Crista Ampullaris (start of semicircular canals) detect angular acceleration. At each ampullae there is hair cells with cilium and stereocilim, sticking up in the cupula (round circle filled with fluid). Each semicircle canal resides in frontal, horizontal, and saggital plane to detect all direction of rotations. As head turns, endolymph (fluid) lags behind, pushes capula, and stimulate the hair cells.