Which process is mainly responsible for neurotransmitter release?

The process primarily responsible for neurotransmitter release is synaptic transmission. When a neural impulse (action potential) travels down the axon of a neuron, it reaches the axon terminals, where the neurotransmitters are stored in vesicles. The arrival of the action potential at the terminal triggers the opening of voltage-gated calcium channels, leading to an influx of calcium ions. This calcium influx causes the vesicles containing neurotransmitters to fuse with the presynaptic membrane and release their contents into the synaptic cleft through a process known as exocytosis.

Synaptic transmission involves not only the release of neurotransmitters but also their binding to receptors on the postsynaptic neuron, thereby facilitating communication between neurons. While action potential generation is a crucial precursor to this process, it is the specific mechanisms of synaptic transmission that lead to the actual release of neurotransmitters, making it the correct choice for this question. Conduction refers to the propagation of nerve impulses along axons, while neuroplasticity pertains to the brain's ability to change and adapt, which is not directly related to the mechanics of neurotransmitter release.