The passage of sound through the organ of hearing. Anatomical structure of the sound-conducting system of hearing

The ear is the organ of hearing and balance. Its components provide sound reception and balance.

Irritant to the organ of hearing - mechanical energy in the form of sound vibrations, which are an alternation of thickening and rarefaction of air, propagating in all directions from the sound source at a speed of about 330 m / s. Sound can travel through air, water, and solids. The propagation velocity depends on the elasticity and density of the medium.

The auditory analyzer consists of:

1. Peripheral department-contains outer, middle and inner ear (Fig. 25);

2. Subcortical department- consists of the striatal body of the pons (4th ventricle of the brain), the lower tubercles of the quadrigemina of the midbrain, the medial (middle) geniculate body, the thalamus.

3. Hearing zone cerebral cortex, located in the temporal region.

Outer ear. The function is to capture sounds and conduct them to the eardrum. It consists of an auricle built of cartilaginous tissue and an external auditory meatus, going to the middle ear and rich in glands that secrete earwax, which accumulates in the external ear and from which dust and dirt are removed. The external auditory canal is up to 2.5 cm long and about 1 cm 3 wide. The tympanic membrane is stretched on the border between the outer and middle ear. Its thickness in humans is about

The auricle collects sound waves. Due to the fact that the dimensions of the auricle are 3 times larger than the tympanic membrane, the sound pressure falling on the latter is 3 times greater than on the auricle. The tympanic membrane has elasticity, so it resists the pressure wave, which contributes to the rapid decay of its vibrations, and it perfectly transmits the pressure of sound, almost without distorting the shape of the sound wave.

Middle ear represented by a tympanic cavity of irregular shape and a capacity of 0.75 cm 3 located inside the temporal bone. It communicates with the nasopharynx with the help of the auditory (Eustachian) tube and has a chain of articulated small bones - the hammer, anvil and stirrup, transmitting accurately and in an enhanced form the vibrations of the tympanic membrane to a thin oval plate in the inner ear.

The ossicular system increases the pressure of a sound wave during transmission from the tympanic membrane to the membrane of the oval window approximately 60-70 times. This amplification of sound occurs as a result of the fact that the surface of the tympanic membrane (70 mm 2) is larger than the surface of the stirrup (3.2 mm 2) attached to the oval window by 22-25 times, therefore the sound increases by 22-25 times. Since the lever apparatus of the ossicles reduces the amplitude of sound waves by approximately 2.5 times, the same amplification of the shocks of sound waves to the oval window occurs, and the total amplification of sound is obtained by multiplying 22-25 by 2.5. The outer and middle ear conduct sound pressure, reducing sound wave vibrations. Thanks to eustachian tube equal pressure is maintained on both sides of the tympanic membrane. This pressure equalizes with swallowing movements.

The only way for air to enter and exit in the middle ear is Eustachian tube- a canal that goes to the back of the nasal cavity and communicates with the nasopharynx. Thanks to this channel, the air pressure in the middle ear is equalized with atmospheric pressure, and thus the air pressure on the eardrum is equalized. When flying on an airplane - when climbing or descending, it “lays” the ears. This is due to a sharp change in atmospheric pressure, which causes the deflection of the eardrum. Then a yawn or a simple swallow of saliva leads to the opening of the valve located in the Eustachian tube, and the pressure in the middle ear equalizes with atmospheric pressure; at the same time, the eardrum returns to its normal position and the ears "open".

Human organism. Structure and activity of organs and organ systems. Human hygiene.

Task 14: the human body. Structure and activity of organs and organ systems. Human hygiene.

(sequencing)

1. Establish the correct sequence of passage through the auditory analyzer of a sound wave and a nerve impulse from a shot to the cerebral cortex. Write down the corresponding sequence of numbers in the table.

1. Shot sound
2. auditory cortex
3. auditory ossicles
4. cochlear receptors
5. Auditory nerve
6. Eardrum

Answer: 163452.

2. Establish the sequence of curves of the human spine, starting with the head. Write down the corresponding sequence of numbers in the table.

1. Lumbar
2. Cervical
3. Sacral
4. thoracic

Answer: 2413.

3. Set the correct sequence of actions to stop arterial bleeding from the radial artery. Write down the corresponding sequence of numbers in the table.

1. Transport the victim to a medical facility
2. Free your forearm from clothing
3. Put a soft cloth above the wound, and put a rubber tourniquet on top
4. Tie the tourniquet in a knot or pull it off with a wooden stick-by-twist
5. Attach a piece of paper to the tourniquet indicating the time of its application.
6. Put a sterile gauze bandage on the wound surface and bandage

Answer: 234651.

4. Establish the correct sequence of movement of arterial blood in a person, starting from the moment it is saturated with oxygen in the capillaries of the small circle. Write down the corresponding sequence of numbers in the table.

1. left ventricle
2. Left atrium
3. Small circle veins
4. Great circle arteries
5. small circle capillaries

Answer: 53214.

5. Set the correct sequence of elements of the reflex arc of the cough reflex in humans. Write down the corresponding sequence of numbers in the table.

1. Executive neuron
2. Laryngeal receptors
3. center of the medulla oblongata
4. Sensory neuron
5. Respiratory muscle contraction

Answer: 24315.

6. Set the correct sequence of processes occurring during blood coagulation in humans. Write down the corresponding sequence of numbers in the table.

1. Prothrombin formation
2. Thrombus formation
3. fibrin formation
4. Damage to the vessel wall
5. The effect of thrombin on fibrinogen

Answer: 41532.

7. Set the correct sequence of human digestion processes. Write down the corresponding sequence of numbers in the table.

1. The supply of nutrients to the organs and tissues of the body
2. The passage of food into the stomach and its digestion by gastric juice
3. Grinding food with teeth and changing it under the influence of saliva
4. Absorption of amino acids into the blood
5. Digestion of food in the intestine under the influence of intestinal juice, pancreatic juice and bile

Answer: 32541.

8. Set the correct sequence of elements of the human knee reflex reflex arc. Write down the corresponding sequence of numbers in the table.

1. Sensory neuron
2. motor neuron
3. Spinal cord
4. Quadriceps femoris
5. tendon receptors

Answer: 51324.

9. Set the correct sequence of the bones of the upper limb, starting from the shoulder girdle. Write down the corresponding sequence of numbers in the table.

1. wrist bones
2. Metacarpal bones
3. Phalanges of fingers
4. Radius
5. Brachial bone

Answer: 54123.

10. Establish the correct sequence of digestion processes in humans. Write down the corresponding sequence of numbers in the table.

1. Breakdown of polymers to monomers
2. Swelling and partial breakdown of proteins
3. Absorption of amino acids and glucose into the blood
4. Beginning of starch breakdown
5. Intensive water suction

Answer: 42135.

