Describe how a nerve impulse is transmitted from a receptor to an effector through the central nervous system.

Eduqas GCSE Biology — 2.5.1 The nervous system · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

A receptor detects a stimulus and generates a nerve impulse
The impulse travels along a sensory neurone to the central nervous system (brain or spinal cord)
The impulse passes through a relay neurone (in the CNS) which connects sensory and motor neurones
The impulse travels along a motor neurone to the effector, which produces a response

Examiner tips

Use the exact sequence of steps, matching the mark scheme order
Include both sensory and motor neurones and the relay neurone
Mention the CNS (brain or spinal cord) as the site of the relay
Keep each point concise and separate with line breaks

Common mistakes

Omitting the relay neurone or the CNS step
Confusing sensory with motor neurone roles
Using vague terms like ‘signal’ instead of ‘nerve impulse’

Mark scheme (4 marks)

A receptor detects a stimulus and generates a nerve impulse
The impulse travels along a sensory neurone to the central nervous system (brain or spinal cord)
The impulse passes through a relay neurone (in the CNS) which connects sensory and motor neurones
The impulse travels along a motor neurone to the effector, which produces a response

Key terms in this question

receptor · effector · central nervous system