Maintenance of muscular tone. Both semicircular canals and otolithic organs participate in this reflex. Following ipsilateral labyrinthectomy an increased extensor tone is demonstrated ipsilateral to the lesion. In decerebrate rigidity the muscular tone is maintained by the continued uncontrolled input of the vestibular organs, sectioning the vestibular nerves removes this rigidity. The semicircular canals, are angular accelerometers, and the otolithic organs, the utricle and saccule detect linear accelerations of the head, including gravity.
Vestibular receptors lie within the temporal bone.
Each is precisely oriented to detect head movement in a specific direction or plane. Changes in the pitch of the head are detected by the superior and posterior SSC's. The receptors are tonically active. There is always a resting, spontaneous outflow of action potentials from the vestibular portion of the eighth nerve. Head motion in one direction that produces an increased firing activity in the receptors of one canal will cause a decreased firing activity in the corresponding paired canal.