IB Biology SL C2.2 Neural signalling Questions

Practise IB Biology SL C2.2 by linking neuron structure, resting potential, myelin and impulse conduction to exam evidence.

30 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam analysis

SL · 2010–2025
Papers with this topic59 / 141in the analysed sample
Latest appearanceNovember 2025
Tagged question parts78
Paper types5

Most tested objectives

  1. C2.2.12 (HL)—Exogenous chemicals16 papers
  2. C2.2.8 (HL)—Depolarization and repolarization11 papers
  3. C2.2.6—Neurotransmitter release9 papers
  4. C2.2.1—Neurons8 papers
  5. C2.2.2—Resting potential generation5 papers

Common question formats

  • Calculation
  • Comparison
  • Data analysis
  • Diagram interpretation
  • Process explanation
  • Structured response
  • Definition or recall

Recent exam appearances

November 2025Paper 2 SL · TZ1Q5(a), 5(b), 5(c)[ 4 ]
November 2025Paper 1A SL · TZ1Q11[ 1 ]
May 2025Paper 2 SL · TZ3Q6(a), 6(b)[ 5 ]

141 papers analysed · Tagging incomplete

Exam points

  • Label neuron structures and distinguish sensory, relay and motor neuron roles, directions and connections.
  • Define resting potential, read its approximate negative voltage, and explain the ATP-driven pump moving 3 Na⁺ out for 2 K⁺ in.
  • Trace nerve impulses through threshold, Na⁺ influx/depolarization and K⁺ efflux/repolarization, using membrane-potential diagrams.
  • Relate axon diameter and myelin sheath to faster impulse transmission and saltatory conduction.
  • Distinguish presynaptic release sites from postsynaptic receptors and explain how the narrow cleft supports rapid diffusion.
  • Explain one-way synaptic transmission from action-potential/Ca²⁺-triggered vesicle release through cleft diffusion to postsynaptic receptor activation.
  • Explain how neurotransmitter binding opens postsynaptic ion channels to generate an EPSP and make threshold more likely.

Covered syllabus points

C2.2.1—NeuronsC2.2.2—Resting potential generationC2.2.3—Nerve impulses as action potentialsC2.2.4—Variation in impulse speedC2.2.5—Synapses as junctionsC2.2.6—Neurotransmitter releaseC2.2.7—Excitatory postsynaptic potential

Exam points

  • Label neuron structures including cell body, dendrites, axon, myelin sheath and nodes of Ranvier.
  • Distinguish sensory, relay and motor neuron functions by impulse direction and CNS/effector connections.

Question 1

[Maximum number: 1]

The image shows a neuron. Which letter shows a dendrite?

Figure for Question 1 — IB Biology SL

Exam points

  • Define resting potential and state its approximate membrane-potential value (about −70 mV).
  • Explain how the sodium-potassium pump uses ATP to move 3 Na⁺ out and 2 K⁺ in, maintaining axon ion gradients and polarization.

Question 1

[Maximum number: 1]

What occurs during the establishment of a resting membrane potential of a neuron?

A

Both sodium and potassium ions are pumped outside the neuron.

B

Sodium ions are pumped out while potassium ions are pumped into the neuron.

C

Both sodium and potassium ions are at rest inside the membrane of the neuron.

D

Sodium ions leave by diffusion and potassium ions enter the neuron by active transport.

Exam points

  • Explain how sodium influx depolarizes the membrane and potassium efflux repolarizes it during an action potential.
  • Describe how an action potential propagates along a nerve fibre and identify its axonal location.
  • Identify resting and depolarized regions on a nerve-fibre diagram.

Question 1

[Maximum number: 2]

On the diagram, label the part of the axon representing resting potential with R and the depolarized part with D.

Exam points

  • Identify myelin sheath and node structures on an axon diagram.
  • Relate increasing axon diameter and myelin structure to faster impulse transmission.

Question 1

[Maximum number: 1]

The diagrams represent sections through different axons. Which axon has the slowest speed of impulse?

A
Figure for Question 1 — IB Biology SL — Option A
B
Figure for Question 1 — IB Biology SL — Option B
C
Figure for Question 1 — IB Biology SL — Option C
D
Figure for Question 1 — IB Biology SL — Option D

Exam points

  • Explain one-way chemical synaptic transmission from presynaptic calcium entry and vesicle release to postsynaptic receptor activation.
  • Distinguish presynaptic and postsynaptic membrane locations and roles, including calcium channels, neurotransmitter release and receptors.
  • Explain why a narrow synaptic cleft increases the speed of neurotransmitter transmission.
  • Identify the synaptic junction region where chemical transmission occurs on a neuron diagram.

Question 1

[Maximum number: 1]

Which encircled area shows a region where the chemical transmission of nerve impulses is most likely to occur between neurons?

A
Figure for Question 1 — IB Biology SL — Option A
B
Figure for Question 1 — IB Biology SL — Option B
C
Figure for Question 1 — IB Biology SL — Option C
D
Figure for Question 1 — IB Biology SL — Option D

Exam points

  • Identify a neurotransmitter vesicle and its neurotransmitter contents in a synapse diagram.
  • Identify calcium-ion entry and exocytosis as the processes involved in neurotransmitter release.
  • Explain how an arriving action potential opens calcium channels, causes vesicle fusion and releases neurotransmitter into the synaptic cleft.

Question 1

[Maximum number: 3]

The diagram shows the release of a neurotransmitter across a synapse.

Figure for Question 1 — IB Biology SL
Figure for Question 1 — IB Biology SL

Question (a)

(a)

Identify the structure labelled X .

[ 1 ]

Question (b)

(b)

Outline how the neuron is stimulated to release the neurotransmitter.

[ 2 ]

Exam points

  • Explain how neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane.
  • Explain how postsynaptic ion movement depolarizes the membrane and makes threshold more likely, generating an excitatory postsynaptic potential.

Question 1

[Maximum number: 3]

The diagram shows a neuron.

Figure for Question 1 — IB Biology SL

Describe how an excitatory postsynaptic potential is generated.

Up to one additional mark is available for the construction of your answer.

Question 1

[Maximum number: 5]

Question (a)

(a)

Label the structures X, Y and Z on the diagram of a motor neuron.

Figure for Question (a) — IB Biology SL

The section of the axon between the solid black lines in the motor neuron diagram is enlarged and shown.

Figure for Question (a) — IB Biology SL
[ 3 ]

Question (b)

(b)

On the diagram, label the part of the axon representing resting potential with R and the depolarized part with D.

[ 2 ]
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