otolith organ

The otolith organs, the utricle and saccule, are part of the inner ear's vestibular system, responsible for balance and detecting linear acceleration. These organs contain sensory cells called hair cells, topped with cilia. A gelatinous membrane, embedded with tiny calcium carbonate crystals known as otoliths, rests on these hair cells.1234

When the head tilts or moves linearly, gravity causes the dense otoliths to shift, bending the hair cell cilia. This bending stimulates the hair cells, altering their electrical potential and sending signals via the vestibulocochlear nerve to the brain, informing it about the head's position and movement relative to gravity. The utricle primarily monitors horizontal movements and head tilts, while the saccule is thought to respond more to forward and backward tilts.1234