thermoregulation

Thermoregulation is the biological process by which organisms maintain a stable internal body temperature despite changes in the surrounding environment. It relies on temperature sensors, a central regulatory center, and effectors that adjust heat production and heat loss. The system uses negative feedback to keep core temperature within a narrow, optimal range for cellular function and metabolic efficiency.

Endotherms, such as mammals and birds, keep a relatively constant core temperature through autonomic and endocrine responses. When cold, the hypothalamus triggers vasoconstriction, shivering, and non-shivering thermogenesis, including brown adipose tissue activity. When hot, it promotes vasodilation, sweating or panting, and often a reduction in metabolic rate. Behavioral responses, such as seeking shade, seeking sun, or changing posture, also help regulate heat exchange.

Ectotherms rely more on environmental temperature and behavior to regulate their body temperature. Their body temperature tends to track ambient conditions, with regulation achieved mainly through basking, seeking shade or shelter, burrowing, nocturnal activity, or seasonal migration. Some organisms employ physiological adaptations such as altered metabolic rates or, in some species, antifreeze compounds to cope with temperature extremes.

Fever represents a regulated shift in the hypothalamic temperature set point in response to infection, mediated by pyrogens. This can raise body temperature to inhibit pathogens but may also carry risks if excessive. Conversely, hypothermia and hyperthermia occur when regulatory mechanisms fail or environmental stress overwhelms the system. Thermoregulation intersects with metabolism, behavior, ecology, and health.