Explain how the structure of a neurone is related to its function in transmitting nerve impulses.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Neurones are specialised cells that carry electrical impulses around the body. They have several structural features that make them well suited to this role.
Model answer (4 marks)
A neurone’s structure is adapted to its role in transmitting impulses.
1. The axon is surrounded by a myelin sheath, which insulates the axon and prevents leakage of ions.
2. This insulation allows the impulse to jump between the gaps in the sheath (nodes of Ranvier), speeding up conduction.
3. Axons can be very long, enabling impulses to travel over great distances to reach distant tissues.
4. The dendrites (or dendrons) have many branches, increasing surface area so they can receive signals from many other neurones.
1. The axon is surrounded by a myelin sheath, which insulates the axon and prevents leakage of ions.
2. This insulation allows the impulse to jump between the gaps in the sheath (nodes of Ranvier), speeding up conduction.
3. Axons can be very long, enabling impulses to travel over great distances to reach distant tissues.
4. The dendrites (or dendrons) have many branches, increasing surface area so they can receive signals from many other neurones.
Examiner tips
- Use the exact terms: axon, myelin sheath, nodes of Ranvier, dendrites/dendrons.
- Show the causal link: insulation → faster conduction; long axon → distance; many dendrites → more input.
- Keep each point short and to the point to fit the 4‑mark structure.
Common mistakes
- Confusing myelin with the axon itself; forgetting to mention nodes of Ranvier.
- Using vague phrases like ‘helps speed up’ without linking to insulation.
- Omitting the role of dendrites or describing them as ‘branches’ without noting surface area.
Mark scheme (4 marks)
- Myelin sheath / myelin insulates the neurone / axon
- Myelin sheath speeds up the transmission of the nerve impulse
- Long axon allows impulses to be carried over long distances / between distant parts of the body
- Dendrites / dendrons increase the surface area to receive impulses from other neurones
Key terms in this question
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →