GLOSSARY

The cochlea is a snail-shaped structure with two and a half turns in the inner ear that converts sound vibrations into nerve signals and encodes the frequency and intensity of sound.

Structure

• Three channels (scalae): the vestibular and tympanic scalae (filled with perilymph) and the cochlear duct in the middle (filled with endolymph).
• Basilar membrane: the organ of Corti sits on it.
• Organ of Corti: inner hair cells (about 3,500; the main hearing receptors, supplying about 95 percent of auditory nerve fibres) and outer hair cells (about 12,000; active sound amplifiers).

Mechanism