Which ion triggers the fusion of synaptic vesicles with the plasma membrane for exocytosis?

Question

BlackTom AI · Accepted Answer

The question asks which ion triggers the fusion of synaptic vesicles with the plasma membrane during exocytosis.
Option 1: K+. Potassium ions mainly influence membrane potential and repolarization, but they do not directly trigger the vesicle fusion machinery for neurotransmitter release. Therefore, this choice is incorrect.
Option 2: Cl-. Chloride ions are primarily involved in setting inhibitory postsynaptic potentials and maintaining ionic balance; they are not the trigger for vesicle fusion in exocytosis. This makes this option incorrect.
Option 3: Ca2+. Calcium ions are the key trigger for vesicle fusion at the presynaptic terminal. Influx of Ca2+ through voltage-gated calcium channels upon an action potential binds to sensors like synaptotagmin, promoting SNARE complex-mediated fusion and neurotransmitter release. This is the correct mechanism.
Option 4: Na+. Sodium ions drive the depolarization phase of the action potential and are essential for signaling, but they do not directly trigger the vesicle fusion event in exocytosis. Thus, this option is incorrect.
In summary, exocytosis at the synapse is calcium-dependent, whereas the other ions play different roles in electrical signaling and membrane dynamics without directly initiating vesicle fusion.

Which ion triggers the fusion of synaptic vesicles with the plasma membrane for exocytosis?单项选择题

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