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Diagram of a chemical synaptic connection. In the nervous system, a synapse [1] is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons.
Artistic interpretation of the major elements in chemical synaptic transmission. An electrochemical wave called an action potential travels along the axon of a neuron. When the action potential reaches the presynaptic terminal, it provokes the release of a synaptic vesicle, secreting its quanta of neurotransmitter molecules. The ...
Quantal release is the mechanism by which most traditional endogenous neurotransmitters are transmitted throughout the body. The aggregate sum of many MEPPs is 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. [1]
Mechanisms of action include binding to receptors on the presynaptic cell activating the IP3/DAG pathway and release of calcium from intracellular stores and pore formation resulting in influx of calcium ions directly. Either mechanism causes increased calcium in presynaptic cell, which then leads to release of synaptic vesicles of acetylcholine.
An action potential briefly amplifies this process. Neurotransmitters containing vesicles cluster around active sites, and after they have been released may be recycled by one of three proposed mechanisms. The first proposed mechanism involves partial opening and then re-closing of the vesicle.
Two molecular mechanisms for synaptic plasticity involve the NMDA and AMPA glutamate receptors. Opening of NMDA channels (which relates to the level of cellular depolarization) leads to a rise in post-synaptic Ca 2+ concentration and this has been linked to long-term potentiation, LTP (as well as to protein kinase activation); strong depolarization of the post-synaptic cell completely ...
There was substantial debate on whether the transmission of information between neurons was chemical or electrical in the first decades of the twentieth century, but chemical synaptic transmission was seen as the only answer after Otto Loewi's demonstration of chemical communication between neurons and heart muscle. Thus, the discovery of ...
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 ...