BRAINCAKENeuromuscular Junction
When an action potential arrives at a neuromuscular junction it stimulates calcium ion channels to open. Calcium ions diffuse from the synapse into the synaptic knob. This causes vesicles to fuse with the presynaptic membrane and release acetylcholine. Acetylcholine binds to receptors on the post-synaptic membrane opening sodium channels. The influx of sodium ions causes depolarisation of the sarcolemma.
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Key terms in this lesson
- Action potential
- The temporary reversal of the electrical charge across an axon membrane, from about -70mV to +40mV, that occurs when a neurone is stimulated above threshold.
- Depolarisation
- A change in the potential difference across a membrane that makes the inside less negative, caused by an influx of sodium ions.
- Acetylcholine
- A neurotransmitter released at cholinergic synapses and neuromuscular junctions that causes depolarisation of the postsynaptic membrane.
- Sarcolemma
- The specialised cell surface membrane of a muscle fibre.