11. Establish the sequence of stages of inflammation when microbes penetrate (for example, when damaged by a splinter). Write down the corresponding sequence of numbers in the table.

1. Destruction of pathogens
2. Redness of the affected area: capillaries expand, blood flows, local temperature rises, pain sensation
3. White blood cells arrive at the inflamed area with blood
4. A powerful protective layer of leukocytes and macrophages is formed around the accumulation of microbes
5. The concentration of microbes in the affected area

Answer: 52341.

12. Establish the sequence of stages of the human cardiac cycle after a pause (that is, after filling the chambers with blood). Write down the corresponding sequence of numbers in the table.

1. Blood supply to the superior and inferior vena cava
2. The blood gives away nutrients and oxygen and receives metabolic products and carbon dioxide.
3. Blood supply to arteries and capillaries
4. Contraction of the left ventricle, the flow of blood into the aorta
5. Blood supply to the right atrium of the heart

Answer: 43215.

13. Establish the sequence of the human airways. Write down the corresponding sequence of numbers in the table.

1. Bronchi
2. Nasopharynx
3. Larynx
4. Trachea
5. nasal cavity

Answer: 52341.

14. Arrange in the correct order the sequence of the bones of the leg skeleton from top to bottom. Write down the corresponding sequence of numbers in the table.

1. Metatarsus
2. Femur
3. Shin
4. Tarsus
5. Phalanges of fingers

Answer: 23415.

15. Signs of fatigue during static work are recorded in the experiment of holding the load in the arm extended strictly horizontally to the side. Establish the sequence of manifestation of signs of fatigue in this experiment. Write down the corresponding sequence of numbers in the table.

1. Hand trembling, loss of coordination, staggering, facial flushing, sweating
2. The arm with the load is lowered
3. The arm drops, then jerks back up to its original position.
4. Recovery
5. The hand with the load is motionless

Answer: 53124.

16. Establish the sequence of stages of carbon dioxide transport from brain cells to lungs. Write down the corresponding sequence of numbers in the table.

1. Pulmonary arteries
2. Right atrium
3. Jugular vein
4. Pulmonary capillaries
5. Right ventricle
6. superior vena cava
7. brain cells

Answer: 7362514.

17. Set the sequence of processes in the cardiac cycle. Write down the corresponding sequence of numbers in the table.

1. The flow of blood from the atria to the ventricles
2. Diastole
3. Atrial contraction
4. Closing of the cuspid valves and opening of the semilunar
5. Blood supply to the aorta and pulmonary arteries
6. Contraction of the ventricles
7. Blood from the veins enters the atria and partially drains into the ventricles

Answer: 3164527.

18. Establish the sequence of processes occurring during the regulation of the work of internal organs. Write down the corresponding sequence of numbers in the table.

1. The hypothalamus receives a signal from the internal organ
2. The endocrine gland produces a hormone
3. The pituitary gland produces tropic hormones
4. The work of the internal organ changes
5. Transport of tropic hormones to endocrine glands
6. Isolation of neurohormones

Answer: 163524.

19. Establish the sequence of location of the intestines in humans. Write down the corresponding sequence of numbers in the table.

1. Skinny
2. sigmoid
3. blind
4. Straight
5. Colon
6. duodenal
7. Iliac

Answer: 6173524.

20. Establish the sequence of processes occurring in the human female reproductive system in the event of pregnancy. Write down the corresponding sequence of numbers in the table.

1. Attachment of the embryo to the wall of the uterus
2. The release of the egg into the fallopian tube - ovulation
3. Ovum maturation in graph vesicle
4. Multiple divisions of the zygote, the formation of the germinal vesicle - blastula
5. Fertilization
6. The movement of the egg due to the movement of the cilia of the ciliated epithelium of the fallopian tube
7. Placentation

Answer: 3265417.

21. Set the sequence of periods of development in humans after birth. Write down the corresponding sequence of numbers in the table.

1. Newborn
2. Pubertal
3. Early childhood
4. teenage
5. Preschool
6. thoracic
7. Youthful

Answer: 1635247.

22. Establish the sequence of transmission of information along the links of the reflex arc of the ciliary reflex. Write down the corresponding sequence of numbers in the table.

1. Transfer of excitation to the circular muscle of the eye, closing the eyelids
2. Transmission of a nerve impulse along the axon of a sensitive neuron
3. Transfer of information to the executive neuron
4. Reception of information by an intercalary neuron and its transmission to the medulla oblongata
5. The emergence of excitation in the center of the blinking reflex
6. Mote in the eye

Answer: 624531.

23. Set the sequence of propagation of a sound wave in the organ of hearing. Write down the corresponding sequence of numbers in the table.

1. Hammer
2. oval window
3. Eardrum
4. Stapes
5. Fluid in the cochlea
6. Anvil

Answer: 316425.

24. Establish the sequence of movement of carbon dioxide in humans, starting from the cells of the body. Write down the corresponding sequence of numbers in the table.

1. Superior and inferior vena cava
2. body cells
3. Right ventricle
4. Pulmonary arteries
5. Right atrium
6. Capillaries of the systemic circulation
7. Alveoli

Answer: 2615437.

25. Set the sequence of information transfer in the olfactory analyzer. Write down the corresponding sequence of numbers in the table.

1. Irritation of cilia of olfactory cells
2. Analysis of information in the olfactory zone of the cerebral cortex
3. Transmission of olfactory impulses to subcortical nuclei
4. When inhaled, odorous substances enter the nasal cavity and dissolve in mucus.
5. The emergence of olfactory sensations, which also have an emotional connotation
6. Transmission of information along the olfactory nerve

Answer: 416235.

26. Set the sequence of stages of fat metabolism in humans. Write down the corresponding sequence of numbers in the table.

1. Emulsification of fats under the influence of bile
2. Absorption of glycerol and fatty acids by intestinal villus epithelial cells
3. The entry of human fat into the lymphatic capillary, and then into the fat depot
4. Dietary fat intake
5. Synthesis of human fat in epithelial cells
6. Breakdown of fats into glycerol and fatty acids

Answer: 416253.

27. Set the sequence of steps for the preparation of tetanus toxoid. Write down the corresponding sequence of numbers in the table.

1. Tetanus toxoid administration to a horse
2. Development of stable immunity in the horse
3. Preparation of tetanus toxoid serum from purified blood
4. Purification of the horse's blood - removal of blood cells, fibrinogen and proteins from it
5. Repeated administration of tetanus toxoid to a horse at regular intervals with increasing dose
6. Horse blood sampling

Answer: 152643.

