Fight-or-Flight Response

topic

The sympatho-adrenal stress response activates within seconds of threat perception — the hypothalamus triggering the sympathetic nervous system to release noradrenaline from sympathetic nerve terminals throughout the body (accelerating heart rate, dilating coronary and skeletal muscle arteries, constricting gut vasculature, releasing liver glycogen), while the adrenal medulla releases adrenaline (epinephrine) into circulation — collectively producing the cardiovascular, metabolic, and attentional changes that optimize immediate physical performance for fight or flight: elevated heart rate, increased muscle blood flow, dilated airways, heightened alertness, and suppressed digestive and reproductive function.

Role

The fight-or-flight response is an extraordinary evolutionary solution to acute physical threat — and a profoundly mismatched response to the psychological stressors of modern life. The body does not distinguish between the stress of a predator attack and the stress of an email deadline: both activate the same adrenaline cascade that prepares muscles for immediate physical exertion — exertion that almost never occurs in response to modern stressors, leaving the mobilized energy, elevated heart rate, and redirected blood flow without the physical resolution they were designed to accompany. The chronic activation of a response designed for seconds-to-minutes that is now sustained for hours to years is the fundamental biological mismatch driving the stress-disease relationship in modern life.

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