Parasympathetic rebound
Parasympathetic rebound is a possible delayed (over-)reaction of the parasympathetic nervous system .
During intense and/or prolonged stress the opposed sympathetic nervous system via the hormones cortisol and catecholamines (such as adrenaline) suppresses the parasympathetic activities, such as the immune- and digestive system. When this suppression vanishes, the parasympathetic system may overreact, as typical for any Closed-loop transfer function.