Describe how a nervous impulse is transmitted from one neurone to the next across a synapse.

Eduqas A-Level Biology — 4.6 The nervous system · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

A neurotransmitter is released from the presynaptic neurone
The neurotransmitter diffuses across the synaptic cleft
The neurotransmitter binds to receptors on the postsynaptic neurone
This binding triggers a new nerve impulse in the postsynaptic neurone
The myelin sheath speeds up the transmission of the impulse along the neurone

Examiner tips

Use the exact sequence of events; include the myelin sheath as a final point
Show the role of the synaptic cleft and receptors
Keep each point brief but complete
Use UK spelling (neuron)

Common mistakes

Omitting the myelin sheath or describing it as part of the synapse
Confusing the presynaptic and postsynaptic neurone
Using vague terms like ‘signal’ instead of ‘neurotransmitter’

Mark scheme (5 marks)

A neurotransmitter is released from the presynaptic neurone
The neurotransmitter diffuses across the synaptic cleft
The neurotransmitter binds to receptors on the postsynaptic neurone
This triggers a new nerve impulse in the postsynaptic neurone
The myelin sheath speeds up the transmission of the impulse along the neurone

Key terms in this question

synapse