Neurons function in the central nervous system by generating signals from synapses, and this only works in the proper chemical environment [REF].
A chemical signal (synaptic transmission) begins with the action potential that propagates down the axon of so-called presynaptic terminal to trigger Ca2+ influx, which causes the synaptic vesicles to fuse and release neurotransmitters, via exocytosis, to the synaptic cleft [REF].