Synapse

A synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to neuronal function: neurons are cells specialized to pass signals to individual target cells, and synapses are the means by which they do so.

Structure

There are two types of synapses: chemical synapses and electrical synapses.

In a chemical synapse, the process of synaptic transmission is mediated by molecules known as neurotransmitters. These are released from the axon terminal of a neuron into the synaptic cleft, where they bind to receptors on the post-synaptic cell.

Electrical synapses are a little different. Instead of using neurotransmitters, they allow the direct passage of ions and electrical currents from one neuron to the next. This is possible thanks to structures known as gap junctions.

Function

The primary function of a synapse is to pass signals from one neuron to the next. These signals can be either excitatory or inhibitory. Excitatory signals push the neuron closer to triggering an action potential, or 'firing'. Inhibitory signals do the opposite – they decrease the likelihood that the neuron will fire.

Clinical significance

Synapses play a crucial role in the function of the nervous system and thus have a significant clinical relevance. Abnormalities in synaptic function can lead to a variety of disorders, including Alzheimer's disease, Parkinson's disease, schizophrenia, and autism.

See also

• Neuron
• Neurotransmitter
• Axon
• Gap junction

Synapse

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  Diagram of a synapse
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  Neuro-muscular junction
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  Active zone of a synapse
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  Chemical synapse schema