28. Set the sequence of processes occurring during the development of a conditioned reflex. Write down the corresponding sequence of numbers in the table.

1. Presentation of a conditional signal
2. Multiple repetition
3. Development of a conditioned reflex
4. The emergence of a temporary connection between two foci of excitation
5. Unconditional Reinforcement
6. The emergence of foci of excitation in the cerebral cortex

Answer: 156243.

29. Establish the sequence of passage through the organs of the human respiratory system of a labeled oxygen molecule that has penetrated into the lungs during inhalation. Write down the corresponding sequence of numbers in the table.

1. Nasopharynx
2. Bronchi
3. Larynx
4. nasal cavity
5. Lungs
6. Trachea

Answer: 413625.

30. Establish the path that nicotine passes through the blood from the pulmonary alveoli to the brain cells. Write down the corresponding sequence of numbers in the table.

1. Left atrium
2. Carotid artery
3. Pulmonary capillary
4. brain cells
5. Aorta
6. Pulmonary veins
7. left ventricle

Answer: 3617524.

Biology. Preparation for the exam-2018. 30 training options for the demo version of 2018: teaching aid / A. A. Kirilenko, S. I. Kolesnikov, E. V. Dadenko; ed. A. A. Kirilenko. - Rostov n / a: Legion, 2017. - 624 p. - (USE).

1. Set the correct sequence of nerve impulse transmission along the reflex arc. Write down the corresponding sequence of numbers in the table.

1. Interneuron
2. Receptor
3. effector neuron
4. sensory neuron
5. Working body

Answer: 24135.

2. Set the correct sequence for the passage of a portion of blood from the right ventricle to the right atrium. Write down the corresponding sequence of numbers in the table.

1. Pulmonary vein
2. left ventricle
3. pulmonary artery
4. Right ventricle
5. Right atrium
6. Aorta

Answer: 431265.

3. Establish the correct sequence of respiratory processes in humans, starting with an increase in the concentration of CO2 in the blood. Write down the corresponding sequence of numbers in the table.

1. Increasing oxygen concentration
2. Increasing CO2 concentration
3. Excitation of chemoreceptors in the medulla oblongata
4. Exhalation
5. Contraction of the respiratory muscles

Answer: 346125.

4. Set the correct sequence of processes occurring during blood coagulation in humans. Write down the corresponding sequence of numbers in the table.

1. Thrombus formation
2. The interaction of thrombin with fibrinogen
3. Platelet destruction
4. Damage to the vessel wall
5. fibrin formation
6. Prothrombin activation

Answer: 436251.

5. Establish the correct sequence of first aid measures for bleeding from the brachial artery. Write down the corresponding sequence of numbers in the table.

1. Apply a tourniquet to the tissue above the wound
2. Take the victim to the hospital
3. Put a note under the tourniquet indicating the time of its application.
4. Press the artery against the bone with your finger
5. Apply a sterile dressing over the tourniquet
6. Check the correct application of the tourniquet by probing the pulse

Answer: 416352.

6. Set the correct sequence of measures to provide first aid to a drowning person. Write down the corresponding sequence of numbers in the table.

1. Press rhythmically on the back to remove water from the airways
2. Transport the victim to a medical facility
3. Place the victim face down on the hip of the rescuer's leg bent at the knee
4. Perform mouth-to-mouth artificial respiration by pinching your nose
5. Clean the cavities of the nose and mouth of the victim from dirt and mud

Answer: 53142.

7. Set the sequence of processes occurring during inhalation. Write down the corresponding sequence of numbers in the table.

1. The lungs, following the walls of the chest cavity, expand
2. Nerve impulse in the respiratory center
3. Air rushes through the airways into the lungs - inhalation occurs
4. When the external intercostal muscles contract, the ribs rise
5. The volume of the chest cavity increases

Answer: 24513.

8. Establish the sequence of processes of passage of a sound wave in the organ of hearing and a nerve impulse in the auditory analyzer. Write down the corresponding sequence of numbers in the table.

1. Fluid movement in the cochlea
2. Transmission of a sound wave through the hammer, anvil and stirrup
3. Transmission of a nerve impulse along the auditory nerve
4. Vibration of the eardrum
5. Conduction of sound waves through the external auditory canal

Answer: 54213.

9. Set the sequence of stages of formation and movement of urine in the human body. Write down the corresponding sequence of numbers in the table.

1. Accumulation of urine in the renal pelvis
2. Reabsorption from nephron tubules
3. Plasma Filtration
4. Drainage of urine through the ureter into the bladder
5. The movement of urine through the collecting ducts of the pyramids

Answer: 32514.

10. Establish the sequence of processes occurring in the human digestive system during the digestion of food. Write down the corresponding sequence of numbers in the table.

1. Grinding, mixing food and primary breakdown of carbohydrates
2. Water absorption and fiber breakdown
3. Breakdown of proteins in an acidic environment under the action of pepsin
4. Absorption through the villi into the blood of amino acids and glucose
5. Conducting a food coma through the esophagus

Answer: 15342.

11. Set the sequence of processes occurring in the human digestive system. Write down the corresponding sequence of numbers in the table.

1. Breakdown of proteins by pepsin
2. Breakdown of starch in an alkaline environment
3. Breakdown of fiber by symbiotic bacteria
4. Movement of the food bolus through the esophagus
5. Absorption through the villi of amino acids and glucose

Answer: 24153.

12. Establish the sequence of thermoregulation processes in humans during muscular work. Write down the corresponding sequence of numbers in the table.

1. Transmission of signals along the motor pathway
2. Relaxation of the muscles of the blood vessels
3. The effect of low temperatures on skin receptors
4. Increased heat transfer from the surface of blood vessels

The process of obtaining sound information includes the perception, transmission and interpretation of sound. The ear picks up and converts auditory waves into nerve impulses that the brain receives and interprets.

There are many things in the ear that are not visible to the eye. What we observe is only part of the outer ear - a fleshy-cartilaginous outgrowth, in other words, the auricle. The outer ear consists of the concha and the ear canal, which ends at the tympanic membrane, which provides a connection between the outer and middle ear, where the auditory mechanism is located.

Auricle directs sound waves into the auditory canal, much like the old auditory tube directed sound into the auricle. The channel amplifies sound waves and directs them to eardrum. Sound waves hitting the eardrum cause vibrations that are transmitted further through the three small auditory ossicles: the hammer, anvil and stirrup. They vibrate in turn, transmitting sound waves through the middle ear. The innermost of these bones, the stirrup, is the smallest bone in the body.

Stapes, vibrating, strikes the membrane, called the oval window. Sound waves travel through it to the inner ear.

What happens in the inner ear?

