The role of endocooling potential (ECP) in the auditory reception between endolymph and Perelimfoy to the potential difference is maintained from 60 to 80 mV. This difference is called ECP. Endolimfa

The role of endocooling potential (ECP) in the auditory reception

Between endolymph and Perelimfoy, the difference in potentials is maintained from 60 to 80 mV. This difference is called ECP. Endolimf bears positive potential relative to Perelimfi. The source of the ECP serves a vascular strip, lining the outer wall of the snelled duct (8). The drop in the ECP is observed in disruption of the oxygen supply of the vascular strip, or with a violation of this strip (mechanical damage).

Cells included in the vascular strip contain very large mitochondria. This structural feature of the vascular strip in aggregate with data on its role in cellular respiration to maintain the potential difference between endolymph and Perelimfoy, suggest that the ECP may be similar to the proton potential at the mitochondrial membrane.

Sounds cause ECP fluctuations, the amplitude of which does not exceed 1% of its permanent level, that is, these oscillations are 0.6-0.8 mV. This phenomenon received the name of the microphone snail effect, and the oscillations themselves themselves are called microphone potentials. The microphone effect is based on a telephone theory of hearing, according to which, frequency analysis of sounds is not connected with mechanical oscillations of the structures of Wu, but with the excitation of auditory receptors with microphone potentials. The frequency of these potentials coincides with the harmonic spectrum of sound tones. Currently, the ECP is considered as an important condition for the normal functioning of auditory receptors, but not leading its mechanism.

Due to the existence of the ECP, a very large potential difference is maintained (up to 150 mV) between endolymph and cytoplasm of the hairs cell. This difference is formed as a result of the summation of the PP of the hairs cell (the potential difference between its cytoplasm and perlimfoy) and the ECP.

The level of electric potentials of the hairs cell

Essentially, the potential difference between endolymph and cytoplasma of the hairs cell acts on its PP, relative to which the receptor potential is generated. Such a significant PP has no other cell in the human body. This high steepness of the front front of the ECP makes the hairs cell plasmolym extremely unstable and capable of giving sharp and rapid membrane potential shifts, with low changes in the electrical resistance of the membrane that occur in response to minor shifts stereocylcy.

Fundamentals of Physiological Acoustics

It is customary to compare physical acoustics with objective (physical) and subjective (psychological) characteristics of sound.

Physical characteristics of sound

Psychological characteristics of sound

1. Harmonic spectrum (characterized by the sum of all frequencies):

a) fundamental harmonic;

b) higher harmonics.

1. Acoustic spectrum, characterized by:

a) main tone (height); measured in [mel] or [bark];

b) overtones (timbre).

2. Intensity (flux density of sound energy), denoted by .

2. Loudness, measured in [sleep].

Sound, when distributed in a medium, is a wave of condensation and rarefaction of its particles. In areas of condensation, the pressure is greater than in areas of rarefaction. The amplitude of periodic pressure fluctuations in the medium, occurring under the action of a propagating sound, is called sound pressure – p. It has the dimension [Pa] or [] The sound pressure determines the sound intensity, which is defined as follows:

v is the speed of sound distribution in a given environment;

is the acoustic impedance of the medium.

In addition, I, as the Umov vector, can be calculated using the formula:

, if w is known – the volume density of the sound energy, that is, the energy per unit volume of the medium in which the sound propagates. To establish the relationship between intensity and loudness, two more physical quantities are introduced that characterize the sound:

Intensity level – L.

Volume level – E.

L, or sound pressure level, is given by:

– any studied sound.

usually choose less W/. This intensity of a pure tone, f = 1 kHz, is set as the average threshold of auditory sensitivity for a person. This intensity corresponds to a sound pressure equal to Pa. When k = 1, the unit of the intensity level L is [B] bel. For k = 10, the unit of intensity level L is [dB], decibel. In medicine, it is customary to use the decibel scale. If, then L = 0, therefore, 3 values ​​and , and L=0 dB – characterize the same sound. At , L takes on a positive value, at , L < 0. The smaller L, the better (higher) the auditory sensitivity. A person hears sound tones best with f between 3 and 4 kHz.

Loudness level (E) is an expression of differences in human perception of sounds of different frequencies. The sound loudness level of a given f is the level of intensity of the sound tone with f = 1 kHz, the loudness of which, when compared by ear, is equivalent to the loudness of the sound under study.

The dimension of the physical quantity E – background, – for sounds with a frequency f = 1 kHz, the value of E and L are the same. So, if the first of them L is 0 dB, then E = 0 phons (at f = 1 kHz). The average hearing threshold in humans is approximately 4 backgrounds. Pain in the ear occurs under the influence of sounds, the volume level of which reaches approximately 130 phons. Thus, everything that a person hears is limited to sound tones, the frequency of which is in the range from 16 Hz to 20 kHz, and E – from 4 to 130 phons.

Sound volume is a psychological (subjective) characteristic.It is rated on the sleep scale. To express the loudness of a particular sound in sons, an audio tone with f = 1 kHz, with an intensity level of L = 40 dB, is taken as a standard. After allowing the subject to listen to the reference tone, the doctor presents him with the tested sound, while he asks to determine how many times the tested sound is louder or quieter than the reference. So, for example, the volume of the tested sound, if it hears 2 times louder than the reference tone, will be equal to 2 sons, and if it is 2 times quieter, then 0.5 sons.