Bass form. Lateral amyotrophic sclerosis: symptoms, treatment, diagnosis, forecast

The human hearing body has a complex structure and performs two functions: perception of oscillations of sound waves and orientation of the position of the body in space. The hearing body is divided into 3 parts, anatomically and functionally interconnected: external, average and inner ears. The outer and secondary ear conduct sound oscillations to the inner ear and, thus, these two parts are a sound-conducting device. The inner ear in which the bone and membrane labyrinths distinguish between the bone and the organ of hearing itself and the equilibrium body.

Outdoor Earresponsible for collecting sounds and submit information about them analyzers. The outdoor ear consists of ear shell and an outdoor auditory passage.

Auricle It consists of an elastic elastic ear cartilage covered with a skin fold, which is firmly connected to cartilage on the side surface and moving on the inner. At the bottom edge of the ear shell, the cartilage moves into a fat layer of fiber, which is called the urine or a groom.

The free edge of the ear shell, a little flexing inward, forms a curl that goes from the lobe and passes along the entire edge of the ear shell, gradually thickening. Before the curl there is a small recess that expands up and is called a rook. On the opposite side of the rook is the opposite. It begins another deepening from it, the ear smoothly turning into the sink is an external auditory passage. In the lateral part of the ear sink, there is an outer hearing aid, from two sides limited by small cartilage protrusions: a kozelkom and antiques. Here the curl ends, slightly flexing the book and forming the leg of the curl. Some parts of the cartilage are connected to each other muscles of the ears of the sink.

External hearing aisle It is a curved tube (S-shaped) with a length of from 2.5 to 3.5 cm (and diameter 9 mm at the beginning and 6 mm at the end), which ends at the drumpipe, burning it from the middle ear. It consists of two departments: the outer cartilage auditory passage formed by a cartilage and a connecting tissue, which binds it to an internal bone hearing aisle located in the field of temporal bone and the formed bone substance. The inner surface of the outer auditory pass is covered with leather containing hair bags, greasy and wax glands. The latter allocate ear sulfur.

The dimensions and shape of the auricle are individual. The ear sink is arranged in such a way that the sounds as much as possible concentrates and sends them to the outer hearing aid.

Middle earwhich is also called the drum cavity is a sound system, which includes several components: a drum cavity, hearing bones, an auditory tube.

Eardrum It is located on the boundary of the outer and middle ear and is the outer wall of the eardrity. Its task includes the perception of air fluctuations and their further transmission to the middle ear.

The eardrum is a junction tissue, from the outside of the outer ear, covered with skin, and from the middle side - mucous membrane. In the center of the eardrum, there is a deflection towards the middle ear. The convex side of the funnel is attached to the handle of the hammer, forming the navel of the eardrum.

Drum cavity -the sloping space volume of 0.75 cm³ is located in the temporal bone, from the inside is lined with a mucous membrane. In the cavity there are 3 auditory bones, muscle tendons that stretch the drumpoint and stirring. It also takes place drum string - branch of intermediate nerve (sensitive part of the facial nerve). The drum cavity continues into the hearing tube, which opens in the nasopharynx by the pharyngeal hole of the hearing pipe.

In the drum cavity there are auditory bones, which are connected to each other joints and are a sound-conducting system of the middle ear. There are 3 bones in total, each of which is called according to its form.

Hearing bones -strong, anvil and hammer are named so thanks to their form. These bones are the smallest in the human body, together they make up a chain connecting the eardrum with a running window leading to the inner ear. Bones are designed to transmit sound oscillations. Handle hammer fucked with a drumpot. The head of the hammer and the body of the anvil is connected by the joint and are strengthened by bundles, the long turn of the anvil is connected to the punching head. The base of the plenty is part of the runway window, connecting with its edge by means of a ring bundle. Bones are covered with mucous membrane. The tendon of the muscles straining the drum membrane is attached to the handle of the hammer, aspiring muscles - to strive. These muscles regulate the movement of the bones.

Hearing trumpet Connects a drum cavity with the upper pharynx cavity department. Its length is 3.5-4 cm, 2/3 of which are cartilaginous formation, and 1/3 - bone. From the inside the auditory tube is lined with a mucous membrane, in which tube glands and lymph nodes are located. Normally, the walls of the cartilage department are located in the saving condition, the disclosure of this part of the pipe occurs at the time of swallowing. The hearing tube performs an important function - contributes to aligning the pressure of the air inside the drum cavity with respect to the outer environment.

