Biology presentation - auditory analyzer. Age features of the auditory sensory system

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Due to the fact that the functional significance of the auricle is small, all its diseases, as well as damage and developmental anomalies, up to its complete absence, do not entail a significant hearing impairment and are mainly only cosmetic.

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Another thing is the external auditory meatus. Any processes that entail the closure of its lumen, thereby lead to a violation of air sound transmission, which in turn is accompanied by a significant decrease in hearing.

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A) Atresia of the external auditory canal. Occurs rarely. Atresia is a complete infection. Congenital atresia of the external auditory canal usually occurs simultaneously with an anomaly in the development of the auricle, most often with its underdevelopment. Causes of atresia: Chronic diffuse inflammation of the walls of the passage. Such inflammation can be primary, when the inflammatory process occurs due to the introduction of an infection from the outside (for example, when scratching or picking contaminated objects in the ear), or secondary, when inflammation develops as a result of prolonged irritation of the skin of the external auditory canal with pus flowing from the middle ear. The consequence of scarring of the walls of the passage after an injury (blow, bruise, gunshot wound) or burn. 2. Pathology of the ear canal

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In all cases, only a complete infection of the external auditory canal leads to a significant and persistent hearing loss. With incomplete overgrowth, when there is at least a narrow gap in the ear canal, hearing usually does not suffer; dysfunction in these cases (with incomplete fusions) occurs only as a result of a simultaneously existing pathological process in the middle or inner ear. In the presence of a purulent process in the middle ear, a sharp narrowing of the external auditory canal is of great danger, since it prevents the outflow of pus from the middle ear and can contribute to the transition of purulent inflammation to deeper parts (inner ear, meninges).

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With atresia of the external auditory canal, hearing loss is in the nature of damage to the sound-conducting apparatus, that is, the perception of low sounds suffers mainly; the perception of high tones is preserved, bone conduction remains normal or even improves somewhat. Treatment of atresia of the external auditory canal can only consist in the artificial restoration of the lumen through plastic surgery.

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B) Sulfur plug.

When describing the diseases of the external ear, it is necessary to dwell on one pathological process, which, although it does not lead to a persistent hearing loss, often causes great anxiety in the patient himself and in his relatives. We are talking about the so-called sulfur plug. Under normal conditions, earwax, mixing with dust particles that enter the external auditory canal from the outside air, turns into crumb-like lumps, which imperceptibly, usually at night when lying on your side, are released from the ear or accumulate at the entrance to the external auditory canal and are removed when washing. . In some children, this process of self-cleaning of the ears from wax is impaired and the wax accumulates in the external auditory canal.

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1) increased function of the sulfur glands (usually as a result of irritation of the skin of the ear canal); 2) narrowness and abnormal curvature of the external auditory canal, making it difficult to remove sulfur to the outside; 3) the chemical properties of sulfur: its increased viscosity, stickiness, which contributes to the adhesion of sulfur to the walls of the ear canal. Reasons for the formation of sulfur plug:

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Gradually accumulating, sulfur forms a plug that fills the lumen of the external auditory canal. The accumulation of sulfur is very slow and imperceptible to the patient. As long as there is at least a narrow gap between the cork and the wall of the ear canal, hearing is not impaired. However, it is worth getting a drop of water into the ear under these conditions, as sulfur swells and closes this gap. Complaints of patients in these cases are very characteristic: suddenly, in the midst of complete well-being, after swimming in the river or washing in the bath, deafness occurred in one, and sometimes in both ears, there was noise in the ear and in the head, a distorted perception of one's own voice, which became resonate in the blocked ear and cause an unpleasant sensation.

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The formation of sulfur plugs is often observed in children. Treatment for sulfur plugs is very simple: after preliminary softening with special drops, the plug is removed by washing the ear with warm water from a special syringe. Such washing can only be performed by a doctor or a specially trained paramedical worker (nurse, paramedic). Any attempts to independently remove sulfur plugs using all kinds of sticks, spoons, hairpins, etc. are unacceptable.

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B) Foreign bodies

Foreign bodies in the ear are most often found in children who, out of prank, put various small objects into their ears: peas, cherry pits, seeds, beads, ears of cereal, etc. In adults, who have the habit of scratching and picking in their ears, fragments of a pencil are often found, matches, branches and other items. Sometimes cotton balls are left in the ear and pushed into the depths, put by some to prevent colds. In the summer, while sleeping outdoors, small insects sometimes crawl into the ear, which can cause great anxiety and sometimes severe pain with their movements and irritation of the eardrum. You should know that the danger is not so much the presence of a foreign body in the ear as unsuccessful attempts to remove it. In no case should one be tempted by the apparent accessibility of a foreign body and try to remove it with tweezers, head pins or other improvised items. All such attempts, as a rule, end with pushing the foreign body deep and driving it into the bone part of the auditory canal, from where the foreign body can be removed only by a rather serious surgical intervention. There are cases when, with inept attempts to remove a foreign body, it was pushed into the middle ear with a rupture of the tympanic membrane, dislocation of the auditory ossicles, and even the development of inflammation of the meninges.

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Pre-hospital measures when a foreign body enters the ear canal

It must be remembered that the presence of a foreign body in the ear, even for several days, cannot cause harm, so a child with a foreign body should be taken to a specialist doctor as soon as possible. Pre-hospital measures may include the following: 1) killing of live foreign bodies by letting a few drops of any pure liquid oil (in a warm form) into the ear; 2) with swelling foreign bodies (peas, beans, etc.) - infusion of warm alcohol into the ear in order to cause wrinkling of the foreign body; 3) with non-swelling bodies (beads, pebbles, cherry pits), as well as living foreign bodies - careful washing of the ear with warm boiled water from an ordinary rubber syringe. If you suspect a perforation of the eardrum, washing is not performed.

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Isolated diseases, injuries and abnormal development of the tympanic membrane are rare. Congenital underdevelopment or absence of the tympanic membrane usually accompanies congenital atresia of the external auditory canal. Underdeveloped in these cases are also the tympanic cavity, auditory ossicles, muscles of the middle ear, etc. 3. Diseases of the tympanic membrane

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Perforation is a violation of its integrity, which occurs as a result of mechanical action, pressure difference inside and outside the tympanic cavity, and an inflammatory process. Damage to the eardrum, accompanied by its perforation, is observed when picking in the ear with hairpins, matches and other objects, as well as in inept attempts to remove a foreign body from the external auditory canal. Tympanic membrane ruptures often occur with rapid fluctuations in atmospheric pressure. In wartime, eardrum ruptures most often occur with air concussion as a result of loud sounds from the explosions of artillery shells, aerial bombs, mines, hand grenades, and also shots fired near the ear.

