Final answer:
The hair-like cilia on the top of a hair cell in the inner ear are known as stereocilia, which act as mechanoreceptors for detecting vibrations from sound waves, leading to the transmission of nerve impulses to the brain.
Step-by-step explanation:
The hair-like cilia attached to the top of a hair cell in the inner ear are called stereocilia. These structures act as mechanoreceptors, which are triggered by the vibrations caused by sound waves. Within the organ of Corti in the cochlea, the stereocilia of the hair cells protrude into the tectorial membrane and are arranged in an array from tallest to shortest. When sound waves cause the basilar membrane to move, this, in turn, causes the tectorial membrane to slide across the stereocilia, bending them. This bending opens protein-tethered ion channels when the movement is toward the tallest stereocilium, leading to depolarization of the hair cell membrane and the triggering of nerve impulses that are sent to the brain via the cochlear nerve. The intensity and frequency of sound are interpreted by the brain based on this electrical signaling.