The peripheral section of the auditory sensory system consists of three parts: the outer, middle and inner ear (Fig. 5.8). The organ of hearing occupies an important place in the body’s receipt of information. From him normal functioning The success of students in mastering educational material, as well as the development of speech, which has a decisive influence on mental development as a whole, largely depends. The organ of hearing is connected with the organs of maintaining balance, which are involved in maintaining a certain body posture.

The outer ear includes the pinna and the external auditory canal.

The auricle is designed to capture sound vibrations, which are then transmitted through the external auditory canal to the eardrum. The external auditory canal is about 24 mm long and is lined with skin equipped with fine hairs and special sweat glands that secrete earwax. Earwax is made up of fat cells that contain pigment. Hairs and earwax play a protective role.

The eardrum is located on the border between the outer and middle ear. It is very thin (about 0.1 mm), covered on the outside with epithelium, and on the inside with mucous membrane. The eardrum is located obliquely and when exposed to sound waves it begins to vibrate. And since the eardrum does not have its own period of vibration, it vibrates with any sound according to its frequency and amplitude.

The middle ear is represented by an irregularly shaped tympanic cavity in the form of a small flat drum, on which a vibrating membrane is tightly stretched, and the auditory, or Eustachian, tube.

In the cavity of the middle ear there are auditory ossicles that articulate with each other - the hammer, incus, and stapes. The middle ear is separated from the inner ear by a membrane oval window.

The handle of the malleus is connected at one end to the eardrum, at the other to the anvil, which in turn is movably connected to the stapes using a joint. The stapedius muscle is attached to the stapes, holding it against the membrane of the oval window of the vestibule. The sound, passing the outer ear, acts on the eardrum, to which the hammer is connected. The system of these three bones increases the pressure of the sound wave by 30-40 times and transmits it to the membrane of the oval window of the vestibule, where it is transformed into vibrations of the fluid - endolymph.

The tympanic cavity is connected to the nasopharynx through the auditory tube. The function of the Eustachian tube is to equalize the pressure on the eardrum from the inside and outside, which creates the most favorable conditions for her to hesitate. The entry of air into the tympanic cavity occurs during swallowing or yawning, when the lumen of the tube opens, and the pressure in the pharynx and tympanic cavity leveled out.

Inner ear It is a bony labyrinth, inside of which there is a membranous labyrinth of connective tissue. Between the bony and membranous labyrinth there is a fluid - perilymph, and inside the membranous labyrinth - endolymph.

In the center of the bony labyrinth is the vestibule, in front of it is the cochlea, and behind it are the semicircular canals. The bony cochlea is a spirally convoluted canal that forms 2.5 turns around a conical rod. The diameter of the bone canal at the base of the cochlea is 0.04 mm, and at the apex - 0.5 mm. A bony spiral plate extends from the rod, which divides the canal cavity into two parts, or stairs.

In the cochlear passage, inside the middle canal of the cochlea, there is a sound-receiving apparatus - the spiral, or organ of Corti (Fig. 5.9). It has a basal (main) plate, which consists of 24 thousand thin fibrous fibers of various lengths, very elastic and weakly connected to each other. Along it, in 5 rows, there are supporting and hair sensory cells, which are the actual auditory receptors.

Receptor cells have an elongated shape. Each hair cell carries 60-70 tiny hairs (4-5 µm long), which are washed by the endolymph and come into contact with the integumentary plate. The auditory analyzer perceives the sound of various tones. The main characteristic of each sound tone is the length of the sound wave.

The length of a sound wave is determined by the distance that sound travels in 1 second, divided by the number of complete oscillations performed by the sounding body during the same time. How larger number vibrations, the shorter the wavelength. High sounds have a short wave, measured in millimeters, while low sounds have a long wave, measured in meters.

The pitch of a sound is determined by its frequency, or the number of vibrations in 1 second. Frequency is measured in Hertz (Hz). The higher the frequency of the sound, the higher the sound. The strength of sound is proportional to the amplitude of the vibrations of the sound wave and is measured in bels (decibels, dB, are more often used).

A person is able to hear sounds from 12-24 to 20,000 Hz. In children, the upper limit of hearing reaches 22,000 Hz, in older people it is lower - about 15,000 Hz.

Wiring department. The hair cells are covered by the nerve fibers of the cochlear branch of the auditory nerve, which carries the nerve impulse to the medulla oblongata, then, crossing with the second neuron of the auditory tract, it is directed to the posterior colliculus and the nuclei of the internal geniculate bodies of the diencephalon, and from them to the temporal region of the cortex, where is the central part located? auditory analyzer.

