synapse

Definition

Target type: cellularcomponent

The junction between an axon of one neuron and a dendrite of another neuron, a muscle fiber or a glial cell. As the axon approaches the synapse it enlarges into a specialized structure, the presynaptic terminal bouton, which contains mitochondria and synaptic vesicles. At the tip of the terminal bouton is the presynaptic membrane; facing it, and separated from it by a minute cleft (the synaptic cleft) is a specialized area of membrane on the receiving cell, known as the postsynaptic membrane. In response to the arrival of nerve impulses, the presynaptic terminal bouton secretes molecules of neurotransmitters into the synaptic cleft. These diffuse across the cleft and transmit the signal to the postsynaptic membrane. [GOC:aruk, ISBN:0198506732, PMID:24619342, PMID:29383328, PMID:31998110]

A synapse is a specialized junction between two neurons or between a neuron and a target cell, such as a muscle cell or gland. It is the site of communication between these cells, allowing for the transmission of electrical or chemical signals. The cellular component of a synapse can be broadly divided into two parts: the presynaptic terminal and the postsynaptic terminal.

**Presynaptic Terminal**
- The presynaptic terminal is the end of the axon of the neuron that is sending the signal. It contains synaptic vesicles, which are small, membrane-bound sacs that store neurotransmitters.
- The presynaptic terminal also contains a complex of proteins that are involved in the release of neurotransmitters into the synaptic cleft. This process is triggered by the arrival of an action potential at the presynaptic terminal.
- The presynaptic terminal is also rich in mitochondria, which provide the energy needed for the synthesis and release of neurotransmitters.

**Postsynaptic Terminal**
- The postsynaptic terminal is the part of the neuron or target cell that receives the signal. It contains receptors that bind to neurotransmitters released from the presynaptic terminal.
- The binding of neurotransmitters to receptors triggers a change in the electrical or chemical state of the postsynaptic cell. This change can lead to the generation of an action potential in the postsynaptic neuron or a change in the activity of the target cell.
- The postsynaptic terminal also contains a complex of proteins that are involved in the regulation of synaptic transmission. These proteins can modulate the sensitivity of receptors, the amount of neurotransmitter released, or the rate of neurotransmitter degradation.

**Synaptic Cleft**
- The synaptic cleft is a narrow space between the presynaptic and postsynaptic terminals. It is filled with extracellular fluid that contains neurotransmitters, enzymes, and other molecules.
- The synaptic cleft is the site of communication between the presynaptic and postsynaptic terminals. Neurotransmitters released from the presynaptic terminal diffuse across the synaptic cleft and bind to receptors on the postsynaptic terminal.

**Other Structures**
- In addition to the presynaptic and postsynaptic terminals, a synapse may also contain other structures, such as astrocytes, which are glial cells that provide support for neurons and help to regulate synaptic transmission.
- The cellular components of a synapse are highly specialized and work together to ensure the efficient and precise transmission of signals between neurons or between neurons and target cells.'
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Proteins (190)

Compounds (3,181)