Presynaptic and severe braking

The Processes of inhibition in the Central nervous system (CNS) was presented as a scientific discovery in 1962 by I. M. Sechenov. The researcher noticed this phenomenon when studying the bending reflex of the frog, excitation of which regulate chemical reactions of irritation in secondary areas of the brain. Today it is recognized that this behavior of the nervous system is essential for the protective reactions of the organism. While modern scholars identify the different stages and characteristics of this process. Special attention is given presynaptic and severe the braking, which have different impacts on the coordination of reflexes and performing their protective function in nerve cells.

The Process of inhibition in the CNS as a biochemical reaction

Synapses are responsible for the regulation of excitation and irritation, mostly working with ferric chloride channels, opening them. On the background of this reaction before the ions can pass through the neural membrane. In this process it is important to understand the value of the Nernst potential for ions. It is equal to -70 mV, while the charge of the membrane of a neuron in a resting state is also negative, but corresponds to -65 mV. This difference causes the opening of channels ensuring the movement of negative ions from the extracellular fluid.

In the course of this reaction also varies and the membrane potential. For example, he may rise to the level of -70 mV. But also the opening of potassium channels can induce severe braking. Physiology with the processes of regulation of excitation in this case will be expressed in the movement of positive ions to the outside. They are gradually increasing negative potential as the loss of peace. In the end, both processes contribute to the increase of negative potentials, which causes the irritating reaction. Another thing that further charges can be controlled and external factors of regulation, which, in particular, sometimes have the effect of stopping a new wave of excitation of nerve cells.

Recommended

A tablet from worms – the relevance of the application for the person

How relevant today, drugs against worms in humans? What kind of creatures these worms, what are modern methods of treatment? We will try to answer these questions, since ignorance in this area is undesirable. Imagine a mummy, which is misleading in k...

What to do if you cracked skin on hands?

Each of us at least once in a lifetime encounter with a small, but very, when the crack the skin on the hands. At this time there are wounds of different sizes, which hurt and cause inconvenience, especially when in contact with water or detergents. ...

Spray Macho man - the key to a proper relationship between the two spouses

Male impotence is a pathological condition associated with abnormal physiological capacity of the penis to reginout and bring sexual partner pleasure in bed.sex impotenceimpotence may not men to pass unnoticed – it usually spoils his nervous sy...

Presynaptic inhibition processes

Such reactions provoke the inhibition of nerve impulses in the axonal endings. In fact, the place of their occurrence led to the name of this type of braking – they precede the channels, interacting with synapses. Active link are exactly axonal elements. By stimulating the cell is sent a foreign axon, releasing the brake mediator. The latter has an impact on the postsynaptic membrane, causing it the process of depolarization. The result is a braking input from the synaptic gap into the excitation of the axon, the release of neurotransmitter is reduced and comes short of stopping the reaction.

Just at this stage, it is sometimes severe braking which can be represented as re. It develops in cases when the primary excitation process on the back of strong depolarization does not stop under the influence of multiple impulses. As to the presynaptic completion of the reaction, it reaches its peak after 15-20 MS and lasts 150 MS. Blocking such inhibition is provided by a convulsive poisons – picrotoxin and Bakulina opposing the mediators of the axon.

Localization in the departments of the Central nervous system may also differ. As a rule, presynaptic processes occur in the spinal cord and other structures of the brain stem. A side effect of the reaction may increase synaptic bubbles that are released by neurotransmitters in stimulating environment.

Types of presynaptic inhibition processes

Usually provided with lateral and reverse reactions of this type. Moreover, the structural organization of both processes is largely converges with postsynaptic inhibition. Their fundamental difference is due to the fact that the excitation stops not on the neuron and on the way to his body. When lateral inhibition of the chain reaction is characterized by an influence not only on the target neurons, in respect to which there is arousal but also in neighboring cells that initially may be weak and not inflamed. This process is called lateral for the reason that the area where the excitation is localized in the lateral parts relative to the neuron. Similar phenomena occur in sensory systems.

As for the reactions of reverse type, for example, especially notable is the dependence of the behavior of nerve cells from the source of pulses. In some ways the opposite of this reaction can be called severe braking. Physiology of the Central nervous system in this case determines the dependence of the excitation not only on sources, but from the frequency of the stimulus. Reverse the inhibition suggests that the target neurons will be sent mediators axons across multiple channels and collaterals. This process is implemented on the principle of negative feedback. Many researchers note that it is required for the possibility of self-regulation of excitation of neurons to the prevention of convulsive reactions.

The mechanism of the severe inhibition

While the above presynaptic process is determined through the interaction of individual cells with other sources of irritation, in this case, the key factorwill be the response of neurons to excitation. For example, with frequent rhythmic impulses to muscle cells can respond to increased irritation. This mechanism is also called severe braking Vvedensky by the name of the scientist who discovered and formulated this principle of the interaction of nerve cells.

To get started is to emphasize that each nervous system has its own optimal threshold of excitation, stimulated by irritation of a certain frequency. With the increasing rate pulses will increase and tetanic contraction of the muscles. Moreover, there is a higher frequency at which the nerves stop being irritated and will enter into a stage of relaxation, despite the continuation of the excitatory processes. The same thing is happening with the reduction in the intensity of the action of mediators. You could say it's the reverse recovery mechanism severe braking. The physiology of synapses in this context, it is necessary to consider the characteristics of lability. Synapses this figure is lower than in muscle fibers. This is due to the fact that the stream is caused by the excitation processes of the release and the further splitting of the mediator. Again, depending on the specific behavior of a particular system of such a reaction can occur with different speeds.

What is the optimum and pessimum?

