Control of body temperatureSpec 4.5.2.4
Body temperature is monitored and controlled by the thermoregulatory centre in the brain. It contains receptors sensitive to the temperature of the blood. The skin also contains temperature receptors and sends nervous impulses to the thermoregulatory centre.
| If body temperature is… | Responses |
|---|---|
| Too high | Blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both cause a transfer of energy from the skin to the environment |
| Too low | Blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver) |
Explaining how the mechanisms work
- Vasodilation: more blood flows through the vessels near the skin surface, so more energy is transferred from the blood to the surroundings.
- Sweating: the sweat evaporates from the skin surface, which transfers energy from the skin to the environment and cools the body.
- Vasoconstriction: less blood flows near the skin surface, so less energy is transferred to the surroundings.
- Shivering: skeletal muscles contract rapidly, and the respiration in the muscle cells releases energy that warms the body.
- Sweating stops, so less energy is lost by evaporation.
Quick check
What is the CNS?
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The central nervous system: the brain and spinal cord.
Put these in order: motor neurone, sensory neurone, relay neurone.
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Sensory neurone, relay neurone, motor neurone.
Why are reflex actions important?
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They are automatic and rapid, protecting the body from harm without involving the conscious part of the brain.
Triple only What happens to the ciliary muscles and lens when focusing on a near object?
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The ciliary muscles contract, the suspensory ligaments loosen and the lens becomes thicker.
Triple only Name the type of lens that corrects myopia.
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A concave lens.