A synapse is where the cell membranes of two adjacent cells communicate. It may be a nerve cell or an effector (i.e., executive organ) cell. It carries information in the nervous system and controls the work of secretory glands and muscles.
Synapses – types
Synapsy they are divided according to the type of cells between which the signal is transmitted and the way the impulse is transmitted.
In the case of cell types, division is as follows:
- nerve-nerve – connect two nerve cells with each other,
- neuromuscular – connect the nerve and muscle cells,
- neuroglandular – connect the nerve and gland cells with each other.
Due to the way the impulse is transmitted synapses are divided into two types – electrical and chemical.
Chemical synapse
W synapsach this type of distance between cells is approx. 20 nanometers, and the space created between them is the so-called synaptic cleft. The tip of a presynaptic neuron is called the synaptic flask. It produces neurotransmitters, i.e. mediators. There are currently 60 known compounds that perform this function, and they are divided into stimulating or inhibiting the excitation of an action potential. Mediators bind to the receptor, resulting in depolarization of the postsynaptic membrane. They are essential for the fast impulse transmission. The main inhibitory neurotransmitter is γ-aminobutyric acid (GABA), and the excitatory one is glutamic acid.
As soon as the nerve impulse reaches the end of the axon, ion channels are opened. They selectively introduce calcium ions, which activates the migration of presynaptic vesicles containing serotonin, adrenaline, histamine, acetylcholine, i.e. the so-called mediator. By exocytosis, they release their contents into the synaptic cleft, opening channels for sodium ions. This results in depolarization of the postsynaptic membrane.
When the depolarization reaches a threshold value, further voltage-sensitive sodium channels open up, creating an action potential. This induces a wave that travels through the entire neuron. Since there are prescriptions on the presynaptic membrane for reuptake of the mediator, the molecules only work for a certain period of time.
Electrical synapse
Electrical synapses they work differently than chemical ones because there are no neurotransmitters in them. The process of transferring the depolarization of the presynaptic membrane to the postsynaptic membrane takes place via the gap junction between nerve cells. The gap between the presynaptic and postsynaptic flasks is approximately 3,5 nm wide. The pulse produced by electrical synapses is almost a thousand times faster than that produced by chemical synapses, but cannot be amplified.
The transmitted information is in the form of inorganic ions. It can flow in both directions between neurons. Examples of inorganic ions that transmit information are Na +, Ca +, and H +.
Synapses in medicine
In modern medicine, knowledge about the mechanism of synaptic conduction allows the regulation of processes in the body through pharmacological agents. This enables, among other things, the treatment of nervous and somatic diseases.
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