Determination of hearing acuity laboratory work. The effect of headphones on the hearing acuity of schoolchildren

Laboratory work 1. Study h meanings auricle.

In animals, the auricle plays a rather important role: it is mobile and is an organ of alertness. Many animals, such as horses, direct its bell to the source sound waves. In humans, the importance of the auricle is much less, but it still plays a certain role.

Goal of the work: A study of the meaning of the auricle.

Equipment: ticking clock; rubber tube; cotton wool; roulette.

Progress.

Determine the maximum distance (in meters) at which the ticking of a clock can still be heard when in good condition ear and when turning off the auricle. To turn the auricle into the outer ear canal a rubber tube is inserted, and the auricle is filled with cotton wool. The second ear closes in both cases cotton bandage. The distance at which the ticking of a clock can be heard shortens. On the contrary, when the bell of the auricle is enlarged with the hand, as is done when listening, the distance at which the ticking of a watch begins to be heard increases.

Laboratory work 2. Study h Functions of the Eustachian tube (Valsalva experience).

Eustachian tube, through which the middle ear cavity communicates with oral cavity, ensures equal pressure is maintained on both sides of the eardrum.

Goal of the work: A study of the significance of the Eustachian tube.

Equipment: ticking clock.

Progress.

Having inhaled as much as possible and tightly closed your nose with your hand, exhale with your mouth closed and nose closed, puffing out your cheeks (you cannot do the Valsalva experiment with a runny nose). The sound of air passing is heard. It should be ensured that under the conditions of the Valsalva experience, the threshold for hearing the ticking of a clock increases due to increased pressure in the middle ear cavity, which weakens the transmission of auditory waves.

Laboratory work 3. Determination of hearing acuity.

The strength of sound perceived by the human auditory sensory system depends on the distance from the sound source to the subject. A person with normal hearing perceives whispered speech at a distance of 4-5 m. A ticking clock (as well as a metronome, tuning fork) can be used as a sound source.

Goal of the work: approximate assessment of hearing acuity.

Equipment: roulette; ticking clock; fork.

Progress.

1. The subject is asked to move away 4-5 meters, turn his back to the researcher, and cover one ear with a cotton swab so that it does not cause discomfort.

2. The researcher whispers various words and numbers, which must include voiceless and voiced consonants, and gradually moves away from the subject. The distance at which the subject cannot correctly repeat the spoken word will characterize hearing acuity.

3. Then the subject closes the other ear with a cotton swab and the test is repeated.

Laboratory work 4. Study of binaural audibility.

The hearing analyzer has an exceptionally high ability to determine the direction of a sound source. This is only possible due to the difference in time that is necessary for the perception of sound by the left and right auditory analyzers.

Goal of the work: A study of binaural audibility.

Equipment: thick fabric; cotton wool

Progress.

1. To perform the work, the subject stands in the middle of the room and is blindfolded with thick cloth.

2. The remaining students are located in various areas rooms and begin to pronounce some numerals one by one.

3. The student must, without saying the name and surname of the speaker, point his finger in the direction of him.

Note the approximate deviation error in degrees.

4. Then the experiment is repeated, covering one ear with a cotton swab.

It is noted that the accuracy of determining the direction of the sound source decreases. A person accurately localizes sound if it is located opposite the open ear.

Laboratory work 5. Auditory reflexes.

Goal of the work: study of auditory reflexes.

A) Cochlear-pupillary reflex.

Progress.

The subject is asked to look forward at one point in diffuse daylight; a strong unexpected sound causes a constriction of the pupil followed by its dilation (sometimes vice versa). The reflex closes with auditory nerve at the level of the midbrain, where the lateral loop (lemniscus lateralis) of the acoustic pathway partially enters the nucleus of the oculomotor nerve.

B) General acoustic muscle reflex.

Progress.

General acoustic muscle reflex - twitching of the muscles of the whole body when sharp sound- used to test hearing infants. In adults, it is sometimes possible to obtain a separate flinch that is easily inhibited.

The study of absolute thresholds of auditory sensitivity is carried out using whispered speech. It is recommended to make 2 groups of words.

