What is homeostasis, and how does the body keep its temperature steady?
Homeostasis as keeping a constant internal environment, and how body temperature is controlled by the skin.
A focused answer to the WJEC GCSE Science Double Award Unit 4 topic on homeostasis, covering what homeostasis means, why it matters, and how body temperature is controlled by sweating, vasodilation, shivering and vasoconstriction in the skin.
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What this dot point is asking
WJEC Double Award Unit 4 wants you to explain what homeostasis is and why it matters, and describe how body temperature is controlled.
What homeostasis is
Homeostasis matters because the body's cells and enzymes only work properly within a narrow range of conditions. If the temperature, glucose or water level moves too far from normal, enzymes can be denatured and cells can be damaged.
Why a steady temperature matters
The body is kept at about 37 degrees Celsius, the temperature at which its enzymes work best. If the body gets too hot, enzymes can be denatured and stop working; if it gets too cold, reactions slow down too much. Keeping a steady temperature lets the body's chemical reactions, including respiration, run at the right rate.
Cooling down when too hot
Warming up when too cold
These responses are controlled automatically to bring the temperature back to normal.
How temperature control is coordinated
The body's temperature is monitored by the brain, which detects the temperature of the blood, and by receptors in the skin that detect the temperature outside. If the temperature moves away from normal, the brain sends signals to the effectors in the skin and muscles - the sweat glands, the blood vessels and the muscles - to make the right response. This is another example of negative feedback: the responses always act to bring the temperature back towards the normal 37 degrees Celsius. Knowing that the brain coordinates the response links temperature control to the nervous system.
Other parts of homeostasis
Temperature is only one thing kept constant. The body also controls blood glucose (using insulin from the pancreas) and water and salt levels (using the kidneys), among others. All of these use the same idea: a change is detected, a response is triggered, and the level is brought back to normal by negative feedback. Listing more than one example of homeostasis, and recognising the common pattern behind them, shows a good understanding of why a constant internal environment matters for the body's cells and enzymes.
Try this
Q1. State one condition kept constant by homeostasis. [1 mark]
- Cue. Any one of: temperature, blood glucose, or water level.
Q2. What happens to skin blood vessels when the body is too cold? [1 mark]
- Cue. They narrow (vasoconstriction) to reduce heat loss.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style4 marksExplain how the body cools down when it gets too hot.Show worked answer →
A Unit 4 explain question worth 4 marks. Reward: sweat glands release more sweat, which evaporates from the skin, taking heat away and cooling the body (2); the blood vessels near the skin surface widen (vasodilation), so more blood flows near the surface and more heat is lost by radiation (2). Markers credit sweating with evaporation and vasodilation increasing heat loss. A common error is to say the blood vessels "move" to the surface (they widen, they do not move).
WJEC style3 marksDescribe two ways the body responds when it gets too cold.Show worked answer →
A Unit 4 describe question. Reward two of: shivering - muscles contract rapidly, and the respiration this needs releases heat (1); the blood vessels near the skin narrow (vasoconstriction), so less blood flows near the surface and less heat is lost (1); less sweat is produced; and hairs stand up to trap an insulating layer of air (1). Markers credit two valid responses linked to keeping heat in or generating it. A common error is to say blood vessels "close" completely.
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