Interior Earlocated in the pyramid of the temporal bone. Functionally, the inner ear is divided into two parts: auditory (snail) and vestibular (retail and semicircular channels). In the bone maze, there is a membrane labyrinth, repeating the shape of the bone, between the labyrinates is a slit filled with perilimph. The bone labyrinth is located between the drum cavity and the inner hearing aisle and consists of the run-up, three semiccage channels and snails. The bone run-up - an oval cavity, which is reported to semicircular channels, on the side wall there are 2 windows: the running windows and the snail window.

Three bone semicircular channels (front, rear and lateral) lie in three mutually perpendicular planes. Each semicircular channel has two legs, one of which is expanding before shouting in the run toothery, forming an ampoule. The bone snail forms 2.5 curls around the horizontally lying rod - spios, around which the bone spiral plate is spinled around the screw staircase. The plate shall divide the cavity of the snail channel for two stairs: the run-up and drum, which communicate among themselves in the area of \u200b\u200bthe dome through the hole.

The wall of the reconciliated labyrinth is formed by a connective tissue, from the inside it is lined with epithelium and filled with endolymph. The membered labyrinth is represented on the eve of two small extensions (bag and squeezing). Reflective semicircular channels are opened in trees. Plots of bags containing sensitive cells are called stains, similar sections of ampoules of semicircular webbed channels - scallops. Sensitive stain cells contain hairs that are covered with a student membrane containing calcium carbon dioxide (otolith) crystals. Spots perceive the change in gravity and linear acceleration. The sensitive cells of scallops also contain the hairs covered with the gelatinous dome. They perceive the change in the angular acceleration (for example, when the head turns).

With the change in gravity, the position of the head, the body, with accelerations, the riot membrane and the gelatinous dome are shifted, this leads to the voltage of hairs and the change in the activity of sensitive cell enzymes, the nerve impulse is transmitted to the brain of the brain, and then in the cerebellum and the bark of dark and temporal lobes ( Cork center equilibrium).

Snailit is located in the front of the bone labyrinth, has a cone-shaped shape and is an eppection spiral channel forms 2.5 curls around the rod and ending in a snail dome. The dome rises above the base of the snail by 4-5 mm. Each curl is separated from the other wall formed by the snail bone substance. The stem of the snail consists of spongy bone tissue and is an inner wall of the channel. The base of the rod goes to the inner auditory passage. In the cavity of the spiral canal over the entire length of the rod is a spiral bone plate. Through it, the snail cavity is divided into 2 parts: the upper move, which is combined with the thread of the labyrinth and is called the runner's staircase, and the lower course combined with the drum snail window and called the drum staircase. In the area of \u200b\u200bthe dome of the snail both strokes are combined, forming a hole of the snail. Spiral (Cortiyev) organ performs the perception of sounds. Perceiving cells are located on the membrane. Its perceiving cells have microscopic hairs, which when the membrane oscillations relate to another plate hanging over them in the form of a canopy. This is a stimulus to form the nerve impulses.

An irritant for Cortiene organ is a sound, the human ear can perceive sound oscillations with a frequency of 16 to 20,000 Hz. Sounds having a frequency of 1,000 - 3,000 Hz (oscillations per second), the ear is most sensitive, in this frequency range there is a human speech.

The human hearing body is designed to take from outside sound signals, transform them into nervous impulses and transmission to the brain. The structure of the ear and its functions are quite complex, despite the seeming simplicity of the basic principle of operation of all structures. Everyone knows that the ears are a pair of organ, their inner part is in the temporal bones on both sides of the skull. Only the outer parts of the ear can be seen with the naked look - all the well-known ear shells located outside and closing an overview for the complex internal structure of the human ear.

Building of ear rinks

The anatomy of the human ear is studied in the lessons of biology, so each schoolchild is known that the auditory body can distinguish between different oscillations and noises. This is ensured by a feature of the structure of the organ:

• outdoor ear (sink and beginning of the auditory channel);
• middle Human Ear (eardrum, cavity, auditory bones, Eustachyeva Pipe);
• inner (snail, transforming mechanical sounds in brain-minded pulses, vestibular apparatus, serving to hold the equilibrium of the human body in space).

The outer, visible part of the auditory body is an ear shell. It consists of elastic cartilage tissue, which is closed with a small fold of fat and leather.