The first group of words includes vowels y, oh and consonants m,n,v,r. For example, raven, yard, number, etc.

The second group of words is vowels a, i, uh and hissing, whistling consonants. For example: chas, cabbage soup, siskin, hare, wool, etc.

Goal of the work: determine hearing acuity.

Equipment: tape measure or meter tape, cotton swabs and a prepared list of words.

Progress: work is carried out in a group. Before the experiment begins, one ear of the subject is plugged with a moistened cotton swab. Next, the researcher from a short distance begins to whisper words from groups 1 and 2, gradually moving away. As soon as the subject begins to correctly name 50% of the spoken words, this distance is considered a threshold value. After which the distance between the researcher and the subject begins to quickly increase (if necessary, the researcher can turn his back to the subject, which corresponds to doubling the distance). The final point of distance from the subject will be the point from which he will not be able to hear a single word. This distance is measured. Changing cotton swabs alternately in each ear, the experiment is carried out several times.

Evaluation of the results obtained: 1) words of group 1 normally differ at a distance of 5 m (low-frequency); 2) words of group 2 normally differ at a distance of about 20 m (high-frequency).

Functional state of the vestibular analyzer.

Goal of the work: determine the functional state of the vestibular apparatus.

Equipment: stopwatch or watch with a second hand

Romberg test used in determining functional state vestibular analyzer.

Progress: work is carried out in pairs. One subject performs the commands, and the researcher records the time and condition of the subject.

Option 1.

The subject stands with his feet closed (heels and toes together), eyes closed, arms extended forward, fingers spread several times. The researcher determines the time of stability in this position before loss of balance.

Option 2.

The subject must stand so that his legs are on the same line; in this case, the heel of one foot touches the toe of the other, otherwise the position of the subject is the same as in option 1, i.e. arms extended forward, fingers spread and eyes closed.

Evaluation of results: in option 1, in healthy untrained people, this position can usually be maintained within 30-55 s; There is no trembling of the fingers and eyelids. For athletes it can be 100-120 s or more. For adolescents who do not engage in sports, in option 2 these fluctuations are 13-53 s.

TASKS FOR EXTRACLUDOR INDEPENDENT WORK:

1. Make a table of the structure of analyzers:

1. Solve situational problems:

a) Why do children have inflammation of the middle ear more often than adults? Give anatomical justification.

b) When flying on an airplane during a drop in air pressure, passengers to prevent the occurrence of unpleasant feeling“ear pluggers” offer candy canes. Explain the physiological meaning of using such a technique.

c) During examination of the patient, a violation of the central and preservation of peripheral vision. About the pathology in which part of the retina can we draw a conclusion?

2. Compose a crossword puzzle on the topic “Sensory systems”

PRACTICAL LESSON No. 7

ON THIS TOPIC: " Endocrine system»

CLASS TIME: 4 hours

OBJECTIVE OF THE LESSON:

1. Learn to navigate the topography endocrine glands according to tables and models.

The universality of knowledge of this topic is necessary for future pharmacists, since in interaction with nervous system endocrine glands regulate all body functions. When exposed to adverse factors external environment which affects the functioning of the glands internal secretion and causes a pathological change in them, while pharmacists must know the mechanism of action medicinal substances.

For execution practical work the student must know:

1. Types of gland secretion.

2. Hormones, mechanism of action, types of hormones, properties of hormones.

3. Pituitary-dependent and pituitary-independent endocrine glands (pituitary gland, pineal gland, thyroid, parathyroid, pancreas, thymus, gonads, adrenal glands - location, external and internal structure), hormones and their physiological effects, manifestation of hypo- and hyperfunction of the glands.

TASKS FOR AUDIENCE INDEPENDENT WORK:

1. Repeat the structure and functions of the endocrine glands: thyroid, parathyroid, thymus, pancreas, pituitary gland, pineal gland, adrenal glands, gonads.

