vasovagal reaction

vasovagal reaction A reflex of the involuntary nervous system that causes the heart to slow down and, at the same time, affects the nerves to the blood vessels in the legs, permitting those vessels to dilate (widen). As a result, the heart puts out less blood, the blood pressure drops, and the blood that is circulating tends to go into the legs rather than to the head. The brain is deprived of oxygen, and a fainting episode (syncope) occurs. See also syncope.