The ear shell is easily deformed and is damaged, often due to this, the initial structure of the hearing body is disturbed.

The outer part of the auditory body is designed to receive and transmit sound waves coming from the surrounding space in the brain. Unlike similar organs in animals, these parties of the organ of hearing in people are almost still and do not play any additional roles. To perform the transmission of sounds and create in the auditory channel of the surround sound, the sink from the inside is completely covered with folds, helping to process any external sound frequencies and noises, followed by the brain transmitted. The human ear is clearly depicting below.

The maximum possible measured distance in meters (m), from where the human hearing organs differ and catch the noises, sounds and oscillations is an average of 25-30 m. Helps it to make an ear sink direct connection with the ear, the cartilage of which on the end turns into bone tissue and It goes into the thickness of the skull. The ear canal also contains sulfur glands: the sulfur produced by them protects the earspace from the pathogenic bacteria and their devastating influence. Periodically, the glands are self-cleaning, but sometimes fails in this process. In this case, sulfur plugs are formed. To remove them require qualified assistance.

Sound oscillations "caught" into the cavity moves inside the folds and enter the auditory channel, then face the eardrum. That is why when flying to air transport or trips to a deep metro, as well as any sound overloads, it is better to drive a mouth. It will help to protect the gentle cloths of the membrane from the break, repulse with the power incoming the sound of the hearing organ back.

The structure of the middle and inner ear

The middle part of the ear (the scheme below reflects the structure of the hearing body), located inside the bones of the skull, serves to transform and further send the sound signal or fluctuations in the inner ear. If you look in the context, it will clearly be seen that its main parts are a small cavity and auditory bones. Each such bone bears its special name, conjugate with the functions performed: Pephing, hammer and anvil.

The structure and function of the hearing body in this part is special: hearing bones form a single mechanism configured to thin and consistent transmission of sounds. The hammer is connected to its lower part with the drummeal, and the top - with an anvil associated directly with the sprinkle. Such a sequential device of the human ear is fraught with a violation of the work of the entire hearing body in the event that even only one element of the chain fails.

The middle part of the ear is associated with the nose and throat organs through Eustachiev pipes that control the air incoming from outside and the pressure we exerted. It is these parts of the hearing body that sensitively catches any pressure drops. Increased or lowering pressure is felt by a person in the form of laying ears. Due to the peculiarities of the anatomy of oscillation of external atmospheric pressure can provoke reflex yew. Periodic swallowing will be able to help quickly get rid of this reaction.

This part of the human auditory is located deeper than all, it is considered the most difficult in their anatomy. The inner ear includes a labyrinth, half-breached tubules and snail. The labyrinth itself is very complex on its device: its composition includes snail, receptor fields, uteros and bag bonded among themselves in one duct. The semicircular channels of 3 species are located behind them: lateral, front, as well as rear. Each such channel includes an ampular end and a small leg. Snail is a complex of a variety of structures. Here, the hearing body has a running outstanding staircase and a drum staircase, a snail duct and a spiral body, within which the so-called pillars cells are located.

Communication of the elements of the hearing agency

Knowing how the ear is arranged, you can understand the essence of its destination. The auditory body must fulfill its functions constantly and smoothly, providing an adequate repeater of external noise into brain-minded sound nerve impulses and allowing the body of a person to remain in equilibrium regardless of the overall position in space. To maintain this function, the vestibular apparatus never stops its work, remaining active and afternoon, and at night. The ability to maintain the strain is provided by an anatomical structure of the inner part of each ear, where the components that are located from the inside are embodied by reporting vessels acting on the principle of the same name.

The fluid pressure is maintained by semicircular tubules that are adjusted to any change to the position of the body in the surrounding world - be it movement or, on the contrary, rest. With any movements in space they are regulated by intracranial pressure.

Poor bodies provide a matwork and a bag in which the liquid is constantly moving, due to which the nerve impulses come directly into the brain.

The same impulses support general reflexes of the human body and the concentration of attention on a specific object, that is, they not only perform the direct functions of the hearing organ, but also support visual mechanisms.

Ears are one of the most important organs of the human body. Any disorders of its functionality entail the difficult consequences affecting the quality of human life. It is important not to forget to monitor the condition of this body and in the event of any unpleasant or unusual sensations to consult from medical professionals specializing in this direction of medicine. People should always be responsible to their health.