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Violation of the integrity of the tympanic membrane, while the remaining parts of the auditory organ are intact, has relatively little effect on the auditory function (in this case, only the transmission of low sounds suffers). The main danger in perforations and ruptures of the tympanic membrane is the possibility of infection entering the tympanic cavity with the subsequent development of purulent inflammation of the middle ear. Therefore, in case of ear injuries accompanied by a rupture of the eardrum, it is impossible to wash the ear, it should be closed with sterile cotton wool.

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Inflammatory diseases of the eardrum in an isolated form are almost never observed. Most often they occur as secondary changes in inflammatory processes in the middle ear.

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Diseases of the middle ear

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Diseases of the middle ear are considered very common in all age groups, especially in childhood. With an unfavorable course, these diseases often lead to a persistent hearing loss, sometimes reaching a sharp degree. Due to the anatomical and physiological connection of the middle ear with the inner and its topographic proximity to the meninges, inflammatory processes in the middle ear can cause severe complications in the form of a disease of the inner ear, meninges and the brain itself.

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There are two main forms of inflammatory processes in the middle ear - it is catarrhal and purulent.

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Inflammatory processes in the nasopharynx that occur with a runny nose, flu, tonsillitis and other diseases can spread to the auditory tube and cause its lumen to close due to inflammatory swelling of the mucous membrane. Closure of the lumen of the auditory tube can also occur with adenoid growths in the nasopharynx. Blockage of the auditory tube leads to the cessation of air flow into the tympanic cavity. The air in the middle ear is partially absorbed by the mucous membrane (due to the absorption of oxygen by capillary vessels), so that the pressure in the tympanic cavity decreases, and the tympanic membrane, due to the predominance of external pressure, is drawn inward. The rarefaction of air in the tympanic cavity also leads to the leakage of blood plasma from the vessels of the mucous membrane and to the accumulation of this fluid in the tympanic cavity (secretory otitis media). This fluid sometimes becomes viscous due to the formation of a large amount of protein in it, or acquires a hemorrhagic character. Therefore, chronic catarrhal inflammation of the middle ear is described under the names of mucosal otitis, "sticky" ear, "blue" ear.

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Connective tissue bridges are sometimes formed between the tympanic membrane and the walls of the tympanic cavity. As a result of impaired mobility of the tympanic membrane, hearing loss occurs, noise in the ear appears. Acute catarrh of the middle ear in the absence of timely and proper treatment can become chronic. Chronic catarrhal inflammation of the middle ear can develop without a previous acute one, namely, with chronic inflammatory processes in the nasopharynx and with adenoids. In these cases, the process in the middle ear develops slowly, gradually and becomes noticeable to the patient and others only when the hearing loss reaches a significant degree. Sometimes patients note some improvement in hearing, usually in dry weather, and, conversely, hearing loss in wet weather and during a runny nose.

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Catarrh of the middle ear is especially often observed in children of preschool and primary school age as one of the main causes of persistent hearing impairment that occurs at this age. The main role in its occurrence in children is played by adenoid growths in the nasopharynx.

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Treatment is reduced to restoring the patency of the auditory tube. To do this, first of all, it is necessary to eliminate the reasons that caused its closure. The nose and nasopharynx are treated, in the presence of adenoid growths, they are removed. In a number of cases, these measures already lead to an improvement in the patency of the Eustachian tube and to the restoration or improvement of hearing; but often, especially with prolonged catarrhs, one has to resort to special ear treatment - blowing, massage, physiotherapy. The ear is blown out using a special rubber balloon. Air is blown into the auditory tube through the corresponding half of the nasal cavity. Blowing helps to restore the patency of the auditory tube and leads to pressure equalization in the middle ear.

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Sometimes parents and caregivers fear a child's hearing loss as a result of blowing out their ears. This fear is unfounded, since blowing out the ear, performed in the presence of appropriate indications, not only does not impair hearing, but, on the contrary, leads to an improvement or restoration of hearing, however, sometimes not immediately after the first blowing, but only after several such procedures. In some cases (in the presence of persistent retraction of the tympanic membrane), in addition to blowing, a pneumatic massage of the tympanic membrane is performed: using a special device, rarefaction and condensation of air in the external auditory canal are caused, as a result of which the mobility of the tympanic membrane is restored. Pneumomassage of the right tympanic membrane with a pneumatic funnel Sigle APMU - "Compressor". Apparatus for pneumomassage of the tympanic membrane of the ear

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To accelerate the resorption of the inflammatory swelling of the mucous membrane of the auditory tube, various physiotherapeutic procedures are used. In cases of a persistent process, in the absence of the effect of conservative treatment, and also if the function of the auditory tube is not restored after adenomia, operations are also currently performed. The tympanic membrane is dissected and a shunt is inserted into the hole. There is a possibility of outflow from the tympanic cavity and the impact on its mucous membrane by administering drugs. After 2-3 months. the shunt is removed, the hole closes on its own.

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Acute purulent inflammation of the middle ear (acute purulent otitis media).

Acute inflammation of the middle ear occurs mainly due to the passage of infection from the nose and nasopharynx through the auditory tube into the tympanic cavity. Most often, acute otitis media develops in acute infectious diseases - influenza, tonsillitis, measles, scarlet fever, etc. More rare ways for infection to enter the middle ear is the penetration of microbes from the outer ear through a damaged eardrum and the introduction of pathogens from other organs through the blood vessels.

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Symptoms of acute inflammation of the middle ear are earache, hearing loss; usually elevated temperature. The pain in the ear can be very sharp, sometimes it becomes unbearable. It is explained by the accumulation of inflammatory fluid in the tympanic cavity and its pressure on the tympanic membrane, which has a very high sensitivity. The inflammatory process usually also captures the tympanic membrane, its tissues loosen, and under the influence of pus pressure, perforation of the tympanic membrane occurs. After a breakthrough, the fluid that has accumulated in the tympanic cavity receives a free outflow to the outside, and in connection with this, the pain in the ear usually subsides immediately, the temperature drops.

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Sometimes, with a mild degree of inflammation, recovery occurs without perforation of the eardrum. The inflammatory fluid in these cases is partially absorbed by the mucous membrane of the tympanic cavity, partially poured out through the auditory tube into the nasopharynx. If independent perforation of the eardrum does not occur, and the patient's condition does not improve, the pain in the ear does not subside or even increases, the temperature does not decrease, then the doctor makes an incision in the eardrum (paracentesis), after which discharge from the ear usually immediately appears and the patient's condition quickly is improving.

