Explain how the structure of a motor neurone is adapted to carry out its function efficiently.

Edexcel GCSE Biology (1BI0) — 2.3 The nervous system · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

The axon is long, extending from the cell body to the effector, allowing impulses to travel over long distances.
The axon is surrounded by a myelin sheath, which acts as an electrical insulator.
The myelin sheath increases the speed of nerve impulses along the axon.
The dendrites provide a large surface area to receive impulses from other neurones and the CNS.

Examiner tips

Use the exact terms "axon", "myelin sheath", "dendrites". Show the link between structure and function (long axon = long distance, myelin = speed, dendrites = surface area).
Keep the answer concise – 4 points, one sentence each.
Use UK spelling (e.g. "neuron" not "neural cell").

Common mistakes

Confusing dendrites with axons. Forgetting to mention the myelin sheath. Using vague language such as "long" without explaining the functional advantage.

Mark scheme (4 marks)

The axon is long / extends from the cell body to the effector, so nerve impulses can be conducted over a long distance
The myelin sheath surrounds the axon and acts as an electrical insulator
The myelin sheath increases the speed of nerve impulses along the axon
Dendrites / dendrons provide a large surface area to receive nerve impulses from other neurones / the CNS

Key terms in this question

motor neurone