There goes the sensory part of the auditory process. inner ear consists of two main parts: the labyrinth and the snail. The part that starts at the oval window and curves like a real snail acts as a translator, converting sound vibrations into electrical impulses that can be transmitted to the brain.

Snail filled with liquid, in which the basilar (basic) membrane is suspended, resembling a rubber band, attached to the walls with its ends. The membrane is covered with thousands of tiny hairs. At the base of these hairs are small nerve cells. When the vibrations of the stirrup hit the oval window, the fluid and hairs begin to move. The movement of the hairs stimulates nerve cells that send a message, already in the form of an electrical impulse, to the brain through the auditory, or acoustic, nerve.

Labyrinth is a group of three interconnected semicircular canals that control the sense of balance. Each channel is filled with liquid and is located at right angles to the other two. So, no matter how you move your head, one or more channels capture that movement and relay information to the brain.

If you happen to catch a cold in your ear or blow your nose badly, so that it “clicks” in the ear, then there is a hunch the ear is somehow connected with the throat and nose. And that's right. Eustachian tube directly connects the middle ear to the oral cavity. Its role is to let air into the middle ear, balancing the pressure on both sides of the eardrum.

Impairments and disorders in any part of the ear can impair hearing if they interfere with the passage and interpretation of sound vibrations.

How does the ear work?

Let's trace the path of the sound wave. It enters the ear through the pinna and travels through the auditory canal. If the shell is deformed or the canal is blocked, the path of sound to the eardrum is impeded and hearing ability is reduced. If the sound wave has safely reached the eardrum, and it is damaged, the sound may not reach the auditory ossicles.

Any disorder that prevents the ossicles from vibrating will prevent sound from reaching the inner ear. In the inner ear, sound waves cause fluid to pulsate, setting tiny hairs in the cochlea in motion. Damage to the hairs or nerve cells to which they are connected will prevent the conversion of sound vibrations into electrical ones. But, when the sound has successfully turned into an electrical impulse, it still has to reach the brain. It is clear that damage to the auditory nerve or brain will affect the ability to hear.

Dr. Howard Glicksman

Ear and hearing

The soothing sound of a babbling brook; the happy laugh of a laughing child; the rising sound of a squad of marching soldiers. All these sounds and more fill our lives every day and are the result of our ability to hear them. But what exactly is sound and how can we hear it? Read this article and you will get answers to these questions and moreover, you will understand what logical conclusions can be drawn regarding the theory of macroevolution.

Sound! What are we talking about?

Sound is the sensation we experience when vibrating environmental molecules (usually air) hit our eardrum. Plotting these changes in air pressure, which are determined by measuring the pressure on the eardrum (middle ear) versus time, produces a waveform. In general, the louder the sound, the more energy it takes to produce it, and the more range air pressure changes.

Loudness is measured in decibels, using as a starting point the threshold level of hearing (that is, a loudness level that can sometimes be barely audible to the human ear). The loudness measurement scale is logarithmic, which means that any jump from one absolute number to the next, as long as it is divisible by ten (and remember that a decibel is only one tenth of a bela), means an increase of the order of ten times. For example, the hearing threshold is labeled 0, and normal conversation occurs at about 50 decibels, so the loudness difference is 10 raised to the power of 50 divided by 10, which is 10 to the fifth power, or one hundred thousand times the loudness of the hearing threshold. Or take, for example, a sound that makes you feel a lot of pain in your ears and can actually hurt your ear. Such a sound usually occurs at a vibration amplitude of approximately 140 decibels; a sound such as an explosion or a jet plane means a fluctuation in sound intensity that is 100 trillion times the threshold level of hearing.

The smaller the distance between the waves, that is, the more waves fit in one second of time, the greater the height or the higher frequency audible sound. It is usually measured in cycles per second or hertz (Hz). The human ear is normally able to hear sounds whose frequency ranges from 20 Hz to 20,000 Hz. Normal human conversation includes sounds in the frequency range from 120 Hz for men to about 250 Hz for women. A medium-volume C note played on the piano has a frequency of 256 Hz, while an A note played on an oboe for an orchestra has a frequency of 440 Hz. The human ear is most sensitive to sounds that have a frequency between 1,000-3,000 Hz.

Concert in three parts

The ear is made up of three main sections called the outer, middle, and inner ear. Each of these departments has its own unique function and is necessary for us to hear sounds.

Figure 2.

1. outer part of the ear or the auricle of the outer ear acts as your own satellite antenna, which collects and directs sound waves into the external auditory canal (which enters the auditory canal). From here, the sound waves travel further down the canal and reach the middle ear, or tympanic membrane, which, by pulling in and out in response to these changes in air pressure, forms the vibrational path of the sound source.
2. The three ossicles (ossicles) of the middle ear are called hammer, which is directly connected to the eardrum, anvil and stirrup, which is connected to the oval window of the cochlea of ​​the inner ear. Together, these ossicles are involved in transmitting these vibrations to the inner ear. The middle ear is filled with air. By using eustachian tube, which is located just behind the nose and opens during swallowing to let outside air into the middle ear chamber, it is able to maintain the same air pressure on both sides of the eardrum. Also, the ear has two skeletal muscles: the muscles that strain the eardrum and the stirrup muscles that protect the ear from very loud sounds.
3. In the inner ear, which is made up of the cochlea, these transmitted vibrations pass through oval window, which leads to the formation of a wave in internal structures snails. Inside the snail is located Organ of Corti, which is the main organ of the ear that is able to convert these fluid vibrations into a nerve signal, which is then transmitted to the brain, where it is processed.

So, this is a general overview. Now let's take a closer look at each of these departments.

What are you talking about?

Obviously, the mechanism of hearing begins in the outer ear. If we didn't have a hole in our skull that allows sound waves to travel further to the eardrum, we wouldn't be able to talk to each other. Maybe some would like it to be so! How could this opening in the skull, called the external auditory meatus, be the result of a random genetic mutation or random change? This question remains unanswered.

It has been revealed that the outer ear, or with your permission the auricle, is an important department of sound localization. The underlying tissue that lines the surface of the outer ear and makes it so elastic is called cartilage and is very similar to the cartilage found in most of the ligaments in our body. If one supports the macroevolutionary model of hearing development, then in order to explain how the cells that are able to form cartilage acquired this ability, not to mention how they, after all this, unfortunately for many young girls, stretched out from each side heads, something like a satisfactory explanation is required.

Those of you who have ever had a wax plug in your ear can appreciate the fact that while they don't know the benefits of this earwax for the ear canal, they are certainly glad that this natural substance has no consistency. cement. Moreover, those who must communicate with these unfortunate people appreciate having the ability to raise the volume of their voice in order to produce enough sound wave energy to be heard.