The central section of the auditory analyzer is located in the temporal lobe. The primary auditory cortex occupies the upper edge of the superior temporal gyrus and is surrounded by the secondary cortex (Fig. 5.1). The meaning of what is heard is interpreted in associative zones. In humans, in the central nucleus of the auditory analyzer, Wernicke's area, located in the posterior part of the superior temporal gyrus, is of particular importance. This zone is responsible for understanding the meaning of words; it is the center of sensory speech. With prolonged exposure to strong sounds, the excitability of the sound analyzer decreases, and with prolonged exposure to silence it increases. This adaptation is observed in the zone of higher sounds.

Age characteristics. The formation of the peripheral part of the auditory sensory system begins in the 4th week of embryonic development. In a 5-month-old fetus, the snail already has the shape and size characteristic of an adult. By the 6th month of prenatal development, the differentiation of receptors ends.

Myelination conductor department progresses at a slow pace and ends only by the age of 4.

The auditory cortex is allocated in the 6th month of intrauterine life, but the primary sensory cortex develops especially intensively during the second year of life, development continues until 7 years.

Despite the immaturity of the sensory system, already at 8-9 months of prenatal development, the child perceives sounds and reacts to them with movements.

In newborns, the hearing organ is not fully developed, and it is often believed that the child is born deaf. In reality, there is relative deafness, which is associated with the structural features of the ear. The external auditory canal in newborns is short and narrow and initially located vertically. Up to 1 year it is presented cartilage tissue, which subsequently ossifies, this process lasts up to 10-12 years. The eardrum is located almost horizontally and is much thicker than in adults. The middle ear cavity is filled with amniotic fluid, which makes it difficult for the auditory ossicles to vibrate. With age, this fluid resolves and the cavity fills with air. The auditory (Eustachian) tube in children is wider and shorter than in adults, and through it microbes, fluids from a runny nose, vomiting, etc. can enter the middle ear cavity. This explains the fairly common inflammation of the middle ear (otitis media) in children.

From the first days after birth, the child reacts to loud sounds shuddering, change in breathing, cessation of crying. At the 2nd month the child differentiates qualitatively different sounds, at 3-4 months he distinguishes the pitch of sounds ranging from 1 to 4 octaves, at 4-5 months the sounds become conditioned reflex stimuli. By the age of 1-2 years, children differentiate sounds, the difference between which is 1-2, and by the age of 4-5 years - even s and s musical tones.

The hearing threshold also changes with age. For children 6-9 years old it is 17-24 dB, for 10-12 year olds it is 14-19 dB. The greatest hearing acuity is achieved by middle and high school age (14-19 years). For an adult, the hearing threshold is within 10-12 dB.

The sensitivity of the auditory analyzer to different frequencies varies at different ages. Children perceive better low frequencies than tall. In adults under 40 years of age, the highest threshold of hearing is observed at a frequency of 3000 Hz, in 40-50 years - 2000 Hz, after 50 years - 1000 Hz, and from this age the upper limit of perceived sound vibrations decreases.

The functional state of the auditory analyzer depends on the action of many factors environment. With special training you can increase its sensitivity. For example, music, dancing, figure skating, sports and rhythmic gymnastics develop fine hearing. On the other hand, physical and mental fatigue, high noise levels, sharp fluctuations temperature and pressure significantly reduce the sensitivity of the hearing organs.

Effect of noise on functional state body. Noises can affect the body in different ways. Specific action to one degree or another, manifested by hearing impairment, nonspecific - various kinds deviations from the central nervous system, autonomic reactivity, endocrine disorders, impaired functional state of the cardiovascular system and digestive tract.

Thus, it has been shown that in young and middle-aged people, exposure to noise with an intensity of 90 dB for an hour leads to a decrease in visual acuity, increases latent period visual and auditory analyzers, impairs coordination of movements. Children experience more sudden violations nervous processes in the cortex, the formation of extreme inhibition, headaches, insomnia, etc.

Greatest negative impact noise affects the fragile bodies of children and adolescents. Noise up to 40 dB does not affect the functional state of the central nervous system, and exposure to noise of 50 dB already causes an increase in the threshold of auditory sensitivity in students, a decrease in attention, as a result of which they make many mistakes when performing various tasks.

Teachers and parents should be aware that excessive noise can cause neuropsychiatric disorders in children and adolescents. And since children spend a significant part of their time at school, fulfilling hygiene measures noise reduction is a must.

General physiology of sensory systems

The sensory system (analyzer, according to I.P. Pavlov) is the part of the nervous system consisting of perceptive elements - sensory receptors, receiving stimuli from the external or internal environment, the neural pathways that transmit information from receptors to the brain, and those parts of the brain that process this information. Thus, sensory system enters information into the brain and analyzes it. The work of any sensory system begins with the perception by receptors of physical or chemical energy external to the brain, transforming it into nerve signals and transmitting them to the brain through chains of neurons. The process of transmitting sensory signals is accompanied by their repeated transformation and recoding and ends with higher analysis and synthesis (image recognition), after which the body’s response is formed.

