Pearson Edexcel · GCSE · Biology
Course version: 1BI0 · Version from Sept 2016
Explain the structure and function of sensory receptors, sensory neurones,…
Full specification wording
Topic 2 – Cells and control: 2.13 Explain the structure and function of sensory receptors, sensory neurones, relay neurones in the CNS, motor neurones and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters
A stimulus is detected by a sensory receptor, which generates an electrical impulse.
Checked against the Pearson Edexcel 1BI0 specification (opens in a new tab) on .
- Point 12 of 16
Study notes
From the checked teaching notes for this specification point.
The idea
A stimulus is detected by a sensory receptor, which generates an electrical impulse. This travels along a sensory neurone towards the central nervous system (CNS). A sensory neurone has a dendron carrying impulses towards the cell body and an axon carrying impulses away; the myelin sheath insulates the fibre and speeds transmission. In the CNS a relay neurone links the sensory and motor neurones. A motor neurone then carries the impulse to an effector such as a muscle. Where neurones meet, a synapse is a small gap; the impulse cannot cross directly, so a neurotransmitter is released, diffuses across the gap and triggers a new impulse in the next neurone. This explains how impulses pass from receptor to effector.
What earns the marks
- Sensory receptors detect a stimulus and initiate an electrical impulse.
- Sensory neurones carry impulses from receptors to the CNS, with a dendron conducting towards the cell body and an axon conducting away.
- Relay neurones in the CNS connect sensory neurones to motor neurones.
- Motor neurones carry impulses from the CNS to effectors such as muscles.
- The myelin sheath insulates the neurone and increases the speed of impulse transmission.
- At a synapse, a neurotransmitter is released, diffuses across the gap and stimulates a new impulse in the next neurone.
Common mistakes and how to put them right
Saying the electrical impulse crosses the synapse directly.
Put it right: A chemical neurotransmitter diffuses across the gap to trigger a new impulse.
Confusing dendron and axon direction.
Put it right: The dendron carries impulses towards the cell body and the axon carries them away.
Thinking relay neurones carry impulses to muscles.
Put it right: Relay neurones link neurones within the CNS; motor neurones carry impulses to effectors.
Exam tips
- Name the neurone in order — sensory, relay, motor — and state the direction of each impulse.
- When describing a synapse, include release, diffusion and stimulation of the next neurone as separate steps.
- Link the myelin sheath to its function of speeding up transmission rather than just naming it.
Try the lesson
The start of the Topic 2 – Cells and control: 2.13 Explain the structure and function of sensory receptors, sensory neurones, relay neurones in the CNS, motor neurones and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters lesson, made from checked teaching notes for this specification point.
Have a go first
Which part of a neurone carries electrical impulses away from the cell body towards the next cell?
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Test your understanding of Topic 2 – Cells and control: 2.13 Explain the structure and function of sensory receptors, sensory neurones, relay neurones in the CNS, motor neurones and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters
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