Changes

==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

*[http://en.wikipedia.org/wiki/19th_century 1899]

*[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). [http://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 [http://en.wikipedia.org/wiki/Neuron_doctrine neuron doctrine]. The word "synapse" comes from "synaptein", which [http://en.wikipedia.org/wiki/Charles_Scott_Sherrington Sir Charles Scott Sherrington] and colleagues coined from the [[Greek]] "syn-" ("together") and "haptein" ("to clasp").

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 [http://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 [http://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 [http://en.wikipedia.org/wiki/Dendrite dendrite] or [http://en.wikipedia.org/wiki/Soma_(biology) soma]. [http://en.wikipedia.org/wiki/Astrocyte Astrocytes] also exchange [[information]] with the synaptic neurons, responding to synaptic activity and, in turn, regulating [http://en.wikipedia.org/wiki/Neurotransmission neurotransmission].

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 [http://en.wikipedia.org/wiki/Chemical_synapse chemical synapse], electrical activity in the presynaptic neuron is converted (via the activation of [http://en.wikipedia.org/wiki/Voltage-dependent_calcium_channel voltage-gated calcium channels]) into the release of a chemical called a [http://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 [http://en.wikipedia.org/wiki/Signal_transduction signal transduction], chemical synapses can have complex [[effects]] on the postsynaptic cell.

*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 [http://en.wikipedia.org/wiki/Electrical_synapse electrical synapse], the presynaptic and postsynaptic cell membranes are connected by special [[channels]] called [http://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.

*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 [http://en.wikipedia.org/wiki/Ephaptic_coupling ephaptic coupling], in which [[communication]] between [[neurons]] occurs via indirect [[electric]] fields.[http://en.wikipedia.org/wiki/Synapse]

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]]