Information entering the brain is necessary for simple and complex reflex acts, up to mental activity person. THEM. Sechenov wrote that “a mental act cannot appear in consciousness without external sensory stimulation.” Processing of sensory information may or may not be accompanied by awareness of the stimulus. If awareness occurs, we talk about sensation. Understanding sensation leads to perception.

I.P. Pavlov considered the analyzer to be a set of receptors (peripheral section of the analyzer), pathways of excitation (conducting section), as well as neurons that analyze the stimulus in the cerebral cortex (central section of the analyzer).

Methods for studying sensory systems

To study sensory systems, electrophysiological, neurochemical, behavioral and morphological studies on animals, psychophysiological analysis of perception in a healthy and sick person, methods of mapping his brain. Sensory functions are also simulated and prosthetic.

Modeling of sensory functions makes it possible to study, using biophysical or computer models, functions and properties of sensory systems that are not yet available to experimental methods. Prosthetics of sensory functions practically tests the truth of our knowledge about them. An example would be electrophosphene visual prostheses, which restore visual perception in blind people with various combinations of point electrical stimulation of the visual area of ​​the cerebral cortex.

General principles of the structure of sensory systems

Main general principles The structures of the sensory systems of higher vertebrates and humans are as follows:

1) multi-layering , i.e. presence of several layers nerve cells, the first of which is associated with receptors, and the latter with neurons of the motor areas of the cerebral cortex. This property makes it possible to specialize neural layers for processing different types sensory information, which allows the body to quickly respond to simple signals analyzed already at the first levels of the sensory system. Conditions are also created for selective regulation of the properties of neural layers through ascending influences from other parts of the brain;

2) multichannel sensory system, i.e. the presence in each layer of many (from tens of thousands to millions) of nerve cells connected with many cells of the next layer. The presence of many such parallel channels for processing and transmitting information provides the sensor system with accuracy and detail of signal analysis and greater reliability;

3) a different number of elements in adjacent layers, which forms “sensory funnels”. Thus, in the human retina there are 130 million photoreceptors, and in the layer of retinal ganglion cells there are 100 times fewer neurons (“tapering funnel”).

At the next levels visual system an “expanding funnel” is formed: the number of neurons in the primary projection area of ​​the visual cortex is thousands of times greater than the number of retinal ganglion cells. In the auditory and a number of other sensory systems, an “expanding funnel” runs from the receptors to the cerebral cortex. The physiological meaning of the “tapering funnel” is to reduce the redundancy of information, and the “expanding” funnel is to provide a detailed and complex analysis of various signal features; differentiation of the sensory system vertically and horizontally. Vertical differentiation consists of the formation of sections, each of which consists of several neural layers. Thus, the section is a larger morphofunctional formation than the layer of neurons. Each section (for example, the olfactory bulbs, the cochlear nuclei of the auditory system, or the geniculate bodies) performs a specific function. Horizontal differentiation is various properties receptors, neurons and connections between them within each layer. Thus, in vision there are two parallel neural channels running from the photoreceptors to the cerebral cortex and differently processing information coming from the center and from the periphery of the retina.

Basic functions of the sensor system

The sensor system performs the following main functions, or operations, with signals: 1) detection; 2) discrimination; 3) transmission and transformation; 4) coding; 5) feature detection; 6) pattern recognition. Detection and primary discrimination of signals is provided by receptors, and detection and identification of signals by neurons of the cerebral cortex. Transmission, transformation and coding of signals is carried out by neurons of all layers of sensory systems.

Signal detection. It begins in a receptor - a specialized cell, evolutionarily adapted to perceive a stimulus of a certain modality from the external or internal environment and transform it from a physical or chemical form into a form of nervous excitation.

Classification of receptors. In practical terms, the most important is the psychophysiological classification of receptors according to the nature of the sensations that arise when they are irritated. According to this classification, humans have visual, auditory, olfactory, taste, tactile receptors, thermo-, proprio- and vestibuloreceptors (receptors for the position of the body and its parts in space) and pain receptors.

There are external receptors (exteroceptors) and internal ones (interoreceptors). Exteroceptors include auditory, visual, olfactory, gustatory, and tactile. Interoreceptors include vestibulo- and proprioceptors (receptors of the musculoskeletal system), as well as visceroreceptors (signaling the state of internal organs).

Based on the nature of contact with the environment, receptors are divided into distant, receiving information at a distance from the source of stimulation (visual, auditory and olfactory), and contact - excited by direct contact with the stimulus (gustatory, tactile).

Depending on the nature of the stimulus to which they are optimally tuned, the receptors can be divided into photoreceptors, mechanoreceptors, which include auditory, vestibular receptors, and tactile skin receptors, musculoskeletal receptors, baroreceptors of the cardiovascular system; chemoreceptors, including taste and olfactory receptors, vascular and tissue receptors; thermoreceptors (skin and internal organs, as well as central thermosensitive neurons); pain (nociceptive) receptors.