Organ hearing - Ear - in humans and mammals consists of three parts:

• outdoor ear
• middle Ear
• inner ear

Outdoor Ear It consists of ear shells and an outdoor auditory pass, which enters into the depths of the skull's temporal bone and is closed by the eardrum. The shell is formed by a cartilage covered on both sides of the skin. With the help of the sink, the sound fluctuations of air are collected. The mobility of the shell is provided with muscles. In humans, they are rudimentary, in animals their mobility provides better orientation towards the sound source.

The outer hearing aisle has a type of a tube with a length of 30 mm lined with leather in which there are special glands that allocate ear sulfur. The auditory pass guides the captible sound to the middle ear. Parry auditory passes allow you to more accurately localize the sound source. In the depth of the auditory passage, tightened with a thin eardrum of oval shape. From the middle ear, in the middle of the eardrum, the handle of the hammer is strengthened. Elastic membrane, with the impact of sound waves, it repeats these oscillations without distortion.

Middle ear - Starts behind the drummeal and is a camera filled with air. The average ear is connected using a hearing (Evstachiyeva) pipe with a nasopharynk (therefore the pressure on both sides of the eardrum is equally). There are three hearing bones related to each other:

1. hammer
2. anvil
3. stapes

The hammer is connected to the drum blade, perceives its oscillations and through two other bones transfers these oscillations to the oval window of the inner ear in which air fluctuations are converted into fluid oscillations. In this case, the amplitude of oscillations decreases, and their strength increases about 20 times.

In the wall separating the middle ear from the internal, in addition to the oval window, there is still a round window tightened with a membrane. The membrane of a round window makes it possible to fully transmit the energy of the oscillations of the hammer of the liquid and allows the fluid to fluid as a whole.

Located in the thickness of the temporal bone and consists of a complex system of communicating channels and cavities called the labyrinth. It distinguishes two parts:

1. bone labyrinth - filled with liquid (perilimph). Bone labyrinth divide into three parts:
   • spell
   • bone snail
   • three semicircular bone canals
2. meat Labyrinth - filled with liquid (endolymph). It has the same parts as bone:
   • the overfit predver represented by two bags is an elliptical (oval) bag and spherical (round) bag
   • refluenced snail
   • three webbed semicircular channels

   The recharge maze is located inside the bone, all parts of the refigble labyrinth in size is less than the corresponding size of the bone, therefore there is a cavity between their walls, called perilimphotic space, made by lymphovenial fluid - perilimph.

The hearing body is snail, the remaining parts of the labyrinth are an equilibrium organ holding the body in a certain position.

Snail - A body that perceives sound oscillations and turns them into nervous excitement. Channel Snail forms a 2,5 coat. The entire length of the bone snail channel is divided into two partitions: a more thin - vestibular membrane (or a raisner membrane) and a more dense - the main membrane.

The main membrane consists of a fibrous tissue, which includes about 24 thousand special fibers (hearing strings) of different lengths and stretched across the membrane stroke - from the axis of the snail to its outer wall (like the staircase). The longest strings are located at the top, at the base - the most shortened. At the top of the membrane snail, they have a snail hole (helixrea) for a message of the upper and lower stroke.

With the cavity of the middle ear, the snail is reported through a round window, tightened with a membrane, with the cavity of the run-in - through the oval window.

The vestibular membrane and the main membrane share the bone snail channel for three strokes:

• top (from oval windows to the top of the snail) - vestibular staircase; reported with the lower channel of the snail through the snippled hole
• nizhny (from the round window to the top of the snail) - the drum staircase; Reported with the top channel snail.

  The top and bottom moves of the snail are filled with perilimph, which is separated from the cavity of the middle ear of the membrane of oval and round windows.

• middle - membrane channel; Its cavity is not reported to the cavity of other channels and filled with endolymph. Inside the middle channel on the main membrane, there is a sound-visible apparatus - Cortis organ consisting of receptor cells with protruding hairs (hairs cells) with a coating membrane hanging over them. The sensitive ending of nerve fibers contact the hairsth cells.

Sound perception mechanism

Sound oscillations of air, passing through the outer hearing pass, cause oscillations of the eardrum and through the hearing bones in reinforced form are transmitted to the oval window leading on the trial of the snail. The resulting oscillation leads to the movement of periilimf and endolymph of the inner ear and is perceived by the fibers of the main membrane carrying cells of the Cortiyev organ. The oscillation of the Cortium body's hair cells causes a touch of hairs with a coating membrane. The hairs are bent, which leads to a change in the membrane potential of these cells and the occurrence of the excitation in the nerve fibers that are powered by the hair cells. According to nervous hearing nerves, the excitation is transmitted to the auditory analyzer of the cerebral cortex.

