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Chemical synaptic transmission is the transfer of neurotransmitters or neuropeptides from a presynaptic axon to a postsynaptic dendrite. [3] Unlike an electrical synapse, the chemical synapses are separated by a space called the synaptic cleft, typically measured between 15 and 25 nm. Transmission of an excitatory signal involves several steps ...
At the nerve terminal, neurotransmitters are present within 35–50 nm membrane-encased vesicles called synaptic vesicles. To release neurotransmitters, the synaptic vesicles transiently dock and fuse at the base of specialized 10–15 nm cup-shaped lipoprotein structures at the presynaptic membrane called porosomes . [ 15 ]
This reuptake of neurotransmitters plays a significant role in the overall process of synaptic transmission. The GABA transporter is an active system, electrogenic , a voltage-dependent which relies on the inward electrochemical gradient of Na+ ions instead of ATP. [ 5 ]
Illustration of the major elements in chemical synaptic transmission. An electrochemical wave called an action potential travels along the axon of a neuron.When the wave reaches a synapse, it provokes release of a puff of neurotransmitter molecules, which bind to chemical receptor molecules located in the membrane of another neuron, on the opposite side of the synapse.
Here is a summary of the sequence of events that take place in synaptic transmission from a presynaptic neuron to a postsynaptic cell. Each step is explained in more detail below. Note that with the exception of the final step, the entire process may run only a few hundred microseconds, in the fastest synapses. [14]
The trisynaptic circuit or trisynaptic loop is a relay of synaptic transmission in the hippocampus. The trisynaptic circuit is a neural circuit in the hippocampus, which is made up of three major cell groups: granule cells in the dentate gyrus, pyramidal neurons in CA3, and pyramidal neurons in CA1. The hippocampal relay involves 3 main regions ...
Synaptic gating is the ability of neural circuits to gate inputs by either suppressing or facilitating specific synaptic activity. Selective inhibition of certain synapses has been studied thoroughly (see Gate theory of pain ), and recent studies have supported the existence of permissively gated synaptic transmission.
early synaptic vesicle docking to the presynaptic membrane via interaction with β-neurexin [4] or SNAP-25 [5] late steps of Ca 2+-evoked synaptic vesicle fusion with the presynaptic membrane. [6] [7] [8] It was also shown that synaptotagmin 1 can displace complexin from the SNARE complex in the presence of calcium.