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How do semicircular canals detect head rotation?

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Meissner's corpuscle; mechanoreception — Mechanoreception In human skin, specialized nerve endings known as Meissner's corpuscles (or tactile corpuscles) are sensitive to touch. They are one of several different types of mechanoreceptors found in human skin.

The semicircular canals detect head rotation through the movement of endolymph, a fluid contained within the canals. Because the three canals are oriented at right angles to one another, they can sense rotational movement in three-dimensional space.123

When the head begins to rotate, the inertia of the endolymph causes it to lag behind the movement of the canal walls. This fluid displacement exerts pressure on the cupula, a gelatinous structure located within the ampulla at the base of each canal. The cupula covers the crista, a ridge containing sensory hair cells with protruding stereocilia.1425

As the cupula is deflected by the moving endolymph, it bends these cilia. This mechanical bending alters the electrical potential of the hair cells:12
* Depolarization: Bending stereocilia toward the kinocilium opens ion channels, increasing the rate of nerve impulses sent to the central nervous system.12
* Hyperpolarization: Bending them away from the kinocilium closes these channels, decreasing the discharge rate.124

These signals allow the brain to perceive the direction and rate of head rotation.14