Which part of the vestibular apparatus is influenced by changes in gravity and linear acceleration?

The sacculus and utriculus, part of the vestibular apparatus, play a crucial role in detecting changes in gravity and linear acceleration. These structures contain specialized sensory cells that respond to head position and movement relative to gravity.

The otolith organs, which include the sacculus and utriculus, are equipped with tiny calcium carbonate crystals (otoliths) that shift in response to gravitational forces and linear acceleration. When the head moves in a straight line or changes orientation, these crystals move, causing the hair cells beneath them to bend. This bending generates nerve signals that inform the brain about the position and movement of the head.

In contrast, the cochlea is primarily responsible for hearing, and the semicircular canals are more involved with detecting rotational (angular) movements of the head. While the otoliths are related to the sacculus and utriculus in function, the answer specifically calling out the sacculus and utriculus highlights their critical role in linear acceleration and gravity sensing more directly.