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Neurotransmission (Latin: transmissio "passage, crossing" from transmittere "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron), and bind to and react with the receptors on the dendrites of another neuron (the postsynaptic neuron) a ...
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 ...
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.
This difference across the membrane is what the neuron uses to actually do the work of sending messages from the axon hillock of the neuron all the way down to the presynaptic terminal and then on to the postsynaptic terminal because of the release of neurotransmitter into the synaptic cleft. [3]
The presynaptic axon terminal, or synaptic bouton, is a specialized area within the axon of the presynaptic cell that contains neurotransmitters enclosed in small membrane-bound spheres called synaptic vesicles (as well as a number of other supporting structures and organelles, such as mitochondria and endoplasmic reticulum).
Postsynaptic potentials occur when the presynaptic neuron releases neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic terminal, which may be a neuron , or a muscle cell in the case of a neuromuscular junction . [ 1 ]
When the presynaptic terminal is electrically stimulated, an array of molecules embedded in the membrane are activated, and cause the contents of the vesicles to be released into the narrow space between the presynaptic and postsynaptic membranes, called the synaptic cleft.
A diagram of temporal summation. At any given moment, a neuron may receive postsynaptic potentials from thousands of other neurons. Whether threshold is reached, and an action potential generated, depends upon the spatial (i.e. from multiple neurons) and temporal (from a single neuron) summation of all inputs at that moment.