2. Compile a summary table of hormones, endocrine glands, diseases and disorders with hypo- and hyperfunction.

TASKS FOR EXTRACLUDOR INDEPENDENT WORK::

1. Make a diagram of the “Endocrine system” (performed in preparation for practical lesson)

2. Prepare a draft health bulletin on the topic: “Prevention of iodine deficiency”, “Prevention diabetes mellitus»

3. Solve situational problems:

a. The patient complains of headaches, sharp deterioration vision. At the same time, there is a significant increase in size facial skull, hands and feet. What pathology should a doctor think about? Give anatomical justification.

b. It is known that each adrenal gland is supplied with blood by 25-30 arteries originating from different sources. One of the features vascular system The adrenal gland is that some of the arterial branches feed predominantly the cortex of the organ, others - the medulla. How can this phenomenon be explained anatomically?

4. . Create a situational task on the topic “Endocrine system”

NOTE: Write down the skills learned on the topic.

PRACTICAL LESSON No. 8

Where D is the distance at which normal eye sees the signs of this row (indicated to the left of the optotypes in each row of the table), d is the distance to the patient’s location.
Eg:
the patient reads the 1st row of the table from a distance of 5 meters. An eye with normal visual acuity can identify the signs in this row from 50 meters away.

That is, following the formula: VISUS = 5/50 = 0.1.

The value indicating the patient’s visual acuity increases by one tenth with each subsequent line of the table and the studies are performed in the decimal system based on arithmetic progression

B) Determination of hearing acuity
Hearing acuity is the minimum sound volume that can be perceived by the subject's ear.
Option 1.
1. Take a mechanical watch in your hand.
2. Move the watch closer to you until you hear a sound.
3. Place the watch tightly against your ear and move it away from you until the sound disappears.
4. Measure the distance (in the first and second cases) between the ear and the watch (in cm).
5. Calculate average value two indicators.
The test can be performed with the right and left ears alternately.
Evaluation of results: hearing can be considered normal when ticking wristwatch medium size can be heard at a distance of 10-15 cm from the subject’s ear. If this distance is less, then the hearing acuity is quite high, but if this distance significantly exceeds 25 cm, then the subject’s hearing acuity is reduced.

Conclusion. Assess the subject's color perception.
Laboratory work No. 43. DETERMINATION OF HEARING ACUTUITY ACCORDING TO V.I. VOYACHEK (WHISPERING SPEECH)
Theoretical part. By using auditory analyzer a person navigates, forms appropriate behavioral reactions, for example, defensive or food-procuring. A person’s ability to perceive spoken and vocal speech and musical works makes the auditory analyzer a necessary component of the means of communication, cognition, and adaptation.

An adequate stimulus for the auditory analyzer is sounds, those. oscillatory movements of particles elastic bodies, propagating as waves in a wide variety of media, including air environment, and perceived by the ear. Sound wave vibrations (sound waves) are characterized by frequency And amplitude.

The frequency of sound waves determines the pitch of the sound. A person distinguishes sound waves with a frequency from 20 to 20,000 Hz. Sounds with a frequency below 20 Hz - infrasounds and above 20,000 Hz (20 kHz) - ultrasounds, are not felt by humans. Sound waves that have sinusoidal, or harmonic, vibrations are called tone. A sound consisting of unrelated frequencies is called noise. When the frequency of sound waves is high, the tone is high; when the frequency is low, the tone is low.

The second characteristic of sound that the auditory sensory system distinguishes is its force, depending on the amplitude of sound waves. The power of sound or its intensity is perceived by a person as volume. The sensation of loudness increases as the sound intensifies and also depends on the frequency of sound vibrations, i.e. The loudness of a sound is determined by the interaction of intensity (strength) and pitch (frequency) of sound. The unit of measurement for sound volume is white, in practice it is usually used decibel(db), i.e. 0.1 bel. A person also distinguishes sounds by timbre, and whether "coloring". The timbre of the sound signal depends on the spectrum, i.e. on the composition of additional frequencies (overtones) that accompany the fundamental tone (frequency). By timbre, you can distinguish sounds of the same height and volume, which is the basis for recognizing people by voice. The sensitivity of the auditory analyzer is determined by the minimum sound intensity sufficient to produce an auditory sensation. In the range of sound vibrations from 1000 to 3000 Hz, which corresponds to human speech, the ear has the greatest sensitivity. This set of frequencies is called speech zone. In this area, sounds are perceived that have a pressure of less than 0.001 bar (1 bar = 7.5 x 10 2 mm Hg, which is approximately one millionth of normal atmospheric pressure).

