Connect synaptic transmission with the next electrical impulse
Describe an electrical chemical electrical sequence without merging the cells.
Section 14.1 · Coordination and response
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
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
What is stimulated in the next neurone in the required account?
What you will learn
- Follow a change in signal mechanism
- Use the specified stimulatory model
Connect synaptic transmission with the next electrical impulse
Within-cell propagation is electrical; the supplied between-cell junction uses chemical transmitter release, diffusion and binding before the next electrical impulse. Original teaching model.
| Feature | Meaning |
|---|---|
| First neurone | Electrical impulse along cell |
| Gap | Chemical transmitter diffusion |
| Next-cell membrane | Transmitter binds receptor proteins |
| Next neurone | Electrical impulse stimulated in this model |
Follow a change in signal mechanism
The first neurone carries an electrical impulse along its own membrane. At the chemical synapse, arrival at the terminal stimulates neurotransmitter release from vesicles into the gap. The mechanism between the two cells therefore differs from propagation along one cell, even though both stages contribute to communication through the same overall pathway.
Released neurotransmitter molecules diffuse across the separating space and bind to receptor proteins on the next neurone. In the required stimulatory account, this binding leads to an electrical impulse being stimulated in the next cell. That impulse then travels along the receiving neurone, rather than the same released transmitter molecules flowing all the way along its entire length.
Use the specified stimulatory model
A useful summary is electrical along the first cell, chemical across the gap, electrical along the next cell. This is a description of the supplied chemical junction, not a claim that every biological synapse everywhere has identical effects. Some wider examples can inhibit activity, but this requirement asks you to explain the stated sequence leading to stimulation in the next neurone.
The two cells remain separate throughout transmission. A continuous route drawn on a larger reflex map often hides the very small junction to make the sequence legible. It should not be interpreted as proof of a fused cell or an electrical signal jumping through the gap. When asked for a mechanism, expand the schematic link into release, diffusion, receptor binding and stimulation.
Pause and explain
Which mechanism summary matches this junction?
Worked example
Summarise the signal mechanisms before across and after the junction.
Show the worked solution
- Electrical impulse along the first neurone; transmitter release and diffusion across the gap.
- Receptor binding stimulates an electrical impulse along the next neurone.
Answer Electrical along first neurone → chemical transmission across gap → electrical along next 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.
State the signal mechanism along first cell across gap and along next cell.
Give me a hint
Keep the chemical stage at the junction.
Compare my reasoning
- First electrical impulse stimulates chemical release.
- Diffusion and binding lead to the next electrical impulse.
Electrical impulses travel along the first and next neurones; neurotransmitter molecules provide chemical transmission across the gap between them.
Look for these in your work
- Identify both electrical stages
- Place the chemical stage between cells
Correct: the first neurone transfers its whole cell body into the next neurone to transmit the signal.
Give me a hint
Separate communication from movement of cell material.
Compare my reasoning
- The neurones remain two cells.
- Chemical release, diffusion and binding stimulate the next impulse.
The cells remain separate; neurotransmitter release, diffusion and receptor binding transmit between them and stimulate an electrical impulse in the next neurone in this model.
Look for these in your work
- Keep two separate cells
- State the connecting chemical events
Does this required stimulatory account prove that every possible synapse has only stimulatory effects?
Give me a hint
The stated model defines the inference scope.
Compare my reasoning
- This model ends with stimulation of the next impulse.
- Other synaptic effects exist outside this specified explanation.
No. It explains stimulation in the supplied chemical-synapse model; it does not establish that all biological synapses have only stimulatory effects.
Look for these in your work
- State the required model result
- Keep the inference bounded
Common mistakes
- Claiming the released molecules are the impulse along the entire next cell.
- Applying the specified stimulatory model to every possible synapse without qualification.
What can you explain now?
Which mechanism summary matches this junction?
Compare with the explanation
Electrical then chemical then electrical
It distinguishes along-cell and across-gap stages.
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Make it stick
Connect electrical and chemical signalling through the complete required junction sequence.
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.