Final answer:
Neurotransmitter release at the presynaptic terminal requires the activation of voltage-gated calcium channels, leading to the fusion of synaptic vesicles with the presynaptic membrane and the release of neurotransmitters into the synaptic cleft.
Step-by-step explanation:
Neurotransmitter release from the presynaptic terminal requires the activation of voltage-gated Ca²+ channels. When an action potential reaches the axon terminal, it causes the presynaptic membrane to depolarize, triggering these calcium channels to open. The influx of calcium ions into the cell causes synaptic vesicles to fuse with the presynaptic membrane, thereby releasing neurotransmitter molecules into the synaptic cleft.
The released neurotransmitter then diffuses across the synaptic cleft and may bind to ligand-gated ion channels on the postsynaptic membrane, resulting in either depolarization or hyperpolarization of the postsynaptic neuron. Therefore, the correct answer to which ion channel's activation is required for neurotransmitter release is B) Calcium channels.