Final answer:
Neurotransmitter release is facilitated by an action potential triggering the opening of Ca2+ channels, leading to the exocytosis of neurotransmitters into the synaptic cleft.
Step-by-step explanation:
The release of neurotransmitters by an excited neuron is achieved through a mechanism called exocytosis. During this process, an action potential arriving at the axon terminal triggers the opening of voltage-gated Ca²⁺ channels.
The influx of Ca²⁺ ions results in the fusion of neurotransmitter-filled vesicles with the presynaptic membrane, leading to the discharge of neurotransmitters into the synaptic cleft.