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Exam questions · Biology · The Nervous System

Reflex Arcs

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

    State what a reflex action is.

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    Model answer

    A rapid, automatic response to a stimulus.

    Mark scheme

    • Rapid, automatic response — 1 mark
  2. 2 Name [3 marks]

    Figure 1 shows a reflex arc. Name the neurones shown at A, B and C.

    A reflex arc with three neurones marked A, B and C.
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    Model answer

    A is the sensory neurone. B is the relay neurone. C is the motor neurone.

    Mark scheme

    • A: sensory neurone — 1 mark
    • B: relay neurone — 1 mark
    • C: motor neurone — 1 mark
  3. 3 Name [3 marks]

    Figure 2 shows a synapse. Name the parts shown at A, B and C.

    A synapse with three parts marked A, B and C.
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    Model answer

    A is a vesicle (containing neurotransmitter). B is a neurotransmitter (molecule). C is a receptor.

    Mark scheme

    • A: vesicle — 1 mark
    • B: neurotransmitter — 1 mark
    • C: receptor — 1 mark
  4. 4 Describe [5 marks]

    Describe the pathway taken by the impulse when a person touches a sharp pin and pulls their hand away.

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    Model answer

    The receptors in the skin detect the pin. An impulse passes along a sensory neurone to the spinal cord. A relay neurone passes it to a motor neurone. The motor neurone carries the impulse to a muscle in the arm, the effector. The muscle contracts and the hand is pulled away.

    Mark scheme

    • Receptor detects the stimulus — 1 mark
    • Sensory neurone to the spinal cord — 1 mark
    • Relay neurone — 1 mark
    • Motor neurone to the effector — 1 mark
    • Muscle contracts — 1 mark
  5. 5 Explain [3 marks]

    Explain why a reflex action is faster than a voluntary action.

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    Model answer

    The reflex arc is a short pathway with few neurones and synapses. The impulse goes through the spinal cord without going to the brain. No conscious thought is needed, so the response is faster.

    Mark scheme

    • Short pathway with few neurones and synapses — 1 mark
    • Does not go through the brain — 1 mark
    • No conscious thought — 1 mark
  6. 6 Explain [3 marks]

    Explain how the structure of a reflex arc is related to its function.

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    Model answer

    The sensory and motor neurones are long, so they can reach from the skin to the spinal cord and back to the muscle. The myelin sheath makes the impulse fast. The relay neurone in the spinal cord makes the pathway short, so the response is rapid and protects the body.

    Mark scheme

    • Long neurones reach receptors and effectors — 1 mark
    • Myelin sheath speeds up the impulse — 1 mark
    • Short pathway through the spinal cord gives a rapid response — 1 mark
  7. 7 Calculate [2 marks]

    A student catches a dropped ruler at 12 cm, 15 cm and 18 cm. Calculate the mean distance. Give a unit.

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    Model answer

    15 cm

    Mark scheme

    • \(12 + 15 + 18 = 45\), then \(45 \div 3\) — 1 mark
    • 15 cm — 1 mark

Quick check

  1. 1

    What is a reflex action?

    1. AA slow action that you choose
    2. BAn action that needs a lot of thought
    3. CA rapid, automatic response to a stimulus
    4. DAn action of the brain only
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    C: A rapid, automatic response to a stimulus

    A reflex is a rapid, automatic response to a stimulus.

  2. 2

    Where is the relay neurone in a reflex arc?

    1. AIn the spinal cord
    2. BIn the muscle
    3. CIn the skin
    4. DIn the eye
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    A: In the spinal cord

    The relay neurone is in the spinal cord.

  3. 3

    Which of these is the correct order for a reflex arc?

    1. AEffector, motor neurone, relay neurone, receptor
    2. BReceptor, motor neurone, relay neurone, effector
    3. CSensory neurone, receptor, effector, motor neurone
    4. DReceptor, sensory neurone, relay neurone, motor neurone, effector
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    D: Receptor, sensory neurone, relay neurone, motor neurone, effector

    The impulse passes from the receptor along a sensory neurone, relay neurone and motor neurone to the effector.

  4. 4

    What crosses the gap at a synapse?

    1. AMyelin
    2. BNeurotransmitter
    3. CBlood cells
    4. DHormones
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    B: Neurotransmitter

    Neurotransmitter diffuses across the synapse.

  5. 5

    Why is a reflex action so fast?

    1. AIt uses hormones
    2. BIt needs a lot of thought
    3. CThe pathway is short
    4. DIt uses the blood
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    C: The pathway is short

    The pathway is short, with few neurones and synapses, and does not go through the brain.

  6. 6

    Which is an example of a reflex action?

    1. APicking up a pen
    2. BPulling a hand away from a hot object
    3. CRiding a bike
    4. DReading a book
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    B: Pulling a hand away from a hot object

    Pulling a hand away from a hot object is a reflex.

  7. 7

    In the ruler drop test, what does a smaller distance caught mean?

    1. AA slower reaction
    2. BNo reaction
    3. CA bigger ruler
    4. DA faster reaction
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    D: A faster reaction

    A shorter distance means the person reacted faster.

  8. 8

    What does the effector in a reflex arc do?

    1. AProduces the response
    2. BDetects the stimulus
    3. CCarries impulses to the spinal cord
    4. DLinks two neurones
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    A: Produces the response

    The effector, a muscle or gland, produces the response.