Sypnases

Synapse
From Wikipedia, the free encyclopedia
This article is about synapses of the nervous system. For other uses, see Synapse (disambiguation).
Structure of a typical chemical synapsePostsynaptic
density Voltage-
gated Ca++
channel Synaptic
vesicle Reuptake
pump Receptor Neurotransmitter Axon terminal Synaptic cleft Dendrite
In the nervous system, a synapse is a structure thatpermits a neuron 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 communicatewith each other, an idea known as the neuron doctrine.[1]. 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. Ata 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 andpostsynaptic 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, butsome 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 synaptictransmission.[2]
There are two fundamentally different types of synapses:
In a chemical synapse, the presynaptic neuron releases a chemical called a neurotransmitter that binds to receptors located in thepostsynaptic 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...