The synapse
Introduced| English | Meaning |
|---|---|
| synapse/ˈsɪnæps/ | A junction through which a neuron communicates with another cell, usually using a chemical transmitter. |
| cholinergic/ˌkɒlɪˈnɜːdʒɪk/ | cholinergic |
| neurotransmitter/ˈnjuːrətrænsmɪtə/ | A chemical released by a neuron that transmits a signal across a synapse by binding to receptors on a target cell. |
| acetylcholine/ˈæsɪtɪlkəliːn/ | A neurotransmitter released at neuromuscular junctions and at many other synapses. |
| neuromuscular junction/ˌnjuːrəˈmʌskjʊlə ˈdʒʌŋkʃn/ | The specialised synapse through which a motor neurone signals to a muscle fibre. |
| summation/sʌˈmeɪʃn/ | summation |
The gap between neurones
- A synapse 突触 is a tiny gap between two neurones.
- The electrical impulse can't jump the gap — so it's carried across by a chemical.
- The same idea connects a neurone to a muscle.
Neurotransmitters carry the signal across the synaptic gap from one neurone to the next.
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They diffuse across the cleft because the electrical impulse cannot jump the gap directly.
The tiny gap between two neurones at a synapse is the synaptic ______.
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The neurotransmitter diffuses across the synaptic cleft to the next neurone.
A cholinergic 胆碱能 synapse
- the impulse arrives and makes calcium ions enter the first neurone.
- this makes vesicles release a neurotransmitter 神经递质, acetylcholine 乙酰胆碱, into the gap.
- acetylcholine diffuses across and binds receptors on the next neurone.
- this starts a new impulse in the next neurone.
A cholinergic synapse passing a signal across the cleft
Across a synapse
Step through it. The electrical impulse becomes a chemical one — neurotransmitter carries the signal across the gap.
When an impulse arrives at a synapse, the first thing that happens is:
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Ca²⁺ entering the presynaptic neurone causes vesicles to release acetylcholine into the cleft.
Acetylcholine carries the signal across the synapse by:
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The neurotransmitter diffuses across the cleft and binds receptors, starting a new impulse.
Put the events at a cholinergic synapse in order.
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Impulse → Ca²⁺ in → ACh released → ACh binds receptors → new impulse.
Match each part of the synapse to its role.
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Ca²⁺ triggers release, ACh crosses and binds receptors, then the enzyme clears it so signals stay separate.
The neuromuscular junction 神经肌肉接头
- A neuromuscular junction works just like a synapse.
- But it is between a motor neurone and a muscle.
- The neurotransmitter triggers the muscle to contract.
A neuromuscular junction is a synapse between:
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It works like any synapse, but the second cell is a muscle that is made to contract.
Why synapses matter
- Synapses make transmission one-way (only the ending releases neurotransmitter).
- They also allow summation 总和 and integration — many signals combining to decide the response.
You've got it
- a synapse is a gap between neurones; the signal crosses it as a chemical
- cholinergic synapse: impulse → Ca²⁺ in → vesicles release acetylcholine → binds receptors → new impulse
- a neuromuscular junction is a synapse between a motor neurone and a muscle