Thermoregulation is the control of body temperature. In humans the core body temperature is kept close to 37 °C, usually within about 0.5 °C either way.Why temperature must be controlled:• Enzymes work best at an optimum temperature. If body temperature falls, molecules have less kinetic energy, there are fewer successful enzyme-substrate collisions and metabolic reactions slow down.
• If body temperature rises too high, hydrogen bonds and other bonds in enzymes break, the active site changes shape and the enzymes are denatured, so metabolism fails.
• A core temperature above about 40 °C (hyperthermia) or below about 35 °C (hypothermia) can be fatal if it continues.Thermoregulation is controlled by the thermoregulatory centre in the hypothalamus. It receives information from two sets of thermoreceptors:• central (core) thermoreceptors in the hypothalamus itself, which monitor the temperature of the blood flowing through the brain
• peripheral thermoreceptors in the skin, which detect changes in the temperature of the surroundings and give early warning, before the core temperature changesThe hypothalamus compares this information with the set point of 37 °C and coordinates the responses of the effectors, mainly through the autonomic nervous system and hormones. It has a heat gain centre and a heat loss centre.Keeping a constant high body temperature lets mammals stay active in cold conditions and at night, and keeps metabolic reactions fast and predictable. The cost is a large energy requirement, because much of the food a mammal eats is respired just to release heat.The ways heat is gained and lost, and how the hypothalamus controls each response, are explained in the next lessons.
• If body temperature rises too high, hydrogen bonds and other bonds in enzymes break, the active site changes shape and the enzymes are denatured, so metabolism fails.
• A core temperature above about 40 °C (hyperthermia) or below about 35 °C (hypothermia) can be fatal if it continues.Thermoregulation is controlled by the thermoregulatory centre in the hypothalamus. It receives information from two sets of thermoreceptors:• central (core) thermoreceptors in the hypothalamus itself, which monitor the temperature of the blood flowing through the brain
• peripheral thermoreceptors in the skin, which detect changes in the temperature of the surroundings and give early warning, before the core temperature changesThe hypothalamus compares this information with the set point of 37 °C and coordinates the responses of the effectors, mainly through the autonomic nervous system and hormones. It has a heat gain centre and a heat loss centre.Keeping a constant high body temperature lets mammals stay active in cold conditions and at night, and keeps metabolic reactions fast and predictable. The cost is a large energy requirement, because much of the food a mammal eats is respired just to release heat.The ways heat is gained and lost, and how the hypothalamus controls each response, are explained in the next lessons.