A waxy product commonly referred to as earwax, is a mixture of secretions from various glands, and is contained in the external ear canal and consists of a material that includes cells that are constantly desquamated. This material extends along the surface of the auditory canal and forms a white, yellow, or brown substance. Earwax serves to lubricate the external auditory canal and at the same time protects the eardrum from dust, dirt, insects, bacteria, fungi, and anything else that may enter the ear from the environment.

It is very interesting that the ear has its own clearing mechanism. The cells that line the external auditory canal are located closer to the center of the tympanic membrane, then extend to the walls of the auditory canal and extend beyond the external auditory canal. All the way through their location, these cells are covered with an ear waxy product, the amount of which decreases as one moves towards the external canal. It turns out that jaw movements enhance this process. In fact, this whole scheme is like one big conveyor belt, the function of which is to remove earwax from the auditory canal.

Obviously, to fully understand the formation of earwax, its consistency, due to which we can hear well, and which at the same time performs a sufficient protective function, and how the auditory canal itself removes this earwax to prevent hearing loss, some kind of logical explanation is required. . How could a simple gradual evolutionary growth, resulting from a genetic mutation or a random change, be the cause of all these factors and, despite this, ensure the correct functioning of this system throughout its existence?

The tympanic membrane is made up of a special tissue, the consistency, shape, fastenings, and precise positioning of which allow it to be in a precise place and perform a precise function. All of these factors must be taken into account when explaining how the tympanic membrane is able to resonate in response to incoming sound waves, and thus set off a chain reaction that results in an oscillatory wave within the cochlea. And just because other organisms have partly similar structural features that allow them to hear, does not in itself explain how all these features came about with the help of undirected natural forces. Here I am reminded of a witty remark made by G. K. Chesterton, where he said: “It would be absurd for an evolutionist to complain and say that it is simply unbelievable for an admittedly unimaginable God to create 'everything' from 'nothing' and then claim that that 'nothing' itself turned into 'everything' is more likely”. However, I digress from our topic.

Correct vibrations

The middle ear serves to transmit the vibrations of the tympanic membrane to the inner ear, where, in which the organ of Corti is located. Just as the retina is the "organ of the eye," the organ of Corti is the true "organ of the ear." Therefore, the middle ear is actually the "intermediary" that participates in the auditory process. As often happens in business, the intermediary always has something and thus reduces the financial efficiency of the deal that is being made. Similarly, the transmission of the vibration of the tympanic membrane through the middle ear results in a negligible loss of energy, with the result that only 60% of the energy is conducted through the ear. However, if it were not for the energy that spreads to the larger tympanic membrane, which is set on the smaller foramen ovale by the three auditory ossicles, together with their specific balancing action, this energy transfer would be much less and it would be much more difficult for us. hear.

An outgrowth of part of the malleus, (the first auditory ossicle), which is called lever attached directly to the eardrum. The malleus itself is connected to the second auditory ossicle, the incus, which in turn is attached to the stapes. stirrup has flat part, which is attached to the oval window of the cochlea. As we have already said, the balancing actions of these three interconnected bones allow the vibration to be transmitted to the cochlea of ​​the middle ear.

A review of my two previous sections, namely "Hamlet familiar with modern medicine, parts I and II", may allow the reader to see what needs to be understood about bone formation itself. The way in which these three perfectly formed and interconnected ossicles are placed in the exact position by which the correct transmission of the sound wave vibration occurs requires another “same” explanation of macroevolution, which we must look at with a grain of salt.

It is curious to note that two skeletal muscles are located inside the middle ear, the muscles that strain the eardrum and the stapes muscles. The tensor tympanic membrane muscle is attached to the manubrium of the malleus and, when contracted, pulls the tympanic membrane back into the middle ear, thus limiting its ability to resonate. The stapedius ligament is attached to the flat portion of the stapes and, when contracted, is pulled away from the foramen ovale, thus reducing the vibration that is transmitted through the cochlea.

Together, these two muscles reflexively try to protect the ear from sounds that are too loud, which can cause pain and even damage it. The time it takes the neuromuscular system to respond to a loud sound is about 150 milliseconds, which is about 1/6th of a second. Therefore, the ear is not as protected against sudden loud sounds, such as artillery fire or explosions, as compared to sustained sounds or noisy environments.

Experience has shown that sometimes sounds can hurt, as can too much light. The functional parts of hearing, such as the tympanic membrane, the ossicles, and the organ of Corti, perform their function by moving in response to the energy of the sound wave. Too much movement can cause damage or pain, just like if you overexert your elbow or knee joints. Therefore, it seems that the ear has a kind of protection against self-harm, which can occur with prolonged loud sounds.

A review of my three previous sections, namely “Not just for conducting sound, parts I, II and III”, which deal with neuromuscular function at the bimolecular and electrophysiological levels, will allow the reader to better understand the specific complexity of the mechanism that is a natural defense against hearing loss. It remains only to understand how these ideally located muscles ended up in the middle ear and began to perform the function that they perform and do it reflexively. What genetic mutation or random change occurred one time in time that led to such a complex development within the temporal bone of the skull?

Those of you who have been on an airplane and experienced a feeling of pressure on your ears during landing, which is accompanied by hearing loss and a feeling that you are talking into the void, have actually become convinced of the importance of the Eustachian tube (auditory tube), which is located between the middle ear. and the back of the nose.

The middle ear is a closed, air-filled chamber in which the air pressure on all sides of the eardrum must be equal in order to provide sufficient mobility, which is called distensibility of the tympanic membrane. Distensibility determines how easily the eardrum moves when stimulated by sound waves. The higher the distensibility, the easier it is for the tympanic membrane to resonate in response to sound, and accordingly, the lower the distensibility, the more difficult it is to move back and forth and, therefore, the threshold at which a sound can be heard increases, that is, sounds must be louder in order to they could be heard.

Air in the middle ear is normally absorbed by the body, resulting in a decrease in air pressure in the middle ear and a decrease in the elasticity of the eardrum. This is due to the fact that instead of remaining in the correct position, the tympanic membrane is pushed into the middle ear by external air pressure, which acts on the external auditory canal. All this is the result of the external pressure being higher than the pressure in the middle ear.

The Eustachian tube connects the middle ear to the back of the nose and pharynx.

During swallowing, yawning, or chewing, the action of the associated muscles opens the Eustachian tube, allowing external air to enter and pass into the middle ear and replace the air that has been absorbed by the body. In this way, the tympanic membrane can maintain its optimal extensibility, which provides us with sufficient hearing.

