C2.2 Neural signalling
Practice exam-style IB Biology questions for Neural signalling, aligned with the syllabus and grouped by topic.
Question 1
What is the function of dendrites in a neuron?
A.
They pump sodium ions out of the neuron using ATP.
B.
They form the lipid-rich insulation around an axon.
C.
They release neurotransmitter into the synaptic cleft.
D.
They receive signals and conduct impulses towards the cell body.
Question 2
What directly supplies the energy used by sodium–potassium pumps in neuron membranes?
A.
ATP hydrolysis
B.
Diffusion of sodium ions into the axon
C.
Binding of acetylcholine to receptors
D.
Movement of potassium ions down its gradient
Question 3
What is the typical membrane potential of a resting neuron?
A.
Approximately +70 mV, with the inside positive relative to the outside
B.
Approximately +30 mV, with the inside positive relative to the outside
C.
Approximately 0 mV, with equal charge on both sides
D.
Approximately −70 mV, with the inside negative relative to the outside
Question 4
What feature of a typical chemical synapse makes transmission one-way?
A.
Sodium–potassium pumps are present only on the postsynaptic membrane.
B.
Neurotransmitter vesicles are presynaptic and receptors are postsynaptic.
C.
The synaptic cleft contains myelin between the two cells.
D.
Action potentials can pass directly through the synaptic cleft.
Question 5
A student draws a motor neuron.
State the name of the long single fibre that conducts impulses away from the cell body.
[1]
Outline one way in which dendrites are structurally suited to their function.
[1]
Question 6
Why is a nerve impulse described as electrical?
A.
It involves ATP moving from one node to the next.
B.
It involves movement of charged ions across neuron membranes.
C.
It involves neurotransmitter molecules diffusing along the whole axon.
D.
It involves electrons flowing along the axon cytoplasm.
Question 7
A squid giant axon conducts impulses faster than a small non-myelinated axon mainly because it has a greater
A.
diameter, reducing internal resistance to ion movement.
B.
concentration of acetylcholine in the synaptic cleft.
C.
number of synaptic vesicles in each node of Ranvier.
D.
rate of breakdown of neurotransmitter by acetylcholinesterase.
Question 8
What ion enters a presynaptic terminal after depolarization and triggers neurotransmitter release?
A.
Cl⁻
B.
K⁺
C.
Ca²⁺
D.
Na⁺
Question 9
What happens when acetylcholine binds to its receptor on a postsynaptic membrane at many excitatory synapses?
A.
Synaptic vesicles fuse with the postsynaptic membrane.
B.
Voltage-gated potassium channels close and chloride ions leave the cell.
C.
Acetylcholinesterase pumps acetylcholine into the presynaptic neuron.
D.
An ion channel opens and positive ions diffuse into the postsynaptic cell.
Question 10
What event occurs when threshold potential is reached in an axon membrane?
A.
Sodium–potassium pumps stop maintaining ion gradients.
B.
Acetylcholine is broken down by acetylcholinesterase.
C.
Voltage-gated potassium channels close and K⁺ diffuses into the axon.
D.
Voltage-gated sodium channels open and Na⁺ diffuses into the axon.
Question 11
On an oscilloscope trace of an action potential, what does the steep rising phase represent?
A.
Rapid depolarization due to Na⁺ entry through voltage-gated channels
B.
Resting potential maintained by acetylcholine receptors
C.
Repolarization due to K⁺ entry through leak channels
D.
Hyperpolarization due to prolonged Na⁺ entry
Question 12
What feature of myelinated axons allows saltatory conduction?
A.
The cell body is wrapped in lipid-rich insulation.
B.
Ion channels and pumps are clustered at nodes of Ranvier.
C.
Synaptic vesicles are present under each myelin sheath.
D.
Acetylcholine diffuses continuously under the myelin sheath.
Question 13
Explain how the sodium–potassium pump contributes to the resting potential of a neuron. [4]
Question 14
Distinguish between membrane potential and membrane polarization in a resting neuron. [3]
Question 15
Explain how a nerve impulse is propagated along a nerve fibre at SL level. [3]
Question 16
The diagram shows a chemical synapse.
Identify the synaptic cleft.
[1]
Outline why a signal normally passes in only one direction across this synapse.
[1]
Question 17
The graph shows conduction speed in non-myelinated axons of different diameters.
