The cochlea

The cochlea contains the cochlear duct, which
forms the organ of Corti. The organ of Corti converts
sound waves in the endolymph of the
cochlea into intracellular signals. These are
transmitted to auditory regions of the brain.
The organ of Corti contains two types of sensory
cells: one row of inner hair cells and three rows
of outer hair cells. The inner hair cells are pure
receptor cells. Vibrations induced by sound lead
to slight deflections of the stereocilia and open
potassium channels at the tips of the stereocilia.
The influx of potassium ions at the tips of the
cilia of the hair cells (see C) causes a change in
membrane potential that results in a nerve impulse,
which is transmitted as an auditory signal
to the auditory cortex of the brain.
Potassium ions are recycled to the supporting
cells and the spiral ligament into the endolymph
of the scala media. The tectorial membrane
amplifies the sound waves as a resonator.