AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
If the body temperature is too high, blood vessels dilate (vasodilation)…
Full specification wording
Control of body temperature (biology only): If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands.
When the thermoregulatory centre detects that core body temperature has risen above the normal set point, it triggers two coordinated cooling responses.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 4 of 7
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When the thermoregulatory centre detects that core body temperature has risen above the normal set point, it triggers two coordinated cooling responses. Vasodilation occurs when the smooth muscle in the walls of arterioles supplying the skin capillaries relaxes, so the arterioles widen and more blood flows through the skin capillaries. This increases the volume of blood close to the skin surface, so more energy is transferred by radiation and convection to the surroundings. At the same time, sweat glands secrete sweat onto the skin surface. As sweat evaporates, it takes latent heat from the skin, removing energy and cooling the body.
For example: During exercise on a hot day, a person's skin may redden and become wet with sweat as both responses operate together to lower core temperature.
What earns the marks
- Vasodilation involves widening of arterioles that supply skin capillaries.
- More blood flows through skin capillaries, increasing energy transfer to the environment.
- Sweat glands produce sweat, which is released onto the skin surface.
- Evaporation of sweat transfers energy from the skin to the surroundings.
- The responses continue until core body temperature returns to its normal set point.
Common mistakes and how to put them right
Confusing vasodilation with vasoconstriction.
Put it right: Vasodilation widens vessels and increases blood flow to the skin when too hot.
Stating that sweat itself cools the body.
Put it right: It is the evaporation of sweat that transfers energy away from the skin.
Claiming that blood vessels move closer to the skin surface.
Put it right: The vessels dilate, and the increased blood flow through existing skin capillaries causes the effect.
Exam tips
- Use the terms vasodilation and sweat glands accurately, and link each to its cooling effect.
- Explain the mechanism in terms of energy transfer rather than simply saying the body cools down.
- When describing vasodilation, refer to arterioles widening and increased blood flow through skin capillaries.
Try the lesson
The start of the Control of body temperature (biology only): If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. lesson, made from checked teaching notes for this specification point.
Have a go first
When the body temperature becomes too high, what happens to the blood vessels near the skin surface?
Listen
When the thermoregulatory centre detects that core body temperature has risen above the normal set point, it triggers two coordinated cooling responses. Vasodilation occurs when the smooth muscle in the walls of arterioles supplying the skin capillaries relaxes, so the arterioles widen and more blood flows through the skin capillaries. This increases the volume of blood close to the skin surface, so more energy is transferred by radiation and convection to the surroundings. At the same time, sweat glands secrete sweat onto the skin surface. As sweat evaporates, it takes latent heat from the skin, removing energy and cooling the body. For example, during exercise on a hot day, a person's skin may redden and become wet with sweat as both responses operate together to lower core temperature. A strong answer earns marks for these points. Vasodilation involves widening of arterioles that supply skin capillaries. More blood flows through skin capillaries, increasing energy transfer to the environment. Sweat glands produce sweat, which is released onto the skin surface. Evaporation of sweat transfers energy from the skin to the surroundings. Exam tip: Use the terms vasodilation and sweat glands accurately, and link each to its cooling effect.
Key words
Say what each word means before you turn the card.
Vasodilation
Try answering aloud or in your head before turning the card.
Sweat glands
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See every definition
- Vasodilation
- The smooth muscle in the walls of arterioles supplying the skin capillaries relaxes, so the arterioles widen and more blood flows through the skin capillaries.
- Sweat glands
- These secrete sweat onto the skin surface, and as the sweat evaporates it takes latent heat from the skin, removing energy and cooling the body.
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