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Discharge from the ear is at first liquid, sanious, then becomes mucous, stretches when rubbing the ear in the form of threads, then acquires a purulent character and becomes thick, sometimes creamy. Pus in acute otitis media has no odor. With modern methods of treatment, most often acute inflammation of the middle ear is cured. The duration of the disease usually does not exceed three to four weeks. The amount of secretions gradually decreases, then the suppuration stops, the hole in the tympanic membrane closes with a tender scar, hearing is restored.

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Acute otitis media in children is observed much more often than in adults, since it very often complicates all childhood infectious diseases (measles, scarlet fever, whooping cough, mumps, rubella, etc.). Middle ear disease in infants is facilitated by constant lying on the back, which facilitates the flow of mucus and pus from the nose into the nasopharynx, as well as the presence of a short and wide auditory tube. In infancy, otitis occurs most often with influenza, while other infections are complicated by otitis media, usually in preschool and early school age. In preschoolers and younger schoolchildren, adenoid growths in the nasopharynx often contribute to the development of inflammation of the middle ear.

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In infants, acute otitis media may go unnoticed by others until a leak appears from the diseased ear. However, with careful observation of the child's behavior, one can notice some characteristic signs of the disease: the child becomes restless, does not sleep well, cries out during sleep, turns his head, sometimes grabs his sore ear with his hands. Due to increased pain in the ear when swallowing and sucking, the child stops sucking or refuses the breast and nipple. Sometimes it is noted that the child is more willing to suckle the breast corresponding to his healthy ear (for example, with right-sided otitis - the left breast): apparently, when lying on the side of the diseased ear, sucking and swallowing are less painful.

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The temperature in children, especially young children, is often very high - reaches 40 ° and above. Often in children with acute otitis media, symptoms of irritation of the meninges are observed - vomiting, convulsions, tilting the head. After perforation of the eardrum or paracentesis, these phenomena usually disappear. Acute inflammation of the middle ear - otitis media (from the Greek. otos - ear) is a very serious disease, so at the first of its symptoms, you must contact a specialist in ear diseases and strictly follow the doctor's instructions about the regimen and treatment.

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Chronic purulent inflammation of the middle ear (chronic otitis media). Acute inflammation of the middle ear in most cases ends, as already mentioned, within 3-4 weeks of recovery. However, often under adverse conditions, acute otitis media takes a protracted course and becomes chronic: the perforation of the eardrum remains persistent, the inflammatory process in the middle ear does not end, suppuration from the ear sometimes continues continuously for many years or periodically resumes, hearing remains reduced and even gradually worsens. The transition of acute otitis into a chronic form is facilitated by the severity of the infection and the weakened general condition of the body. An important role in maintaining the inflammatory process in the middle ear is played by diseases of the nose and nasopharynx: chronic runny nose, polyps, adenoid growths, etc.

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There are two forms of chronic suppurative otitis media. In the first form (mesotympanitis), the inflammatory process is limited only to the mucous membrane of the middle ear, without moving to the bone walls of the tympanic cavity. This form is characterized by a benign course and, as a rule, does not give complications. Pus with benign otitis media usually has no smell, and if a bad smell appears, it is only due to poor care, when pus lingers in the ear, mixes with the sloughing elements of the skin and undergoes putrefactive decomposition. In the second form (epithympanitis), the inflammatory process passes to the bone walls of the tympanic cavity, causes the so-called carnivore, i.e., necrosis (necrosis) of bone tissue, growth of granulation and polyps and is accompanied by the release of pus with a sharp putrefactive odor.

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With careful care and careful treatment, chronic suppurative otitis media can end in recovery. However, only in a very limited number of cases can a real recovery be achieved, that is, the healing of the eardrum and the restoration of hearing. In most cases, recovery is relative: the suppuration stops, but the perforation of the eardrum remains. Scars often form in the tympanic cavity, which limit the mobility of the auditory ossicles. At the same time, hearing not only does not improve, but sometimes even worsens. Despite the relativity of such a recovery, it is still a favorable outcome of chronic purulent otitis media, since the elimination of a purulent focus in the ear protects the patient from dangerous complications.

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However, it must be remembered that the presence of a perforated tympanic membrane poses a constant threat of a new outbreak of inflammation due to the possibility of a new infection penetrating through the external auditory canal. Of particular danger is the ingress of contaminated water into the middle ear; therefore, all patients with perforation of the eardrum should be warned about the need to plug their ears with cotton, lubricated or soaked in some kind of fat (vaseline, petroleum jelly or other liquid oil) when washing their hair and when bathing. Earplugs

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Diseases of the inner ear

Isolated diseases of the labyrinthine fluid or the main membrane are almost never found, and are usually accompanied by a violation of the functions of the organ of Corti as well; therefore, almost all diseases of the inner ear can be attributed to the defeat of the sound-perceiving apparatus. Wardenburg's syndrome The most common are a wide protruding bridge of the nose (75%), fused eyebrows (50%), heterochromia of the irises (45%), sensorineural deafness due to hypoplasia of the organ of Corti (20%), a white strand of hair above the forehead (17-45%), areas of depigmentation on the skin and fundus.

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Defects and damage to the inner ear.

Congenital defects include anomalies in the development of the inner ear, for example, the complete absence of the labyrinth or the underdevelopment of its individual parts. In most congenital defects of the inner ear, underdevelopment of the organ of Corti is noted, and it is precisely the specific terminal apparatus of the auditory nerve, the hair cells, that is undeveloped. In place of the organ of Corti, in these cases, a tubercle is formed, consisting of nonspecific epithelial cells, and sometimes this tubercle does not exist, and the main membrane turns out to be completely smooth. In some cases, underdevelopment of hair cells is noted only in certain parts of the organ of Corti, and in the rest of the length it suffers relatively little. In such cases, it may be partially preserved auditory function in the form of islands of hearing. Usher syndrome congenital sensorineural deafness and retinitis pigmentosa is a combination of congenital sensorineural hearing loss, slowly progressive pigmentary degeneration of the retina (onset in the first or second decade of life) and vestibular disorders. Additional signs: glaucoma, cataract, nystagmus, macular degeneration, mental retardation, psychosis.

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Causes of congenital pathologies

In the occurrence of congenital defects in the development of the auditory organ, all kinds of factors that disrupt the normal course of development of the embryo are important. These factors include the pathological effect on the fetus from the mother's body (intoxication, infection, injury to the fetus). A certain role can be played by hereditary predisposition.