Goal of the work. Determination of hearing acuity.

Equipment and materials. Cotton wool.

Progress. The subject is first located at a distance of 6 meters from the experimenter. One ear canal must be closed with cotton wool. The open ear should be facing the sound source, the subject stands sideways and looks to the side to prevent guessing words by lip movements. The subject must loudly repeat the word he heard. The examiner pronounces in a whisper with equal intensity after exhalation, first words with low sounds, and then - at a distance of 20 m - with high sounds (Table 8).

If the subject does not hear the whispered words, then the experimenter approaches one meter and resumes the study, and so on until the subject begins to repeat the words correctly.

With normal hearing, a person perceives low sounds spoken in a whisper from a distance of 6 meters, high sounds - 20 meters.
Table 8

Conclusion. Compare hearing acuity for words with low and high sounds, compare the result with the norm.
Laboratory work No. 44. BINAURAL HEARING

Theoretical part. A person has spatial hearing, i.e. the ability to localize a sound source, which is due to the presence of two symmetrical halves of the auditory sensory system.

Determining the localization of a sound source is possible using binaural hearing, i.e., the ability to hear with two ears at the same time. Thanks to binaural hearing, a person is able to more accurately localize the source of a sound than with monaural hearing and determine the direction of the sound. For high-pitched sounds, the determination of their source is determined by the difference in the strength of the sound arriving at both ears, due to their different distances from the sound source. For low sounds What is important is the time difference between the arrival of identical phases of the sound wave to both ears. Determining the location of a sounding object is carried out either by perceiving sounds directly from the sounding object - primary localization, or by perceiving sound waves reflected from the object - secondary localization, or echolocation. Some animals (dolphins, bats) navigate in space using echolocation.

Goal of the work. Evidence for the role of binaural hearing in determining the spatial localization of sound.

Equipment and materials. Phonendoscope with tubes of different lengths.

Progress. The subject is seated on a chair with his back to the experimenter. The tips of the rubber tubes of the phonendoscope are inserted into the subject's ears and lightly tapped on the phonendoscope. The subject is asked to indicate from which side he hears the sound. Then the phonendoscope tubes are changed and the experiment is repeated. The subject again reports in which direction the sound source is located, indicating the sound source from the side of the short tube of the phonendoscope.

Report preparation. Write down your observations in your notebook. Explain why the sound is heard from the side of the short tube.

Conclusion. Note the importance of binaural hearing in determining the location of a sound source.
Laboratory work No. 45. STUDY OF BONE AND AIR CONDUCTIVITY OF SOUND

Theoretical part. There are bone and air sound conduction. Air conduction of sound is ensured by the propagation of a sound wave in the usual way through a sound transmitter. Bone conduction of sound is the transmission of sound waves directly through the bones of the skull. At pathological changes In the sound transmitting apparatus, hearing sensitivity is partially preserved due to bone conduction of sound.

Target. Proof of the possibility of bone conduction of sound vibrations and more high efficiency air conduction.

Equipment and materials. Tuning forks with different vibration frequencies, a hammer, a stopwatch, cotton swabs, two subjects.

Progress. To observe bone conduction of sound, perform Weber's experience: Place the stem of a sounding tuning fork on the middle of the subject’s crown. Note how strong the subject hears the sound through both ears. Then repeat the experiment, first placing a cotton swab in one ear. Note the nature of the change in the perceived intensity of sound from the ear plugged with a tampon. Explain the observed changes. Verify that sound travels through the open ear using two subjects. Connect the ear of one subject to the ear of the second subject with a rubber tube and apply a tuning fork to the crown of the first subject. Will the second subject hear the sound? Why.

To compare air and bone conduction of sound, carry out Rinne's experience: attach the stem of the sounding tuning fork to mastoid process temporal bone. The subject hears a gradually weakening sound. When the sound disappears (judged by the verbal signal of the subject), the tuning fork is transferred directly to the ear. The subject hears the sound again. Using a stopwatch, determine the time during which the sound is heard. Air conduction is examined separately for the right and left ears.

