The central nervous system is complex and cannot be oversimplified. In depth presentation of the anatomy of the system is beyond the scope of this paper. Extensive ascending and descending pathways are responsible for motor responses and balance. No doubt, what is understood about the nervous system and how it functions is but a fraction of how it works.
The vestibular receptors are a portion of the inner ear comprised of three parts:
(A) the utricle
(B) the saccule
(C) semicircular canals
The semicircular canals are sensitive to rotary movement and stimulation promotes dynamic balance. Together, the utricle and the saccule make up the otolith. The saccule is thought to perceive vibratory sensation, vertical input, and to influence eye movements. (4,5) Stimulating the utricle is most effective when low frequency sustained movement is used.(5) The otolith is sensitive to linear vestibular stimulation. Stimulating the otolith promotes stable balance, tonic postural control, and support reactions.
The role of the vestibular system is to:
(A) make the body aware of positional movement in space,
(B) enable postural tone and equilibrium, and
(C) stabilize the eyes during head movement (5)
Balance and equilibrium responses are the result of proprioception, the inner ear, other parts of the vestibular system, and the visual system working together to enable awareness of the bodys position in space and making appropriate corrections. Vestibular function is more important than proprioceptive function to control postural sway.(3) It is difficult to differentiate proprioceptive versus vestibular dysfunction in the clinic setting. Clinically, we do not know which function the individual is using at a given moment.