Responses to heat and coldSpec 7.12B
When the body is too hot
- Sweat glands release sweat onto the skin. Sweat evaporates and takes heat from the skin, which cools the body.
Higher tier
- Vasodilation: the blood vessels supplying the skin surface widen. More blood flows near the surface, so more heat is lost to the surroundings.
When the body is too cold
- Shivering: muscles contract rapidly. This needs more respiration in the muscle cells, which transfers energy as heat and warms the body.
Higher tier
- Vasoconstriction: the blood vessels supplying the skin surface narrow. Less blood flows near the surface, so less heat is lost.
- Sweating is reduced when the body is cold.
Higher tier
Higher tier
Tap to enlargeVasodilation brings more blood near the surface to lose heat; vasoconstriction reduces heat loss.
Tap to enlargeQuick check
Define homeostasis.
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Maintaining a constant internal environment in response to internal and external change.
Why does a high body temperature stop reactions in cells? (Triple only)
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Enzymes are denatured, so substrates no longer fit the active site.
What happens to animal cells if the blood is too dilute? (Triple only)
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Water enters by osmosis. The cells swell and may burst.
Which part of the brain coordinates temperature control? (Triple only)
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The hypothalamus.
How does shivering warm the body? (Triple only)
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Muscles contract rapidly. Respiration in the muscle cells transfers energy as heat.