Explain how a nerve impulse is transmitted across a synapse from one neurone to the next.

Cambridge International IGCSE Biology (0610) — 14.1 Nervous control in humans · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Nerve impulse arrives at the presynaptic neurone, causing synaptic vesicles to fuse with the membrane.
Neurotransmitters are released into the synaptic cleft.
Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic neurone.
This triggers a new nerve impulse in the postsynaptic neurone, ensuring the impulse can only travel in one direction.

Examiner tips

Use the sequence of events: arrival, vesicle fusion, release, diffusion, receptor binding, new impulse.
Mention the directionality of the impulse.
Use correct terminology: presynaptic, postsynaptic, synaptic cleft, neurotransmitter, receptor.

Common mistakes

Confusing the direction of impulse (e.g., saying it can travel both ways).
Omitting the step of vesicle fusion or neurotransmitter release.

Mark scheme (4 marks)

Nerve impulse arrives at the presynaptic neurone, causing synaptic vesicles to fuse with the membrane
Neurotransmitters are released into the synaptic cleft
Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic neurone
This triggers / generates a new nerve impulse in the postsynaptic neurone, ensuring the impulse can only travel in one direction

Key terms in this question

synapse