synapse (redirected from synapses)

synapse /syn·apse/ (sin´aps) the site of functional apposition between neurons, where an impulse is transmitted from one to another, usually by a chemical neurotransmitter released by the axon terminal of the presynaptic neuron. The neurotransmitter diffuses across the gap to bind with receptors on the postsynaptic cell membrane and cause electrical changes in that neuron (depolarization/excitation or hyperpolarization/inhibition).

Diagram of three synapses. Nerve impulse is indicated by arrows, showing that the direction of passage is from the terminal arborization (TA) or nerve endings of the axon of one neuron to the dendrites (D) of another neuron.

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syn·apse (snps, s-nps)

n.

The junction across which a nerve impulse passes from an axon terminal to a neuron, a muscle cell, or a gland cell.

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Synapse

A connection between nerve cells, by which nervous excitation is transferred from one cell to the other.

Mentioned in: Alpha 1 -Adrenergic Blockers, Cocaine

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synapse

[sin′aps, sinaps′]

Etymology: Gk, synaptein, to join

1  n, the region surrounding the point of contact between two neurons or between a neuron and an effector organ, across which nerve impulses are transmitted through the action of a neurotransmitter, such as acetylcholine or norepinephrine. When an impulse reaches the terminal point of one neuron, it causes the release of the neurotransmitter. The neurotransmitter diffuses across the gap between the two cells to bind with receptors in the other neuron, muscle, or gland, triggering electric changes that either inhibit or continue the transmission of the impulse. Synapses are polarized so that nerve impulses normally travel in only one direction; they are also subject to fatigue, oxygen deficiency, anesthetics, and other chemical agents. Kinds of synapses include axoaxonic synapse, axodendritic synapse, axodendrosomatic synapse, axosomatic synapse, and dendrodendritic synapse. Compare ephapse.

2  v, to form a synapse or connection between neurons.

3  v, (in genetics) to form a synaptic fusion between homologous chromosomes during meiosis. synaptic, adj.

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synapse (siˑ·naps),

n the junction between two neurons across which nerve impulses are conducted.

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synapse (sin´aps),

n the region of contact between the processes of two adjacent neurons forming the place where a nervous impulse is transmitted from the axon of one neuron to the dendrites of another. It also is called the
synaptic junction.

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synapse

the junction between the processes of two neurons or between a neuron and an effector organ, where neural impulses are transmitted by chemical means. The impulse causes the release of a neurotransmitter (e.g. acetylcholine or norepinephrine) from the presynaptic membrane of the axon terminal. The neurotransmitter molecules diffuse across the synaptic cleft, bind with specific receptors on the postsynaptic membrane, causing depolarization or hyperpolarization of the postsynaptic cell. See also neuron.

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adrenergic synapse

the neurotransmitter is norepinephrine. See also adrenergic (1).

axoaxonic synapse

see axoaxonic.

axodendritic synapse

see axodentritic.

axodendrosomatic synapse

one between the axon of one neuron and the dendrites and body of another.

axosomatic synapse

see axosomatic.

cholinergic synapse

the neurotransmitter is acetylcholine. See also cholinergic.

dendrodendritic synapse

one from a dendrite of one cell to a dendrite of another.

excitatory synapse

a synapse in which the transmission of impulses is electrical not chemical. Found only in fish and invertebrates.

inhibitory synapse

hyperpolarizing electrical current is used to raise the threshold for the stimulation of a discharge of an impulse from the particular kind of nerve cell, found only in fish.

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synapse 

The place where a nerve impulse is transmitted from one neuron to another. This transmission is usually mediated by neurotransmitters (e.g. acetylcholine, noradrenaline (norepinephrine), glutamate, etc.) that are released by the presynaptic neuron, then diffuse across the synaptic cleft (about 20-50 nm wide) to bind to receptor sites on the postsynaptic membrane and generate an electrical change in the postsynaptic neuron, which results in either depolarization (excitation) or hyperpolarization (inhibition). This is often referred to as a chemical synapse. There is another type of synapse called an electrotonic synapse (electrical synapse) in which electrical impulses are transmitted via ionic currents from one neuron to another by direct propagation across a gap junction (2-3nm wide). Electrotonic synapses are rare in vertebrates and have been found at only a few central nervous sites. It is estimated that a cortical neuron, for example, makes some 5000-10 000 synapses with surrounding neurons. See neuron; neurotransmitter; receptor potential.