This set has ten original questions, ordered from easier to harder, covering all five lessons in coordination and responses. Questions 1 to 4 are warm-ups, 5 to 8 need comparison and data, and 9 and 10 mix skills. Any data are invented for practice.
Attempt each question on paper first and write your answer in full sentences where a question says “explain”. Then open the answer and mark yourself honestly. The routing list at the end shows which lesson to revisit.
Questions
1. A person steps on a sharp stone and lifts the foot at once. Put these in the correct order: muscle in the leg, sensory neurone, pain receptor in the foot, relay neurone, motor neurone, sharp stone.
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Follow the reflex arc from stimulus to response.
Sharp stone (stimulus), pain receptor in the foot, sensory neurone, relay neurone, motor neurone, muscle in the leg (effector). The muscle contracts and lifts the foot.
2. Name the type of neurone that carries impulses from the central nervous system to an effector.
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The neurone that carries impulses from the CNS to the effector is a motor neurone. A sensory neurone carries impulses to the CNS.
3. Describe what happens at a synapse when an impulse arrives.
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Neurotransmitter is released from the first neurone into the gap. It diffuses across the gap and binds to receptors on the next neurone. This starts a new impulse in the next neurone.
4. Explain why impulses pass across a synapse in one direction only.
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Only the first neurone releases neurotransmitter, and only the membrane of the next neurone has receptors that detect it. The chemical signal can therefore only pass one way, from the first neurone to the next.
5. Copy and complete the table by writing “nervous” or “hormonal” in each row.
| Feature | System |
|---|---|
| Carried in the blood | ? |
| Very fast response | ? |
| Effect usually lasts longer | ? |
| Signal travels along neurones | ? |
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Carried in the blood: hormonal. Very fast response: nervous. Effect usually lasts longer: hormonal. Signal travels along neurones: nervous.
6. Decide whether each response is mainly nervous or hormonal, and give a reason. (a) blinking when something flies towards the eye; (b) the body preparing for action, with a faster heart rate lasting several minutes, because adrenaline is released.
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(a) Nervous. It is very fast, automatic and uses neurones, like a reflex.
(b) Hormonal. Adrenaline is carried in the blood to the heart and other organs, and its effect lasts longer than a single impulse.
7. Invented data. Seedlings are grown with light from one side only. The bend towards the light after 24 hours was measured for five seedlings in each group.
| Group | Tip | Bend (°) |
|---|---|---|
| X | Left alone | 22, 25, 28, 24, 26 |
| Y | Covered with foil | 3, 5, 2, 4, 1 |
Calculate the mean bend for each group and say what the results suggest.
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Group X: 22 + 25 + 28 + 24 + 26 = 125, and 125 ÷ 5 = 25°.
Group Y: 3 + 5 + 2 + 4 + 1 = 15, and 15 ÷ 5 = 3°.
Check: the difference is 25 − 3 = 22°, which is large compared with the spread inside each group. The results suggest that the tip is needed to detect the light. Auxin made in the tip is redistributed to the shaded side, which makes the cells there elongate more. Group X is the control.
8. A seedling is laid on its side in the dark. After two days the root curves downwards and the shoot curves upwards. Name the response and describe what each part is doing.
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The response is gravitropism. The root shows positive gravitropism because it grows in the direction of gravity. The shoot shows negative gravitropism because it grows away from it. The investigation was in the dark, so the direction comes from gravity and not from light.
9. A student says, “The retina focuses light and the lens detects it.” Correct the statement and explain what happens to the pupil when the student walks from a bright corridor into a dim room.
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The statement has the parts swapped. The lens focuses light (with the cornea), and the retina detects it using receptor cells.
In the dim room, the muscles of the iris make the pupil larger, which lets more light enter the eye so more reaches the retina.
10. A person touches a hot pan and pulls away at once. A second later they feel pain. Use the idea of a reflex arc to explain the order of these two events.
Show answer
The withdrawal is a reflex. The impulse passes from the receptor along a sensory neurone to a relay neurone in the spinal cord and straight to a motor neurone, so the muscle acts quickly without a decision.
The impulses also travel to the brain, which takes a little longer. The person feels pain after the protective response has begun.
If you got these wrong
| Where you lost marks | Go back to |
|---|---|
| Jumbled sequence, wrong neurone direction (1, 2, 10) | Trace a reflex pathway |
| Missing the chemical step or the one-way reason (3, 4) | Explain the role of a synapse |
| Facts without a matched comparison (5, 6) | Compare nervous and hormonal signalling |
| Mean or conclusion from the data (7, 8) | Interpret a simple tropism investigation |
| Part and function mixed up (9) | Connect a sensory structure with its function |
Write each error in the mistake log and retest queue with one line on what you would do differently. Retest yourself on the same lesson a few days later with a new example.
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