physiological stress response

Meaning: The physiological stress response is the body's coordinated reaction to a perceived threat. The fast arm is the sympathetic nervous system: the adrenal medulla releases epinephrine and norepinephrine within seconds, raising heart rate, blood pressure and available glucose (fight-or-flight). The slower arm is the HPA axis: the hypothalamus releases CRH, the anterior pituitary releases ACTH, and the adrenal cortex releases cortisol, which mobilizes energy and, at high levels over time, suppresses immune function. Selye's general adaptation syndrome describes the course: alarm, resistance, exhaustion.

On the MCAT: Passages ask you to order the HPA steps, match each hormone to its gland, or predict the effects of chronic stress, such as elevated cortisol, weakened immunity and raised blood pressure. Questions may contrast the fast neural route with the slower hormonal one. Lazarus's cognitive appraisal also links in: whether an event triggers the response depends on how threatening it is judged to be and whether coping resources seem adequate.

Common confusion: Students often equate the response with adrenaline alone, or think cortisol comes first. The sympathetic and adrenal medulla route acts first; cortisol follows over minutes. Also, the response is adaptive in the short term; harm comes mainly from prolonged activation.