Explain how a nerve impulse is transmitted from a motor neurone to an effector.

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).

The nervous system allows the body to respond rapidly to stimuli. Motor neurones carry impulses from the central nervous system to effectors such as muscles.

Model answer (4 marks)

The nerve impulse travels along the axon of the motor neurone.
The myelin sheath insulates the axon and increases the speed of the nerve impulse.
Neurotransmitters are released at the junction between the motor neurone and the effector.
Neurotransmitters bind to receptors on the effector, triggering a response.

Examiner tips

Use the exact terminology: axon, myelin sheath, neurotransmitters, receptors. Show the sequence: axon → myelin → synapse → effector. Keep each point brief but complete.
Include the word "junction" to show the synapse.
Mention that the response is triggered by receptor binding.

Common mistakes

Mixing up sensory and motor neurones. Forgetting to mention the myelin sheath. Using vague terms like "signal" instead of "nerve impulse".

Mark scheme (4 marks)

The nerve impulse travels along the axon of the motor neurone
The myelin sheath insulates the axon and increases the speed of the nerve impulse
Neurotransmitters are released at the junction between the motor neurone and the effector
Neurotransmitters bind to receptors on the effector, triggering a response

Key terms in this question

motor neurone · effector