<Table> <Tr> <Td> </Td> <Td> This article is an orphan, as no other articles link to it . Please introduce links to this page from related articles; try the Find link tool for suggestions . (April 2015) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article is an orphan, as no other articles link to it . Please introduce links to this page from related articles; try the Find link tool for suggestions . (April 2015) </Td> </Tr> <P> Neurotransmitters are released into a synapse in packaged vesicles called quanta . One quantum generates what is known as a miniature end plate potential (MEPP) which is the smallest amount of stimulation that one neuron can send to another neuron . Quantal release is the mechanism by which most traditional endogenous neurotransmitters are transmitted throughout the body . The aggregate sum of many MEPPs is known as an end plate potential (EPP). A normal end plate potential usually causes the postsynaptic neuron to reach its threshold of excitation and elicit an action potential . Electrical synapses do not use quantal neurotransmitter release and instead use gap junctions between neurons to send current flows between neurons . The goal of any synapse is to produce either an excitatory postsynaptic potential (EPSP) or an inhibitory postsynaptic potential (IPSP), which generate or repress the expression, respectively, of an action potential in the postsynaptic neuron . It is estimated that an action potential will trigger the release of approximately 20% of an axon terminal's neurotransmitter load . </P> <P> Neurotransmitters are synthesized in the axon terminal where they are stored in vesicles . These neurotransmitter - filled vesicles are the quanta that will be released into the synapse . Quantal vesicles release their contents into the synapse by binding to the presynaptic membrane and combining their phospholipid bilayers . Individual quanta may randomly diffuse into the synapse and cause a subsequent MEPP . These spontaneous occurrences are completely random and are not the result of any kind of signaling pathway . </P>

Neurotransmitter filled packets in the presynaptic neuron are called