Report preparation. Enter the research results into the table:

Conclusion. Assess bone and air conduction. Compare the data obtained with the norm.
Laboratory work No. 46. DETERMINATION OF DISCITING THRESHOLDS
Theoretical part. The discrimination threshold refers to the subjectively perceived smallest increase or smallest decrease in the intensity of stimulation.

In 1834, Weber formulated the following law: the perceived increase in irritation (threshold of discrimination) must exceed by a certain proportion the irritation that acted previously. Thus, an increase in the sensation of pressure on the skin of the hand occurs only when an additional load is applied, which amounts to certain part cargo placed earlier. The dependence is expressed by the formula:

Where I- irritation, Δ I- its noticeable increase (discrimination threshold).

Target. Make sure there is a relationship between the discrimination threshold and the magnitude of the original stimulus.

Equipment and materials. 500 ml graduated cylinder, 2 kg weight

Progress. The subject takes a cylinder into which 100 ml of water is poured into his hand and closes his eyes. Slowly add water to the cylinder until the subject reports that he felt an increase in heaviness. Note the amount of water added to the cylinder at this point. Then repeat the experiment, each time pouring the original volume of water into the measuring cylinder: 200, 300 and 500 ml. Repeat the series of experiments, having previously asked the subject to hold it for 1-2 minutes. outstretched arm a weight weighing 2 kg.

Report preparation. Enter the results of the experiment in the table:

Use the obtained data to calculate the constant (K) in the Weber equation K = ΔI/ I. Compare the constant values ​​of K obtained in 1-4 experiments (separately before and after physical activity).

Conclusion. Draw a conclusion about how the degree of adaptation of the receptor apparatus affects the ability to sense changes in the intensity of stimulation.
Laboratory work No. 47. RESEARCH OF TASTE ANALYZER
Theoretical part. Taste analyzers are based on chemoreception. Taste buds contain information about the nature and concentration of the substance present in the mouth. Taste buds (taste receptors) are located on the tongue, back wall pharynx, soft palate, tonsils, epiglottis. Most of them are on the tip of the tongue, its edges and the back. Excitation of the taste buds triggers a chain of reactions in parts of the brain, which leads to different functioning of the digestive organs. Each taste bud consists of two to six receptor cells and supporting cells. A person distinguishes four main taste qualities: sweet, sour, bitter And salty, which are quite well characterized by their typical substances. The taste of sweet is associated mainly with natural carbohydrates such as sucrose and glucose; sodium chloride – salty; other salts, such as potassium chloride, are perceived as both salty and bitter. Such mixed feelings are characteristic of many natural taste stimuli and correspond to the nature of their components. For example, orange is sweet and sour, and grapefruit is bittersweet and sour. Acids taste sour; many plant alkaloids are bitter.

N

Rice. 29. Scheme of human language.
and the surfaces of the tongue can be distinguished zones of specific sensitivity. Bitter taste is perceived mainly basis language; other taste qualities affect him lateralsurfaces And tip, Moreover, these zones overlap (Fig. 29).

Between chemical properties There is no clear correlation between a substance and its taste. For example, not only sugar, but also lead salts are sweet, and the sweetest taste is found in artificial sugar substitutes such as saccharin. Moreover, the perceived quality of a substance depends on its concentration. Table salt tastes sweet in low concentrations and only becomes purely salty when the concentration is increased. Sensitivity to bitter substances is significantly higher. Since they are often poisonous, this feature warns us against danger, even if their concentration in water or food is very low. Strong bitter irritants easily cause vomiting or the urge to vomit. Since the absolute measure of the intensity of the stimulus has not been established due to the unclear nature of the sensation, it is measured by the concentration of a standard substance accepted as the standard of the taste stimulus. These substances include table salt(salty), sugar (sweet), citric acid(sour) and quinine hydrochloride (bitter). Unimolar solutions are prepared as the starting material. Taste thresholds are measured using serial dilutions of these solutions. The threshold of taste sensitivity is understood as the lowest concentration of a solution of a flavoring substance, which, when applied to the tongue, causes a corresponding taste sensation. The following concentrations are taken as the norm for taste sensitivity thresholds determined by the droplet stimulation method: for sweet and salty - 0.25-1.25%; for sour - 0.05-1.25%; for bitter - 0.0001-0.003%.

