Britannica Sources used in this answer

How do stereocilia help hair cells create electrical signals?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Cross-section diagram of the human ear showing the outer ear, middle ear, and inner ear, with labeled parts including the auricle, auditory canal, tympanic membrane, ossicles, cochlea, semicircular canals, and nerves. — human ear Structure of the human ear.

Stereocilia play a critical role in the transduction of mechanical sound vibrations into electrical signals within the inner ear. These sensory hairs are arranged in graded lengths on the top of hair cells and are interlinked, ensuring they move in unison.12

When sound vibrations cause the basilar membrane to move, shearing forces between the reticular lamina and the tectorial membrane displace or bend the stereocilia. This mechanical movement creates an alternating receptor potential through the following process:1

Depolarization: When stereocilia are bent toward the direction of increasing length, ion channels in the cell membrane open. This allows potassium ions from the surrounding endolymph to flow into the hair cell, causing it to depolarize.1
Neurotransmitter Release: This depolarization triggers the hair cell to release neurotransmitters from its base.1
Signal Transmission: These neurotransmitters are absorbed by the nerve fibres of the cochlear nerve, which then transmit electrical signals to the brain.1

Conversely, when stereocilia are deflected in the opposite direction, the ion channels close, inhibiting the cell through hyperpolarization.1