

At the junction of the cartilaginous part and the bone part, the auditory canal narrows somewhat (isthmus). The bony part of the passage has an irregular S-shape, due to which the anterior inferior portions of the tympanic membrane are not sufficiently visible. To expand the space and better see the eardrum, you need to pull the auricle up and back. This structure of the external auditory canal has practical significance in the clinic. In particular, the presence sebaceous glands and water only in the cartilaginous part predetermines the occurrence of boils and folliculitis; narrowing of the passage at the border of its membranous-cartilaginous and bone parts is dangerous, since it creates a threat of pushing foreign body into the depths of the ear canal with inept removal.

The outer ear and nearby tissues are supplied with blood from the small vessels of the external carotid artery - a. auhcularis posterior, a. temporalis superfacialis, a. maxillaris interna and others. The innervation of the external ear is carried out by the branches of the V, VII and X cranial nerves. Participation in this process vagus nerve, in particular its ear child (g. auricularis), explains the cause of reflex cough in individual patients with mechanical irritation of the skin of the external auditory canal (wax removal, ear toilet).

The middle ear (auris media) is a system of air cavities, including tympanic cavity(cavum tympani), cave (antrum), air cells of the mastoid process (cellulae $astoideas) and auditory tube (tuba auditiva). Outer wall The tympanic cavity is the tympanic membrane, the inner is the lateral wall of the inner ear, the upper is the roof of the tympanic cavity (tegmen tympani), separating the tympanic cavity from the middle cranial fossa, the lower is the bone formation separating the bulb of the jugular vein (bulbus venae jugularis).

On the front wall there is a tympanic opening of the auditory tube and a canal for the muscle that strains the tympanic membrane (tensor tympani), on the back there is an entrance to the cave (aditus ad antrum), which connects the tympanic cavity through the epitympanic space (attic) with the mastoid cave ( antrum mastoideum). The auditory tube connects the tympanic cavity to the nasal part of the throat. Behind and below the opening of the auditory tube there is a bone canal in which the internal carotid artery passes, with its branches providing blood supply to the inner ear. Anatomical structure

DI. Zabolotny, Yu.V. Mitin, S.B. Bezshapochny, Yu.V. Deeva