Thermoregulation
The regulation of body temperature, normally held close to 37 °C (98.6 °F) — warm enough for the body’s chemistry to run efficiently, stable enough to keep its proteins working.
The control center
Section titled “The control center”The hypothalamus acts as the body’s thermostat: it holds the setpoint, reads temperature from sensors in the skin and the body’s core, and triggers correction.
Cooling, when too warm
Section titled “Cooling, when too warm”- Sweating — evaporating sweat carries away heat.
- Vasodilation — skin blood vessels widen, releasing heat from the blood at the surface.
Warming, when too cold
Section titled “Warming, when too cold”- Shivering — rapid muscle contraction generates heat.
- Vasoconstriction — skin vessels narrow, keeping warm blood in the core.
- Other responses — raising body hair, and hormonal increases in metabolic rate.
A fever is not a failure of regulation but a deliberate raising of the setpoint by the immune system, making the body less hospitable to invaders.
Key idea
Section titled “Key idea”Body temperature is defended from both sides — distinct mechanisms for shedding and for conserving heat — all coordinated by the hypothalamus, with the skin as the main effector. Behavior (seeking shade, adding clothing) is part of the system too.