DETERMINATION OF VISUAL ACUTUITY AND HEARING ACUITY

Target: get acquainted with the structural features and functions of the visual and auditory sensory systems, hygienic recommendations for the protection of vision and hearing, and methods for the prevention of sensory disorders.

Tasks:

1) determine visual acuity;

2) assess hearing acuity;

Equipment: tables for determining visual acuity, tape measure

5 m long, pointer, measuring tape

DETERMINATION OF VISUAL ACUITY

Visual acuity refers to the ability of the eye to distinguish two luminous points separately. To see two points separately, it is necessary that there be at least one unexcited photoreceptor between the excited photoreceptors. Since the diameter of, for example, cones is 3 µm, then for separate vision of two points it is necessary that the distance between the images of these points on the retina be at least 4 µm, and this image size is obtained at a visual angle of 1". When viewed at a visual angle of less 1" two luminous points merge into one.

To determine visual acuity, use standard tables with alphabetic characters arranged in 12 lines. The size of letters in each line decreases from top to bottom. On the side of each line there is a number indicating the distance from which a normal eye can distinguish the letters of that line at a visual angle of 1".

Visual acuity can be assessed using tables of various types: for young children - Orlova's table; to determine visual acuity in the range from 1.0 to 2.0 units. – table by O. M. Novikov. The Golovin–Sivtsev letter table is also used.

Hang the table on a well-lit wall (illuminance should be at least 100 lux) or additionally illuminate it with an electric light bulb. Place the subject on a chair at a distance of 5 m from the table and ask him to close one eye with a shield or palm. Use a pointer to show the subject the letters and ask them to name them. Definition start from the top

lines and, going down, find the lowest line, all the letters of which the subject clearly sees within 2–3 s and names correctly. If the subject correctly names the signs of the tenth row, visual acuity is 1.0 according to the Golovin-Sivtsev table and 2.0 units. according to the table by O. M. Novikov.

Then determine the visual acuity of the other eye. Calculate visual acuity using the formula

where V is visual acuity; d – distance from the subject to the table; D is the distance from which a normal eye should clearly see this line.

Write down the results of the study in a notebook of experimental protocols, compare them with normal visual acuity.

DETERMINATION OF HEARING ACUITY

Our auditory organ is very sensitive. With normal hearing, we are able to distinguish sounds that cause negligible (calculated in fractions of a micron) vibrations of the eardrum.

The sensitivity of the auditory analyzer to sounds of different heights is not the same. The human ear is most sensitive to sounds with vibration frequencies between 1000 and 3000. As the vibration frequency decreases or increases, sensitivity decreases. A particularly sharp drop in sensitivity is observed in the region of the lowest and highest sounds.

With age, hearing sensitivity changes. The greatest hearing acuity is observed in 15-20 year olds, and then it gradually decreases. The zone of greatest sensitivity up to 40 years of age is in the 3000 Hz region, from 40 to 60 years - in the 2000 Hz region, and over 60 years - in the 1000 Hz region.

The minimum sound intensity capable of causing the sensation of a barely audible sound is called threshold of hearing, or threshold of auditory sensation. The smaller the amount of sound energy required to obtain the sensation of a barely audible sound, i.e., the lower the threshold of auditory sensation, the higher the sensitivity of the ear to a given sound. From the above it follows that in the region of medium frequencies (from 1000 to 3000 Hz) the thresholds of auditory perception are the lowest, and in the region of low and high frequencies thresholds are rising.

The study of spoken and whispered speech is quite simple, but precise rules must be followed in order to obtain a correct judgment about the state of the auditory system.

The hearing test is carried out in complete silence, in a room isolated from extraneous noise. Normal hearing (good hearing acuity) is characterized by the detection of whispered speech at a distance of more than 6 m, decreased hearing at a distance of less than 5 meters.

To study the discrimination of whispered speech, the following approximate table of words (table) can be used.

Table

Word tables for studying whispered speech in children

Draw a conclusion about the indicators of visual acuity and hearing acuity.