Final answer:
The secretion of neurotransmitters in response to an action potential requires voltage-gated Ca2+ channels to open, allowing Ca2+ to enter the cell and trigger the release of neurotransmitters into the synaptic cleft.
Step-by-step explanation:
The process of neurotransmitter release in response to an action potential involves several key steps, one of which is the critical role of voltage-gated Ca2+ channels. When an action potential reaches the axon terminals, it triggers these channels to open, causing an influx of Ca2+ ions into the cell. The increased concentration of Ca2+ inside the end bulb associates with proteins on the outer surface of neurotransmitter vesicles. This association facilitates the merging of the vesicles with the presynaptic membrane, leading to the exocytosis of neurotransmitters into the synaptic cleft, where they can then bind to receptors on the postsynaptic cell and elicit a response.