A-Level Biology Topic 15: Control and Coordination MCQs – 30 Practice Questions with Answers (Cambridge 9700)
Free practice for Cambridge International AS and A Level Biology 9700 on control and coordination in mammals and in plants, with every question followed by a short explanation to help you check your understanding.
Neurones and Action Potentials
Q1. Which feature distinguishes the endocrine system from the nervous system in mammals?
- (A) endocrine signals travel only along neurones
- (B) endocrine signals travel in the blood and are generally slower and longer lasting
- (C) endocrine signals act only on muscles, never on glands
- (D) endocrine signals are always faster than nerve impulses in a healthy adult under normal conditions
Show Answer
Answer: B – Hormones are carried in the blood, so endocrine responses are generally slower and longer lasting than nervous responses.
Q2. What is the main function of a sensory neurone?
- (A) to carry impulses from a receptor towards the central nervous system
- (B) to carry impulses from the central nervous system to an effector in a healthy adult under normal conditions
- (C) to connect two motor neurones directly
- (D) to release hormones into the blood
Show Answer
Answer: A – Sensory neurones carry impulses from receptors to the central nervous system, while motor neurones carry impulses to effectors.
Q3. What connects sensory neurones to motor neurones in the central nervous system?
- (A) sensory receptors in a healthy adult under normal conditions
- (B) effector cells
- (C) hormone molecules
- (D) intermediate neurones
Show Answer
Answer: D – Intermediate neurones connect sensory neurones and motor neurones.
Q4. What do sensory receptor cells do?
- (A) produce hormones in response to any stimulus in a healthy adult under normal conditions
- (B) contract in response to a stimulus
- (C) detect a stimulus and stimulate the transmission of impulses in sensory neurones
- (D) transmit impulses directly to muscles
Show Answer
Answer: C – Sensory receptor cells detect stimuli and stimulate impulse transmission in sensory neurones.
Q5. In the taste bud example in the syllabus, what happens first when a chemical stimulates a chemoreceptor cell?
- (A) chemical-gated channels open and the cell membrane depolarises, triggering an impulse in the sensory neurone
- (B) the sensory neurone releases acetylcholine into the taste bud in a healthy adult under normal conditions during normal activity in a typical mammal
- (C) the chemoreceptor cell divides to form a new neurone
- (D) calcium ions block all ion channels in the cell
Show Answer
Answer: A – Stimulation of the chemoreceptor cell leads to depolarisation and the initiation of an action potential in the sensory neurone.
Q6. How is the resting potential of a neurone maintained?
- (A) by the continuous opening of all sodium channels in a healthy adult under normal conditions
- (B) by the absence of any ions inside the cell
- (C) by the sodium-potassium pump and differential permeability of the membrane to ions
- (D) by the release of neurotransmitter at rest
Show Answer
Answer: C – The sodium-potassium pump, together with ion channels, maintains the resting potential, with the inside of the membrane negative relative to the outside.
Q7. During an action potential, what causes depolarisation of the membrane?
- (A) potassium ions diffusing into the neurone in a healthy adult under normal conditions
- (B) sodium ions being pumped out rapidly
- (C) chloride ions leaving the neurone
- (D) sodium ions diffusing into the neurone through open voltage-gated sodium channels
Show Answer
Answer: D – Depolarisation occurs when voltage-gated sodium channels open and sodium ions diffuse in.
Q8. How is the resting potential restored after an action potential?
- (A) sodium ions diffuse out through open sodium channels only in a healthy adult under normal conditions
- (B) potassium ions diffuse out, and the sodium-potassium pump restores the ion distribution
- (C) the membrane becomes impermeable to all ions permanently
- (D) calcium ions flood into the cell
Show Answer
Answer: B – Repolarisation involves potassium efflux, followed by restoration of the resting ion distribution during the refractory period.
Q9. What is the refractory period of a neurone?
- (A) a period when the neurone fires continuously
- (B) a period when the resting potential is positive inside in a healthy adult under normal conditions during normal activity in a typical mammal
- (C) a period when no ions cross the membrane at all
- (D) a period after an action potential during which a new action potential cannot easily be initiated
Show Answer
Answer: D – During the refractory period the membrane cannot immediately generate another action potential.
Q10. Why does the refractory period limit the frequency of impulses?
- (A) it sets a minimum time between successive action potentials
- (B) it increases the speed of saltatory conduction
- (C) it prevents any impulse from travelling at all
- (D) it allows impulses to travel in both directions at once in a healthy adult under normal conditions
Show Answer
Answer: A – Because a new action potential cannot start until the refractory period ends, there is a maximum frequency of impulses.
