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Exam questions · Biology · Homeostasis and the Nervous System

Control of Body Temperature

  • 7 exam questions
  • 22 marks
  • 8 quick checks
  1. 1 State [1 mark]

    State the part of the brain that monitors and controls body temperature.

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    Model answer

    The thermoregulatory centre.

    Mark scheme

    • Thermoregulatory centre — 1 mark
  2. 2 Name [3 marks]

    Figure 1 shows how body temperature is controlled. Name the parts shown at A, B and C.

    A temperature control loop with three boxes marked A, B and C.
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    Model answer

    A is the (temperature) receptors. B is the thermoregulatory centre. C is the effectors.

    Mark scheme

    • A: receptors — 1 mark
    • B: thermoregulatory centre — 1 mark
    • C: effectors — 1 mark
  3. 3 Describe [3 marks]

    Describe how sweating helps to cool the body.

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    Model answer

    The sweat glands produce sweat on the surface of the skin. The sweat evaporates. Evaporation takes energy from the skin, so energy is transferred away from the body.

    Mark scheme

    • Sweat is produced on the skin — 1 mark
    • The sweat evaporates — 1 mark
    • Evaporation takes energy from the skin / body — 1 mark
  4. 4 Describe [4 marks]

    Describe how the body responds when the temperature of the surroundings falls.

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    Model answer

    Temperature receptors in the skin send impulses to the thermoregulatory centre, which also detects the cooler blood. The blood vessels in the skin constrict, so less energy is transferred to the environment. Sweating stops. The skeletal muscles shiver, which releases energy.

    Mark scheme

    • Receptors detect the fall / impulses to the thermoregulatory centre — 1 mark
    • Blood vessels constrict — 1 mark
    • Sweating stops — 1 mark
    • Muscles shiver — 1 mark
  5. 5 Explain [4 marks]

    Explain how vasodilation helps to lower body temperature on a hot day.

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    Model answer

    The thermoregulatory centre detects the high temperature. The blood vessels in the skin dilate. More blood flows close to the surface of the skin, so more energy is transferred from the blood to the environment. The body temperature falls.

    Mark scheme

    • The thermoregulatory centre detects the rise — 1 mark
    • Blood vessels in the skin dilate — 1 mark
    • More blood flows close to the skin surface — 1 mark
    • More energy is transferred to the environment — 1 mark
  6. 6 Explain [4 marks]

    A runner finishes a race on a hot day. Explain how the runner's body returns its temperature to normal.

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    Model answer

    The runner's muscles have released a lot of energy and the blood temperature has risen. The thermoregulatory centre detects this. Sweat is produced, and as it evaporates it takes energy from the skin. The blood vessels in the skin dilate, so more energy is transferred to the environment. The body temperature falls back to about 37 °C.

    Mark scheme

    • Detected by the thermoregulatory centre — 1 mark
    • Sweat is produced and evaporates, taking energy from the skin — 1 mark
    • Blood vessels dilate and more energy is transferred to the environment — 1 mark
    • Temperature returns towards 37 °C — 1 mark
  7. 7 Explain [3 marks]

    A student says that blood vessels move closer to the surface of the skin when the body is hot. Explain why the student is wrong and what really happens.

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    Model answer

    Blood vessels cannot move. When the body is hot the blood vessels in the skin dilate, which means they get wider. More blood flows near the surface of the skin, so more energy is transferred to the environment.

    Mark scheme

    • Blood vessels cannot move — 1 mark
    • They dilate / get wider — 1 mark
    • More blood flows near the skin surface, so more energy is transferred — 1 mark

Quick check

  1. 1

    Which part of the brain monitors the temperature of the blood?

    1. AThe cerebellum
    2. BThe medulla
    3. CThe thermoregulatory centre
    4. DThe optic nerve
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    C: The thermoregulatory centre

    The thermoregulatory centre contains receptors that are sensitive to the temperature of the blood.

  2. 2

    What happens to the blood vessels in the skin when the body is too hot?

    1. AThey dilate
    2. BThey constrict
    3. CThey move closer to the surface
    4. DThey close
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    A: They dilate

    They dilate, which is vasodilation.

  3. 3

    What does shivering do?

    1. ACools the body
    2. BMakes sweat
    3. CWidens the blood vessels
    4. DReleases energy from the muscles
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    D: Releases energy from the muscles

    Shivering is rapid contraction of the skeletal muscles, and respiration in the muscles releases energy.

  4. 4

    Why does sweating cool the body?

    1. ASweat is cold
    2. BEvaporation takes energy from the skin
    3. CSweat blocks the pores
    4. DSweat makes the blood vessels constrict
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    B: Evaporation takes energy from the skin

    Evaporation of the sweat takes energy from the skin.

  5. 5

    What is vasoconstriction?

    1. AThe widening of the blood vessels
    2. BThe release of sweat
    3. CThe narrowing of the blood vessels
    4. DThe contraction of the muscles
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    C: The narrowing of the blood vessels

    Vasoconstriction is the narrowing of the blood vessels in the skin.

  6. 6

    What happens to sweating when the body is too cold?

    1. AIt increases
    2. BIt stays the same
    3. CIt makes the skin red
    4. DIt stops
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    D: It stops

    The sweat glands stop producing sweat.

  7. 7

    Why does the skin look pale when the body is cold?

    1. ALess blood flows near the surface
    2. BMore blood flows near the surface
    3. CThe blood is cold
    4. DThe sweat glands are working
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    A: Less blood flows near the surface

    The blood vessels constrict, so less blood flows near the surface of the skin.

  8. 8

    Which of these best explains why a runner's face goes red?

    1. AThe blood vessels move closer to the skin
    2. BThe blood vessels in the skin dilate
    3. CThe sweat glands stop working
    4. DThe blood vessels in the skin constrict
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    B: The blood vessels in the skin dilate

    The blood vessels in the skin dilate, so more blood flows near the surface and more energy is transferred to the environment.