NEURONAL SYNAPSIS: what it is, types and how it works

The transfer of information between nerve cells is carried out by neurotransmitters, whose message is recognized by the recipient cell and translated into biological responses in a specialized structure called "synapse". All nervous activities, from the simplest reflected activities to higher functions, such as learning and memory, depend on the transfer of information between nerve cells and, therefore, the number of synapses and the efficiency of each synapse in releasing the neurotransmitter. Synaptic transmission plays a key role in understanding the functioning of the nervous system, and in this Psychology-Online article we will take a closer look what is a neural synapse, the different types and how it works.

Index

1. What is the neuronal synapse
2. Structure of the neuronal synapse
3. Types of neuronal synapses and how they work
4. How to improve neuronal synapse

The definition of neuronal synapses says synapses are the

Neurons are made up of a larger central part, the cell body, and subtle "tentacles" (the axons) that reach out to other neurons. Along the axons, the nerve impulse travels that will be transformed into instructions for the organism. These "tentacles", in their terminal part, are made up of unions in charge of transmitting (by means of impulses and particular substances) the information, touching the nearby cells. They are the synapses and there are thousands for each neuron (between 5,000 and 100,000). The Nobel Prize in Medicine christened them "synapsis" Charles Scott Sherrington, in 1897. And only in the middle of the 20th century were they "photographed" for the first time, thus giving a first visual proof of their existence.

There are different types of neurons with different structures and functions.

Each nerve cell (neuron) is made up of a wider part, the cell body, and of filaments, called axons, along the throughout which the nerve impulse spreads thanks to small and brief changes in the electrical potential of the membrane mobile. The filaments end in an enlarged area, called synaptic button, which generally rests or is very close to the cell body of another neuron. The signal transfer between excitable cells takes place in these specialized regions, and more precisely the cell that sends the signal is called a presynaptic cell, while the one that receives it is called a postsynaptic cell. The space that physically separates the two communicating cells is the intersystemic space or synaptic cleft.

According to communication strategies, synapses are divided into two types:

Electrical synapses

Electrical synapses are found in the Central Nervous System, in smooth muscle and cardiac tissue and neuroendocrine tissues. In electrical synapses the cells are separated by a synaptic cleft 2-4 nm, therefore so narrow that it can be considered a virtual space. Indeed, it can also be stated that between pre and postsynaptic cells there is a true electrical continuity guaranteed by the presence of gap junctions.

Electrical synapses can pass current in both directions and it's a kind of very fast transmission, because the result of a direct passage of current from the presynaptic element to the postsynaptic element (the delay with which the postsynaptic cell responds by producing an action potential is a few tenths of a millisecond). Therefore, electrical synapses are located in areas of the central nervous system and in tissues where cells must generate synchronous action potentials to carry out their task.

How does the electrical neural synapse work? Electrical synapses directly communicate the interior of the presynaptic cell with the interior of the postsynaptic cell. The cells, in this case, are joined by ion channels very low resistance, which allow the passage of ion currents induced by the action potential. Nerve transmission through electrical synapses is very fast, almost immediate. Its function includes the coordination of cardiac action potentials, the synchronization of the Neural electrical activity, metabolite exchange, and passage of signal molecules from a cell to another.

Chemical synapses

At chemical synapses, the arrival of an action potential to the presynaptic cell triggers the release of a neurotransmitter which determines the electrical response in the postsynaptic element. In the case of chemical synapses there is a relatively wide synaptic cleft (20-40 nm), as well as structural specializations that allow distinguishing the presynaptic element from the postsynaptic.

• The presynaptic cell it is characterized by an esocitotic system and synaptic vesicles.
• The postsynaptic neuron it is characterized by the presence of receptor molecules for the neurotransmitter located in the region of the plasma membrane facing the presynaptic cell. This specialization of the pre and postsynaptic element makes transmission by chemical synapses is unidirectional.

How does the chemical neuronal synapse work? At chemical synapses, the two cells are not in contact with each other, but they are seperated by a small space (0.03 μm), called a synaptic fissure. The presence of this interruption makes the direct passage of ionic currents impossible, therefore, in order to continue its journey, the impulse must "change its identity". Thus, the electrical signal becomes a chemical signal and traverses the synaptic space in this form, to later be converted back into an electrical impulse.

Today it has been shown that specific experiences can increase the number of synapses per neuron, as an effect of axonal stimulation and a dendrite growth process. In favor of this hypothesis, it is interesting to note that, for example, cognitive therapy and stimulating experiences increase the number of synapses and how, in view of the role of synaptic enhancement phenomena in learning processes, it is possible to affirm that neuronal remodeling, activated by cognitive therapy, constitutes a true process of "reabsorption synaptic ". In these articles you will find more information about How does the nervous system work Y how the human brain works.

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