PHYSIOLOGY OF HEARING ::;
The events involved in the mechanism of ear illustrated in and can be summarised as follows ::
1.Sound waves that reach the ear are directed by the pinna into the external auditory canal to strike the tympanic membrane
2.When sound waves strike the tympanic membrane they cause it to vibrate
3.The central area of tympanic membrane is connected to the malleus which also start vibrating These vibrations are passed on to the oval window through incus and stapes
4. As the stapes moves back and forth it pushes the oval window in and out
5.The movement of the oval window pushes the perilymph of scala vestibuli and a wave of motion is set in perilymph
6.The pressure thus created in the scala vestibuli and tympani pushes the vestibular membrane inwards and increases the pressure of the endolymph inside the cochlear duct
7.The basilar membrane gives the pressure under the resonance and bulges out into the scala tympani
8.This pressure then pushes the perilymph towards the round window causing it to bulge back into the middle ear Conversely as the sound waves subside the stapes move backwards and the procedure is reversed
The movement of basilar membrane causes the movement of the hairs and by some unknown mechanism develops generator potentials that ultimately lead to the generation of nerve impulses The impulses are then passed on to the cochlear branch of VIII cranial nerve They reach the medulla and from here to midbrain and thalamus to be finally relayed into the auditory area of the temporal lobe of the cerebral cortex
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