Final answer:
An action potential results in neurotransmitter release when Ca2+ ions enter the axon terminal, prompting vesicles to release their contents into the synaptic cleft through exocytosis.
Step-by-step explanation:
An action potential triggers the release of neurotransmitters into the synaptic cleft through a multi-step process. When the action potential arrives at the axon terminal, it depolarizes the membrane, causing voltage-gated Na+ channels to open and further depolarize the membrane.
This depolarization opens voltage-gated Ca2+ channels, allowing Ca2+ ions to enter the neuron. These ions bind to proteins on the neurotransmitter vesicles, causing the vesicles to move to and merge with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft through exocytosis. The neurotransmitters can then bind to receptors on the postsynaptic cell, continuing the transmission of the signal.