Fight-or-flight response

The fight-or-flight or the fight-flight-or-freeze-fawn (also called 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. His theory states that animals react to threats with a general discharge of the sympathetic nervous system, preparing the animal for fighting or fleeing. More specifically, the adrenal medulla produces a hormonal cascade that results in the secretion of catecholamines, especially norepinephrine and epinephrine. The hormones estrogen, testosterone, and cortisol, as well as the neurotransmitters dopamine and serotonin, also affect how organisms react to stress. The hormone osteocalcin might also play a part. This response is recognised as the first stage of the general adaptation syndrome that regulates stress responses among vertebrates and other organisms. Originally understood as the fight-or-flight response in Cannon's research, the state of hyperarousal results in several responses beyond fighting or fleeing. This has led people to calling it the fight, flight, freeze response (or fight-flight-faint-or-freeze, among other variants). The wider array of responses, such as freezing, fainting, fleeing, or experiencing fright, has led researchers to use more neutral or accommodating terminology such as hyperarousal or the acute stress response. Autonomic nervous system The autonomic nervous system is a control system that acts largely unconsciously and regulates heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response and its role is mediated by two different components: the sympathetic nervous system and the parasympathetic nervous system. Sympathetic nervous system The sympathetic nervous system originates in the spinal cord and its main function is to activate the physiological changes that occur during the fight-or-flight response.