Written by Travis M. Moore
Last edited Sep-2019
The vestibular end organ consists of five independent structures. Three semicircular canals (SCC) sense angular motion and two otolith organs sense linear motion and static position.
The SCCs are roughly oriented in three different planes: pitch, yaw and roll. These are the same planes as a plot of 3D space (and since we live in three dimensions, it makes sense the vestibular system can compute in three dimensions!). Because the SCCs are in your head, it's useful to identify the planes by relating them to head movements. When you shake your head "no," it is rotating around the y axis, or yaw plane. When you nod your head "yes," it is rotating around the x axis, or pitch plane. Finally, when you try to touch your ear to your shoulder your head is rotating around the z axis, or roll plane.