Final answer:
Neurotransmitters are released from synaptic vesicles through the process of exocytosis when an action potential arrives at the axon terminal, allowing the neurotransmitters to enter the synaptic cleft and interact with the postsynaptic neuron. Option exocytosis is the correct answer.
Step-by-step explanation:
Neurotransmitter Release During an Action Potential
When an action potential arrives at the axon terminal, it triggers a series of events that result in the release of neurotransmitter molecules. The arrival of the action potential depolarizes the presynaptic membrane and causes voltage-gated Ca²+ channels to open.
This influx of calcium ions initiates a cascade that enables synaptic vesicles, packed with neurotransmitters, to merge with the presynaptic membrane and release their contents. The process through which synaptic vesicles containing neurotransmitters are released is known as exocytosis. These vesicles release neurotransmitters into the synaptic cleft, the narrow space between the presynaptic and postsynaptic neurons. Once released, neurotransmitters can bind to receptors on the postsynaptic membrane, potentially triggering an action potential in the next neuron.
The correct option for the question, "Synaptic vesicles containing neurotransmitters are released by ________ when the action potential arrives," is exocytosis.