Cochlear microphonic potentials exhibits
i.e. (Produced by outer hair cells):COCHLEAR MICROPHONIC (CM) - when basilar membrane moves in response to sound stimulus, electrical resistance at the tip of hair cells changes allowing flow of K+ through hair cells and produces voltage fluctuations called cochlear microphonic. It is an alternating current (AC) potentialsElectrical Potentials of Cochlea and CN VIIIFROM COCHLEA1. Endocochear potentials - It is direct current (DC) potential recorded from scala media. It is +80 mV and is generated from the stria vascularis by Na+ / K+ ATPase pump and provides source of energy for cochlear transduction. It is present at rest and does not require sound stimulus. This potential provides a sort of "battery" to drive the current through hair cells when they move in response to a sound stimulus.2. (Cochlear microphonic (CM)3. Summating potentials (SP) - It is a DC potential and follows "envelop" of stimulating sound It is produced by hair cells. It may be negative or positive. SP has been used in diagnosis of Meniere's disease. It is superimposed on VIII nerve lesionsFROM NERVE FIBRERS (CN VIII)4. Compound action potential - It is an all or none response of auditory nerve fibresBoth CM and SP are receptor potentials as seen in other sensory end organs - The differ from action potentials in that(a) They are graded rather than all or none phenomenon(b) Have no latency(c) Are not propagated(d) Have no post response refractory period
Produced by outer hair cells
Produced by inner hair cells
Electrodes have to be inserted over round window
Surface electrodes can not measure it
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