What is The process by which the neurotransmitter substance leaves presynaptic terminal button called?

The process by which the neurotransmitter substance leaves presynaptic terminal button is called exocytosis.

- During the arrival of an action potential at the synaptic terminal, voltage-gated calcium channels in the presynaptic membrane open, allowing calcium ions to flood into the terminal button.

- The influx of calcium triggers the release of neurotransmitter substance from vesicles in a process called exocytosis.

- Exocytosis is the process by which a cell releases material by secreting it through the plasma membrane.

- The membrane of the vesicle fuses with the presynaptic membrane, releasing the neurotransmitter molecules into the synaptic cleft, the space between the presynaptic and postsynaptic neurons.