going before another in time or order I'd like to follow up on an antecedent question from another reporter Synonyms previous, anterior, foregoing, former, precedent, preceding, priorRelated Words advance, early, premature; earliest, first, inaugural, initial, maiden, original, pioneer; preexisting; introductory, preliminary; erstwhile, whilomNear ...
Neurotransmitters are formed in a presynaptic neuron and stored in small membrane-bound sacks, called vesicles, inside this neuron. When this neuron is activated, these intracellular vesicles fuse with the cell membrane and release their contents into the synapse, a process called exocytosis.
Synapses are composed of three main parts: 1  The presynaptic ending that contains neurotransmitters. 2  The synaptic cleft between the two nerve cells. 3  The postsynaptic ending that contains receptor sites.