Final answer:
Hair cells on the apical surface have long, stiff microvilli called stereocilia, which are crucial for converting sound waves into nerve impulses.
Step-by-step explanation:
Hair cells in the organs of Corti are named for the long, stiff microvilli called stereocilia that cover their apical surface. These hair-like structures are arranged from tallest to shortest and are tethered together by proteins. The bending of stereocilia in response to sound waves leads to the opening and closing of ion channels, which in turn depolarizes the hair cell membrane, triggering nerve impulses.