Britannica Sources used in this answer

How does the cochlea turn sound vibrations into nerve impulses?

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

Watch a suspended vibrating spring to learn about the propagation of sound waves — sound Learn about the propagation of sound waves from a point source by observing the motion of a suspended vibrating spring.

The cochlea converts sound vibrations into nerve impulses through a process of mechanical transduction occurring within the organ of Corti.12

When sound waves enter the cochlea, they cause the basilar membrane to vibrate. This movement creates shearing forces between the reticular lamina and the tectorial membrane, which displace the stereocilia (sensory hairs) located atop the hair cells.31

The conversion process relies on a steep electrical gradient maintained by the difference in potassium content between the endolymph and perilymph. When stereocilia are bent in the direction of increasing length, ion channels open, allowing potassium ions to flow into the hair cell. This influx depolarizes the cell, triggering the release of neurotransmitters at the base of the cell. These neurotransmitters are absorbed by the nerve fibres of the cochlear nerve, which then transmit electrical signals to the brain. Conversely, bending the stereocilia in the opposite direction inhibits the cell by closing these channels.134