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Inner ear damage

occur during childbirth, for example, as a result of compression of the fetal head by narrow birth canals or a consequence of the imposition of obstetric forceps during pathological childbirth. sometimes observed in young children with bruises of the head (fall from a height); at the same time, hemorrhages in the labyrinth and displacement of individual sections of its contents are observed. Sometimes in these cases, both the middle ear and the auditory nerve can also be damaged at the same time. The degree of hearing impairment in the case of injuries of the inner ear depends on the extent of the damage and can vary from partial hearing loss in one ear to complete bilateral deafness.

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Inflammation of the inner ear (labyrinthitis)

occurs in three ways: due to the transition of the inflammatory process from the middle ear; due to the spread of inflammation from the meninges due to the introduction of infection by blood flow (with common infectious diseases).

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1 reason

With purulent inflammation of the middle ear, the infection can enter the inner ear through a round or oval window as a result of damage to their membranous formations (secondary tympanic membrane or annular ligament). In chronic purulent otitis media, the infection can pass into the inner ear through the bone wall destroyed by the inflammatory process, which separates the tympanic cavity from the labyrinth.

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2 reason

From the side of the meninges, the infection enters the labyrinth, usually through the internal auditory meatus along the sheaths of the auditory nerve. Such a labyrinthitis is called meningogenic and is observed most often in early childhood with epidemic cerebrospinal meningitis (purulent inflammation of the meninges). It is necessary to distinguish cerebrospinal meningitis from meningitis of ear origin, or the so-called otogenic meningitis. The first is an acute infectious disease and gives frequent complications in the form of damage to the inner ear, and the second itself is a complication of purulent inflammation of the middle or inner ear.

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According to the prevalence of the inflammatory process, diffuse (diffuse) and limited labyrinthitis are distinguished. As a result of diffuse purulent labyrinthitis, the organ dies and the cochlea is filled with fibrous connective tissue. With a limited labyrinth, the purulent process does not capture the entire cochlea, but only part of it, sometimes only one curl or even part of the curl. Diffuse purulent labyrinthitis leads to complete deafness; The result of a limited labyrinthitis is a partial hearing loss for certain tones, depending on the location of the lesion in the cochlea. Since the dead nerve cells of the organ of Corti are not restored, deafness, complete or partial, that arose after a purulent labyrinthitis, is persistent.

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In cases where, with labyrinthitis, the vestibular part of the inner ear is also involved in the inflammatory process, in addition to impaired auditory function, symptoms of damage to the vestibular apparatus are also noted: dizziness, nausea, vomiting, loss of balance. These phenomena are gradually subsiding. With serous labyrinthitis, the vestibular function is restored to one degree or another, and with purulent labyrinthitis, as a result of the death of receptor cells, the function of the vestibular analyzer completely drops out, and therefore the patient remains unsure of walking for a long time or forever, a slight imbalance.

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Diseases of the auditory nerve, pathways and auditory centers in the brain

Damage to the conduction section of the auditory analyzer can occur on any of its segments. The most common are diseases of the first neuron, united in a group called acoustic neuritis. This name is somewhat arbitrary, since this group includes not only diseases of the auditory nerve trunk, but also lesions of the nerve cells that make up the spiral ganglion, as well as some pathological processes in the cells of the organ of Corti

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The bipolar nerve cells of the spiral ganglion are very sensitive to all sorts of harmful influences. They easily undergo degeneration (rebirth) when exposed to chemical poisons, in particular, when intoxicated with certain medicinal substances, household and industrial poisons (quinine, streptomycin, salicylic drugs, arsenic, lead, mercury, nicotine, alcohol, carbon monoxide, etc.). Some of these substances (quinine and arsenic) have a special affinity for the nerve elements of the auditory organ and act selectively on these elements, just as, for example, methyl alcohol (wood alcohol) acts selectively on the nerve endings in the eye and causes blindness due to the upcoming optic atrophy. Cell intoxication of the spiral ganglion occurs not only when poisoned with chemical poisons, but also when exposed to bacterial poisons (toxins) circulating in the blood in many diseases, such as meningitis, scarlet fever, influenza, typhoid, mumps, etc. As a result of intoxication with both chemical poisons, and bacterial death of all or part of the cells of the spiral node occurs, followed by complete or partial loss of auditory function.

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The nature of the violation of the auditory function depends on the location of the lesion. In those cases when the process develops in one half of the brain and captures the auditory pathways to their intersection, hearing is impaired in the corresponding ear; if at the same time all the auditory fibers die, then there is a complete loss of hearing in this ear, with a partial death of the auditory pathways - a greater or lesser decrease in hearing, but again only in the corresponding ear. With unilateral lesions of the pathways above the intersection, a bilateral hearing loss occurs, more pronounced on the side opposite to the lesion; complete loss of hearing even in one ear does not occur in these cases, since impulses from both receptors will be conducted to the central end of the analyzer along the preserved pathways of the opposite side.

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Diseases of the auditory cortex

Causes: hemorrhages, tumors, encephalitis. Unilateral lesions lead to a decrease in hearing in both ears, more - in the opposite. Bilateral lesions of the conduction pathways and the central end of the auditory analyzer - single. And if they do occur, it is usually only with extensive brain damage and is accompanied by such profound impairment of other brain functions that hearing loss itself is relegated to the background in the overall picture of the lesion.

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hysterical deafness

developing in people with a weak nervous system under the influence of strong stimuli (fear, fear). Cases of hysterical deafness are sometimes observed in children. surdomutism - occurs after a concussion, accompanied by a violation of speech.

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Classification of persistent hearing impairment

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Medical and pedagogical classification of hearing loss (B.S. Preobrazhensky)

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Conclusion

In the prevention and correct, timely treatment of ear diseases in children, the role of a teacher and educator is great. Teachers and educators should have the necessary stock of knowledge about the manifestations of the most important ear diseases and the possibilities available to medicine for their treatment. This knowledge is needed by the teacher in order to send the child to a specialist doctor in time; to promote the spread of correct views on the treatment of deafness and hearing loss; assist the specialist doctor in carrying out therapeutic and preventive measures.

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The purpose of the lesson: to form students' knowledge about the importance of hearing in human life on the basis of interdisciplinary integration.

Lesson objectives:

Educational:

to continue the formation of knowledge about the structure of analyzers on the example of the auditory analyzer;

consider the structure and functions of the ear;

to study how sound energy is converted into mechanical energy;

develop rules for hearing hygiene.

