In this article, we will learn about ‘potential differences’ between different structures of the inner ear and Cochlear microphone potential, and more.
Table of content
| 1. | Introduction |
| 2. | Potential differences |
| 3. | Cochlear microphone potential and its features |
| 4. | Impedance matching |
Introduction
Interior of the cells of ‘organ of corti’ stria vascularis and other structures in the inner ear are minus 30 millivolts (-30 mV ) to the perilymph present in the scala vestibuli and scala tympani.
There is no potential difference between perilymph present in the scala vestibuli and scala tympani.
The endolymph in the scala vestibule is positive at 80 mV compared with the perilymph in the scala vestibuli and scala tympani.
The potential difference between:
1. Endolymph +80 mV to perilymph
2. Perilymph to perilymph, no potential difference
3. Internal of cell -30 mV to perilymph.
Cochlear microphone potential
Cochlear microphone potential is one of the electrical responses of the cochlea. It is a potential difference between an active electrode placed on or near the cochlea and an indifferent electrode placed on the mastoid process.
The Amplification of cochlear microphone potential by suitable instruments: the loudspeaker records pure tone; this is why it is called cochlear microphone potential.
(Indifferent electrodes may be placed anywhere on the body.)
This potential is like a generation potential.
A few characteristics of Cochlear microphone potential are:
1. Cochlear microphone potentials show no latency or refractory period.
2. Cochlear microphone potentials do not obey ‘all or none law.’
3. Cochlear microphone potentials are resistant to ischemia
4. Cochlear microphone potentials are resistant to anesthesia.
5. Cochlear microphone potential has a linear relationship to the magnitude of the basilar membrane.
6. Cochlear microphone or generation potential converts mechanical energy into electrical energy.
High-frequency sound produces vibration in the basal part of the basilar membrane.
The middle-frequency sound produces vibration in the middle part, while that of low frequency vibrates the apical part of the basilar membrane.
Impedance matching:
Middle ear ossicles magnify sound intensities by 1.2 to 1.3 times.
The effective surface area of the tympanic membrane is about 50-millimeter squares, and that of the oval window is only 3-millimeter squares. This increases pressure within the middle ear and at the oval window by 22 times. This is referred to as ‘impedance matching.’
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