How do hair cells in the cochlea turn sound vibrations into electrical signals?

Hair cells in the cochlea convert mechanical sound vibrations into electrical signals through a process called transduction.1

When sound waves cause the basilar membrane to vibrate, the organ of Corti moves against the tectorial membrane. This creates shearing forces that bend the stereocilia located at the top of the hair cells.1

The conversion process relies on a steep electrical gradient maintained by the difference in potassium content between the endolymph and perilymph. When stereocilia bend toward their longest length, ion channels open, allowing potassium ions to flow into the cell. This influx depolarizes the hair cell, triggering the release of neurotransmitters from the base of the cell. These chemicals are absorbed by the nerve fibres of the cochlear nerve, which then transmit the electrical signal to the brain. Conversely, bending in the opposite direction shuts the channels, inhibiting the cell.12