stereocilium

Sensory hair cell found on the cochlea in the inner ear. When the cochlear fluid vibrates in response to sound the hairs move together pushing on protein molecules on their surface. On each stereocilium the protein molecule triggers the opening of an ion gate that enables the flow of potassium ions through the hair. The ion flow causes an electrical signal to be transmitted to the brain as a nerve impulse, where it is interpreted as sound.