Now let's get back to the plane. At 35,000 feet, the air pressure on both sides of the eardrum is the same, although the absolute volume is less than it would be at sea level. What is important here is not the air pressure itself, which acts on both sides of the tympanic membrane, but the fact that no matter what air pressure acts on the tympanic membrane, it is the same on both sides. As the aircraft begins to descend, the external air pressure in the cabin begins to rise and immediately acts on the eardrum through the external auditory canal. The only way to correct this imbalance of air pressure across the eardrum is to be able to open the Eustachian tube in order to let in more external air pressure. This usually occurs when chewing gum or sucking on a lollipop and swallowing, this is when the force on the tube occurs.

The speed at which the aircraft descends and the rapidly changing increases in air pressure cause some people to feel stuffy in their ears. In addition, if the passenger has a cold or has recently been ill, if they have a sore throat or a runny nose, their Eustachian tube may not work during these pressure changes and they may experience severe pain, prolonged congestion, and occasionally severe bleeding in the middle ear!

But the disruption of the functioning of the Eustachian tube does not end there. If any of the passengers are chronically ill, over time the effect of the vacuum in the middle ear can pull fluid out of the capillaries, which can lead (if left untreated) to a condition called exudative otitis media. This disease is preventable and treatable with myringotomy and tube insertion. An otolaryngologist-surgeon makes a small hole in the eardrum and inserts tubes so that the fluid that is in the middle ear can flow out. These tubes replace the Eustachian tube until the cause of this condition is eliminated. Thus, this procedure preserves proper hearing and prevents damage to the internal structures of the middle ear.

It is remarkable that modern medicine is able to solve some of these problems when the Eustachian tube is malfunctioning. But the question immediately pops up: how did this tube originally appear, which parts of the middle ear formed first, and how did these parts function without all the other necessary parts? Thinking about this, is it possible to think of a multi-stage development based on hitherto unknown genetic mutations or random change?

A careful examination of the component parts of the middle ear and their absolute necessity for the production of sufficient hearing, so necessary for survival, shows that we have a system that presents an irreducible complexity. But nothing that we have considered so far can give us the ability to hear. There is one major component to this whole puzzle that needs to be considered, and which in itself is an example of irreducible complexity. This wonderful mechanism takes vibrations from the middle ear and converts them into a nerve signal that enters the brain, where it is then processed. That main component is the sound itself.

Sound Conduction System

The nerve cells that are responsible for transmitting the signal to the brain for hearing are located in the “organ of Corti”, which is located in the cochlea. The snail consists of three interconnected tubular channels, which are approximately two and a half times rolled into a coil.

(see figure 3). The superior and inferior canals of the cochlea are surrounded by bone and are called staircase of vestibule (upper channel) and correspondingly drum ladder(lower channel). Both of these channels contain a fluid called perilymph. The composition of the sodium (Na+) and potassium (K+) ions of this fluid is very similar to that of other extracellular fluids (outside cells), i.e. they have a high concentration of Na+ ions and a low concentration of K+ ions, in contrast to intracellular fluids (inside cells).

Figure 3

The channels communicate with each other at the top of the cochlea through a small opening called helicotrema.

The middle channel, which enters the membrane tissue, is called middle staircase and consists of a liquid called endolymph. This fluid has the unique property of being the only extracellular body fluid with a high concentration of K+ ions and a low concentration of Na+ ions. The middle scala is not connected directly to other canals and is separated from the scala vestibuli by an elastic tissue called Reisner's membrane and from the scala tympani by an elastic basilar membrane (see Figure 4).

The organ of Corti is suspended, like a bridge over the Golden Gate, on the basilar membrane, which is located between the scala tympani and the middle scala. Nerve cells that are involved in the formation of hearing, called hair cells(because of their hairlike outgrowths) are located on the basilar membrane, which allows the lower part of the cells to come into contact with the perilymph of the scala tympani (see figure 4). Hair-like outgrowths of hair cells known as stereocilia, are located at the top of the hair cells and thus come into contact with the middle ladder and the endolymph that is contained within it. The importance of this structure will become clearer when we discuss the electrophysiological mechanism that underlies the stimulation of the auditory nerve.

Figure 4

The organ of Corti consists of about 20,000 of these hair cells, which are located on the basilar membrane that covers the entire coiled cochlea, and is 34 mm long. Moreover, the thickness of the basilar membrane varies from 0.1 mm at the beginning (at the base) to approximately 0.5 mm at the end (at the apex) of the cochlea. We will understand how important this feature is when we talk about the pitch or frequency of a sound.

Let's remember: sound waves enter the external auditory canal, where they cause the tympanic membrane to resonate at an amplitude and frequency that is inherent in the sound itself. The internal and external movement of the tympanic membrane allows vibrational energy to be transmitted to the malleus, which is connected to the anvil, which in turn is connected to the stirrup. Under ideal circumstances, the air pressure on either side of the eardrum is the same. Because of this, and the ability of the Eustachian tube to pass external air into the middle ear from the back of the nose and throat during yawning, chewing and swallowing, the eardrum has a high extensibility, which is so necessary for movement. Then the vibration is transmitted through the stirrup into the cochlea, passing through the oval window. And only after that the auditory mechanism starts.

The transfer of vibrational energy into the cochlea results in the formation of a fluid wave, which must be transmitted through the perilymph to the scala vestibuli. However, due to the fact that the scala vestibulum is protected by bone and separated from the scala medius, not by a dense wall, but by an elastic membrane, this oscillatory wave is also transmitted via Reissner's membrane to the endolymph of the scala medius. As a result, the scala media fluid wave also causes the elastic basilar membrane to undulate. These waves quickly reach their maximum, and then also quickly fall off in the area of ​​the basilar membrane in direct proportion to the frequency of the sound that we hear. Higher frequency sounds cause more movement at the base or thicker part of the basilar membrane, and lower frequency sounds cause more movement at the top or thinner part of the basilar membrane, in the helicorheme. As a result, the wave enters the scala tympani through the helicorema and dissipates through the round window.

That is, it is immediately clear that if the basilar membrane sways in the “breeze” of endolymphatic movement inside the middle scala, then the suspended organ of Corti, with its hair cells, will jump like on a trampoline in response to the energy of this wave movement. So, in order to appreciate the complexity and understand what actually happens in order for hearing to arise, the reader must become familiar with the function of neurons. If you don't already know how neurons function, I recommend you check out my article "Not just for conducting sound, parts I and II" for a detailed discussion of the function of neurons.

At rest, hair cells have a membrane potential of approximately 60mV. We know from neuron physiology that the resting membrane potential exists because when the cell is not excited, K+ ions leave the cell through K+ ion channels, and Na+ ions do not enter through Na+ ion channels. However, this property is based on the fact that the cell membrane is in contact with the extracellular fluid, which is usually low in K+ ions and rich in Na+ ions, similar to the perilymph that the base of the hair cells comes into contact with.