Educational:

develop the ability to compare, analyze, formulate conclusions, work independently with information sources, apply the acquired knowledge to solve practical problems;

to promote the development of the ability to integrate the material of different sciences (biology, physics, history, music, literature).

Educational:

to cultivate a sense of responsibility, mutual assistance, communication skills;

to continue the formation of skills and habits of respect for one's health.

Lesson type: combined.

Equipment: multimedia projector, computer, thought sheet, didactic material (biological loto - cards with a task for matching), cotton swabs.

During the classes

1. Organizational moment. Psychological attitude to the lesson.

Hello guys. Now I will ask everyone who came to school in a good mood to smile now. Now raise your hands those guys who were in a hurry to get to school. Those guys who will help me in the lesson today, clap your hands. I am also glad to meet you.

2. Actualization of knowledge and skills.

Today you will work not only with a textbook and presentation fragments, but also with thought sheets (application 2) that you see on your desk.

Tell me, what parts of the nervous system are we studying with you?

That's right, analyzers.

What are analyzers for?

Yes, to live in the world, to feel it, to know it. Any analyzer has its own components, name them.

(slide 2).Task number 1. Break into groups. On the slide you see the sections of the analyzer. On the thought sheet application 2 ) are departments of different analyzers. Break into groups.

Let's look at slide 3 and compare with the correct answer.

Task number 2. Remind me which analyzer we talked about in the last lesson.

That's right, about the visual.

Each of you has a biological loto on the tables, after working in pairs, connect the cards according to their meaning.

Let's check if we did it right ( slide 4).

Look at ( slide 5). What is he talking about?

That's right, about color blindness - a disease in which a person does not distinguish between certain colors.

(slide 6). The disease was named after the scientist Dalton, who suffered from this disease.

3. Learning new material.

Now look at the epigraph of our lesson, which is placed on the board. Let's read it aloud:

The world of sounds is so diverse
Rich, beautiful, diverse,
But we are all tormented by the question:
Where do sounds come from?
That our ears are delighted everywhere?
It's time to think seriously.

So what is the topic of our lesson?

auditory analyzer.

And what is sound, after reading Zabolotsky's poem on a mental sheet ( application 2 ), you will understand what it is.

Born of the desert, the sound fluctuates
A blue spider oscillates on a thread.
The air oscillates
Transparent and pure
In shining stars
The leaf is shaking.

(N. Zabolotsky)

Let's turn to physics. The fact is that sound is a mechanical vibration, occurring with a frequency of 20 to 20,000 Hz i.e. 20 to 20,000 times per second. Speaking about the structure of the human body, we should not forget that we study ourselves in order to maintain health.

4. Physical culture break.

Working in the classroom, we strain our eyes, so it is very important to do gymnastics for the eyes. We rotate our eyes, draw the sign of infinity with our eyes, look intently at the tip of the finger, bringing it closer and further away.

5. Continued study of new material.

Now we will talk about the structure of the auditory analyzer.

Receptors - the auditory nerve - the temporal zone of the cerebral cortex.

We study the structure of the ear. ( slide7): Organ of hearing - ear: outer, middle, inner.

Work with the textbook (pp. 85-87). Fill in the chart application 2 ):

Let's look at the board where the correctly completed diagram is placed, I suggest comparing and correcting the errors if you have any.

(slide 8.9) . Now let's talk about functions:

Auricle: picks up sounds

External auditory meatus: conducts sound vibrations

Eardrum: converts sound vibrations into mechanical vibrations, transmits them to the middle ear.

Auditory ossicles: the hammer and anvil are levers, the stirrup is a kind of piston. They amplify the weak vibrations of the eardrum and transmit them to the inner ear. The stirrup rests against the oval window.

auditory tube: connects the middle ear to the nasopharynx. Equalizes the pressure that occurs with increased noise. (Ear-nose-throat doctor).

Snail: sink in 2.5 turns. Inside the bony labyrinth of the cochlea is the membranous labyrinth. Both of them are filled with liquid, the vibrations of which are caused by the strikes of the stirrup against the oval window. Inside the membranous labyrinth, five rows of cells with the finest fibers (60-70 for each cell) stretch along the entire length of the coils of the cochlea. These are auditory hair cells (there are about 24 thousand of them) attached to the membrane, which consists of individual fibers. As soon as fluctuations arise in the fluid of the cochlea, the curtain begins to touch the hairs of the auditory cells, generating electrical impulses of various strengths. The auditory nerve collects these impulses and transmits them through the subcortical nodes to the cortex of the temporal lobes of the brain. They provide analysis and synthesis of sounds.

Made by Plotnikova Anastasia ML 502

Slide 2: Features of the visual analyzer

Slide 3: visual analyzer

1. The diameter of the eyeball of a newborn is 17.3 mm (in an adult - 24.3 mm). It follows that the rays of light coming from distant objects converge behind the retina, that is, physiological farsightedness is characteristic of newborns. Up to 2 years, the eyeball is 40 %, by 5 years - by 70% and by 12-14 years it reaches the size of an adult's eyeball

Slide 4: visual analyzer

2. The visual analyzer is immature at the time of birth. The development of the retina ends only by the 12th month and the myelination of the optic nerves is completed at 3-4 months The maturation of the cortical analyzer is completed only by the age of 7 years The underdevelopment of the iris muscle is characteristic, which is why the pupils of the newborn are narrow

Slide 5: visual analyzer

3. in the first days of life, the eyes of a newborn move uncoordinated (up to 2-3 weeks) Visual concentration appears only by 3-4 weeks after birth and the duration of the reaction is 1-2 min max

Slide 6: visual analyzer

4. A newborn does not distinguish colors due to the immaturity of the cones of the retina, in addition, their number is much less than the rods. Differentiation of colors begins at about 5-6 months, but conscious color perception occurs only at 2-3 years. By the age of 3, the child distinguishes the ratio of brightness colors. The ability to distinguish colors increases significantly by the age of 10-12 years.

