This how it works covers How It Works: Thermoregulation as a Negative Feedback Loop within Temperature Regulation for GCSE Biology. Topic 5: Temperature Regulation It is section 6 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
How It Works: Thermoregulation as a Negative Feedback Loop
Body temperature is regulated by the hypothalamus in the brain, which acts as both the receptor (detecting temperature changes in the blood) and the coordination centre (sending instructions to effectors). Temperature-sensitive receptors in the skin also send signals to the hypothalamus about the external environment.
When too hot (above 37°C):
- Vasodilation: Blood vessels supplying skin capillaries widen, allowing more blood to flow near the skin surface. Heat is lost to the surroundings by radiation.
- Sweating: Sweat glands produce sweat on the skin surface. As sweat evaporates, it takes heat energy from the skin — this is the cooling mechanism (evaporation requires latent heat).
- Hairs lie flat: The erector pili muscles relax, so body hairs flatten. This reduces the insulating layer of trapped air.
When too cold (below 37°C):
- Vasoconstriction: Blood vessels supplying skin capillaries narrow, reducing blood flow near the skin surface. Less heat is lost to the surroundings.
- Shivering: Skeletal muscles contract rapidly and repeatedly. Muscle contraction generates heat through increased cellular respiration.
- Hairs stand on end: Erector pili muscles contract, raising body hairs. This traps a layer of air next to the skin, providing insulation (more effective in animals with thick fur).
In both cases, once temperature returns to 37°C, the stimulus disappears and the effector responses stop — this is the negative feedback completing the loop.
Practice questions for Temperature Regulation
What is the normal core body temperature in humans?
Explain how sweating helps to reduce body temperature.