All receptors are divided into primary-sensing and secondary-sensing. The first include olfactory, tactile and proprioceptors. They differ in that the transformation of the energy of irritation into the energy of a nerve impulse occurs in the first neuron of the sensory system. Secondary sensory receptors include taste, vision, hearing, and vestibular receptors. Between the stimulus and the first neuron there is a specialized receptor cell that does not generate impulses. Thus, the first neuron is not excited directly, but through a receptor (not nerve) cell.

General mechanisms of receptor excitation. When a stimulus acts on a receptor cell, the energy of external stimulation is converted into a receptor signal, or sensory signal transduction. This process includes three main steps:

1) stimulus interaction, i.e. molecules of an odorous or taste substance (smell, taste), a quantum of light (vision) or mechanical force (hearing, touch) with a receptor protein molecule, which is part of the cell membrane of the receptor cell;

Hearing is a human sense organ that contributes to the mental development of a full-fledged personality and its adaptation in society. Hearing is associated with sound language communication. With the help of an auditory analyzer, a person perceives and distinguishes sound waves consisting of successive condensation and rarefaction of air.

The auditory analyzer consists of three parts: 1) the receptor apparatus contained in the inner ear; 2) pathways represented by the eighth pair of cranial (auditory) nerves; 3) the hearing center in the temporal lobe of the cerebral cortex.

Auditory receptors (phonoreceptors) are contained in the cochlea of ​​the inner ear, which is located in the pyramid temporal bone. Sound vibrations, before reaching the auditory receptors, pass through the entire system of sound-conducting and sound-amplifying parts.

Ear - This is an organ of hearing that consists of 3 parts: the outer, middle and inner ear.

Outer ear consists of the auricle and outer ear canal. The outer ear is used to catch sounds. The auricle is formed by elastic cartilage and is covered with skin on the outside. At the bottom it is complemented by a fold - the lobe, which is filled with adipose tissue.

External auditory canal(2.5 cm), where sound vibrations are amplified by 2-2.5 times, is sent out by thin skin with fine hair and modified sweat glands that produce earwax, consisting of fat cells and containing pigment. Hairs and earwax play a protective role.

Middle ear consists of the eardrum, tympanic cavity and auditory tube. At the border between the outer and middle ear is the eardrum, which is covered externally by epithelium and internally by the auditory membrane. Sound vibrations that approach the eardrum cause it to vibrate at the same frequency. WITH inside the eardrum contains the tympanic cavity, inside which are located auditory ossicles, interconnected - hammer, anvil and stirrup. Vibrations from the eardrum are transmitted through the ossicular system to the inner ear. The auditory ossicles are placed so that they form levers that reduce the range of sound vibrations and increase their strength.

Tympanic cavity connected to the nasopharynx via the eustachian tube, which maintains equal pressure from the outside and inside on the eardrum.

At the junction of the middle and inner ear is a membrane that contains oval window. The stapes is adjacent to the oval window of the inner ear.

Inner ear is located in the cavity of the pyramid of the temporal bone and is a bone labyrinth, inside of which there is membranous labyrinth from connective tissue. Between the bony and membranous labyrinths there is a fluid - perilymph, and inside the membranous labyrinth - endolymph. In the wall separating the middle ear from the inner ear, in addition to the oval window, there is also a round window, which makes vibrations of the fluid possible.

Bone labyrinth consists of three parts: in the center - the vestibule, in front of it snail, and behind - semicircular canals. Inside the middle canal of the cochlea, the cochlear duct contains a sound-receiving apparatus - a spiral or Corti's organ. It has a main lamina, which consists of approximately 24 thousand fibrous fibers. On the main plate along it in 5 rows there are supporting and hair sensory cells, which are actually auditory receptors. The hairs of the receptor cells are washed by the endolymph and come into contact with the integumentary plate. The hair cells are covered by the nerve hairs of the cochlear branch of the auditory nerve. The medulla oblongata contains the second neuron of the auditory pathway; then this path goes, mostly crossing, to the posterior colliculus of the quadrigeminal, and from them to the temporal region of the cortex, where the central part of the auditory analyzer is located.

For the auditory analyzer, sound is an adequate stimulus. All vibrations of air, water and other elastic media are divided into periodic (tones) and non-periodic (noise). There are high and low tones. The main characteristic of each sound tone is the length of the sound wave, which corresponds to a certain number of vibrations per second. Sound wavelength determined by the distance that sound travels per second, divided by the number of complete vibrations carried out by the body that sounds, per second.

Human ear perceives sound vibrations within the range of 16-20,000 Hz, the strength of which is expressed in decibels (dB). Humans cannot hear sound vibrations with a frequency of more than 20 kHz. These are ultrasounds.