The human ear can perceive sounds with a frequency of 20 to 20,000 Hz. Physically sounds are characterized by a frequency (by the number of periodic oscillations per second) and the force (oscillation amplitude). Physiologically corresponds to the height of the sound and its volume. The third important characteristic is a sound spectrum, i.e. The composition of additional periodic oscillations (overtones) arising along with the main frequency and exceeding it. Sound spectrum is expressed by the timbre of sound. This is how the sounds of different musical instruments and a human voice are distinguished.

The distinction of sounds is based on the phenomenon of the resonance arising in the fibers of the main membrane.

The width of the main membrane, i.e. The length of its fibers, non-etinakov: the fibers are longer at the top of the snail and in short at its base, although the width of the snail channel here is more. From the length of the fibers, their own oscillation frequency depends: the shorter the fiber, the more frequent sound it resonates. When the sound of high frequency comes into the ear, the short fibers are resonated by the main membrane, located at the base of the snail, and the sensitive cells located on them are excited. In this case, not all cells are excited, but only those that are on fibers of a certain length. Low sounds are perceived by the sensitive cells of the Cortiyev organ, located on the long fibers of the main membrane at the vertex of the snail.

Thus, the primary analysis of sound signals begins in the Cortium organ, from which the excitation of the hearing nerve fibers is transmitted to the hearing center of the cerebral cortex in the temporal share where their high-quality assessment occurs.

The human auditory analyzer is most sensitive to the sounds with a frequency of 2000-4000 Hz. Some animals (bats, dolphins) hear sounds of much greater frequency - up to 100,000 Hz; They serve them for echolocation.

Equilibrium authority - vestibular apparatus

The vestibular apparatus regulates the position of the body in space. It consists of each ear located in the labyrinth:

• three semicircular channels
• two bags of antifreeze

The vestibular sensitive cells of mammals and humans form five receptor areas - one in semicircular channels, as well as in the oval and round bags.

Semicircular canals - located in three mutually perpendicular planes. Inside there is an interflowed canal, filled with endolymph, between the wall of which and the inside of the bone maze is perilimph. At the heart of each semicircular channel there is an extension - ampoule. On the inner surface of the ampoules of the connecting ducts there is a protrusion - an ampular scallop consisting of sensitive hairs and support cells. Sensitive hairs bonding between themselves are presented in the form of brushes (Coupul).

The irritation of sensitive cells of semicircular channels occurs as a result of the movement of endolymphs when the position of the body, acceleration or slowing down movement. Since semicircular channels are located in mutually perpendicular planes, their receptors are irritated when the position or movement of the body is changed in any direction.

Bags in anticipation - contains a healite apparatus, presented by the formations scattered along the inner surface of the bags. The taper apparatus contains receptor cells from which hairs depart; The space between them is filled with a study-shaped mass. On top of it are the olitis - crystals of calcium bugger.

In any position of the body, the ololyta put pressure on some kind of group of hairs cells, they deform their hairs. The deformation causes excitation in the nerve fibers that deteriorate these cells. The excitation enters the nerve center located in the oblong brain, and with an unusual position of the body causes a number of motor reflex reactions that cause the body to normal.

Thus, in contrast to semicircular channels, which perceive the change in the position of the body, acceleration, slowing down or changing the direction of the body, the abandonment bags perceive only the position of the body in space.

The vestibular apparatus is closely associated with the vegetative nervous system. Therefore, the excitation of the vestibular apparatus in the aircraft, on the steamer, on the swing, etc. accompanied by various vegetative reflexes: a change in blood pressure, breathing, secretion, digestive glands, etc.

