stresssystemen

The stress systems refer to the body's coordinated physiological and behavioral responses to perceived threats or demands. In humans, the main components are the autonomic nervous system and two hormonal axes: the sympathetic-adrenomedullary (SAM) system and the hypothalamic-pituitary-adrenal (HPA) axis. They work on different time scales but interact to prepare for action and later restore balance.

The SAM system provides a rapid fight-or-flight response. Activation triggers adrenal medulla release of adrenaline and noradrenaline, increasing heart rate, blood pressure, and glucose availability while diverting blood to muscles and dilating airways. Effects are immediate and short-lived.

The HPA axis governs a slower, sustained response. The hypothalamus releases CRH, triggering pituitary ACTH release, which stimulates the adrenal cortex to produce glucocorticoids such as cortisol. Cortisol supports energy mobilization, modulates immune function, and assists with maintaining vascular tone during ongoing stress; it is subject to negative feedback.

The autonomic and endocrine responses are complemented by circadian regulation; cortisol typically peaks in the morning and declines through the day. Allostasis describes the process of maintaining stability through adaptation, while allostatic load reflects the cumulative wear from chronic stress.

Chronic or repeated activation can contribute to health problems, including cardiovascular, metabolic, and mental health disorders, when regulation becomes dysregulated. Measurement often uses cortisol levels in saliva or plasma and metrics such as heart rate variability.