Sound waves- these are longitudinal vibrations of the medium. The strength of sound depends on the range (amplitude) of vibrations of air particles. The sound is characterized timbre or coloring.

The ear is most excitable to sounds with a frequency of oscillations from 1000 to 4000 Hz. Below and above this indicator, the excitability of the ear decreases.

In 1863 Helmholtz proposed resonance theory of hearing. Airborne sound waves entering the external auditory canal cause vibrations in the eardrum, which are then transmitted through the middle ear. The system of auditory ossicles, acting as a lever, amplifies sound vibrations and transmits them to the fluid contained between the bone and membranous labyrinths of the curls. Sound waves can also be transmitted through the air contained in the middle ear.

By resonance theory, vibrations of the endolymph cause vibrations of the main plate, the fibers of which have different lengths, tuned to different tones and constitute a set of resonators that sound in unison with different sound vibrations. The shortest waves are perceived at the base of the cochlea, and the long ones at the apex.

During the vibration of the corresponding resonating sections of the main plate, the sensitive hair cells located on it also vibrate. The smallest hairs of these cells touch when the integumentary plate oscillates and are deformed, which leads to excitation of the hair cells and conduction of impulses along the fibers of the cochlear nerve to the central nervous system. Since there is no complete isolation of the fibers of the main membrane, neighboring fibers begin to vibrate simultaneously, which corresponds to overtones. ABOUT Burton- a sound whose number of vibrations is 2, 4, 8, etc. times the number of vibrations of the fundamental tone.

With prolonged exposure to strong sounds, the excitability of the sound analyzer decreases, and with prolonged exposure to silence, excitability increases. This adaptation. The greatest adaptation is observed in the zone of higher sounds.

Excessive noise not only leads to hearing loss, but also causes mental disorders in people. Special experiments on animals have proven the possibility of the appearance "acoustic shock" and "acoustic snags", sometimes fatal.

6. Ear diseases and hearing hygiene. Prevention of the negative impact of “school” noise on the student’s body

Ear infection - otitis. The most common occurrence of otitis media is dangerous disease, because next to the middle ear cavity is the brain and its membranes. Otitis media most often occurs as a complication of influenza and acute respiratory diseases; an infection from the nasopharynx can pass through the Eustachian tube into the middle ear cavity. Otitis occurs as a serious disease and manifests itself severe pain in the ear, high temperature body, severe headache, significant hearing loss. If these symptoms occur, you should immediately consult a doctor. Prevention of otitis: treatment of acute and chronic diseases of the nasopharynx (adenoids, runny nose, sinusitis). If you have a runny nose, you should not blow your nose too much so that the infection gets into the middle ear through the Eustachian tube. You cannot blow your nose with both halves of your nose at the same time, but you must do this alternately, pressing the wing of the nose to the nasal septum.

Deafness- total loss hearing in one or both ears. It can be acquired or congenital.

Acquired deafness most often it is a consequence of bilateral otitis media, which was accompanied by rupture of both eardrums or severe inflammation of the inner ear. Deafness can be caused by severe degenerative lesions of the auditory nerves, which are often associated with occupational factors: noise, vibration, exposure to vapors chemical substances or with head injuries (for example, as a result of an explosion). Common cause deafness is otosclerosis- a disease in which the auditory ossicles (especially the stapes) become immobile. This disease was the cause of deafness in the outstanding composer Ludwig Van Beethoven. Deafness can be caused by uncontrolled use of antibiotics, which have a negative effect on the auditory nerve.

Congenital deafness associated with congenital hearing loss. the reasons for which may be viral diseases mother during pregnancy (rubella, measles, influenza), uncontrolled use of certain medications, especially antibiotics, use of alcohol, drugs, smoking. A child born deaf, never hearing speech, becomes deaf and mute.

Hearing hygiene- a system of measures aimed at protecting hearing, creating optimal conditions for the activity of the auditory analyzer, contributes to its normal development and functioning.

Distinguish specific and nonspecific the effect of noise on the human body. Specific action manifests itself in hearing impairment varying degrees, nonspecific- in various deviations in the activity of the central nervous system, disorders of autonomic reactivity, endocrine disorders, functional state of the cardiovascular system and digestive tract. In young and middle-aged people, at a noise level of 90 dB (decibels), which lasts for an hour, the excitability of cells in the cerebral cortex decreases, coordination of movements, visual acuity, stability of clear vision worsen, and the latent period of visual and auditory-motor reactions lengthens. For the same duration of work under conditions of exposure to noise, the level of which is 96 dB, even more dramatic disturbances in cortical dynamics, phase states, extreme inhibition, and disorders of autonomic reactivity are observed. Indicators of muscle performance (endurance, fatigue) and labor indicators deteriorate. Working in conditions of exposure to noise, the level of which is 120 dB, can cause disturbances in the form of asthenic and neurasthenic manifestations. Irritability, headaches, insomnia, and disorders appear endocrine system. Changes are taking place in cardiovascular system: vascular tone and heart rate are disrupted, blood pressure increases or decreases.

