stress response

The stress response is the body's emergency mobilization plan: a coordinated set of hormonal and nervous signals that redirects energy and attention toward meeting a threat. Whether the challenge is a charging predator, an exam, or an infection, the body shifts resources from long-term projects like digestion and repair toward immediate survival.

It unfolds in two waves. The fast wave is driven by the sympathetic nerves and adrenal medulla, which flood the blood with adrenaline within seconds, raising heart rate, blood pressure, and blood sugar. The slow wave is the HPA axis, which over minutes to hours releases cortisol to sustain elevated glucose, restrain inflammation, and reset metabolism. Together these systems are sometimes called the stress hormones.

A stress response is adaptive and life-saving when it is brief and matched to a real demand, the original meaning intended by physiologist Hans Selye. The problems arise when the response is triggered too often or never fully shuts off, since the very hormones that protect us in the short term become corrosive when they remain elevated.