What is a mediator: definition, types and functions
In this article we will look at the answer to the question, what are mediators? The main attention will be paid to the definition of neurotransmitters, which are located in our brain and cause various emotional manifestations, behavioral reactions of the subject, etc. In particular, we will get acquainted with the definition of the term, species diversity and impact.
What is a mediator?
Answering this question, it will be important to learn that this concept exists in different spheres of human activity. Mediators can be as follows:
- Neurotransmitter - a chemically active substance of biological nature necessary for the transmission of nerve impulses between cells.
- Mediator - a device for musical instruments, in particular, for the guitar.
- A mediator is a design pattern.
- The mediator is a 3rd neutral person, a subject who mediates in a conflict and / or a dispute and tries to help resolve it.
- In a computer, a mediator is the process of using and managing the work of saving data during a procedure to stop or start a certain service.
- Mediators of circulating and secreted allergy are participants in immune response. However, in addition to allergies, there are other manifestations of the mediator's effect on the body.
Mediator also called drugs of medicinal origin, in particular, they call it "Benfluorex". Nerve mediators perform the function of transporting signals through specific cells that form our CNS and PNS.
The neurotransmitter is ...
Neurotransmitters are substances of biological origin. They are chemically active and act as intermediaries in the process of transmitting electro-chemical impulses from nerve cells through the synaptic spaces between neutrons to other cells, but located in different parts of the path of the reflex arc (the path of the nerve impulse). When a nerve impulse enters a presynaptic ending, the mediator is released into the synaptic target.
More on the interaction mechanism
Molecules represented by mediators are able to react with some types of receptor proteins that make up the cell membrane. This interaction leads to the initiation of a chain of reactions of a biochemical nature. There is a change in the intermembrane flow of ions, which causes the depolarization of the membrane and the further emergence of the action potential. For example, an unconditioned reflex, in which a person removes a hand from a hot object, is a process of nerve cell activity and transmission of an electrical impulse with its further analysis and solving the “problem” in the form of a response signal, is carried out during signal transmission between cells, as described above .
Mediators of the nervous system are one of the main systems of our body, which in the course of evolution allowed man to achieve a similar level of organization.
All neurotransmitters, as a rule, are divided into three groups: peptides, monoamines and amino acid molecules. The most prominent representatives of amino acids are:
- GABA (gamma-aminobutyric acid) is the main neurotransmitter of the CNS responsible for the inhibitory functions of any mammal, including humans.
- Glycine - has a double amino acid effect. Glycine receptors are located almost throughout the spinal cord and brain. Establishing communication with the receptor, this substance causes the "inhibition" effects on neurons. It also reduces the amount of production of "exciting" a number of amino acids from neural cells. Glycine affects the release of GABA, increasing the performance of this neurotransmitter. It also allows for the process of transmitting a signal from glutamates and aspargates, which stimulate neurotransmitters. For the spinal cord, glycine acts as a mediator, inhibiting the reaction of motoneurons.
- Glutamic acid is a neurotransmitter of the excitatory type, the most common mediator of the nervous system of any vertebrate animal. Most of it is in the cerebellum and spinal cord.
- One of the types of mediators is represented by aspartic acid molecules (aspargate). They are responsible for the excitation of neurotransmitters located in the cerebral cortex.
The concept of catecholamines
Answering the question what mediators are and what types they are, it will be important to mention catecholamines. Substances of this class are divided into hormones such as:
- Adrenaline is an exciting neurotransmitter. His role in synaptic transmissions currently remains not completely clear. This also applies to bombesin, bradykinin, carnosine, neurotensin, somatostatin, cholitsetokinin and VIP.
- Norepinephrine - a mediator of "wakefulness." He is a participant in the process of the rise of the reticular active system (reticular formation, which is responsible for maintaining constant excitation in the brain of the head). This mediator is characteristic of a bluish spot located in the brainstem, as well as for the end regions of the sympathetic nervous system. There are very few noradrenergic neurons in the CNS, however, they have a wide field of innervation.
- Dopamine is a chemical factor in internal maintenance; is a significant component of the system responsible for promoting the consciousness of the subject. Able to evoke a feeling of pleasure at different levels (anticipation or specific satisfaction), which plays an important role in the processes of motivation and / or learning.
A variety of monoamines
One more point, important when getting acquainted with the answer to the question of what mediators are, will be the description of monoamines.
Typical monoamines are histamine and serotonin. Histamine we have already defined above, but it is worth adding that its various lipophilic antagonists may have sedative properties. This is due to their ability to block histamine receptors.
Serotonin is a neurotransmitter of the CNS. Neurons of serotonergic action are collected in groups in the brain stem, namely, in the pons and suture nuclei. The brain has downward projections that descend further into the spinal cord. The neurons of the nucleus are responsible for feeding the ascending projections into the limbic system, the cerebellum, the basal ganglia and the cortex. The dorsal and medial neurons of the suture nuclei include axons, which differ among themselves in the final target of innervation, as well as in sensitivity to certain substances. An example of such compounds is methamphetamine.
There are many other types of mediators. For example, acetylcholine, adenosine triphosphate, anandamides, vasoactive intestinal peptides (VIP), tryptamines, taurine and endocannabionoids.Separately, it is worth mentioning the neurotransmitter NAAG - N-acetylaspartilgumate.
The functions of mediators depend on the characteristics of their chemical structure. They act as primary intermediaries, along with hormones. However, the process of their release and the device mechanism of action in a chemical synapse has a number of extremely important differences that distinguish them from hormones.
The system of mediators in the presynaptic cell vesicle, having a neurotransmitter, is able to release it at a local level into an extremely small synaptic cleft. The “liberated” molecule diffuses and establishes communication with a number of receptors located on the surface of postsynaptic membranes. Diffusion is a slow process, but the presence of such short distances separating the post- and presynaptic space (from 0.1 μm and less) allows this signal transmission to occur in a short period of time. This allows you to quickly set the signals between the neurons themselves and muscle tissue. The lack of certain mediators causes depression in various forms.
Inflammatory mediators are another type of mediators that are involved in the process of inflammation. The phenomenon of immunity is a general biological “incident”.Its brightest manifestation is observed at the stage of “local reaction”. This is the initial phase of the phenomenon. Alteration (a process similar to necrosis, but differing from it by the absence of cell death) causes the onset of many processes of a biochemical nature that help attract inflammatory mediators. Under their influence, a structural transformation of the tissue and its metabolic processes takes place. This allows inflammatory reactions to develop. These mediators are of two types: cellular and plasma. The last mediators work on the principle of a cascade device, activating each other.