On adults and especially children it is extremely Negative influence(non-specific and specific) produces noise in rooms where radios, televisions, tape recorders, etc. are turned on at full volume.

Noise has a strong impact on children and adolescents. Changes in the functional state of the auditory and other analyzers are observed in children under the influence of “school” noise, the intensity level of which in the main premises of the school ranges from 40 to 110 dB. In the classroom, the noise intensity level is on average 50-80 dB, during breaks it can reach 95 dB.

Noise that does not exceed 40 dB does not cause negative changes in the functional state of the nervous system. Changes are noticeable when exposed to noise levels of 50-60 dB. According to research data, solving mathematical problems at a noise volume of 50 dB requires 15-55%, 60 dB - 81-100% more time than when exposed to noise. The weakening of the attention of schoolchildren under conditions of exposure to noise of the specified volume reached 16%. Reducing the levels of “school” noise and its adverse effects on the health of students is achieved through a number of complex measures: construction, technical and organizational.

Thus, the width of the “green zone” on the street side should be at least 6 m. It is advisable to plant trees along this strip at a distance of at least 10 m from the building, the crowns of which will delay the spread of noise.

Important in reducing “school” noise has a hygienically correct location of classrooms in the school building. Workshops and gyms are located on the ground floor in a separate wing or annex.

The dimensions of classrooms must meet hygienic standards aimed at preserving the vision and hearing of students and teachers: length (size from the board to the opposite wall) and depth of classrooms. The length of the classroom, not exceeding 8 m, provides students with normal visual and hearing acuity, who sit on the last desks, a clear perception of the teacher’s speech and a clear vision of what is written on the board. The first and second desks (tables) in any row are reserved for students with impaired hearing, since speech is perceived from 2 to 4 m, and whisper - from 0.5 to 1 m. Restore the functional state of the auditory analyzer and prevent changes in others physiological systems Short breaks (10-15 minutes) help the teenager’s body.

Subject. The structure of the auditory sensory system

The presence in crystals of misoriented regions (blocks), rotated relative to each other at small angles, was noted in early studies of crystals. Soon after the discovery of X-ray diffraction by crystals, it was established that the crystal did not have an ideal structure: the diffracted beams, contrary to theory, propagated over angles of the order of not several seconds, but several minutes, and had an intensity two orders of magnitude higher than the calculated value. We had to assume the presence of small (about 1 μm in diameter) weakly misoriented blocks in the mosaic crystal. This phenomenon began to be called blockiness, or mosaicism of crystal structures (Fig. 14.14).

edges DE and EF. All extra planes end inside the bicrystal in a single damaged region, i.e. at the block boundary. The end of each broken plane forms an edge dislocation, so that the entire block boundary appears as a vertical row of edge dislocations. The misorientation angle of the blocks is determined by the ratio of the Burgers vector b to the distance h between dislocations in the boundary

This boundary is called the “slope boundary.” Its model can be a series of dislocations parallel to the rotation axis, having a Burgers vector along the normal to the boundary and located along the boundary.

Mosaic blocks are an example of three-dimensional (volumetric) defects in the crystal structure. The practical importance in studying the causes of formation and features of the mosaic phenomenon lies in the fact that significant mechanical stresses arise at the boundaries of mosaic blocks in crystals, which in some cases is undesirable.

Subject. The structure of the auditory sensory system

Questions:

2. Eardrum. Structure, meaning, age characteristics.

5. Characteristics of the conductive and cortical sections of the auditory analyzer. Their meaning.

1. External ear: auricle, external auditory canal. Structure, meaning, age characteristics.

The auditory sensory system consists of 3 sections:

Peripheral,

Conductor,

Cortical.

The peripheral section is represented by the outer, middle, and inner ear (Figure 1).

Figure 1. Structure of the ear

Outer ear consists of the auricle and the external auditory canal.

1. The auricle consists of elastic cartilage covered with skin. This cartilage is especially dermal in a child, so even minor blows to the ear can lead to the formation of a hematoma, followed by its suppuration and deformation of the shell. Cartilage has many curls and grooves - this is due to its protective function. The ear has a funnel-shaped shape, which helps to capture sounds and localize them in space. There is no cartilage in the lower part of the auricle - the ear point. It consists entirely of fatty tissue. The size of the auricle, its shape, the level of attachment to the head is individual for each person (inherited genetically). However, the characteristic structure of the auricle in children is excellent ( hereditary diseases, Down's disease). The auricle is attached to the head with the help of muscles and ligaments, and the muscles that move the auricle are rudimentary (underdeveloped).