Table. The structure of the organ of hearing

Parts of the ear	Structure	Functions
Outdoor Ear	Own sink, auditory canal, eardrum - tight tight tendon	Protects the ear, catches and spends sounds. The oscillations of the sound waves cause vibration of the eardrum, which is transmitted to the middle ear
Middle ear	The cavity is filled with air. Hearing bones: hammer, anvil, swpied. Eustachian tube	Conducts sound oscillations. Hearing bones (weight 0.05 g) sequentially and movably connected. The hammer is adjacent to the eardrum and perceives its oscillations, then transmits them to the anvil and rapidly, which is connected to the inner ear through an oval window, tightened with an elastic film (connective tissue). Evstachyeva pipe connects the middle ear with the nasooplip, provides leveling pressure
	The cavity is filled with liquid. Hearing organ: oval window, snail, cortis organ	The oval window by means of an elastic membrane perceives oscillations coming from the plenty, and transmits them through the liquid of the cavity of the inner ear on the snail fiber. Snail has a channel twisting at 2.75 turns. In the middle of the Snail Channel passes the interpretable partition - the main membrane, which consists of 24 thousand fibers of various lengths stretched as strings. The cylindrical cells with hairs are hanging over them, which form the Cortium organ - the auditory receptor. It perceives the fluctuations in the fibers and transfers the excitement into the hearing area of \u200b\u200bthe large hemispheres of the cortex, where the sound signals (words, music) are formed.
	Equilibrium authority: three semicircular channels and a tag	The equilibrium organs perceive the position of the body in space. Transmit excitation to the oblong brain, after which reflex movements arise, leading the body into normal position

Hygiene hearing

To protect the hearing body from harmful effects and infection, some hygienic measures should be observed. An excess of ear sulfur separated by iron in the outer hearing aisle and protecting the ear against penetration of microbes and dust can lead to the formation of a sulfur tube and cause a hearing of hearing. Therefore, it is necessary to constantly monitor the purity of the ears, regularly wash the ears with warm soapy water. If a lot of sulfur accumulated, in no case cannot be removed by its solid objects (the risk of damage to the eardrum); It is necessary to consult a doctor to remove traffic jams

In infectious diseases (flu, angina, measles), nasopharynx microbes can penetrate the hearing tube into the middle ear cavity and cause inflammation.

Overwork of the nervous system and overvoltage of hearing can cause sharp sounds and noises. It is especially harmful to continuous noise, while hearing thugs and even deafness occurs. A strong noise reduces labor productivity to 40-60%. To combat noise under production conditions, the walls of the walls and the ceilings are used with special materials absorbing sound, individual antioxide headphones. Motors and machines are installed on foundations that are devoured noise from concussion mechanisms.

Understanding the physiology of hearing requires acquaintance with the structure of the receptor apparatus. The following is a brief description of publications. If necessary, the reader may apply in addition to the anatomy manuals ..

The organ of hearing consists of an external, middle and inner ear (Fig.1.1.).

Fig.1.1. Scheme of outdoor, middle and inner ear.

Hearing passconnecting the outer and middle ear, overclocking at its inner end drumpowder. This thin membrane .. Behind the eardrum is filled with air the cavity of the middle ear. The cavity is connected to the throat of a narrow passage-eustachius pipe; When swallowing, there is some exchange of air between the throat and the middle ear. The change in the pressure of the outer air, as, for example, on the plane, causes an unpleasant feeling, "lays out" ears. It is explained by the tension of the eardrum due to the difference between atmospheric pressure and pressure in the cavity of the middle ear. When swallowing Eustachiev, the pipe opens, and thus the pressure on both sides of the eardrum aligns.

There are three small bones in the middle ear hammer, anviland stapesThey are flexibly interconnected and form a kind of chain. One of the travers of the hammer is merged with a drumpot. When air oscillations lead the drumpipes, it is transmitted to the bone chain. Swimmingly really similar to the elder, the foundation of which is included in the hole in the bone, called oval window. This plate forms the border between the cavity of the middle ear and the third hearing body, inland ear. Thus, the chain of the seeds is served by the bridge between the eardrum and the oval window, between the atmosphere and the inner ear. On this path, the sound energy reaches the inner ear, where the sensory cells are laid.