When the action of the wave causes the movement of stereocilia, that is, hair-like outgrowths of hair cells, they begin to bend. The movement of the stereocilia leads to the fact that certain channels, intended for signal transduction, and which pass K+ ions very well, begin to open. Therefore, when the organ of Corti is subjected to a jump-like action of a wave that occurs due to vibration at the resonance of the tympanic membrane through three auditory ossicles, K + ions enter the hair cell, as a result of which it depolarizes, that is, its membrane potential becomes less negative.

“But wait,” you would say. “You just told me all about neurons, and my understanding is that when channels for transduction open up, K+ ions should move out of the cell and cause hyperpolarization, not depolarization.” And you would be absolutely right, because under normal circumstances, when certain ion channels open in order to increase the permeability of that particular ion across the membrane, Na+ ions enter the cell and K+ ions go out. This is due to the relative concentration gradients of Na+ ions and K+ ions across the membrane.

But we should remember that our circumstances here are somewhat different. The upper part of the hair cell is in contact with the endolymph of the middle scala cochlea and is not in contact with the perilymph of the scala tympani. The perilymph, in turn, comes into contact with the lower part of the hair cell. A little earlier in this article, we emphasized that the endolymph has a unique feature, which is that it is the only fluid that is outside the cell and has a high concentration of K + ions. This concentration is so high that when the transduction channels, which allow K+ ions to pass through, open in response to the stereocilia's flexion movement, K+ ions enter the cell and thus cause cell depolarization.

Depolarization of the hair cell leads to the fact that in its lower part, voltage-gated channels of calcium ions (Ca ++) begin to open and allow Ca ++ ions to pass into the cell. This releases a hair cell neurotransmitter (that is, a chemical messenger between cells) and irritates a nearby cochlear neuron, which eventually sends a signal to the brain.

The frequency of sound at which a wave forms in a fluid determines where along the basilar membrane the wave will peak. As we have said, this depends on the thickness of the basilar membrane, where higher sounds cause more activity in the thinner base of the membrane, and lower frequency sounds cause more activity in the thicker upper part of the membrane.

It can be easily seen that hair cells that are closer to the base of the membrane will respond maximally to very high sounds at the upper limit of human hearing (20,000 Hz), while hair cells that are at the opposite very top of the membrane will respond maximally to sounds from the lower limits of human hearing (20 Hz).

Nerve fibers of the cochlea illustrate tonotopic map(that is, groupings of neurons with similar frequency responses) in that they are more sensitive to certain frequencies, which are eventually deciphered in the brain. This means that certain neurons in the cochlea are connected to certain hair cells, and their nerve signals are eventually transmitted to the brain, which then determines the pitch of the sound depending on which hair cells were stimulated. Moreover, the nerve fibers of the cochlea have been shown to be spontaneously active, so that when they are stimulated by a sound of a certain pitch with a certain amplitude, this leads to a modulation of their activity, which is eventually analyzed by the brain and deciphered as a certain sound.

In conclusion, it is worth noting that the hair cells that are located in a certain place on the basilar membrane will bend as much as possible in response to a certain height of the sound wave, as a result of which this place on the basilar membrane receives a wave crest. The resulting depolarization of this hair cell causes it to release a neurotransmitter, which in turn irritates a nearby cochlear neuron. The neuron then sends a signal to the brain (where it is decoded) as a sound, which was heard at a certain amplitude and frequency, depending on which cochlear neuron sent the signal.

Scientists have compiled many diagrams of the pathways for the activity of these auditory neurons. There are many more other neurons that are in the connective regions that receive these signals and then relay them to other neurons. As a result, the signals are sent to the auditory cortex of the brain for final analysis. But it is still not known how the brain converts a huge amount of these neurochemical signals into what we know as hearing.

The obstacles to solving this problem can be as puzzling and mysterious as life itself!

This brief overview of the structure and function of the cochlea can help prepare the reader for the questions often asked by admirers of the theory that all life on earth arose as a result of the action of random forces of nature without any reasonable intervention. But there are leading factors whose development must have some plausible explanation, especially given the absolute necessity of these factors for hearing function in humans.

Is it possible that these factors were formed in stages through the processes of genetic mutation or random change? Or maybe each of these parts performed some hitherto unknown function in numerous other ancestors, who later united and allowed a person to hear?

And assuming that one of these explanations is correct, what exactly were these changes, and how did they allow such a complex system to form that converts air waves into something that the human brain perceives as sound?

1. Development of three tubular canals, called the cochlear vestibule, scala media, and scala tympani, which together form the cochlea.
2. The presence of an oval window, through which the vibration from the stirrup is received, and a round window, which allow the action of the wave to dissipate.
3. The presence of the Reisner membrane, due to which the oscillatory wave is transmitted to the middle ladder.
4. The basilar membrane, with its variable thickness and ideal position between the scala media and the scala tympani, plays a role in hearing function.
5. The organ of Corti has such a structure and position on the basilar membrane that allows it to experience a spring effect that plays a very important role in human hearing.
6. The presence of hair cells inside the organ of Corti, the stereocilia of which is also very important for human hearing and without which it would simply not exist.
7. Presence of perilymph in the upper and lower scala and endolymph in the middle scala.
8. The presence of nerve fibers of the cochlea, which are located close to the hair cells located in the organ of Corti.

Final word

Before I started writing this article, I took a look at the medical physiology textbook I used in medical school 30 years ago. In that textbook, the authors noted the unique structure of the endolymph compared to all other extracellular fluids in our body. At that time, scientists did not yet “know” the exact cause of these unusual circumstances, and the authors freely admitted that although it is known that the action potential that was generated by the auditory nerve was associated with the movement of hair cells, how exactly this happened, no one could explain could. So, how can we better understand how this system works from all this? And it's very simple:

Will anyone think while listening to his favorite piece of music that the sounds that sound in a certain order are the result of a random action of the forces of nature?

Of course not! We understand that this beautiful music was written by the composer so that the listeners could enjoy what he created and understand what feelings and emotions he experienced at that moment. To do this, he signs the author's manuscripts of his work, so that the whole world knows who exactly wrote it. If someone thinks differently, he will simply be exposed to ridicule.

Likewise, when you listen to a cadenza played on violins, does it occur to anyone that the sounds of music made on a Stradivarius violin are simply the result of random forces of nature? Not! Intuition tells us that we have before us a talented virtuoso who takes certain notes in order to create sounds that his listener should hear and enjoy. And his desire is so great that his name is put on the packaging of CDs so that buyers who know this musician buy them and enjoy their favorite music.