2. The external auditory canal begins with a depression in the center of the auricle and is directed deep into the temporal bone, ending with the eardrum. That. The eardrum does not belong to either the outer or the middle ear, but only separates them. In adults, the external auditory canal is 2.5-3 cm long. In children, it is shorter due to underdevelopment of the bone section. In a newborn, the ear canal looks like a gap and is filled with exfoliated epithelial cells. Only by 3 months is this passage completely cleared. The outer ear in its parameters approaches the ear of an adult = 12 years. Its lumen becomes oval, and the diameter is 0.7-1 cm. The normal ear canal consists of 2 parts:

External part(membranous-cartilaginous) - is a continuation of the ear cartilage.

The inner part (bone) fits tightly to the eardrum. The peculiarity of the structure is that the narrowest section of the external passage is located at the transition of one part to another. Therefore, this is the favorite place for the formation of sulfur plugs. The skin of the external auditory canal contains hairs and sulfur glands that produce sulfur.

The reason for the formation of sulfur plugs:

1. excess sulfur production;

2. change in the properties of sulfur ( increased viscosity);

3. anatomical (congenital) narrowness and curvature of the external auditory canal.

The external auditory canal has 4 walls. Its anterior wall is adjacent to the head mandibular joint, therefore, when hitting the chin, the head of the mandibular joint of the external auditory canal is injured and bleeding occurs.

2. Eardrum. Structure, meaning, age characteristics

The eardrum separates the outer ear from the middle ear. It is a thin but elastic membrane 0.1 mm thick, diameter 0.8-1 cm. The eardrum has 3 layers:

1. cutaneous (epidermal);

2. connective tissue;

3. slimy.

The first layer is a continuation of the skin of the external auditory canal. The second layer consists of densely interwoven circular and radial fibers. The third layer is a continuation of the mucous membrane of the tympanic cavity.

The handle of the hammer is attached to the center of the eardrum. This place is called the navel. The eardrum has 3 layers only in the outer part. In its second part, relaxed, it has only 2 layers without a middle one. Examination of the eardrum is called otoscopy. Upon examination, a healthy membrane has a pearly white color, a cone shape, with its convexity facing inward, i.e. in ear.

Figure 2. Structure of the eardrum

3. Middle ear: tympanic cavity, auditory ossicles, auditory muscles, auditory tube, mastoid process. Structure, meaning.

The middle ear consists of:

The tympanic cavity contains the auditory ossicles, auditory muscles and eustachian tubes;

Cells of the air mastoid process;

The tympanic cavity has the shape of a hexagon:

A/ top wall tympanic cavity - roof. In small children it has a hole. Therefore, very often in children purulent otitis complicated by breakthrough of pus on meninges(purulent meningitis);

b/ the lower wall - the bottom, has a hole, which can lead to the breakthrough of infection into the blood, into the bloodstream. Since the lower wall is located above the bulb jugular vein. This can lead to complications (ontogenic sepsis);

c/ front wall. On the front wall there are holes - the entrance to the Eustachian tube;

g/ back wall. The entrance to the mastoid cave is located on it. The posterior wall of the tympanic cavity is a bony plate that separates the middle ear from the inner ear. There are 2 openings on it: one of them is called the oval and round window. The oval window is closed by a stirrup. The round window is covered by a secondary tympanic membrane. A bone canal passes through the posterior wall facial nerve. With inflammation of the middle ear, the infection can spread to this nerve, causing neuritis of the facial nerve, and as a result, facial distortions.

The auditory ossicles are connected in a certain sequence:

hammer, anvil, stirrup.

Figure 3. Structure of the auditory ossicles

The handle of the malleus connects to the center of the eardrum. The head of the malleus is connected by a joint to the body of the incus. The footplate of the stapes is inserted into the oval window, which is located on the bony wall of the inner ear. That. Vibrations from the eardrum are transmitted through the ossicular system to the inner ear. The auditory ossicles are suspended in the tympanic cavity by ligaments. In the middle ear cavity there are auditory muscles (2 of them):

The muscle that tightens the eardrum. She belongs protective function. It protects the eardrum from damage due to strong irritants. This is due to the fact that when this muscle contracts, the movement of the eardrum is limited.

Stapes muscle. It is responsible for the mobility of the stapes in the oval window, which has great importance to conduct sounds into the inner ear. It has been established that when the oval window is blocked, deafness develops.

Auditory "Eustachian" tube. This is a paired formation that connects the nasopharynx and the middle ear cavity. The entrance to the Eustachian tube is located on back wall tympanic cavity. The Eustachian tube consists of 2 sections: bony (1/3 of the tube), membranous (2/3 of the tube). The bony section communicates with the tympanic cavity, and the membranous section communicates with the nasopharynx.

