The three orthogonal canals that sense angular acceleration — anatomy, the crista and cupula, push–pull pairing, and the VOR.
Anatomical organisation
Each inner ear contains three semicircular canals — anterior, posterior, and lateral — arranged roughly at right angles to one another, so that together they sense head rotation in any plane.3
The three canals lie in three mutually perpendicular planes — together they sense head rotation about any axis.
The three semicircular canals, arranged orthogonally to cover the three planes of rotation.3
The crista ampullaris and cupula
Inside each ampulla sits the crista ampullaris, a ridge of sensory hair cells. Their projecting hairs are embedded in the cupula, a jelly-like flap that spans the ampulla and is pushed by moving endolymph.2
At rest
90 spikes/sec
← rotaterestrotate →
Endolymph lag during head rotation deflects the cupula, bending the hair-cell stereocilia.2
Coplanar pairing and push–pull signalling
The canals work in pairs across the two ears. A head turn that excites one canal inhibits its partner on the opposite side, so the brain reads the difference between the two — a more sensitive and robust signal than either canal alone.3
Driving the vestibulo-ocular reflex
The canal signal drives the vestibulo-ocular reflex (VOR): the eyes are rotated opposite to the head so that gaze stays fixed on a target while the head moves.11