Synapses and Muscle Contraction
Q11. In a myelinated neurone, how is an impulse transmitted rapidly?
- (A) by continuous conduction along the whole membrane at the same speed as in unmyelinated neurones
- (B) by hormones travelling along the myelin sheath
- (C) by saltatory conduction, with action potentials jumping between nodes of Ranvier
- (D) by electrical signals passing through the Schwann cells only
Show Answer
Answer: C – Myelin insulates the axon, so action potentials occur only at nodes of Ranvier, speeding transmission.
Q12. What is a cholinergic synapse?
- (A) a synapse that uses only hormones in a healthy adult under normal conditions
- (B) a synapse at which acetylcholine is the neurotransmitter
- (C) a synapse with no synaptic cleft
- (D) a synapse found only in plants
Show Answer
Answer: B – In a cholinergic synapse, acetylcholine is released from the presynaptic neurone.
Q13. When an action potential reaches a cholinergic synapse, what role do calcium ions play?
- (A) they trigger the release of acetylcholine from vesicles into the synaptic cleft
- (B) they block the release of acetylcholine
- (C) they break down acetylcholine in the presynaptic neurone in a healthy adult under normal conditions
- (D) they carry the impulse across the cleft directly
Show Answer
Answer: A – Calcium ions entering the presynaptic terminal cause vesicles to fuse with the membrane and release acetylcholine.
Q14. After acetylcholine has acted at a cholinergic synapse, what happens to it?
- (A) it is stored permanently in the postsynaptic membrane
- (B) it diffuses back into the presynaptic neurone unchanged and is reused at once
- (C) it is converted to adrenaline
- (D) it is broken down by acetylcholinesterase in the synaptic cleft
Show Answer
Answer: D – Acetylcholinesterase hydrolyses acetylcholine, ending its action so the postsynaptic membrane can repolarise.
Q15. At a neuromuscular junction, what does acetylcholine cause in the muscle fibre?
- (A) direct synthesis of new muscle proteins
- (B) depolarisation of the muscle cell membrane, leading to contraction
- (C) hyperpolarisation that prevents any contraction in a healthy adult under normal conditions
- (D) release of hormones from the muscle fibre
Show Answer
Answer: B – Acetylcholine at the neuromuscular junction depolarises the muscle membrane, triggering contraction.
Q16. What is the role of the T-tubule system in striated muscle?
- (A) it stores calcium ions for release during contraction in a healthy adult under normal conditions
- (B) it synthesises ATP for contraction
- (C) it carries the depolarisation deep into the muscle fibre, to the sarcoplasmic reticulum
- (D) it anchors actin filaments to the cell membrane
Show Answer
Answer: C – T-tubules transmit the action potential into the fibre, stimulating calcium release from the sarcoplasmic reticulum.
Q17. What is the role of the sarcoplasmic reticulum in muscle contraction?
- (A) it produces acetylcholine for the neuromuscular junction
- (B) it forms the thick filaments of the sarcomere
- (C) it carries impulses between muscle fibres
- (D) it stores calcium ions and releases them when stimulated
Show Answer
Answer: D – Calcium ions released from the sarcoplasmic reticulum trigger contraction.
Q18. In a sarcomere, which filaments are thick and which are thin?
- (A) myosin filaments are thick and actin filaments are thin
- (B) actin filaments are thick and myosin filaments are thin
- (C) both actin and myosin filaments are the same thickness
- (D) tropomyosin filaments are thick and troponin filaments are thin
Show Answer
Answer: A – Sarcomeres contain thick myosin filaments and thin actin filaments, arranged in a regular pattern.
Q19. In the sliding filament model, what happens during contraction?
- (A) myosin filaments shorten while actin filaments stay the same length in a healthy adult under normal conditions
- (B) actin filaments slide over myosin filaments, shortening the sarcomere, while filament lengths stay the same
- (C) actin filaments shorten while myosin filaments stay the same length
- (D) both sets of filaments break down and reform
Show Answer
Answer: B – Contraction shortens the sarcomere as actin slides over myosin; the filaments themselves do not shorten.
Q20. What is the role of calcium ions in muscle contraction?
- (A) they bind to myosin and prevent cross-bridge formation in a healthy adult under normal conditions
- (B) they break down ATP in the sarcoplasm
- (C) they bind to troponin, moving tropomyosin away from the binding sites on actin
- (D) they remove tropomyosin from the sarcomere permanently
Show Answer
Answer: C – Calcium binding to troponin exposes myosin-binding sites on actin, allowing cross-bridges to form.