Interior Earis in the temporal bone; It directly communicates with the equilibrium organ. Together both organs are called maze. Because of its form, the inner ear is also called snail. Snail consists of three parallel, rolled tubular channels in the coil. Figure 1.2. The cut across the snail axis is shown, and thus the channels, whining the axis, are cut in several places. These channels are called Scala Vestibuli (Start of the Thread Starter, or Vestibular), Scala Media (Medium Staircase, or Sniddle Doc) and Scala Tympani (Drum Staircase). A man snail forms two and a half. Their arrangement is shown in Fig. 1.2. The postponement plate in the oval window adjoins the vestibular staircase, which (as well as the remaining channels) is filled with liquid. The vestibular and drum stairs contain the so-called perilimfa, and snail duct filled endolimfoy. These fluids differ in chemical composition. Perilimph contains a lot of sodium, approximately at the same concentration that the extracellular liquid, and the endolymph is rich in potassium, as the intracellular fluid vestibular and drum stairs are connected to helicotrema(Helicotrema), the tops of the snail. At the base of the snail both of these channels are separated from the cavity of the middle ear with similar structures. Oval window, leading to the vestibular staircase, is closed by a sword, with the edges of the holes are sealed ring ligament, and round windowat the end of the drum staircase is tightened with a fine membrane, which separates it from the cavity of the middle ear, and the perilimph cannot be leaked into it.

Fig.1.2. Cross section of snail curl.

Here you can see that the border between the vestibular staircase and the smoke is formed by a membrane called vestibular(or rayne-Povo). The border between the snippled duct and the drum staircase forms basilar (basic) membranewhich is the actual sensory apparatus - cortiev Organ. In the Cortium organ, receptor cells are surrounded by clad cells. They're called hair cellsbecause of their submicroscopic, similar to hairs of processes, stereocilium. Differ internaland outdoorhair cells. The exterior is located three rows, and the internal form only one. Thus, the outer hairs cells are much larger than the internal.

Above the cortis organ is the gelatinous mass, tematical (cover) membrane. It is attached to the inside of the snail, near its axis. It also touches the Tsilly of Hair Cells, forming a fairly close contact with them. In any case, this is the case with outer hairsdown cells. Along the outdoor side of the snelled duct stretches the strip, where blood vessels are concentrated ,. This structure plays a major role in meeting the energy needs of the snail, besides other of its functions, it supports the concentration of K + in the endolymph.

Receptor cells in the Cortium organ are secondary sensory cells- It means that they have no axon. Body of cells transmitting excitation from this organ to the central nervous system are in spiral Gangliawho lies in the snail, curling around her axis along with the channels. Nerve cells in this ganglia bipolar. In each cell, one process goes to the periphery, the Cortiyev organic cells, the other in the composition hearing nerveto CNS. Each inner wicketthe cell forms synapses with many afferent nerve fibers, each of which probably contacts only one of this hairs cell. In contrast, nerve fibers supplying exterior Hair Cells, very branching, and each of them receives synaptic inputs from many exterior hairs cells. Therefore, despite the fact that the outer hairs cells are larger, the bulk of the fibers in the auditory nerve comes from the inner hairs cells.

In water, for example, the sound is quenched four times faster than in the air .. and the fluid molecules are actually moving back and forward (in accordance with the local change in pressure gradients along the direction of the wave propagation direction); Therefore, sound waves are called longitudinal(Unlike transverse waves, which apply to a string or water surface).

The amplitude of periodic pressure oscillations is called sound pressure; It can be measured using a microphone and apply to sound description. Like any other, sound pressure is measured in Newton per square meter. But the range of sound pressures acting on the auditory system is so great that it is more convenient - it is really universally accepted in acoustics-use the logarithmic scale, the so-called sound pressure level. It was established by accepting how the initial arbitrarily selected level p0.\u003d \u003d 2-10 -5 N / m 2 (which is close to the threshold of hearingness). Sound Pressure Level (L) of this Sound Pressure rdescribed by equation

and the obtained units L are called decibels (dB). So, for pressure level requal p0., L \u003d 0 dB. The "mysterious 20" is explained simply: the logarithm of the amplitude of pressure was originally called "Bel" (in honor of Alexander Graham Bella, Bell), which, naturally, is 10 dB; but a decibelic scale reflecting the power (proportional square of amplitude), more convenient, A log p 2 \u003d 2 log p; Hence 2 10 \u003d 20.

Since other values, such as electrical potential, are sometimes expressed in the same deciblip scale, sound pressure levels (WSD) are often given as decybelTSD. Such an indication emphasizes that the values \u200b\u200bare obtained by the above formula where the reference level p0.\u003d 2-10 "5 N / m 2.

