AP® Psychology · Unit 5 · Topic 5.1
Stress and the Body
Stress is a physical process, not just a feeling: the brain reads a threat and triggers hormones that prepare the body to fight or flee, but when the threat never ends, those same hormones wear the body down.
A stressor starts as a perception. The brain's appraisal of a situation as threatening sets off the hypothalamus, which signals the pituitary gland, which signals the adrenal glands to release hormones into the bloodstream. Adrenaline spikes first, raising heart rate and blood pressure for an immediate burst of energy. Cortisol follows more slowly, releasing stored glucose for fuel and, crucially, dialing down systems the body doesn't need in the next ten minutes, including the immune system. This is useful for a short sprint away from danger. It becomes a problem when the stressor is a deadline, a conflict, or a caregiving burden that lasts for weeks.
Selye's general adaptation syndrome describes this as three stages. Alarm is the initial jolt of adrenaline and cortisol. Resistance is the body holding elevated cortisol steady while trying to function normally, still fighting the stressor. Exhaustion is what happens if the stressor never lifts: hormonal resources are depleted, immune function stays suppressed, and the body becomes vulnerable to illness, slower healing, and fatigue. The cold that hits right after a brutal work month isn't a coincidence. Resistance kept immunity suppressed the whole time; symptoms just surface once the person stops mobilizing and the body has room to notice what weakened.
This mechanism is the hinge of the unit. It explains why chronic stress is a risk factor for cardiovascular disease and slow wound healing, and it sets up why psychological buffers like optimism, social support, and a sense of control matter: they lower how often and how intensely this cascade fires in the first place.
Key terms
- Cortisol
- A stress hormone released by the adrenal glands that frees up energy and suppresses immune function during prolonged stress.
- General adaptation syndrome
- Selye's three-stage model of the body's stress response: alarm, resistance, and exhaustion.
- Exhaustion phase
- The final stage of general adaptation syndrome, where depleted resources leave the body vulnerable to illness and slow healing.
- Immune suppression
- A reduction in immune system activity, a common effect of sustained high cortisol levels.
- Chronic stress
- Stress that persists over weeks or months rather than resolving quickly, keeping the body in the resistance stage.
Watch it explained
- How it worksHow does a psychological stressor turn into blood pressure, hormones, and immune suppression?
- How it worksWalk me through cortisol rising and staying high under chronic stress.
- Going furtherWhat happens to wound healing rates in people under long-term caregiving stress?
- Ties togetherHow does chronic cortisol connect to the exhaustion phase of general adaptation syndrome?
Check yourself
End of topic.