Too hot for comfort

Organisms – including humans – are adapted to a narrow range of temperatures

In humans internal body temperature is maintained at a remarkably constant 36–37°C, thanks to a variety of homeostatic mechanisms, coordinated by a thermostat in the hypothalamus region of the brain.

When body temperatures rise, negative feedback systems kick in – sweating, blood vessel dilation near the skin (vasodilation), behavioural responses (seeking shade, eating ice cream) and so on.

Ongoing exposure to elevated temperatures is highly dangerous, leading to heatstroke. Symptoms include headache, nausea and confusion, cardiovascular and heart malfunction, and eventually coma and death.

The mechanisms of heatstroke are not well understood. Water loss by sweating leads to loss of blood pressure and reduced blood flow to the brain, followed by organ failure and brain damage. Little is known about the molecules mediating these responses; a better understanding could suggest new ways to treat heatstroke.

Thermoregulation is important because the speed of biochemical reactions – chemical kinetics – varies with temperature. In addition, biological molecules such as proteins lose their shape (denature) and are inactivated if temperatures rise too high. Often this temperature threshold is around 41°C.


About this resource

This resource was first published in ‘Health and Climate Change’ in January 2009 and reviewed and updated in September 2014.

Microbiology, Ecology and environment, Cell biology, Health, infection and disease
Health and Climate Change
Education levels:
14–16, 16–19, Continuing professional development