Endocrine Comparison and Plant Control
Q21. What is the role of ATP in muscle contraction?
- (A) it provides energy for the myosin heads to detach and reset, and for cross-bridge movement
- (B) it binds to troponin in place of calcium ions
- (C) it stores calcium ions in the sarcoplasmic reticulum in a healthy adult under normal conditions
- (D) it breaks down acetylcholine at the junction
Show Answer
Answer: A – ATP is needed for myosin head movement and detachment during the contraction cycle.
Q22. Which statement correctly compares nervous and endocrine coordination?
- (A) nervous coordination is always slower than endocrine coordination in a healthy adult under normal conditions during normal activity in a typical mammal
- (B) endocrine coordination acts only on a single cell
- (C) nervous coordination uses hormones carried in the blood
- (D) nervous coordination is usually fast and short-lived, while endocrine coordination is slower and longer lasting
Show Answer
Answer: D – Nerve impulses are rapid and brief, whereas hormones act more slowly and for longer.
Q23. ADH, glucagon and insulin are used in the syllabus as examples of what?
- (A) neurotransmitters released only at synapses in a healthy adult under normal conditions
- (B) enzymes that digest food in the gut
- (C) hormones of the endocrine system, each acting on specific target cells
- (D) plant growth substances
Show Answer
Answer: C – ADH, glucagon and insulin illustrate endocrine coordination in mammals.
Q24. How does a Venus fly trap respond rapidly to stimulation?
- (A) the leaves grow slowly around the prey over several days
- (B) touching hairs on the lobes triggers closure of the trap, trapping the prey inside
- (C) the trap opens wider when hairs are touched
- (D) the plant releases a hormone that digests prey outside the trap in a healthy adult under normal conditions
Show Answer
Answer: B – Stimulation of hairs on the modified leaves causes rapid closure of the trap.
Q25. How does auxin promote elongation growth in plant shoots?
- (A) by hardening cell walls so cells cannot expand in a healthy adult under normal conditions during normal activity in a typical mammal
- (B) by inhibiting proton pumping in the cell wall
- (C) by causing cells to divide only at the tip
- (D) by stimulating proton pumping, which acidifies cell walls and loosens them so cells can elongate
Show Answer
Answer: D – Auxin stimulates proton pumps, acidifying the wall, which loosens it and allows elongation growth.
Q26. In which plant process, named in the syllabus, does gibberellin play a role alongside its role in stem elongation?
- (A) germination of barley seeds
- (B) opening of stomata in bright light
- (C) closure of the Venus fly trap
- (D) formation of root hairs
Show Answer
Answer: A – Gibberellin is involved in the germination of barley, as well as in stem elongation.
Q27. Why is plant coordination generally slower than mammalian nervous coordination?
- (A) plants have faster nerve impulses than mammals in a healthy adult under normal conditions
- (B) plants respond only to light, never to touch
- (C) plants lack a nervous system and rely on chemical signals and growth responses
- (D) plant cells cannot detect any stimuli
Show Answer
Answer: C – Plants coordinate responses with hormones and growth, without a nervous system, so responses are generally slower.
Q28. Which of these is a rapid plant response, rather than a slow growth response?
- (A) elongation of a shoot towards light over several days
- (B) closure of the Venus fly trap after hair stimulation
- (C) stem elongation in response to gibberellin over days
- (D) germination of a seed over several days
Show Answer
Answer: B – Venus fly trap closure is rapid, unlike growth responses such as elongation, which take much longer.
Q29. A muscle fibre is stimulated repeatedly with no rest. Why does its contraction eventually weaken?
- (A) ATP supplies fall and calcium handling is disrupted, so cross-bridge cycling cannot continue at full rate
- (B) actin filaments permanently disappear from the sarcomere
- (C) the sarcomere lengthens permanently and cannot shorten again
- (D) acetylcholine is produced in ever larger amounts without limit in a healthy adult under normal conditions during normal activity in a typical mammal
Show Answer
Answer: A – Sustained stimulation depletes ATP and disrupts ion balance, reducing the force of contraction.
Q30. If acetylcholinesterase were blocked at a neuromuscular junction, what would be expected?
- (A) acetylcholine would never be released at all
- (B) the muscle membrane would never depolarise
- (C) calcium ions would be trapped in the sarcoplasmic reticulum permanently in a healthy adult under normal conditions
- (D) acetylcholine would persist in the cleft and the muscle would remain stimulated
Show Answer
Answer: D – Without breakdown of acetylcholine, stimulation continues and the muscle cannot relax normally.
Work through any questions you missed again, then revise those areas before moving on to the next topic.