A key causal event in the release of neurotransmitter molecules from vesicles into the synaptic cleft is the
A) influx of sodium ions in response to the arrival of an action potential at the terminal.
B) influx of calcium ions in response to the arrival of an action potential at the terminal.
C) efflux of sodium ions in response to the arrival of an action potential at the terminal.
D) efflux of calcium ions at the axon hillock.

Question

Quizplus · Accepted Answer

The influx of calcium ions in response to the arrival of an action potential at the terminal is the key causal event in the release of neurotransmitter molecules from vesicles into the synaptic cleft. This influx of calcium ions leads to fusion of the vesicles with the presynaptic membrane and subsequent release of neurotransmitters into the synaptic cleft. In contrast, the influx or efflux of sodium ions at the terminal is involved in the generation and propagation of the action potential itself, and the efflux of calcium ions at the axon hillock is not directly related to neurotransmitter release.

A Key Causal Event in the Release of Neurotransmitter Molecules