Chikara's room

Vestibulo-cardiovascular reflex

A postural change from a recumbent to an upright position induces an increase in the hydrostatic pressure gradient, a footward fluid shift, reduced venous return and cardiac output, and reduced arterial pressure. This reduction in arterial pressure is sensed by baroreceptors in the blood vessels, and AP is thought to be stabilized by the arterial baroreflex, an important negative feedback process. Alternatively, postural changes might stimulate the vestibular organ, which is also thought to be involved in AP regulation with postural change because stimulation of the vestibular system by head movement or changes in gravitational forces is known to induce sympathoexcitation. Interaction between the baroreflex and the vestibular system during postural change might contribute to control of arterial pressure during postural change.

 

Space medicine

The vestibular system plays an important role in controlling arterial pressure upon posture change (vestibulo-cardiovascular reflex), although this system is highly plastic, i.e., the sensitivity of the vestibulo-cardiovascular reflex is altered if subjects are exposed to a different gravitational environment. Thus, it is possible that the sensitivity of vestibulo-cardiovascular reflex is diminished after spaceflight, and then orthostatic hypotension is induced. To test this hypothesis, the role of the vestibulo-cardiovascular reflex in maintaining arterial pressure upon posture change is examined before and after spaceflight.

Please see V-C Reflex (http://www.nasa.gov/mission_pages/station/research/experiments/879.html).