general adaptation syndrome

Meaning: General adaptation syndrome (GAS) is Hans Selye's model of how the body responds to a prolonged stressor, largely regardless of what the stressor is. It has three stages, in order. Alarm: the sympathetic nervous system triggers fight-or-flight, and epinephrine and norepinephrine raise heart rate and alertness. Resistance: the body stays mobilized to cope, with the HPA axis releasing cortisol; arousal is lower than in alarm but still above baseline. Exhaustion: if the stressor continues, resources run down and the person becomes more vulnerable to illness.

On the MCAT: A passage describes chronic stress, such as exams or caregiving, and asks which stage fits or which system dominates. Alarm is sympathetic and brief, resistance involves cortisol and apparent coping, and exhaustion shows fatigue and weakened immunity. Questions may also contrast GAS with Lazarus's appraisal model, in which an event is stressful when it is appraised as exceeding one's coping resources.

Common confusion: Resistance is not recovery. The person may seem to cope, but arousal stays elevated and reserves are being used up, which is why exhaustion follows if the stressor persists. Also, GAS describes a physiological sequence, while appraisal theory explains why an event counts as a stressor in the first place.