The diagram shows the route of nerve impulses when a person touches the metal cap of a hot saucepan. This response happens before the person has time to dec...
Question 1 Report
The diagram shows the route of nerve impulses when a person touches the metal cap of a hot saucepan. This response happens before the person has time to decide to move their hand. The labelled structures are part of a reflex arc.
(a) Complete the sequence below using words from the diagram.
receptor → sensory neurone → ________ → ________ → muscle [2]
(b) Describe what happens at a synapse between two neurones. [2]
(c) Explain why the hand is withdrawn before the brain produces a conscious sensation of pain. [3]
(d) Suggest two advantages of this rapid response to the person. [3]
Answer Details
(a) The sequence is:
receptor → sensory neurone → relay neurone → motor neurone → muscle. [2]
(b) At a synapse, the first neurone releases a chemical neurotransmitter. The neurotransmitter diffuses across the gap and starts an impulse in the next neurone. [2]
(c) Impulses from the receptor travel to the spinal cord. A relay neurone transfers the impulse to a motor neurone, which causes the arm muscle to contract. This happens before impulses are processed by the brain to produce conscious pain. [3]
(d) The rapid response reduces the time the hand contacts the hot cap, reducing burns and other damage to skin or body cells. Avoiding injury improves chances of survival. Any three valid points. [3]
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