5.14 Controlling body temperature
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Name the part of the brain that monitors and controls body temperature.
Mark scheme
thermoregulatory centre / hypothalamus
Model answer
The thermoregulatory centre, in the hypothalamus.
A person goes for a run on a hot day and their body temperature rises.
Explain how their body returns its temperature to normal.
Mark scheme
Level 3 (5-6): detection, coordination and both effector responses explained, with the mechanism of energy transfer. Level 2 (3-4): both responses described with some explanation, or one fully explained. Level 1 (1-2): simple statements, e.g. they sweat.
Indicative content:
- rise detected by receptors in the thermoregulatory centre / hypothalamus (blood temperature)
- and by temperature receptors in the skin
- nervous impulses to effectors
- sweat glands produce (more) sweat
- sweat evaporates, transferring energy from the skin
- arterioles supplying skin capillaries dilate (vasodilation)
- more blood flows near the skin surface
- more energy transferred to the surroundings by radiation
- negative feedback: temperature returns to 37 °C
Model answer
The rise in blood temperature is detected by receptors in the thermoregulatory centre in the brain, and temperature receptors in the skin also send impulses to it. The thermoregulatory centre sends impulses to the effectors. Sweat glands produce more sweat, which evaporates from the skin and transfers energy away from the body. The arterioles supplying the skin capillaries dilate (vasodilation), so more blood flows through the capillaries near the skin surface and more energy is transferred to the surroundings by radiation. This negative feedback brings the body temperature back down to about 37 °C.
Explain how shivering helps to raise body temperature.
Mark scheme
- muscles contract (rapidly) (1)
- (so) more respiration releases energy / heat (1)
Model answer
Shivering is rapid contraction of skeletal muscles. The muscles respire faster, and respiration releases energy that warms the body.
On a cold day a person's skin looks pale.
Explain why.
Mark scheme
- vasoconstriction / arterioles (supplying skin capillaries) narrow (1)
- less blood flows (through capillaries) near the skin surface (1)
- so less energy is transferred to the surroundings / reduces heat loss (1)
Model answer
Vasoconstriction happens: the arterioles supplying the skin capillaries narrow, so less blood flows near the skin surface. This makes the skin look pale and reduces the energy transferred from the blood to the surroundings.
A student wrote: "When you are hot, your blood vessels move closer to the surface of the skin."
Explain what is wrong with this statement.
Mark scheme
- blood vessels do not move (1)
- arterioles dilate / widen so more blood flows through capillaries near the surface (1)
Model answer
Blood vessels do not move. Instead, the arterioles supplying the skin capillaries widen, so more blood flows through the capillaries that are already near the surface.
Describe the roles of the dermis and the epidermis in controlling body temperature.
Mark scheme
- dermis contains sweat glands / blood vessels / temperature receptors (1)
- epidermis: outer layer where sweat is released through pores and evaporates (1)
Model answer
The dermis contains the sweat glands, the blood vessels whose diameter changes, and temperature receptors. The epidermis is the outer layer; sweat comes out through pores in it and evaporates from its surface.
Which response happens when body temperature falls too low?
Choose one answer.
Correct Not quite: the answer is Vasoconstriction
Mark scheme
C (vasoconstriction)
Model answer
C: vasoconstriction.
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