IGCSE Biology: Coordination and Response Practice Questions
Organisms coordinate responses using the nervous system and hormones. Nervous responses are fast, short lived and travel as electrical impulses along neurones. Hormonal responses are slower, longer lasting and travel in the blood.
Topic 14 of Cambridge IGCSE Biology 0610 is large and carries a lot of marks. The reflex arc and the synapse are the two structured questions that appear most predictably, and both are marked step by step. The questions below cover those, the nervous versus hormonal comparison, and plant tropisms.
What you need to know for Coordination and Response
- Reflex actionA means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors. It does not involve conscious thought, which is why it is fast and protective.
- The reflex arc pathwayStimulus, receptor, sensory neurone, relay neurone in the spinal cord, motor neurone, effector, response.
- SynapseA junction between two neurones. The impulse causes neurotransmitter to be released from the first neurone, which diffuses across the gap and binds to receptors on the second neurone, triggering a new impulse there.
- Nervous versus hormonal controlNervous impulses are electrical, travel along neurones, act very fast, and have short lived, localised effects. Hormones are chemicals, travel in the blood, act more slowly, and have longer lasting, more widespread effects.
- AdrenalineSecreted by the adrenal glands in situations of fear or stress. It increases heart rate and breathing rate, and increases the conversion of glycogen to glucose, preparing the body for vigorous action.
- TropismsGravitropism is a growth response to gravity, phototropism is a growth response to light. Auxin accumulates on the shaded side of a shoot, causing greater cell elongation there, so the shoot bends towards the light.
IGCSE Biology Coordination and Response questions and answers
4 exam-style questions written to the 0610 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
A student touches a hot object and immediately pulls her hand away. Describe the pathway of the nerve impulse, naming each part in order.
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- The heat is the stimulus. Temperature receptors in the skin of the hand detect it.
- The receptor generates an electrical impulse that passes along a sensory neurone to the spinal cord.
- In the spinal cord the impulse passes across a synapse to a relay neurone.
- It then crosses a second synapse to a motor neurone, which carries the impulse out to the effector.
- The effector is the muscle in the arm, which contracts and pulls the hand away. This is the response. The impulse does not need to travel to the brain first, which is why the action is so fast.
Explain how an impulse crosses a synapse, and explain why an impulse can only travel in one direction across it.
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- When the impulse arrives at the end of the first neurone it causes vesicles to release a chemical neurotransmitter into the synaptic gap.
- The neurotransmitter diffuses across the gap, which is very narrow so this happens quickly.
- It binds to receptor molecules on the membrane of the next neurone, which have a shape complementary to the neurotransmitter, and this triggers a new electrical impulse in that neurone.
- Transmission is one way because only the first neurone contains the vesicles of neurotransmitter, and only the second neurone has the receptors. The chemical cannot work in reverse.
Compare nervous control with hormonal control. Give three differences.
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- Difference 1, nature of the signal: nervous control uses electrical impulses. Hormonal control uses chemical hormones.
- Difference 2, transport: nervous impulses travel along neurones. Hormones are carried dissolved in the blood plasma.
- Difference 3, speed and duration: nervous responses are very fast and short lived. Hormonal responses are slower to start but last much longer.
- A fourth difference: nervous responses act on a precise target such as one muscle, while hormones can affect many organs at once.
A shoot is illuminated from one side and grows towards the light. Explain this response in terms of auxin.
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- Auxin is a plant hormone made at the tip of the shoot.
- Light causes auxin to move away from the illuminated side, so it accumulates on the shaded side of the shoot.
- Auxin stimulates cell elongation, so the cells on the shaded side grow longer than those on the lit side.
- Unequal growth on the two sides makes the shoot bend towards the light. This response is positive phototropism, and it increases the light available for photosynthesis.
Common mistakes in this topic
- Putting the brain into a spinal reflex arc.
- Confusing receptor with effector. Receptors detect, effectors respond.
- Describing the synapse as an electrical connection.
- Saying auxin makes cells divide faster. At IGCSE, auxin causes cell elongation.
- Writing that hormones travel along nerves.
Exam tips
- Learn the reflex arc as seven words in order and write them as a list. Cambridge marks each stage separately.
- For eye questions, learn the pupil reflex and accommodation as two separate mechanisms with the muscles named.
- In any adrenaline question, link each effect back to preparing for vigorous activity.
- For tropism experiments, identify the control clearly, usually a shoot with the tip removed or covered.
- Use complementary shape when describing neurotransmitter binding. It matches the mark scheme language.
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Coordination and Response FAQs
What is the reflex arc pathway in order?
Stimulus, receptor, sensory neurone, relay neurone in the spinal cord, motor neurone, effector, response. In a spinal reflex the impulse is processed in the spinal cord rather than the brain, which is why the response is so rapid and does not require conscious thought.
How does an impulse cross a synapse?
The arriving impulse causes vesicles in the first neurone to release a chemical neurotransmitter into the synaptic gap. The neurotransmitter diffuses across and binds to receptor molecules on the next neurone, triggering a new electrical impulse. Only the first neurone has vesicles and only the second has receptors, so transmission is one way.
What is the difference between nervous and hormonal control?
Nervous control uses electrical impulses carried along neurones, acts within milliseconds, targets specific effectors and has short lived effects. Hormonal control uses chemicals carried in the blood, acts more slowly, can affect many organs at once and produces longer lasting effects.
Why does a shoot bend towards light?
Auxin made at the shoot tip moves away from the illuminated side and accumulates on the shaded side. Auxin causes cells to elongate, so cells on the shaded side grow longer than those on the lit side. The unequal growth bends the shoot towards the light, which increases the light available for photosynthesis.
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Written to the published Cambridge IGCSE Biology (0610) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.