The length of the auditory tube in an adult = 2.5 cm, diameter = 2-3 mm. In children it is shorter and wider than in adults. This is due to underdevelopment bone bone auditory tube. Therefore, in children, the infection can easily pass from the eardrum to the mucous membrane of the auditory tube and nasopharynx, and vice versa, from the nasopharynx to the middle ear. Therefore, children often suffer from otitis media, the source of which is inflammatory process in the nasopharynx. The auditory tube performs a ventilation function. It has been established that in calm state its walls are adjacent to each other. The opening of the tubes occurs during swallowing and yawning. At this moment, air from the nasopharynx enters the middle ear cavity - the drainage function of the pipe. It is the tube that facilitates the outflow of pus or other exudate from the middle ear cavity during inflammation. If this does not happen, the infection may break through the roof onto the meninges, or the eardrum may rupture (perforation).

Figure 4 - Structure of the middle ear.

Air cells of the mastoid process.

The mastoid process is located in the hairless space behind the auricle. When cut through, the mastoid process resembles “porous chocolate.” The largest air cell of the mastoid bone is called the cave. A newborn already has it. It is lined with mucous membrane, which is a continuation of the mucous membrane of the tympanic cavity. Due to the connection of the cave and the tympanic cavity, the infection can pass from the middle ear to the cave, and then to the bone substance of the mastoid process, causing its inflammation - mastoiditis.

4. Inner ear: bony and membranous labyrinth. Organ of Corti, structure, meaning.

The inner ear (labyrinth) consists of 2 parts: the bony and membranous labyrinths. Between them there is a perilymphotic space, which is filled with ear fluid - perilymph. Inside the membranous labyrinth there is also lymph - endolymph. That. In the inner ear there are 2 ear fluids that differ in composition and function. Perilymph - in its composition resembles cerebrospinal fluid, but contains more protein and enzymes. Its main function is to bring the main membrane into an oscillatory state. Endolymph is similar in composition to intracellular fluid. It contains a lot of soluble oxygen, and therefore serves as a nutrient medium for the organ of Corti.

The labyrinth has 3 sections: the vestibule, semicircular canals, and cochlea. The vestibule and semicircular canals belong to the vestibular apparatus. The cochlea belongs to the auditory sensory system. It is shaped like garden snail, is formed by a spiral channel, which is rounded by 2.5 turns. The diameter of the canal decreases from the base to the apex of the cochlea. In the center of the cochlea there is a spiral ridge, around which a spiral plate is twisted. This plate protrudes into the lumen of the spiral channel. In cross-section, this channel has the following structure: two membranes, the main one and vestibular apparatus is divided into 3 parts, forming the cochlear entrance in the center. The upper membrane is called the vestibular membrane, the lower - the main one. On the basilar membrane, the peripheral receptor of the ear is the organ of Corti. Thus, the organ of Corti is located in the cochlear duct, on the main membrane.

The main membrane is the most significant wall of the cochlear duct and consists of many stretched strings, which are called auditory strings. It has been established that the length of the strings and their degree of tension depend on which turn of the cochlea they are located on. There are 3 curls of the cochlea:

main (lower), middle, upper. It has been established that in the lower helix there are short and tightly stretched strings. They resonate to high sounds. On the upper curl there are long and loosely stretched strings. They resonate to low sounds.

The organ of Corti is a peripheral hearing receptor. Consists of 2 types of cells:

1. Support cells (pillar cells) - have an auxiliary value.

2. Hair (external and internal). In them, the transformation of sound energy into the physiological process of nervous excitation occurs, i.e. formation of nerve impulses.

The supporting cells are located at an angle to each other, forming a tunnel. In it, in one row, the inner hair cells are located. By their function, these cells are secondary sensory. Their head end is rounded and has hairs. The hairs are covered on top by a membrane called the integumentary membrane. It has been established that when the integumentary membrane is displaced relative to the hairs, ionic currents arise.

Figure 5 – Structure of the inner ear.

Sound signals (sound emissions) external environment(mainly air vibrations with different frequencies and force), including speech signals. This function is implemented with the participation of the most important component, which has gone through a complex path of evolution.

The auditory sensory system consists of the following sections:

• the peripheral section, which is a complex specialized organ consisting of the outer, middle and inner ear;
• conduction section - the first neuron of the conduction section, located in the spiral ganglion of the cochlea, receives from the receptors of the inner ear, from here information comes through its fibers, i.e. auditory nerve(included in 8 pairs of cranial nerves) to the second neuron in the medulla oblongata and after decussation, some of the fibers go to the third neuron in the posterior colliculus, and some to the nuclei - the internal geniculate body;
• cortical section - represented by the fourth neuron, which is located in the primary (projective) auditory field and the cortical area and ensures the occurrence of sensation, and more complex processing of sound information occurs in the nearby secondary auditory field, which is responsible for the formation of perception and recognition of information. The information received enters the tertiary field of the lower parietal zone, where it is integrated with other forms of information