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A similar process occurs in retrograde neurotransmission, where the dendrites of the postsynaptic neuron release retrograde neurotransmitters (e.g., endocannabinoids; synthesized in response to a rise in intracellular calcium levels) that signal through receptors that are located on the axon terminal of the presynaptic neuron, mainly at ...
The presynaptic bouton has an efficiently orchestrated process to fuse vesicles to the presynaptic membrane to release neurotransmitters and regenerate neurotransmitter vesicles. This process called the synaptic vesicle cycle maintains the number of vesicles in the presynaptic bouton and allows the synaptic terminal to be an autonomous unit.
The release of a neurotransmitter is triggered by the arrival of a nerve impulse (or action potential) and occurs through an unusually rapid process of cellular secretion . Within the presynaptic nerve terminal, vesicles containing neurotransmitter are localized near the synaptic membrane.
This process of synaptic strengthening is known as long-term potentiation (LTP). [39] By altering the release of neurotransmitters, the plasticity of synapses can be controlled in the presynaptic cell. The postsynaptic cell can be regulated by altering the function and number of its receptors.
Axon terminals (also called terminal boutons, synaptic boutons, end-feet, or presynaptic terminals) are distal terminations of the branches of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell that conducts electrical impulses called action potentials away from the neuron's cell body to transmit those ...
Both mechanisms begin with the formation of the synaptic pore that releases transmitter to the extracellular space. After release of the neurotransmitter, the pore can either dilate fully so that the vesicle collapses completely into the synaptic membrane, or it can close rapidly and pinch off the membrane to generate kiss-and-run fusion. [18]
Once bound, the vesicles will fuse into the membrane and the neurotransmitters will be released into the membrane by exocytosis. The exact mechanism of calcium ion signaling to the presynaptic membrane is unknown, but it has been well established that calcium ion influxes in the axon terminal are linked to neurotransmitter release.
Communication between neurons happens primarily through chemical neurotransmission at the synapse.Neurotransmitters are packaged into synaptic vesicles for release from the presynaptic cell into the synapse, from where they diffuse and can bind to postsynaptic receptors.