Final answer:
The bundles of stereocilia tilt, causing linking filaments to either open ion channels when bending towards the longest hair, or close them when bending towards the shortest, initiating or stopping nerve impulses respectively.
Step-by-step explanation:
When the bundles of stereocilia tilt, the linking filaments cause tension which opens ion channels in the hair cell membrane, leading to depolarization and the initiation of nerve impulses. The stereocilia are an array of apical membrane extensions resembling tiny hairs on the surface of hair cells, found within the inner ear. These structures are essential for the transduction of sound vibrations and movement into electrical signals that the brain can interpret.
Specifically, the stereocilia are linked by protein fibers, and when they bend towards the tallest member of the array, this tension causes the ion channels to open. When bent towards the shortest member, tension is reduced, and ion channels close. This process is crucial for our ability to hear and maintain balance.