Describe the relationship shown in the graph.
[1]
State whether the correlation is positive or negative.
[1]
Suggest why larger axon diameter affects conduction speed.
[1]
Question 18
An experiment measured ion concentrations inside and outside an axon before and after adding a substance that inhibits ATP production.
| Ion | Location | Control / mmol dm⁻³ | ATP inhibited / mmol dm⁻³ |
|---|---|---|---|
| Na⁺ | Inside axon | 15 | 45 |
| Na⁺ | Outside axon | 145 | 120 |
| K⁺ | Inside axon | 140 | 105 |
| K⁺ | Outside axon | 5 | 25 |
State the normal direction of sodium ion pumping.
[1]
Describe the change in ion gradients after ATP production is inhibited.
[1]
Explain why inhibiting ATP production affects the resting potential.
[1]
Question 19
What causes repolarization during an action potential?
A.
Binding of acetylcholine to receptors and diffusion of Na⁺ into a muscle fibre
B.
Diffusion of Ca²⁺ into the presynaptic terminal and vesicle fusion
C.
Opening of voltage-gated K⁺ channels and diffusion of K⁺ out of the axon
D.
Opening of voltage-gated Na⁺ channels and diffusion of Na⁺ into the axon
Question 20
How do local currents propagate an action potential along an axon?
A.
Electrons move through the axoplasm and depolarize the next region.
B.
Neurotransmitter diffuses along the axon from one node to the next.
C.
ATP diffuses ahead of the impulse and opens sodium–potassium pumps.
D.
Na⁺ diffuses from a depolarized region to adjacent regions, bringing them to threshold.
Question 21
How does cocaine affect synaptic transmission?
A.
It binds to nicotinic acetylcholine receptors in insects only.
B.
It opens chloride channels, producing an IPSP.
C.
It blocks dopamine reuptake, prolonging receptor stimulation.
D.
It breaks down acetylcholine in the synaptic cleft.
Question 22
What change in the postsynaptic membrane is produced by an inhibitory postsynaptic potential?
A.
Depolarization, making threshold easier to reach
B.
Repolarization, returning from the peak of an action potential
C.
Exocytosis, releasing neurotransmitter into the cleft
D.
Hyperpolarization, making threshold harder to reach
Question 23
Why is consciousness described as an emergent property in neural signalling?
A.
It arises from interactions among many neurons and is not shown by a single neuron.
B.
It results from sodium–potassium pumps in each axon using ATP.
C.
It occurs only when pain receptors in the skin reach threshold.
D.
It is produced by one specialized neuron that stores awareness.
Question 24
Compare impulse transmission in myelinated and non-myelinated nerve fibres of similar diameter. [4]
Question 25
Explain the sequence of events leading to neurotransmitter release from a presynaptic membrane. [4]
Question 26
Explain how acetylcholine can generate an excitatory postsynaptic potential at a neuromuscular junction. [4]
Question 27
Explain the roles of voltage-gated sodium and potassium channels during an action potential. [4]
Question 28
Explain how local currents cause propagation of an action potential along an axon. [4]
Question 29
An oscilloscope trace records 12 action potential spikes in 0.40 s.
Calculate the firing frequency in impulses s⁻¹.
[1]
State the cellular event represented by the falling phase of each spike.
[1]
Question 30
Outline saltatory conduction in a myelinated axon. [4]
Question 31
Distinguish between an excitatory postsynaptic potential and an inhibitory postsynaptic potential. [4]
Question 32
Explain how capsaicin from chilli peppers can lead to perception of pain. [4]
Question 33
A table compares conduction speed in four nerve fibres.
| Fibre | Axon diameter / µm | Myelination | Conduction speed / m s⁻¹ | Dataset R² |
|---|---|---|---|---|
| A | 1.0 | Non-myelinated | 0.7 | 0.33 |
| B | 1.0 | Myelinated | 6.0 | 0.33 |
| C | 10.0 | Non-myelinated | 3.0 | 0.33 |
| D | 10.0 | Myelinated | 60.0 | 0.33 |
Identify the fastest fibre from the table.
[1]
Compare the effect of myelination on fibres of similar diameter.
[1]
The table gives an R² value for the relationship between axon diameter and conduction speed. Evaluate what this value indicates.