Slide 7: visual analyzer

5. Children have a very elastic lens, it is able to change its curvature to a greater extent than in adults. But from the age of 10, the elasticity of the lens decreases, and the volume of accommodation decreases. With age, the nearest point of clear vision “moves away” - at 10 years old it is at a distance of 7 cm, at 15 by 8, etc. 6. binocular vision is formed by the age of 6-7

Slide 8: visual analyzer

7. Visual acuity in newborns is very low. By 6 months - 0.1; at 12 months - 0.2; at 5-6 years old - 0.8-1.0; in adolescents, visual acuity is about 0.9-1.0 8. The visual fields in newborns are much narrower than in adults, by the age of 6-8 they expand, but this process finally ends at the age of 20 9. Spatial vision in a child is formed by 3 months . 10. Volumetric vision is formed from 5 months to 5-6 years

Slide 9: visual analyzer

11. Stereoscopic perception of space begins to develop by 6-9 months. By the age of 6, most children have developed visual acuity and all parts of the visual analyzer are completely differentiated. farsightedness. By the age of 7-12, it is gradually replaced by normal vision, but 30-40% of children develop myopia

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Slide 10: Features of the auditory analyzer

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Slide 11: Hearing Analyzer

The formation of the cochlea occurs at the 12th week of intrauterine development, and at the 20th week myelination of the fibers of the cochlear nerve begins in the lower (main) coil of the cochlea. Myelination in the middle and superior coils of the cochlea begins much later.

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slide 12: auditory analyzer

The subcortical structures related to the auditory analyzer mature earlier than its cortical section. Their qualitative development ends on the 3rd month after birth. The cortical fields of the auditory analyzer approach the adult state by 5-7 years.

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Slide 13: Hearing Analyzer

The auditory analyzer begins to function immediately after birth. The first reactions to sound are in the nature of orienting reflexes carried out at the level of subcortical formations. They are noted even in premature babies and are manifested in closing the eyes, opening the mouth, shivering, reducing the frequency of breathing, pulse, and various facial movements. Sounds that are the same in intensity, but different in timbre and pitch, cause different reactions, which indicates the ability of a newborn child to distinguish them.

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Slide 14: Hearing Analyzer

An orienting reaction to sound appears in infants in the first month of life and from 2–3 months it takes on the character of a dominant. Conditioned food and defensive reflexes to sound stimuli are developed from 3-5 weeks of a child's life, but their strengthening is possible only from 2 months. Differentiation of heterogeneous sounds is clearly improved from 2–3 months. At 6–7 months, children differentiate tones that differ from the original by 1–2 and even by 3–4.5 musical tones.

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Slide 15: Hearing Analyzer

The functional development of the auditory analyzer continues up to 6–7 years, which is manifested in the formation of subtle differentiations to speech stimuli and a change in the hearing threshold. The hearing threshold decreases, hearing acuity increases by the age of 14–19, then they gradually change in the opposite direction. The sensitivity of the auditory analyzer to different frequencies also changes. From birth, he is "tuned" to the perception of the sounds of a human voice, and in the first months - high, quiet, with special caressing intonations, called "baby talk", this is the voice most mothers instinctively talk to their babies.

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Slide 16: Hearing Analyzer

From the age of 9 months, a child can distinguish the voices of people close to him, the frequencies of various noises and sounds of everyday life, the prosodic means of language (pitch, longitude, brevity, different volume, rhythm and stress), listens if they speak to him. A further increase in sensitivity to the frequency characteristics of sounds occurs simultaneously with the differentiation of phonemic and musical hearing, reaches a maximum by 5–7 years of age and largely depends on training.

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Slide 17: Features of the olfactory analyzer

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slide 18: olfactory analyzer

The peripheral part of the olfactory analyzer begins to form at the 2nd month of intrauterine development, and by 8 months it is already completely structurally formed. From the first days of a child's birth, reactions to odor stimuli are possible. They are expressed in the occurrence of various facial movements, general body movements, changes in heart function, respiratory rate, etc. About half of premature and 4/5 full-term children smell, but their olfactory sensitivity is about 10 times less than in adults, and they do not distinguish between unpleasant and pleasant odors. Distinguishing smells appears on the 2nd - 3rd months of life. Conditioned reflexes to olfactory stimuli are developed from 2 months of postnatal development.

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Slide 19: Features of the taste analyzer

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slide 20: taste analyzer

The peripheral part of the taste analyzer begins to form at the 3rd month of intrauterine life. By the time of birth, it is already fully formed, and in the postnatal period, only the nature of the distribution of receptors changes. In the first years of life in children, most receptors are distributed mainly on the back of the tongue, and in the subsequent years, along its edges. In newborns, an unconditioned reflex reaction to all the main types of taste substances is possible. So, under the action of sweet substances, sucking and mimic movements occur, which are characteristic of positive emotions. Bitter, salty and sour substances cause the eyes to close and the face to wrinkle.

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slide 21: taste analyzer

The sensitivity of the taste analyzer in children is less than in adults. This is evidenced by the greater than in adults, the magnitude of the latent period of the occurrence of a reaction to a taste stimulus and a large threshold of irritation. Only by the age of 10 does the duration of the latent period under the action of gustatory stimuli become the same as in adults. By the age of 6, irritation thresholds characteristic of adults are established. Conditioned reflexes to the action of taste stimuli can be developed at 2 months of age. At the end of the 2nd month, differentiation of taste stimuli is developed. The distinguishing ability of children already at the age of 4 months is quite large. From 2 to 6 years, taste sensitivity increases, in schoolchildren it differs little from adults

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Slide 22: Features of the skin analyzer

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slide 23: skin analyzer

At the 8th week of intrauterine development, bundles of unmyelinated nerve fibers are detected in the skin, which freely terminate in it. At this time, there is a motor reaction to touching the skin in the mouth area. At the 3rd month of development, receptors of the lamellar body type appear. In different parts of the skin, nerve elements appear non-simultaneously: first of all in the skin of the lips, then in the pads of the fingers and toes, then in the skin of the forehead, cheeks, and nose. In the skin of the neck, chest, nipple, shoulder, forearm, armpit, the formation of receptors occurs simultaneously.

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Slide 24: Skin analyzer

The early development of receptor formations in the skin of the lips ensures the occurrence of a sucking act under the action of tactile stimuli. At the 6th month of development, the sucking reflex is dominant in relation to the various movements of the fetus carried out at this time. It entails the emergence of various facial movements. In a newborn, the skin is abundantly supplied with receptor formations, and the nature of their distribution over its surface is the same as in an adult.

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Slide 25: Skin analyzer

In newborns and infants, the skin around the mouth, eyes, forehead, palms of the hands, and soles of the feet is most sensitive to touch. The skin of the forearm and lower leg is less sensitive, and the skin of the shoulders, abdomen, back and thighs is even less sensitive. This corresponds to the degree of tactile sensitivity of the skin of adults.

