Definition of cocaine. : a bitter crystalline alkaloid C17H21NO4 obtained from coca leaves that is used especially in the form of its hydrochloride medically as a topical anesthetic and illicitly for its euphoric effects and that may result in a compulsive psychological need.
The inner hair cells transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the auditory brainstem and to the auditory cortex.
Hearing pathway: sound Â» ear Â» nerve of hearing Â» brain. 1  The cochlea is a biological microphone. 2  Its job is to turn the mechanical vibrations of sound into electrical signals in the nerve of hearing.  The electrical signals â digital â are then sent up into the brain, where you hear things.