Quantal neurotransmitter release mechanism
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.
Individual quanta may randomly diffuse into the synapse and cause a subsequent MEPP.
What is quantal content?
Quantal size can then be defined as the synaptic response to the release of neurotransmitter from a single vesicle, while quantal content is the number of effective vesicles released in response to a nerve impulse.
What is Quantal analysis?
In quantal analysis, the average number of quanta released on each EPP is measured and then used to estimate the number of times one expects a single vesicle to be released, or two vesicles, or none, etc.
How do neurons know which neurotransmitter to release?
The release of which neurotransmitter is decided by the frequency of the action potential. The vesicles closer to the plasma membrane where the vesicles fuse to release neurotransmitters into the synaptic cleft would be released when there is a low frequency, because they are closer.
How are neurotransmitters released from axon terminals?
Neurotransmitters are released from the axon terminal when their vesicles “fuse” with the membrane of the axon terminal, spilling the neurotransmitter into the synaptic cleft.