Difference between revisions of "Synapse"
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==Origin== | ==Origin== | ||
New Latin ''synapsis'', from [[Greek]], [[juncture]], from ''synaptein'' to fasten [[together]], from ''syn''- + ''haptein'' to fasten | New Latin ''synapsis'', from [[Greek]], [[juncture]], from ''synaptein'' to fasten [[together]], from ''syn''- + ''haptein'' to fasten | ||
| − | *[ | + | *[https://en.wikipedia.org/wiki/19th_century 1899] |
==Definition== | ==Definition== | ||
*1: the [[point]] at which a nervous [[impulse]] passes from one [[neuron]] to another | *1: the [[point]] at which a nervous [[impulse]] passes from one [[neuron]] to another | ||
==Description== | ==Description== | ||
| − | In the [[nervous system]], a '''synapse''' is a [[structure]] that permits a [[neuron]] (or nerve cell) to pass an [[electrical]] or [[chemical]] [[signal]] to another cell (neural or otherwise). [ | + | In the [[nervous system]], a '''synapse''' is a [[structure]] that permits a [[neuron]] (or nerve cell) to pass an [[electrical]] or [[chemical]] [[signal]] to another cell (neural or otherwise). [https://en.wikipedia.org/wiki/Santiago_Ram%C3%B3n_y_Cajal Santiago Ramón y Cajal] proposed that neurons are not continuous throughout the [[body]], yet still [[communicate]] with each other, an idea known as the [https://en.wikipedia.org/wiki/Neuron_doctrine neuron doctrine]. The word "synapse" comes from "synaptein", which [https://en.wikipedia.org/wiki/Charles_Scott_Sherrington Sir Charles Scott Sherrington] and colleagues coined from the [[Greek]] "syn-" ("together") and "haptein" ("to clasp"). |
| − | Synapses are essential to neuronal [[function]]: neurons are cells that are specialized to pass [[signals]] to individual target cells, and synapses are the means by which they do so. At a synapse, the [ | + | Synapses are essential to neuronal [[function]]: neurons are cells that are specialized to pass [[signals]] to individual target cells, and synapses are the means by which they do so. At a synapse, the [https://en.wikipedia.org/wiki/Plasma_membrane plasma membrane] of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive [[array]]s of [https://en.wikipedia.org/wiki/Molecular_biology molecular machinery] that link the two membranes together and carry out the signaling [[process]]. In many synapses, the presynaptic part is located on an axon, but some presynaptic sites are located on a [https://en.wikipedia.org/wiki/Dendrite dendrite] or [https://en.wikipedia.org/wiki/Soma_(biology) soma]. [https://en.wikipedia.org/wiki/Astrocyte Astrocytes] also exchange [[information]] with the synaptic neurons, responding to synaptic activity and, in turn, regulating [https://en.wikipedia.org/wiki/Neurotransmission neurotransmission]. |
There are two fundamentally different types of synapses: | There are two fundamentally different types of synapses: | ||
| − | *1: In a [ | + | *1: In a [https://en.wikipedia.org/wiki/Chemical_synapse chemical synapse], electrical activity in the presynaptic neuron is converted (via the activation of [https://en.wikipedia.org/wiki/Voltage-dependent_calcium_channel voltage-gated calcium channels]) into the release of a chemical called a [https://en.wikipedia.org/wiki/Neurotransmitter neurotransmitter] that binds to receptors located in the postsynaptic cell, usually embedded in the plasma membrane. The neurotransmitter may initiate an electrical response or a secondary messenger pathway that may either excite or inhibit the postsynaptic neuron. Because of the [[complexity]] of receptor [https://en.wikipedia.org/wiki/Signal_transduction signal transduction], chemical synapses can have complex [[effects]] on the postsynaptic cell. |
| − | *2: In an [ | + | *2: In an [https://en.wikipedia.org/wiki/Electrical_synapse electrical synapse], the presynaptic and postsynaptic cell membranes are connected by special [[channels]] called [https://en.wikipedia.org/wiki/Gap_junction gap junctions] that are capable of passing [[electric]] current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell. The main advantage of an electrical synapse is the rapid transfer of [[signals]] from one cell to the next. |
| − | Synaptic communication is distinct from [ | + | Synaptic communication is distinct from [https://en.wikipedia.org/wiki/Ephaptic_coupling ephaptic coupling], in which [[communication]] between [[neurons]] occurs via indirect [[electric]] fields.[https://en.wikipedia.org/wiki/Synapse] |
[[Category: Physiology]] | [[Category: Physiology]] | ||
[[Category: Biology]] | [[Category: Biology]] | ||
[[Category: Chemistry]] | [[Category: Chemistry]] | ||
Latest revision as of 02:35, 13 December 2020
Origin
New Latin synapsis, from Greek, juncture, from synaptein to fasten together, from syn- + haptein to fasten
Definition
Description
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another cell (neural or otherwise). Santiago Ramón y Cajal proposed that neurons are not continuous throughout the body, yet still communicate with each other, an idea known as the neuron doctrine. The word "synapse" comes from "synaptein", which Sir Charles Scott Sherrington and colleagues coined from the Greek "syn-" ("together") and "haptein" ("to clasp").
Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon, but some presynaptic sites are located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission.
There are two fundamentally different types of synapses:
- 1: In a chemical synapse, electrical activity in the presynaptic neuron is converted (via the activation of voltage-gated calcium channels) into the release of a chemical called a neurotransmitter that binds to receptors located in the postsynaptic cell, usually embedded in the plasma membrane. The neurotransmitter may initiate an electrical response or a secondary messenger pathway that may either excite or inhibit the postsynaptic neuron. Because of the complexity of receptor signal transduction, chemical synapses can have complex effects on the postsynaptic cell.
- 2: In an electrical synapse, the presynaptic and postsynaptic cell membranes are connected by special channels called gap junctions that are capable of passing electric current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell. The main advantage of an electrical synapse is the rapid transfer of signals from one cell to the next.
Synaptic communication is distinct from ephaptic coupling, in which communication between neurons occurs via indirect electric fields.[1]
