Fight or flight
- 1 : relating to, being, or causing physiological changes in the body (as an increase in heart rate or dilation of bronchi) in response to stress <epinephrine is a fight–or–flight hormone> <a fight–or–flight reaction>
The fight-or-flight response (also called the fight-or-flight-or-freeze response, hyperarousal, or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first described by Walter Bradford Cannon by sympathetic nervous system activation that innervates the adrenal medulla, producing a hormonal cascade that results in the secretion of catecholamines, especially. The reaction is activated by the autonomic nervous system, which primes the animal for fighting or fleeing.
An evolutionary psychology explanation is that early humans had to react to threatening stimuli quickly and did not have time to psychologically and physically prepare themselves. The fight or flight response provided prehistoric humans with the mechanisms to rapidly respond to threats against survival.
Prolonged stress responses may result in chronic suppression of the immune system, leaving the body open to infections. However, there is a short boost of the immune system shortly after the fight or flight response has been activated. This may have filled an ancient need to fight the infections in a wound that one may have received during interaction with a predator.
Stress responses are sometimes a result of mental disorders such as post-traumatic stress disorder, in which the individual shows a stress response when remembering a past trauma, and panic disorder, in which the stress response is activated by the catastrophic misinterpretations of bodily sensations.