fight-or-flight response
a pattern of physiological changes elicited by activity of the sympathetic nervous system in response to threatening or otherwise stressful situations that leads to mobilization of energy for physical activity (e.g., attacking or avoiding the offending stimulus), either directly or by inhibiting physiological activity that does not contribute to energy mobilization. Specific sympathetic responses involved in the response include increased heart rate, respiratory rate, and sweat gland activity; elevated blood pressure; decreased digestive activity; pupil dilation; and a routing of blood flow to skeletal muscles. In some theories, such changes are the basis of all human emotions. Also called emergency reaction; emergency syndrome. See also Cannon–Bard theory. [first described by Walter B. Cannon]