Synapses
Introduced| English | Meaning |
|---|---|
| synapse/ˈsɪnæps/ | A junction through which a neuron communicates with another cell, usually using a chemical transmitter. |
| neurotransmitter/ˈnjuːrətrænsmɪtə/ | A chemical released by a neuron that transmits a signal across a synapse by binding to receptors on a target cell. |
The gaps between neurones
- Neurones don't quite touch — there's a tiny gap between them called a synapse 突触.
- How the signal crosses this gap is clever chemistry.
A synapse is:
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A synapse is the junction between neurones.
An impulse cannot jump the synapse directly, so it is carried by ______ chemicals.
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Neurotransmitters carry the signal across.
What a synapse is
- A synapse is the junction between two neurones.
- The electrical impulse cannot jump the gap directly.
At a synapse, neurotransmitter 神经递质 diffuses across the gap, so impulses travel one way only
Across the synapse
Neurons don't touch — the impulse crosses the tiny gap using a chemical messenger.
The signal crosses a synapse as:
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Neurotransmitters diffuse across the gap.
Neurotransmitters move across the synapse by:
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They diffuse across the small gap.
Crossing the gap
- The impulse triggers the release of neurotransmitter chemicals.
- These diffuse across the gap and trigger a new impulse in the next neurone.
Synapses let impulses travel in either direction.
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False. Neurotransmitter is released from one side only and its receptors are on the other, so impulses cross a synapse in one direction only.
One-way only
- Neurotransmitters are released on one side only, so signals cross a synapse in one direction.
- This keeps impulses travelling the right way through the nervous system.
Worked example. An impulse reaches the end of a neurone, releasing neurotransmitter into the synapse. It diffuses across, binds to the next neurone, and starts a fresh impulse — converting electrical → chemical → electrical.
You've got it
- a synapse is the gap between two neurones
- the signal crosses as neurotransmitter chemicals that diffuse across
- synapses transmit in one direction only
Write from a one-way gap
- An impulse reaches the end of one neurone.
- A chemical is released into the gap.
What crosses the synapse, and why does the signal not reverse?
The chemical is released on one side only.
How does a signal cross a synapse?
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The chemical messenger crosses the gap.