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.
There are both small and large vesicles. Small vesicles are produced by the Golgi apparatus located in the soma and transported down the axon via current flow in the cytoplasm (fluid inside the cell). Small vesicles store neurotransmitters. In some neurons, larger vesicles are also found in smaller quantity. These large vesicles store neuropeptides or neuromodulators such as the endorphins. The positively charged ion, calcium (Ca+2), is essential to synaptic transmission.