How the Body Responds to Stress

Last Updated: Dec. 1, 2003

The maintenance of the body’s relatively steady internal state is essential for survival. The body’s delicate balance of biochemical and physiological function is constantly challenged by a wide variety of stressors, including illness, injury, and exposure to extreme temperatures; by psychological factors, such as depression and fear; and by sexual activity and some forms of novelty-seeking.

In response to stress, or even perceived stress, the body mobilizes an extensive array of physiological and behavioral changes. The stress response is a highly complex, integrated network involving the central nervous system, the adrenal system, and the cardiovascular system.

The stress response
When that steady internal state is threatened, the hypothalamus gland, at the base of the brain, initiates the stress response by secreting corticotropin releasing factor (CRF). CRF coordinates the stress response by triggering an integrated series of physiological and behavioral reactions. CRF is transported in blood within the brain and in seconds triggers the pituitary gland to release adrenocorticotropin hormone (ACTH), also referred to as corticotropin. ACTH then triggers secretion of glucocorticoid hormones (i.e., “steroids”) by the adrenal glands, located at the top of the kidneys. Glucocorticoid hormones play a key role in the stress response and its termination.

Activation of the stress response affects smooth muscle, fat, the gastrointestinal tract, the kidneys, and many other organs and the body functions that they control. The stress response affects the body’s regulation of temperature; appetite and satiety; arousal, vigilance, and attention; mood; and more. Physical adaptation to stress allows the body to redirect oxygen and nutrients to the stressed body site, where they are needed most.

Both the perception of what is stressful and the physiological response to stress vary considerably among individuals. These differences are based on genetic factors and environmental influences that can be traced back to infancy.

Stress is usually thought of as harmful; but when the stress response is acute and transient, no adverse effects result. Under chronic stress, however, when the body either fails to compensate or when it overcompensates, damage can occur. Such damage may include suppression of growth, immune system dysfunction, and cell damage.

Source: National Institutes of Health

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