Bones of middle ear are responsible for which of the following?
Correct Answer: Reduction of impedance to sound transmission
Description: Broadly hearing mechanism can be divided into:Mechanical conduction of sound (done by middle ear).Transduction of mechanical energy into electrical impulses (done by sensory system of cochlea)Conduction of electrical impulse to brain (i.e. auditory pathway)i. Conduction of sound:It is done mainly by middle ear. Middle ear not just simply conducts the sound but conves sound of great amplitude and less force to that of less amplitude and greater force.This function of the middle ear is called as impedance matching mechanism or the transformer action.ii. Transduction of mechanical energy to electrical impulse:Movements of the stapes footplate causes vibrations in scala vestibuli followed by scala tympani and is transmitted to the cochlear fluids which brings about movement of the basilar membrane.This sets up shearing force between the tectorial membrane and the hair cells.The distoion of hair cells gives rise to electrical nerve impulse. A sound wave, depending on its frequency, reaches maximum amplitude on a paicular place on the basilar membrane, and stimulates that segment (traveling wave theory of von Bekesy).Higher frequencies are represented in the basal turn of cochlea and the progressively lower one toward the apex.
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