Timothy Budd, of Ohoka School, asks :-

What makes and keeps our body warm?

David Bolton, a physiologist at the Otago University Medical School, responded.

Everything that happens in the body needs energy, which comes from "burning" fuels from the food we eat.

Working muscles use most energy, and their activity produces four times as much heat as useful mechanical work. So this is how we generate heat, which can also be gained from sunlight, glowing fires or a hot bath. Keeping warm means balancing the heat going into us with heat loss. Heat can be lost by conduction to colder things we touch, including the air around us, and by evaporation of water. Both of these are boosted by wind or draughts.

All animals can achieve heat balance by seeking out the proper surroundings, and many can control heat loss, making their skin hot or cold by controlling blood flow, and increasing water evaporation by panting or sweating. If they are too cold they can shiver, which uses more fuel, or curl up in a ball to lose less heat. Insulation can be trimmed by "fluffing up" feathers or fur, but we do this by changing our clothes. In winter clothing a very large part of our heat loss is from the head - if your feet are cold, put on a hat! The saving in heat means the thermostat in the brain can then allow your feet to have some nice warm blood.