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Control of Body TemperatureAQA GCSE Biology: Revision notes

Section 1

What Is Homeostasis and Why Control Body Temperature?

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes. Body temperature is one of the three things homeostasis controls in humans, alongside blood glucose concentration and water levels. Keeping body temperature close to 37°C is essential because it is the temperature at which enzymes in the body work best. Control systems that regulate body temperature may involve both nervous and chemical (hormonal) responses.

Key termshomeostasis

Section 2

Receptors, Coordination Centres and Effectors

Every control system in the body, including temperature control, is built from the same three parts:

  1. Receptors – detect a stimulus (in this case, a change in temperature)
  2. Coordination centre – receives and processes information from receptors (for temperature, this is the thermoregulatory centre in the brain)
  3. Effectors – muscles or glands that bring about a response to restore optimum levels
Key termsreceptoreffector
Exam tip

This pattern (receptor to coordination centre to effector) applies to every homeostatic system, not just temperature.

Section 3

Monitoring Body Temperature

Body temperature is monitored and controlled by the thermoregulatory centre in the brain. This centre contains receptors sensitive to the temperature of the blood flowing through the brain, and it also receives impulses from temperature receptors in the skin, giving information about skin temperature.

Key termsthermoregulatory centre

Section 4

Cooling the Body Down

When the thermoregulatory centre detects that the body is too hot, it triggers responses that increase heat loss:

  • Vasodilation – blood vessels near the skin surface widen, increasing blood flow to the skin so more heat is lost to the surroundings by radiation
  • Sweating – sweat glands release more sweat onto the skin; heat from the body is used to evaporate the sweat, cooling the skin
Key termsvasodilationsweating

Section 5

Warming the Body Up

When the thermoregulatory centre detects that the body is too cold, it triggers responses that reduce heat loss and generate heat:

  • Vasoconstriction – blood vessels near the skin surface narrow, reducing blood flow to the skin so less heat is lost by radiation
  • Shivering – muscles contract rapidly and repeatedly; respiration in the contracting muscles releases heat
Key termsvasoconstrictionshivering
Common mistake

Don't confuse vasodilation (widens vessels, loses heat) with vasoconstriction (narrows vessels, conserves heat).

Must Know

  • Homeostasis maintains optimum internal conditions, including body temperature, for enzymes and cells to function
  • Every control system has receptors, a coordination centre and effectors
  • The thermoregulatory centre in the brain monitors and controls body temperature
  • Too hot: vasodilation and sweating increase heat loss
  • Too cold: vasoconstriction and shivering reduce heat loss and generate heat
  • Vasodilation/vasoconstriction refer to widening/narrowing of blood vessels near the skin

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