Fight‑or‑Flight Response: Mechanism, Purpose, and Chronic Effects

The fight‑or‑flight response is an acute survival mechanism triggered by perceived threat. The amygdala signals the hypothalamus, activating the sympathetic nervous system and the hypothalamic‑pituitary‑adrenal (HPA) axis. This releases adrenaline and cortisol, producing:

• Increased heart rate, blood pressure, and cardiac output
• Bronchodilation and hyperventilation
• Mobilization of glucose and fatty acids
• Heightened alertness and muscle readiness

While adaptive in short bursts, chronic activation contributes to anxiety disorders, hypertension, metabolic syndrome, and PTSD. Stress management techniques (mindfulness, exercise, therapy) help restore balance.