Semicircular canals: Three orthogonal fluid-filled loops (horizontal, anterior, posterior). Angular acceleration deflects the cupula → hair cells bend → afferent firing rate changes. Respond to rotation (not linear motion). Time constant ~7 s (human).
Otolith organs (utricle + saccule) detect linear acceleration via crystals (otoconia) resting on a sensory epithelium (macula). Utricle: horizontal; Saccule: vertical. They also sense gravity, enabling head tilt detection.
VOR: The vestibulo-ocular reflex stabilizes gaze during head movement with ~8 ms latency (fastest reflex in the body). For every degree of head rotation, the eyes rotate exactly opposite, keeping the visual image stable. VOR gain = eye velocity / head velocity ≈ 1.0.