Do the organs of the labyrinth differentially influence the sympathetic and parasympathetic systems?
It has long been recognized that the vestibular system plays a major role in autonomic control. The nature of this control remains in dispute, however, as some evidence points to a vestibularly mediated parasympathetic activation, whereas other evidence points to a sympatho-excitatory role for labyrinthine outputs. A theoretical explanation is offered that attempts to resolve this issue by postulating that the utricles exert a predominantly sympatho-excitatory influence via their interactions with brain noradrenergic pathways, while the semicircular canals (and possibly saccules) increase parasympathetic tone via their cholinergic brain stem and cerebellar projections. This explanation is relevant for understanding the vestibular role in orthostatic regulation, motion sickness, oculomotor control, and in many disorders or situations associated with neurochemical or autonomic imbalances.
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Crew Technology Division, Crew Systems Directorate, Armstrong Laboratory (AFMC), Brooks Air Force Base, TX 78235-5104.
D000818:Animals; D007758:Ear, Inner / Q000502:physiology*; D006801:Humans; D010275:Parasympathetic Nervous System / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*