Fight-or-flight response

Lore & Background

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. The reaction begins in the amygdala, which triggers a neural response in the hypothalamus. The initial reaction is followed by activation of the pituitary gland and secretion of the hormone ACTH. The adrenal gland is activated almost simultaneously, via the sympathetic nervous system, and releases the hormone epinephrine. The release of chemical messengers results in the production of the hormone cortisol, which increases blood pressure, blood sugar, and suppresses the immune system. Catecholamine hormones, such as adrenaline or noradrenaline, facilitate immediate physical reactions associated with a preparation for violent muscular action. Originally understood as the 'fight-or-flight' response in Cannon's research, the state of hyperarousal results in several responses beyond fighting or fleeing. The wider array of responses, such as freezing, flop, faint, flee and fright, has led researchers to use more neutral or accommodating terminology such as 'hyperarousal' or the 'acute stress response'. This has led people to calling it the 'fight, flight, freeze' response, 'fight-flight-freeze-fawn' or 'fight-flight-faint-or-freeze', among other variants.

Reader's Guide

The fight-or-flight response is a foundational concept in stress physiology, first articulated by Walter Bradford Cannon in the early 20th century. It describes the body's automatic physiological reaction to perceived threats, mediated by the autonomic nervous system. The sympathetic nervous system activates arousal responses, while the parasympathetic nervous system later returns the body to homeostasis. This response is recognized as the first stage of the general adaptation syndrome, which regulates stress responses across vertebrates and other organisms. The significance of the fight-or-flight response extends beyond its original formulation. Researchers have expanded the terminology to include freezing, fainting, and other reactions, leading to terms like 'fight-flight-freeze' or 'hyperarousal'. The response involves complex hormonal cascades, including catecholamines like epinephrine and norepinephrine, as well as cortisol, which increases blood pressure and blood sugar while suppressing the immune system. Physiological changes—such as increased blood flow to muscles, dilated pupils, and accelerated blood clotting—prepare the body for violent action. The legacy of this concept lies in its integration into modern understanding of stress, anxiety, and emotional regulation. Emotional reactivity and perceived control influence how individuals respond to threats. The response also has cognitive components, including attention to negative stimuli and attribution of hostility. While originally described in animals, the fight-or-flight response remains central to explaining human reactions to danger and has informed treatments for anxiety disorders and trauma.

Did You Know?

• The response is recognized as the first stage of the general adaptation syndrome that regulates stress responses among vertebrates and other organisms.
• The hormone osteocalcin might also play a part in how organisms react to stress.
• The wider array of responses, such as freezing, flop, faint, flee and fright, has led researchers to use terms like 'hyperarousal' or 'acute stress response'.