Auditory Pathway

Hearing begins when sound waves enter the external acoustic meatus and vibrate the tympanic membrane.

These vibrations are amplified with the help of the auditory ossicles, and transmitted to the internal ear, creating a strong pressure wave in the stiff cochlear fluid.

The sound waves in the audible range pass through the cochlea and vibrate the basilar membrane. At the base of this membrane lies the spiral organ. It contains the inner hair cells, which act as receptors for hearing.

These hair cells have stiff stereocilia bound together by thin fibers called tip links, connected to mechanically-gated ion channels.

The vibrations in the basilar membrane cause tension on the tip links to open or close the ion channels, depolarizing or hyperpolarizing the membrane.

Depolarization increases the release of neurotransmitters, generating a lot more action potential in the cochlear nerve than at the resting state.

From here, impulses are carried to the cochlear nuclei in the medulla oblongata, moving along the brain stem to reach the primary auditory cortex located in the temporal lobe for the conscious awareness of sound.