Identify sensory relay and motor neurones in a diagram
Use both the supplied cell outline and its place in the pathway.
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall cell membranes, diffusion, sensitivity and the difference between cells, tissues and organs.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which direction defines the supplied sensory route?
What you will learn
- Three functional roles have different connections
- Resolve D E and F from the route
Identify sensory relay and motor neurones in a diagram
| Feature | Meaning |
|---|---|
| D | Sensory: receptor → CNS |
| E | Relay: connection within CNS |
| F | Motor: CNS → effector |
| Identification evidence | Leader endpoint plus pathway context |
Three functional roles have different connections
A sensory neurone carries information from a receptor towards the CNS. A relay neurone connects neurones within the CNS in the simple pathway supplied here. A motor neurone carries information from CNS towards an effector. These roles identify pathway direction and connection, not merely the colour used in a drawing.
The original diagram marks D as the sensory neurone on the incoming route, E as the relay neurone in the central region and F as the motor neurone on the outgoing route. The sensory cell body is drawn beside its long pathway, while relay and motor sketches show their cell bodies in the central region. These are teaching examples, not universal shapes for every neuronal subtype.
Resolve D E and F from the route
A cell’s outline can help orientation, but a multipolar outline alone does not establish whether a neurone is motor or relay in every biological setting. The supplied receptor, central connection and effector give the functional evidence. Identify the target from the leader endpoint and route arrows rather than using an isolated cell-body shape without context.
A sensory neurone is not the receptor itself, and a motor neurone is not the contracting muscle. The receptor detects the stimulus; the sensory cell communicates towards central processing; the motor cell communicates towards the effector; the effector carries out the response. Keeping these named roles separate prepares the five-part reflex arc.
Sources for this lesson
Pause and explain
Which target connects the sensory and motor routes within CNS?
Worked example
Identify D, E and F from their pathway connections.
Show the worked solution
- D enters from receptor; E connects within CNS.
- F leads out towards effector.
Answer D sensory neurone; E relay neurone; F motor neurone.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Identify all three labelled neurones D, E and F.
Give me a hint
Use the stated pathway endpoints.
Compare my reasoning
- D carries input towards CNS and E connects within CNS.
- F carries output towards effector.
D sensory neurone; E relay neurone; F motor neurone.
Look for these in your work
- Name all three roles
- Use the route connections
A cell drawing is multipolar but has no connections or location supplied. Does shape alone establish motor rather than relay function?
Give me a hint
Two functional roles can share a general outline.
Compare my reasoning
- The shape does not give the receptor-to-effector route.
- Functional connections or other context are needed.
No. A general multipolar outline alone does not distinguish every motor from relay neurone; location and functional pathway connections provide stronger evidence.
Look for these in your work
- Restrict shape inference
- Name missing functional context
Correct: the sensory neurone detects the stimulus and the motor neurone is the muscle.
Give me a hint
Receptor, communicating cells and effector are separate roles.
Compare my reasoning
- The receptor detects; sensory neurone communicates towards CNS.
- Motor neurone communicates to muscle; muscle contracts.
The receptor detects the stimulus. Sensory and motor neurones communicate along the pathway; the muscle is a separate effector that contracts.
Look for these in your work
- Separate receptor and sensory cell
- Separate motor cell and muscle
Common mistakes
- Identifying all motor and relay cells from shape alone.
- Calling the motor neurone the muscle effector.
What can you explain now?
Which target connects the sensory and motor routes within CNS?
Compare with the explanation
E: relay neurone
Its position and connections supply the functional evidence.
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Make it stick
Identify the three neurone roles from their connections, not colour or shape alone.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.