Final answer:
The gelatinous cap overlying the hair cells of the crista ampullaris is called the cupula. It bends hair cells' stereocilia in response to rotational movements of the head, aiding in balance and spatial orientation. The cupula's function in the ear is analogous to the otolithic membrane in the utricle and saccule.
Step-by-step explanation:
The gelatinous cap overlying the hair cells of the crista ampullaris is known as the cupula. The crista ampullaris is located in the ampulla of each semicircular canal in the ear, which plays a crucial role in the transduction of rotational movement of the head. The hair cells present within the ampulla are topped by the cupula, a structure that bends the stereocilia of hair cells when the head rotates due to the relative movement of the fluid enclosed within the semicircular canals.
The function of the cupula is closely related to that of the otolithic membrane, a gelatinous substance found in the utricle and saccule of the inner ear. This membrane contains calcium carbonate crystals called otoliths and functions to sense head movements and position by causing the stereocilia of hair cells to bend as the otolithic membrane moves separately from the macula in response to movements such as tilting the head.