Cochlea

The organ of the inner EAR that converts sound waves to NERVE impulses. Contained within the bony labyrinth, the cochlea resembles a snail shell. Thousands of specialized nerves, called HAIR cells because of the fine fibers that project from them, line the fluid-filled inner chamber of the cochlea. The membrane that contains the hair cells is the organ of Corti. Sound waves activate the hair cells, which convert the stimulation into nerve signals. The nerve signals converge at the cochlear nerve, which carries them to the vestibulocochlear nerve (eighth cranial nerve) for transport to the BRAIN. The hair cells are very sensitive and vulnerable to damage from excessive noise. The longest of the hair cells are those that respond to sounds in the decibel range of normal speech; because of their length, they are the most vulnerable to such damage. Hair cells also break off with aging. Damaged cochlear hair cells do not regenerate.