The second parameter of the sound, frequency is expressed in cycles per second, or hertzha(In honor of the German physics of the XIX century.), Abbreviated Hz. The high-frequency sounds of the wavelengths are shorter than low-frequency. Frequency F, sound speed C and wavelength λ (lambda) are related to each other:

The sound characterized by only one frequency (for example, 2000 Hz) is called tone. But in the daily life of clean tones almost no happening. Conventional sounds, from the most musical to the most noisy, almost always contain many frequencies. The sounds that we consider musical consist of a limited number of frequencies, usually from the main tone with several harmonics. The main tone defines the "period of repetition" of complex fluctuations of sound pressure. Harmonics are overtones with frequencies, multiple main frequency. With the help of various devices, you can get almost clean tones, but "tones" produced by musical instruments contain harmonics. Different tools differ in the number and relative intensity of overtones associated with the main tone. Some tools cannot publish certain overtones; For example, the sounds made by closed pipes of the organ contain only odd harmonics, frequency ,F, ZF O, 5F 0, etc. It is these features of the frequency spectrum that create a variety of sounds in the orchestra. If the sound turns on a lot of frequencies, then it is "noise", and if all frequencies in such sound have equal intensities, then it is called white noise. Other noise has other frequency spectra, but for all such sounds it is characteristic that there are no obvious frequency in the time of their sound pressure changes.

The ear is one of the most important organs for a person who not only allows us to hear any sounds that surround us, but also helps to maintain balance, so it is important to avoid the danger of a hearing impairment.

Before plunge into the structure of the ear system, see the informative video about how our hearing system works, as accepts and processes sound signals:

The hearing body is divided into three parts:

• Outdoor Ear
• Middle ear
• Inner ear.

Outdoor Ear

The outer ear is the only visible part of the hearing organ. It consists of:

• The ear shell, which collects sounds and sends them to the outer hearing aisle.
• Outdoor auditory passes, which is designed to conduct sound oscillations from the ears of the sink in the middle ear drum cavity. Its length in adults is about 2.6 cm. Also, the surface of the outer auditory pass contains the sebaceous glands that highlight the ear, protecting the ear from microbes and bacteria.
• The eardrum, which separates the outdoor ear from the middle ear.

Middle ear

The average ear is filled with air cavity behind the eardrum. It is associated with the nasopharynx with the help of the Eustachius pipe, which levels the pressure on both sides of the eardrum. That is why if a person lays her ears, he reflexively begins to yawning or performing swallowing movements. Also in the middle ear there are the smallest bones of a skeleton of a person: hammer, anvil and rapidly. They are not only responsible for the transmission of sound oscillations from the outdoor ear in the inner, but also strengthen them.

Interior Ear

The inner ear is the most difficult hearing department, which, due to its intricate form, is also called the labyrinth. It consists of:

• Experience and semicircular channels that are responsible for the sense of equilibrium and body position in space.
• Snails filled with liquid. It is here in the form of vibrations fall sound oscillations. Inside the snail is Cortiyev organ, which is directly responsible for the hearing. It contains about 30,000 hairs cells, which capture sound oscillations and transmit a signal to the hearing zone of the cerebral cortex. Interestingly, each of the hairs cells responds to a certain sound purity, which is why, with their death, a hearing impairment occurs and a person ceases to hear the sounds of the frequency that the deceased cells answered.

Hearing roads

Hearing conductors are a set of nerve fibers responsible for the transfer of nerve pulses from snail to auditory centers, which are located in the temporal fractions of the brain. It is there that there is a processing and analysis of complex sounds, for example, speech. The rate of transmission of the auditory signal from the outer ear to the centers of the brain is approximately 10 amliseconds.

Sound perception

The ear consistently converts the sounds into the mechanical oscillations of the eardrum and hearing bones, then into fluid oscillations in the snail and, finally, into electrical impulses that are transmitted to the conductive paths of the central hearing system to the temporal stakes of the brain for recognition and processing.

Getting nervous impulses, the brain not only transforms them into sound, but also gets an additional information, important for us. So we distinguish the height and volume of the sound and the time interval between the moments of catching sound with the right and left ear, which allows us to determine the direction by which the sound comes. At the same time, the brain analyzes not only information obtained from each ear separately, but also combines it into a single feeling. In addition, in our brain, the so-called "templates" of the sounds of sounds are stored, which helps the brain to distinguish them from strangers faster. When the hearing is reduced, the brain receives distorted information, the sounds become quieter and this leads to errors in their interpretation. The same problems may arise as a result of aging, injuries of the head and neurological diseases. This proves only one thing: For a good hearing, the work is important not only the organ of hearing, but also the brain!