Answer:
The transmission of impulses is chemical, caused by the release of specific neurotransmitters from nerve termination. Neurotransmitters diffuse through the synaptic cleft and briefly bind to specific receptors in the adjacent neuron or effector cell. Depending on the receiver, the response can be exciting or inhibitory.
There is a type of synapse, the electrical one, in which it does not involve neurotransmitters; Ionic channels directly connect the cytoplasm of presynaptic and postsynaptic neurons. This type of transmission is the fastest.
The neuronal soma produces enzymes responsible for synthesizing most neurotransmitters, which are stored in vesicles in nerve endings (see Figure Neurotransmission). The amount contained in a vesicle (usually several miles of molecules) is a quantum. A membrane action potential that reaches termination opens the Ca channels of the axon; The influx of Ca releases neurotransmitter molecules from many vesicles by fusing the vesicle membranes with the nerve termination membrane. The fusion of the membrane generates an opening through which the molecules are expelled into the synaptic cleft through exocytosis.
