Responses of neurons in the rostral ventrolateral medulla of conscious cats to anticipated and passive movements

摘要

When either humans or quadrupeds transition from supine or prone to a head-up position (as during standing in humans), gravity causes an increase in arterial and venous pressures below the heart and a decrease in pressures above the heart (10, 62). As a consequence, there is an increase in lower body intravascular fluid volume and a decrease in venous return to the heart, which can result in reduced cardiac output and blood flow to the brain (7, 20, 21, 60). Orthostatic hypotension occurs after these physiologic alterations unless there are rapid compensatory changes in sympathetic nerve activity (7).