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Slide 26: Skin analyzer

A very intense increase in encapsulated receptors occurs in the first years after birth. At the same time, their number increases especially strongly in areas subjected to pressure. So, with the beginning of the act of walking, the number of receptors on the plantar surface of the foot increases. On the palmar surface of the hand and fingers, the number of polyaxon receptors increases, which are characterized by the fact that many fibers grow into one flask. In this case, one receptor formation transmits information to the central nervous system along many afferent pathways and, therefore, has a large area of ​​representation in the cortex.

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Slide 27: Skin analyzer

This explains the increase in the ontogenesis of the number of such receptors in the skin of the palmar surface of the hand: with age, the hand becomes increasingly important in human life. Therefore, the role of its receptor formations in the analysis and evaluation of objects of the surrounding world, in the evaluation of ongoing movements, increases. Only by the end of the first year, all receptor formations of the skin become very similar to those in adults. Over the years, the excitability of tactile receptors increases, especially from 8-10 years old and in adolescents, and reaches a maximum by 17-27 years. During life, temporary connections of the skin-muscular sensitivity zone with other perceiving zones are formed, which clarifies the localization of skin irritations.

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Slide 28: Skin analyzer

Newborns react to cold and heat after a much longer period than adults. They are more sensitive to cold than to heat. The skin of the face is the most sensitive to heat. The sensation of pain is present in newborns, but without exact localization. To damaging skin irritations that cause pain in adults, for example, to a pin prick, newborns react with movements already on the 1st - 2nd day after birth, but weakly and after a long latent period. The skin of the face is most sensitive to pain stimuli, since the latent period of the motor reaction is approximately the same as in adults.

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slide 29: skin analyzer

The reaction of newborns to the action of electric current is much weaker than in older children. At the same time, they react only to such a strength of current that is unbearable for adults, which is explained by the underdevelopment of centripetal pathways and the high resistance of the skin. Localization of pain caused by irritation of interoreceptors is absent even in children 2-3 years old. There is no exact localization of all skin irritations in the first months or in the first year of life. By the end of the first year of life, children easily distinguish between mechanical and thermal skin irritations.

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The last slide of the presentation: Anatomical and physiological features of analyzers in children

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Slides captions:

"The greatest luxury on earth is the luxury of human communication" Antoine de Saint-Exupery

"Auditory analyzer. Hearing hygiene."

What would you like to know - what would you like to learn - why do you need it. What are your goals?

What is an analyzer? What does it consist of? What parts form the visual analyzer? Questions

What is the importance of hearing in human life?

The meaning of hearing: - hearing contributes to the aesthetic education of a person; - is a channel of communication; -participates in the transfer and accumulation of knowledge accumulated by mankind

The structure of the auditory analyzer Auditory receptor Conductive path Sensitive zone of the CBP

ear structure

The structure and functions of the ear parts Task: Using the textbook Dragomilov A.G., Mash R.D. on pages 203 -204 and the drawing of the endpaper of the textbook, fill in the table Parts of the ear Structure Functions

Structure and functions of the parts of the ear Parts of the ear Structure Functions External auricle, external auditory canal ending with the eardrum Protection (wax release) Capturing and conducting sounds Middle Auditory ossicles: - hammer - anvil - stirrup Eustachian tube Bones conduct and amplify sound vibrations 50 times . Eustachian tube - pressure equalization in the middle ear. Inner ear: vestibule (oval and round windows), cochlea Acoustic receptors in the cochlea Convert sound signals into nerve impulses that go to the auditory area of ​​the CPD

sound waves

Hygiene of the hearing organs Cause Damage to the auditory nerve Formation of sulfuric plug Strong sharp sounds (explosion) Constant loud noises Foreign bodies Pathogenic microorganisms Consequences Violation of the transmission of impulses to the auditory zone of the CBP Violation of the transmission of sound vibrations to the inner ear Rupture of the tympanic membrane Decreased elasticity of the tympanic membrane Swelling of the middle ear Inflammation of the middle ear (otitis media)

Harmful influence of noise on hearing the tympanic membrane gradually loses its elasticity, deafness develops; noise causes inhibition in the cells of the cerebral cortex; noise can cause a variety of physiological (increased heartbeat, increased pressure) and mental (weakening of attention, nervousness) disorders;

Task To the right ear of the subject, who sits with his eyes closed, bring a wristwatch closer. The distance at which he heard the ticking of the clock is fixed. A similar experiment is carried out with the left ear. (A distance of 10-15 cm is considered normal.) After listening to loud music for 2 minutes, and then repeat the experiment. Compare the results obtained and explain them. Make a conclusion. Laboratory work "The impact of noise on hearing acuity"

Checking primary assimilation Insert the missing words into the text: “Each ear consists of three sections: ……., ……., ……… The outer ear ends with ……. ……… In the middle ear are … …. They transmit sound vibrations to … … … the inner ear. The inner ear, unlike the previous sections, is filled with………. In the inner ear there is a vestibule, a cochlea and ……… .. The final analysis of sound stimuli occurs in ………... the zone of the cerebral cortex. A well-mannered person will not become loud …….. in public places.

To summarize: So, the organ of hearing is designed to perceive sound stimuli. In the Bible, in the "Parable of the Sower" there is such a phrase: "Whoever has ears to hear, let them hear!" What is the meaning of this expression? - What is the role of the auditory analyzer (ears) in human communication? What do you mean by "hear"? Do we always "hear" each other? What does it take for one person to hear another?

Let's summarize: - Have you realized all your goals set for the lesson?

Homework: Paragraph 54, pp. 80-82 of the textbook. Think! What measures can you suggest to reduce human exposure to noise? Ear care tips

Verification of primary assimilation When conducting an experiment with an explosion of hydrogen, it is recommended to open your mouth. Why?

Resources used: Dragomilov A.G., Mash R.D. Biology: Man: A textbook for students of the 8th grade of educational institutions. - 2nd ed., revised. - M.: Ventana-Graf, 2005. - 272 p.: ill. Illustrations: CD disk: Education Biology. Grade 9 Anatomy and human physiology / multimedia textbook of a new sample. - M., Education-MEDIA, 2003

slide 2

• The human ear perceives sounds from 16 to 20000 Hz.
• maximum sensitivity from 1000 to 4000 Hz

slide 3

main speech field

• is in the range of 200 - 3200 Hz.
• Old people often do not hear high frequencies.

slide 4

• Tones - contain sounds of the same frequency.
• Noises are sounds made up of unrelated frequencies.
• Timbre is a characteristic of sound determined by the shape of the sound wave.

Slide 7

Psychological correlates of loudness of sound.

