Biology  by Bradford
IB Biology 2025 · Theme C · Interaction and interdependence

C2.2 Neural signalling. Practice questions with markscheme.

46 original IB-style questions on C2.2, written from the 2025 guide: 21 multiple-choice, 15 short-answer, 5 data-based, 2 labelling, 2 drawing, 1 extended-response part. Below is a 21-mark standard-level practice paper built from them, ready to hand out as a class quiz or homework, or to sit yourself and mark against the scheme. Print it, project it, or build a fresh one on the same topic.

What the guide asks for

7 statements at SL and HL, 9 additional higher level.

  1. C2.2.1SL / HL Neurons as cells within the nervous system that carry electrical impulses
  2. C2.2.2SL / HL Generation of the resting potential by pumping to establish and maintain concentration gradients of sodium and potassium ions
  3. C2.2.3SL / HL Nerve impulses as action potentials that are propagated along nerve fibres
  4. C2.2.4SL / HL Variation in the speed of nerve impulses
  5. C2.2.5SL / HL Synapses as junctions between neurons and between neurons and effector cells
  6. C2.2.6SL / HL Release of neurotransmitters from a presynaptic membrane
  7. C2.2.7SL / HL Generation of an excitatory postsynaptic potential
  8. C2.2.8HL Depolarization and repolarization during action potentials
  9. C2.2.9HL Propagation of an action potential along a nerve fibre/axon as a result of local currents
  10. C2.2.10HL Oscilloscope traces showing resting potentials and action potentials
  11. C2.2.11HL Saltatory conduction in myelinated fibres to achieve faster impulses
  12. C2.2.12HL Effects of exogenous chemicals on synaptic transmission
  13. C2.2.13HL Inhibitory neurotransmitters and generation of inhibitory postsynaptic potentials
  14. C2.2.14HL Summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron
  15. C2.2.15HL Perception of pain by neurons with free nerve endings in the skin
  16. C2.2.16HL Consciousness as a property that emerges from the interaction of individual neurons in the brain

In the bank for C2.2

  • 21 multiple-choice
  • 15 short-answer
  • 5 data-based
  • 2 labelling
  • 2 drawing
  • 1 extended-response part
  • 25 higher level only

Every question is original and tagged to a guide statement. See the whole bank →

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The practice paper

Take it on screen → Build a fresh paper Paper code BbB-EAAAAIAAABQAOzuf
Biology · topic quiz
Standard level · topic practice, not an exam format
30 minutes21 marks

Paper code: this paper was generated, so the code is its recipe. Enter it at biologybybradford.com/exam-maker to rebuild this exact paper and its markscheme.

Covers C2.2 Neural signalling
Name:
1.

Where are synapses found?

[1]
  1. Only between the dendrites of one neuron and the axon terminal of another neuron in the brain
  2. Only between sensory receptors and the sensory neurons that carry impulses from them to the CNS
  3. Between two neurons and between a neuron and an effector cell such as a muscle fibre
  4. Between adjacent muscle fibres, so that they contract together as one unit
2.

What is the immediate effect of calcium ions entering the presynaptic neuron?

[1]
presynaptic neuronaction potentialmit.ICa²⁺Ca²⁺IIIVpostsynaptic neuronNa⁺ entersIIIenzyme
  1. Vesicles fuse with the presynaptic membrane and release neurotransmitter
  2. Sodium channels in the postsynaptic membrane open and sodium ions enter
  3. The enzyme in the synaptic cleft starts to break down the neurotransmitter
  4. The action potential is transmitted directly across the synaptic cleft
3.

An action potential is described as "all-or-nothing". What does this mean?

[1]
  1. Action potentials vary in size with the length of the axon
  2. Every stimulus, no matter how weak, produces an action potential
  3. Stronger stimuli produce larger action potentials
  4. Depolarization to threshold fires a full-sized action potential or none
4.

Acetylcholinesterase in the synaptic cleft rapidly breaks down acetylcholine. Why is this essential?

