The Vestibular System
The vestibular system refers to five organs deep within your inner ear. It consists of three semicircular canals, filled with fluid, and 2 otolith organs (the utricle and saccule). Together, they provide information to your brain (via the vestibular nerve) about the alignment and movement of your head, including information about position relative to gravity, velocity, linear acceleration and rotation. This information is relayed to various brain regions which help to coordinate appropriate, automatic responses/reflexes. Two of the most important reflexes are the VOR and VSR.
VOR:
The Vestibulo-Ocular Reflex sends information about head movements from the vestibular system to the muscles of your eyes. When you turn your head one direction, the VOR helps to move your eyes in an equal and opposite direction so that your vision remains clear and focussed. Without this finely-tuned reflex, objects will appear blurred or bouncing.
VSR:
The Vestibulo-Spinal Reflex sends information from your vestibular system to the muscles and joints of your spine and limbs. For instance, when the vestibular system detects that your are tilting forwards, it will relay information to the muscles of your back, hips, knees and ankles, telling them to contract, to prevent you from falling forward. Without this reflex, we are much more likely to lose our balance.