What is the fight-or-flight-or-freeze response?

The answer

The fight-flight-freeze response is an acute stress reaction coordinated by the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. When the amygdala detects a threat, it signals the hypothalamus to activate the sympathetic nervous system, releasing adrenaline and noradrenaline within milliseconds. This triggers a cascade of physiological changes: heart rate and blood pressure spike, pupils dilate, airways open, blood is diverted from the digestive system to skeletal muscles, pain sensitivity decreases, and glucose floods into the bloodstream for instant energy. The freeze response, sometimes called tonic immobility, is a more recently recognized third option in which the body becomes temporarily paralyzed, possibly evolved because predators are less likely to attack motionless prey. Which response occurs depends on the perceived escapability of the threat and individual neurological factors.