[1]
  1. To prevent acetylcholine from ever reaching the receptors
  2. To allow the synapse to transmit impulses in both directions
  3. So that each impulse produces only a brief postsynaptic response
  4. To supply the ATP needed for vesicle exocytosis
5.

Outline what a nerve impulse is and why it is described as an electrical signal.

[3]
6.

The diagram shows a synapse. Identify the structures labelled I–IV.

[4]
presynaptic neuronaction potentialmit.ICa²⁺Ca²⁺IIIVpostsynaptic neuronNa⁺ entersIIIenzyme
I.
II.
III.
IV.
7.

Draw a labelled diagram of a motor neuron to show the cell body, the dendrites and the axon.

[3]
8.

Explain how a signal is passed from one neuron to another across a chemical synapse.

[7]

Original practice questions © Biology by Bradford · CC BY-NC-SA 4.0 · Not affiliated with or endorsed by the International Baccalaureate Organization.
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Show the markscheme

Markscheme BbB-EAAAAIAAABQAOzuf

One mark per point; / separates alternative wording within a point, OR separates alternative answers, words in brackets are not required, underlined words are essential. OWTTE = or words to that effect.

1. C2.2.5 [1]
  • C: synapses are junctions between neurons and between neurons and effectors (muscle, gland);
2. C2.2.6 [1]
  • A: calcium acts as a signalling chemical inside the neuron, causing the vesicles to move to and fuse with the presynaptic membrane (exocytosis);
3. C2.2.4 [1]
  • D: amplitude is fixed; stimulus strength is encoded in the frequency of impulses, not their size;
4. C2.2.7 [1]
  • C: clearing the transmitter ends each signal; without it the postsynaptic membrane stays depolarized/blocked (as with nerve agents and some insecticides);
5. C2.2.3 [3 max]
  • a nerve impulse is an action potential / a brief reversal of the membrane potential (depolarization) that is propagated along a nerve fibre / axon;
  • positively charged ions / sodium ions move into the neuron across the membrane, changing the charge / voltage across the membrane;
  • movement of charged ions is an electric current, so the impulse is electrical, OWTTE;
  • each region of the membrane depolarizes in turn, so the impulse travels along the fibre / is propagated;
  • the impulse is not a flow of electrons along the fibre as in a wire, but the movement of ions across the membrane;

Do not accept 'electrons flow along the axon'. Accept 'depolarization moves along the axon' for the fourth point.

6. C2.2.6, C2.2.7 [4]
  • I, (synaptic) vesicle containing neurotransmitter;
  • II, calcium (ion) channel;
  • III, neurotransmitter receptor / ligand-gated sodium channel;
  • IV, synaptic cleft;
7. C2.2.1 [3 max]
  • cell body drawn as a distinct region containing a labelled nucleus (and cytoplasm);
  • several short, branched fibres labelled as dendrites projecting from the cell body;
  • a single long fibre labelled as the axon, clearly longer than the dendrites, ending in axon terminals / terminal branches;
  • direction of impulse conduction shown by an arrow from the dendrites / cell body along the axon to the terminals;
  • myelin sheath (Schwann cells) and nodes of Ranvier labelled along the axon;

Accept a diagram with or without a myelin sheath. Do not award the axon point if the axon is drawn as several fibres or is no longer than the dendrites.

8. C2.2.6-C2.2.7 [7 max]
  • the action potential arrives at/depolarizes the presynaptic terminal/knob;
  • voltage-gated calcium channels open and Ca²⁺ diffuses in;
  • vesicles (containing neurotransmitter, e.g. acetylcholine) fuse with the presynaptic membrane;
  • neurotransmitter is released into the synaptic cleft by exocytosis;
  • it diffuses across the (narrow) cleft;
  • and binds to (specific) receptors on the postsynaptic membrane;
  • ligand-gated (sodium) channels open, depolarizing the postsynaptic membrane;
  • if threshold is reached, an action potential is initiated in the postsynaptic neuron;
  • the neurotransmitter is (rapidly) broken down (e.g. by acetylcholinesterase) / recycled, ending the signal, OWTTE;

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