Definition
The synaptic gap is a space between two communicating nerve cells that plays an important role in the transmission of action potentials (nerve impulses). In it a modulation of signal transmission takes place, which has a great pharmacological importance.
Construction of a synaptic cleft
A synapse is the transition between two nerve cells or a nerve cell and a muscle cell. The latter is a special form of synapse and is also called motor end plate. However, it is important that there is no direct contact between the two cells, i.e. that there is an interruption, which is called a synaptic gap.
Electrical signals are conducted via nerve cells in order to excite another nerve cell or muscle cell, for example. An excited nerve cell, in turn, passes on the signal, while an excited muscle contracts. Since, as already described, there is no direct contact between the cells, the signal must cross the gap in another way.
This happens with the help of messenger substances, also called neurotransmitters, e.g. acetylcholine, serotonin or dopamine. If an electrical excitation (thus a signal) arrives, then these messengers are released from the presynaptic membrane (cell membrane of the first nerve cell) and diffuse to the postsynaptic membrane (cell membrane of the second nerve or muscle cell), to which the signal is transferred. Here, the transmitters can bind to specific receptors of the postsynaptic membrane and induce excitation.
Tasks of a synaptic cleft
As described above, synapses serve to transfer excitation from one cell to the next. However, due to the structure already described, the signal transfer only works in one direction: Presynapse to postsynapse. Retrograde conduction is therefore not possible and the flow of information is thus directed. However, it is also important that there are not only excitatory synapses, but also so-called inhibitory ones. Here the presynaptic neuron (nerve cell) releases transmitters that do not excite the following neuron but inhibit it.
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