On the mechanism of transition from excitation to inhibition is influenced by many factors, most of which are associated with the characteristics of the stimulus, its strength and frequency. The onset of each wave you can change the settings lability, and this correction be and the current state of the cell. For example, severe braking can occur when the muscle is in accultation or refractory phase. These two States are defined and the concepts of optimum and pessimum. As to the first, in this case, the pulse characteristics correspond to the index of lability of cells. In turn, pessimum suggests that the lability of the nerve is lower than that of muscle fibers.

When pessimum a result of previous irritation can be a sharp decrease or complete blockage of the transition of excitatory waves from nerve endings to the muscle. In the end, there will be no tetanus and come severe braking. Optimum and pessimum in this context are distinguished by the fact that at the same parameters of irritation muscle behavior will be expressed or contraction, or relaxation.

By the way, the optimum forces are just referred to as the maximum reduction of the fiber at the optimum frequency of excitatory signals. However, the increase and even double the increase in potential exposure would not lead to a further reduction, but on the contrary – will reduce the intensity and after a while will cause the muscle to a state of tranquility. There are, however, protivopolozhnye reaction excitation without annoying mediators.

Conditional and unconditional inhibition

For a more complete understanding of responses to irritation is to consider two different forms of inhibition. In the case of a conditioned response it is assumed that the reflex is due to weak or missing reinforcement from the unconditioned stimuli.

We should also consider differentiating the conditional braking, which will be a selection of healthful stimulus. The choice of optimal excitation source is caused by previous experience of interaction with familiar stimuli. If they change in the nature of positive action, reflex reactions will also cease their activity. On the other hand, unconditional severe inhibition requires cell instant and unambiguous response to irritation. However, intense and regular influence from the same pathogen tentative reflex is reduced and also through time reaction braking will be absent.

The Exceptions are stimuli that consistently carry important biological information. In this case, and reflexes will provide response signals.

The Importance of inhibitory processes

The Main role of this mechanism is to ensure the ability of synthesis and analysis in the CNS of nerve impulses. After signal processing there is a coordination of body functions, both among themselves and with the external environment. Thus, an effect of coordination, but it is not only the task of braking. So, considerable importance is security or protective role. It can be expressed in the oppression of the Central nervous system afferent unimportant signals on the background of severe braking. The mechanism and importance of this process can be expressed in coordinated work antagonistic centers, which eliminate the negative factors of excitation.

Reverse braking, in turn, may limit the pulse frequency of the motoneurons in the spinal cord, while performing protective and coordinating role. In one case, a harmonization of impulses motoneurons with the rate of contraction innervated muscles, and the other – prevents overstimulation of nerve cells.

Functional role of presynaptic processes

In the first place it is necessary to emphasize that the characteristics of the synapses are not permanent, so the consequences of inhibitioncan not be regarded as inevitable. Depending on conditions, they may occur with varying degrees of activity. In optimal condition the occurrence of severe braking likely to occur when increasing the frequency of pulses annoying, but as the tests show the influence of previous signals, the increased intensity can lead to the relaxation of muscle fibers. All of this suggests instability of the functional significance of inhibitory processes in the body, but also they depending on the conditions can be expressed quite specifically.

For example, at high frequencies the irritation may be long-term efficiency of interaction between individual neurons. So can occur the functionality of the presynaptic fibers and, in particular, its hyperpolarization activated. On the other hand, in the synaptic apparatus have the signs of depression postactivation that will be expressed in decrease in the amplitude of the excitation potential. This phenomenon can occur in synapses during severe braking on the background of increased sensitivity to the action of the mediator. So the effect of desensitization of the membrane. Plasticity of synaptic processes as a functional property can be determined and the formation of neural connections in the CNS, as well as their strengthening. Such processes positively impact on the mechanisms of learning and memory development.

Features of postsynaptic inhibition

This mechanism occurs at the stage when the mediator is released from the chain, resulting in a reduction in the excitability of membranes of nerve cells. As the researchers note, this kind of braking occur against the background of the primary giperpoliarizatia membrane of the neuron. This reaction provokes an increase in the permeability of the postsynaptic membrane. In the future, the hyperpolarization activated affects the membrane potential, bringing it to its normal balanced state – that is, the critical level of excitability decreases. It is possible to speak about transitional links in the chains of post - and presynaptic inhibition.

Severe reactions in a particular species could be present in both processes, but most of them characteristic of the secondary wave of irritation. In turn, postsynaptic mechanisms are developing graduale and leave of refractoriness. It is already the final stage of braking, although can occur and the reverse process of increasing excitability, if the effect of the additional pulses. Usually, finding the initial state of the neurons and the muscle fiber occurs along with a reduction of negative charges.

Conclusion

Braking is a special process in the Central nervous system, closely related to the factors of irritation and excitement. Despite all the activity the interaction of neurons, impulses and muscle fibers such reactions are quite natural and useful for the organism in nature. In particular, experts point to the importance of inhibition for people and animals as a means of regulation of excitation, coordination, reflexes and implementation of protective functions. The process is quite complicated and multifaceted. Describes the types of reactions that form its basis, and the nature of the interaction between participants is determined by the principles severe braking.

The Physiology of these processes is caused not only by the device of the CNS, but the cell interaction with external factors. For example, depending on the inhibitory neurotransmitter system can give different responses, sometimes with opposite value. It is due to this balance is provided by the interaction of neurons and muscle reflexes.

The research in this direction still leaves a lot of questions, as in the whole brain activity of man. But today it is obvious that the mechanisms of inhibition are an important functional component for the Central nervous system. Suffice it to say that without the natural regulation of the reflex system of the body will not be able to fully protect themselves from the environment, with it being in close contact.