Ampullary cupula

When the head rotates, the endolymph filling the semicircular ducts initially lags behind due to inertia.

As the endolymph pushes the cupula, the stereocilia is bent as well, stimulating the hair cells within the crista ampullaris.

As the endolymph continues to move, the cupula is once again deflected resulting in the compensatory movements of the body when spun.

With each rotation, the hair cells undergo either depolarization or hyperpolarization, depending on whether the endolymph moves them toward or away from their adjacent kinocilia, respectively.

The Buoyancy Hypothesis assumes that alcohol, with a different specific gravity from that of the cupula/endolymph, diffuses at different rates into the cupula and the surrounding endolymph.