At a cholinergic synapse, which event directly causes vesicles to release neurotransmitter into the cleft?
Answer and explanation
Correct answer: C. Calcium ions enter the presynaptic neurone through voltage-gated channels
- Step 1: The action potential arriving at the presynaptic terminal opens voltage-gated calcium channels.
- Step 2: Calcium ions entering the terminal make vesicles fuse with the membrane and release neurotransmitter.
Answer
Calcium ions enter the presynaptic neurone through voltage-gated channels.
Why not the others: Sodium ions enter the postsynaptic neurone through ligand-gated channels: occurs after release, in the postsynaptic membrane. Acetylcholinesterase breaks down acetylcholine in the cleft: occurs after release, ending the signal. Potassium ions leave the presynaptic neurone through leak channels: does not trigger vesicle fusion.
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