• whispered speech - 30 dB
• colloquial speech - 40 - 60 dB
• street noise - 70 dB
• scream at the ear - 110 dB
• loud speech - 80 dB
• jet engine - 120 dB
• pain threshold - 130 - 140 dB

Slide 8

ear structure

Slide 9

outer ear

Slide 10

• The auricle is a sound catcher, a resonator.
• The eardrum receives sound pressure and transmits it to the ossicles of the middle ear.

slide 11

• It does not have its own oscillation period, because its fibers have a different direction.
• Doesn't distort sound. The vibrations of the membrane at very strong sounds are limited by the musculus tensor timpani.

slide 12

Middle ear

slide 13

The handle of the malleus is woven into the eardrum.

Information transfer sequence:

• Hammer →
• Anvil→
• Stremechko →
• oval window →
• perilymph → scala vestibularis

slide 15

• musclestapedius. limits the movement of the stirrup.
• The reflex occurs 10ms after the action of strong sounds on the ear.

slide 16

The transmission of a sound wave in the outer and middle ear occurs in the air.

Slide 19

• The bony canal is separated by two membranes: a thin vestibular membrane (Reissner)
• and a dense, resilient base membrane.
• At the top of the cochlea, both of these membranes are connected, they have a hole in the helicotrema.
• 2 membranes divide the bony canal of the cochlea into 3 passages.

Slide 20

• Stapes
• round window
• oval window
• basement membrane
• Three channel cochlea
• Reisner's membrane

slide 21

cochlear channels

slide 22

1) The superior canal is the scala vestibularis (from the oval window to the top of the cochlea).

2) The lower channel is a tympanic staircase (from the round window). The canals communicate, are filled with perilymph and form a single canal.

3) The middle or membranous canal is filled with ENDOLYMPH.

slide 23

Endolymph is formed by a vascular strip on the outer wall of the middle scala.

slide 26

Internal

• arranged in one row
• there are about 3500 of them.
• They have 30 - 40 thick and very short hairs (4 - 5 MK).

Slide 27

outdoor

• arranged in 3 - 4 rows,
• there are 12,000 - 20,000 cells.
• They have 65 - 120 thin and long hairs.

Slide 28

The hairs of the receptor cells are washed by the endolymph and come into contact with the tectorial membrane.

Slide 29

The structure of the organ of Corti

slide 30

• Internal phonoreceptors
• tectorial membrane
• External phonoreceptors
• Nerve fibers
• basement membrane
• supporting cells

Slide 31

Excitation of phonoreceptors

slide 32

• Under the action of sounds, the main membrane begins to oscillate.
• The hairs of the receptor cells touch the tectorial membrane
• and deform.

Slide 33

• In phonoreceptors, a receptor potential arises and the auditory nerve is excited according to the scheme of secondary sensory receptors.
• The auditory nerve is formed by processes of neurons of the spiral ganglion.

slide 34

Electric potentials of the cochlea

Slide 35

5 electrical phenomena:

1.membrane potential of the phonoreceptor. 2. endolymph potential (both are not related to the action of sound);

3.microphone,

4.summing

5.potential of the auditory nerve (arise under the influence of sound stimuli).

slide 36

Characterization of cochlea potentials

Slide 37

1) The membrane potential of the receptor cell is the potential difference between the inner and outer sides of the membrane. MP = -70 - 80 MV.

2) Endolymph potential or endocochlear potential.

Endolymph has a positive potential in relation to perilymph. This difference is equal to 80mV.

Slide 38

3) Microphone potential (MP).

• It is registered when the electrodes are located on a round window or near receptors in the scala tympani.
• The MP frequency corresponds to the frequency of sound vibrations entering the oval window.
• The amplitude of these potentials is proportional to the sound intensity.

Slide 40

5) Action potential of auditory nerve fibers

It is a consequence of the appearance of microphone and summation potentials in hair cells. The amount depends on the frequency of the acting sound.

Slide 41

• If there are sounds up to 1000 Hz,
• then PD of the corresponding frequency occurs in the auditory nerve.
• At higher frequencies, the frequency of AP in the auditory nerve decreases.

Slide 42

At low frequencies, APs are observed in a large number, and at high frequencies, in a small number of nerve fibers.

slide 43

Block diagram of the auditory system

Slide 44

Sensory cells of the cochlea

• Spiral ganglion neurons
• Cochlear nuclei of the medulla oblongata
• Inferior tubercles of the quadrigemina (midbrain)
• Medial geniculate body of thalamus diencephalon)
• Temporal cortex (fields 41, 42 according to Brodmann)

Slide 45

The role of various departments of the central nervous system

Slide 46

• Cochlear nuclei - primary recognition of the characteristics of sounds.
• The inferior colliculi of the quadrigemina provide primary orienting reflexes to sound.

The auditory cortex provides:

1) reaction to a moving sound;

2) selection of biologically important sounds;

3) reaction to a complex sound, speech.

Slide 47

Theories of perception of sounds of different heights (frequency)

1. Resonance theory of Helmholtz.

2. Rutherford's telephone theory.

3.Theory of spatial coding.

Slide 48

Helmholtz resonance theory

Each fiber of the main cochlear membrane is tuned to its own sound frequency:

At low frequencies - long fibers at the top;

At high frequencies - short fibers at the base.

Slide 49

The theory has not been confirmed because:

The membrane fibers are not stretched and do not have "resonant" vibration frequencies.

Slide 50

Rutherford's telephone theory (1880)

Slide 51

Sound vibrations → foramen ovale → oscillation of the perilymph of the scala vestibularis → oscillation of the perilymph of the scala tympani through helicotrema → oscillation of the main membrane

→ excitation of phonoreceptors

Slide 52

• The AP frequencies in the auditory nerve correspond to the frequencies of the sound acting on the ear.
• However, this is only true up to 1000 Hz.
• The nerve cannot reproduce a higher frequency of AP

Slide 53

Bekesy's spatial coding theory. (Traveling wave theory, place theory)

Explains the perception of sound with frequencies above 1000 Hz

Slide 54

• Under the action of sound, the stirrup continuously transmits vibrations to the perilymph.
• Through a thin vestibular membrane, they are transmitted to the endolymph.

Slide 55

• A "traveling wave" propagates along the endolymphatic canal to the helicotrema.
• The rate of its spread gradually decreases,

Slide 56

• The amplitude of the wave first increases,
• then decreases and weakens
• without reaching the helicotrema.
• Between the place of origin of the wave and the point of its attenuation lies the amplitude maximum.