Fight-or-Flight Response

The fight-or-flight response, also called the fight-flight-or-freeze response, hyperarousal, or the acute stress response, is a physiological reaction that occurs when an organism perceives a harmful event, an attack, or a threat to its survival. It was first described by the physiologist Walter Bradford Cannon, who referred to it in 1915 as the necessities of fighting or flight, and his theory holds that animals respond to threats with a general discharge of the sympathetic nervous system that prepares the body for fighting or fleeing. The adrenal medulla produces a hormonal cascade that releases catecholamines, especially norepinephrine and epinephrine, while hormones such as estrogen, testosterone and cortisol, along with the neurotransmitters dopamine and serotonin, also shape how an organism reacts to stress. The response is recognized as the first stage of the general adaptation syndrome, the broader model describing how vertebrates and other organisms regulate their stress responses.