Final answer:
The vestibule contains receptors for equilibrium, which are part of the body's vestibular system responsible for balance and spatial orientation. Unlike vision, which uses photoreceptors to detect light, the sense of equilibrium relies on mechanoreceptors in the inner ear to sense movement and head positioning.
Step-by-step explanation:
The vestibule contains receptors for the sensory modality of equilibrium (balance). The vestibule, part of the inner ear, is essential for the body's sense of balance and spatial orientation. The vestibular system comprises the utricle, the saccule, and three semicircular canals, all of which work together to detect changes in head position and motion. The utricle and saccule contain mechanoreceptors that respond to changes in orientation due to gravity, such as the shifting of calcium carbonate crystals that activate hair cells. These hair cells are also present in the semicircular canals and respond to the bending caused by the fluid when the head turns.
Signal processing for balance starts in these structures and is transmitted via the vestibular ganglion through the vestibulocochlear nerve to the brainstem and cerebellum, which is paramount for coordinating these signals into movement and balance adjustments. Unlike the sense of vision which relies on photoreceptors in the retina sensitive to light, the vestibular sense is entirely mechanical and is concerned with the body's positioning in space.