7.14—Adrenaline and fight-or-flight

Adrenaline is released during acute stress and prepares the body for rapid action. It increases heart rate and ventilation, redirects blood toward skeletal muscle and raises blood glucose availability.

The response is coordinated by receptors and effectors: more cardiac output and ventilation deliver oxygen, while glycogen breakdown supplies respiratory substrate. It is rapid and short-term rather than a complete long-term adaptation.

A sudden threat can cause heart rate to rise before movement begins, increasing cardiac output; the same response can be unnecessary or costly if stress is prolonged.

Adrenaline does not directly create ATP and “fight-or-flight” is not a single switch. Identify the target tissue and physiological effect.