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A synapse is a structure between two neurons (or between a neuron and a target cell). In this structure, the neuron that propagates the signal (action potential) in the forward direction is denoted by the presynaptic end. Typically, the axon terminals serve as the presynaptic end.

When a signal depolarizes the neuronal membrane of the presynaptic terminal, the ion channels for calcium are stimulated and opened. This opening causes a profuse inflow of calcium ions within the axonal terminal, which regulates further propagation of the signal to the postsynaptic terminal.

Thus, the immediate effect of axon terminal depolarization is the activation of calcium ion channels.

Therefore, the given statement is true.

The synaptic vesicles are the components that contain neurotransmitters. The inflow of calcium in the presynaptic end causes the fusion of the synaptic vesicle鈥檚 membrane with the presynaptic terminal鈥檚 membrane.

Thus, the fusion of the synaptic vesicle with the presynaptic membrane is not a direct effect of depolarization.

Therefore, the given statement is false.

The neurotransmitters are transferred from the presynaptic terminal to the synaptic cleft through a process of exocytosis. In this mechanism, the fused membrane of the synaptic vesicle and presynaptic end opens up, and the neurotransmitters are emitted out.

Thus, ligand-gated ion channels are not involved in the transfer of neurotransmitters to the synaptic cleft.

Therefore, the given statement is false.

A postsynaptic potential, either IPSP (inhibitory postsynaptic potential) or EPSP (excitatory postsynaptic potential), is generated when the molecules of neurotransmitters link with their respective receptors on the postsynaptic end.

Thus, the generation of IPSP or EPSP occurs at a much later stage after depolarization.

Therefore, the given statement is false.