[1]
Question 34
The graph shows neurotransmitter released from presynaptic terminals when extracellular calcium concentration is varied.
Describe the effect of increasing extracellular Ca²⁺ concentration on neurotransmitter release.
[1]
Suggest why no release occurs when Ca²⁺ is absent from the extracellular fluid.
[1]
State the process by which neurotransmitter leaves the presynaptic terminal.
[1]
Question 35
A postsynaptic membrane potential was recorded after acetylcholine was applied, with and without acetylcholinesterase.
Identify the trace showing the longer-lasting depolarization.
[1]
Explain why acetylcholinesterase changes the duration of the postsynaptic response.
[1]
Suggest one consequence for a muscle fibre if acetylcholine remained in the synaptic cleft for too long.
[1]
Question 36
The oscilloscope trace shows membrane potential recorded from an axon during repeated action potentials.
Determine the firing frequency from the trace.
[1]
Identify the phase labelled X.
[1]
Explain the ion movement responsible for phase X.
[1]
Question 37
Compare the effects of neonicotinoids and cocaine on synaptic transmission. [4]
Question 38
A postsynaptic neuron receives inputs from many presynaptic neurons.
Define summation.
[1]
Explain how excitatory and inhibitory inputs determine whether the postsynaptic neuron fires.
[1]
Question 39
The graph shows membrane potential after stimuli of different strengths were applied to an axon.
Identify the stimulus strengths that produced an action potential.
[1]
Explain why some stimuli did not produce an action potential.
[1]
Explain why the action potentials produced have similar peak amplitudes.
[1]
Question 40
The graph compares conduction speed in axons with different internode lengths in a myelinated fibre.
Describe the relationship between internode length and conduction speed.
[1]
Suggest why very short internodes reduce conduction speed.
[1]
State where voltage-gated ion channels are concentrated in a myelinated axon.
[1]
Question 41
A study tested the effect of a neonicotinoid on survival and movement of an insect species.
Describe the effect of increasing neonicotinoid concentration on movement.
[1]
Explain the synaptic mechanism that could account for the effect.
[1]
Evaluate one limitation of using these data to predict effects on pollinating insects in the field.
[1]
Question 42
Outline two reasons why the inside of a resting neuron is negative relative to the outside.
[1]
Explain how ion gradients and membrane changes allow a nerve impulse to travel along a nerve fibre.
[1]
Question 43
State two structural features of nerve fibres that affect impulse speed.
[1]
Compare conduction in squid giant axons, small non-myelinated fibres and myelinated fibres.
[1]
Question 44
A biologist claims that axon diameter alone determines nerve impulse speed.
Outline how a scatter graph and correlation coefficient could be used to test this claim.
[1]
Discuss the claim using knowledge of axon diameter and myelination.
[1]
Question 45
The graph shows the membrane potential at the axon hillock of a postsynaptic neuron receiving excitatory and inhibitory inputs.
Identify the time interval in which an action potential is generated.
[1]
Explain why threshold is not reached during the interval with an inhibitory input.
[1]
Predict the effect of increasing the frequency of excitatory inputs while inhibitory inputs remain unchanged.
[1]
Question 46
Define synapse and neurotransmitter.
[1]
Explain transmission across a chemical synapse from arrival of an action potential to generation of an excitatory postsynaptic potential.
[1]
Question 47
State the meaning of threshold potential and all-or-nothing response in an axon.
[1]
Explain depolarization, repolarization and hyperpolarization during an action potential.
[1]
Question 48
Outline the distribution of ion channels and pumps in a myelinated axon.
[1]
Explain how local currents and saltatory conduction allow rapid propagation of action potentials.
[1]
Question 49
Outline how neonicotinoids and cocaine each alter synaptic transmission.
[1]
Evaluate the statement: “All exogenous chemicals affect synapses by blocking postsynaptic receptors.”
[1]
Question 50
Distinguish between EPSPs and IPSPs.
[1]
Discuss how integration of postsynaptic potentials can lead to all-or-nothing consequences, using pain perception or consciousness as a context.
[1]
The Fast Track To Your
Best IB Coursework & College Essays
All content on this website has been developed independently from and is not endorsed by the International Baccalaureate Organization. International Baccalaureate and IB are registered trademarks owned by the International Baccalaureate Organization.