But how can we even hear the music being played? Could this ability of ours have come about through the undirected forces of nature, as evolutionary biologists believe? Or maybe one day, one intelligent Creator decided to reveal Himself, and if so, how can we find Him? Did He sign His creation and leave His names in nature to help draw our attention to Him?

There are many examples of intelligent design inside the human body that I have covered in articles over the past year. But when I began to understand that the movement of the hair cell leads to the opening of channels for the transport of K + ions, as a result of which K + ions enter the hair cell and depolarize it, I was literally stunned. I suddenly realized that this is such a “signature” that the Creator left us. Before us is an example of how an intelligent Creator reveals Himself to people. And when humanity thinks that it knows all the secrets of life and how everything appeared, it should stop and think about whether this is really so.

Remember that an almost universal mechanism for neuronal depolarization occurs as a result of the entry of Na+ ions from the extracellular fluid into the neuron through Na+ ion channels after they have been sufficiently irritated. Biologists who adhere to evolutionary theory still cannot explain the development of this system. However, the entire system depends on the existence and stimulation of Na+ ion channels, coupled with the fact that the Na+ ion concentration is higher outside the cell than inside. This is how the neurons in our body work.

Now we must understand that there are other neurons in our body that work exactly the opposite way. They require that not Na+ ions enter the cell for depolarization, but K+ ions. At first glance, it may seem that this is simply impossible. After all, everyone knows that all the extracellular fluids of our body contain a small amount of K + ions compared to the internal environment of the neuron, and therefore it would be physiologically impossible for K + ions to enter the neuron in order to cause depolarization in the way that Na + ions do.

What was once considered “unknown” is now completely clear and understandable. Now it is clear why endolymph should have such a unique property, being the only extracellular fluid of the body with a high content of K+ ions and a low content of Na+ ions. Moreover, it is located exactly where it should be, so when the channel through which the K + ions pass opens into the membrane of the hair cells, they depolarize. Evolutionarily minded biologists should be able to explain how these seemingly opposite conditions could have appeared, and how they could have appeared in a certain place in our body, exactly where they are needed. It's like a composer placing the notes correctly, and then the musician correctly playing the piece from those notes on the violin. For me, this is an intelligent Creator who tells us: “Do you see the beauty that I endowed My creation?”

Undoubtedly, for a person who looks at life and its functioning through the prism of materialism and naturalism, the idea of ​​​​the existence of an intelligent designer is something impossible. The fact that all the questions I have asked about macroevolution in this and my other articles are unlikely to have plausible answers in the future does not seem to scare or even worry the advocates of the theory that all life was formed as a result of natural selection. , which influenced random changes.

As William Dembski aptly noted in his work The Design Revolution:“Darwinists use their misunderstanding in writing about the 'undetected' designer, not as a correctable fallacy and not as evidence that the designer's abilities are far superior to ours, but as evidence that there is no 'undetected' designer”.

Next time we will talk about how our body coordinates its muscle activity so that we can sit, stand and stay mobile: this will be the last issue that focuses on neuromuscular function.

Rice. 5.18. Sound wave.

p - sound pressure; t - time; l is the wavelength.

hearing is sound, therefore, to highlight the main functional features of the system, it is necessary to be familiar with some concepts of acoustics.

Basic physical concepts of acoustics. Sound is a mechanical vibration of an elastic medium that propagates in the form of waves in air, liquids and solids. The source of sound can be any process that causes a local change in pressure or mechanical stress in the medium. From the point of view of physiology, sound is understood as such mechanical vibrations that, acting on the auditory receptor, cause a certain physiological process in it, perceived as a sensation of sound.

The sound wave is characterized by sinusoidal, i.e. periodic, fluctuations (Fig. 5.18). When propagating in a certain medium, sound is a wave with phases of condensation (compaction) and rarefaction. There are transverse waves - in solids, and longitudinal - in air and liquid media. The speed of propagation of sound vibrations in air is 332 m/s, in water - 1450 m/s. The same states of a sound wave - areas of condensation or rarefaction - are called phases. The distance between the middle and extreme positions of an oscillating body is called oscillation amplitude, and between identical phases - wavelength. The number of oscillations (compressions or rarefactions) per unit time is determined by the concept sound frequencies. The unit of sound frequency is hertz(Hz), indicating the number of oscillations per second. Distinguish high frequency(high) and low frequency(low) sounds. Low sounds, at which the phases are far apart, have a large wavelength, high sounds with close phases have a small (short) wavelength.

Phase and wavelength play an important role in the physiology of hearing. So, one of the conditions for optimal hearing is the arrival of a sound wave to the windows of the vestibule and the cochlea in different phases, and this is anatomically provided by the sound-conducting system of the middle ear. High-pitched, short-wavelength sounds vibrate a small (short) column of labyrinthine fluid (perilymph) at the base of the cochlea (here they

are perceived), low ones - with a large wavelength - extend to the top of the cochlea (here they are perceived). This circumstance is important for the understanding of modern theories of hearing.

According to the nature of oscillatory movements, there are:

Pure tones;

Complex tones;

Harmonic (rhythmic) sinusoidal oscillations create a clean, simple sound tone. An example would be the sound of a tuning fork. A non-harmonic sound that differs from simple sounds in a complex structure is called noise. The frequencies of various oscillations that create the noise spectrum are chaotically related to the fundamental tone frequency, like various fractional numbers. The perception of noise is often accompanied by unpleasant subjective sensations.

The ability of a sound wave to bend around obstacles is called diffraction. Low-pitched, long-wavelength sounds have better diffraction than short-wavelength high-pitched sounds. The reflection of a sound wave from obstacles in its path is called echo. The repeated reflection of sound in enclosed spaces from various objects is called reverb. The superimposition of a reflected sound wave on a primary sound wave is called "interference". In this case, an increase or decrease in sound waves can be observed. When sound passes through the external auditory canal, it interferes and the sound wave is amplified.

The phenomenon when a sound wave of one oscillating object causes oscillatory movements of another object is called resonance. The resonance can be sharp, when the natural period of the resonator's oscillations coincides with the period of the acting force, and blunt, if the periods of oscillations do not coincide. With an acute resonance, the oscillations decay slowly, with a dull one, quickly. It is important that the vibrations of the structures of the ear that conduct sounds decay quickly; this eliminates the distortion of external sound, so a person can receive more and more sound signals quickly and consistently. Some structures of the cochlea have a sharp resonance, and this helps to distinguish between two closely spaced frequencies.

The main properties of the auditory analyzer. These include the ability to distinguish between pitch, loudness, and timbre. The human ear perceives sound frequencies from 16 to 20,000 Hz, which is 10.5 octaves. Oscillations with a frequency of less than 16 Hz are called infrasound, and above 20,000 Hz - Ultrasound. Infrasound and ultrasound under normal conditions