The nervous system functions due to the interaction of two processes - excitation and inhibition. Both are the form of activity of all neurons.
Excitation is a period of vigorous activity of the body. Outwardly, it can manifest itself in any way: for example, muscle contraction, salivation, students' answers in the lesson, etc. Excitation always gives only an electronegative potential in the tissue excitation zone. This is his indicator.
Braking is just the opposite. It sounds interesting that inhibition is caused by excitation. With it, nervous excitement temporarily stops or weakens. When braking, the potential is electropositive. Human behavioral activity is based on the development of conditioned reflexes (UR), the preservation of their connections and transformations. This becomes possible only when there is excitation and inhibition.
The predominance of excitation or inhibition creates its own dominant, which can cover large areas of the brain. What happens first? At the beginning of excitation, the excitability of the cerebral cortex increases, which is associated with a weakening of the processinternal active braking. In the future, these normal force relationships change (phase states arise) and inhibition develops.
What is braking for
If for some reason the vital significance of any conditioned stimulus is lost, inhibition cancels its effect. It thus protects the cells of the cortex from the action of irritants that have passed into the category of destructive and become harmful. The reason for the occurrence of inhibition lies in the fact that any neuron has its own working capacity limit, beyond which inhibition occurs. It is protective in nature because it protects nerve substrates from destruction.
Types of braking
Inhibition of conditioned reflexes (TUR) is divided into 2 types: external and internal. External is also called innate, passive, unconditional. Internal - active, acquired, conditional, its main feature is an innate character. The innate nature of unconditioned inhibition means that for its appearance it is not necessary to specially develop and stimulate it. The process can occur in any department of the central nervous system, including the cortex.
The reflex of limiting inhibition is unconditioned, i.e., congenital. Its occurrence is not associated with the reflex arc of the inhibited reflex and is outside it. Conditional inhibition is developed gradually, in the process of SD formation. It can only occur in the cerebral cortex.
External braking is divided, in turn, into induction and out-of-limit braking. The internal aspect includes fading, delayed,differential braking and conditional braking.
When external inhibition occurs
External inhibition occurs under the influence of stimuli outside the working conditioned reflex. They are outside the experience of this reflex, at first they can be new and strong. In response to them, an indicative reflex is first formed (or it is also called a reflex to novelty). The response is excitement. And only then it slows down the existing SD until this extraneous irritant ceases to be new and disappears.
Such extraneous stimuli most quickly extinguish and slow down the newly established young URs with weak strengthened ties. Strongly developed reflexes are extinguished slowly. Fading inhibition can also occur if the conditioned signal stimulus is not reinforced by the unconditioned one.
State expression
Excessive inhibition in the cerebral cortex is expressed by the onset of sleep. Why is this happening? Attention is weakened by monotony, and the mental activity of the brain decreases. M. I. Vinogradov also pointed out that monotony leads to rapid nervous exhaustion.
When prohibitive braking appears
It develops only with stimuli exceeding the limit of neuron performance - superstrong or several weak stimuli with total activity. This is possible with prolonged exposure. What happens: prolonged nervous excitementviolates the existing “law of force”, which states that the stronger the conditioned signal, the stronger the reflex arc appears. That is, the process is first spurred on. And already further, the conditioned reflex reaction with a further increase in strength gradually declines. After stepping over the limits of the neuron, they turn off, protecting themselves from exhaustion and destruction.
So, such extreme braking occurs under the following conditions:
- The action of a normal stimulus for a long time.
- A strong irritant acts for a short time. Transmarginal inhibition can also develop with mild stimuli. If they act simultaneously, or their frequency increases.
The biological significance of unconditional transcendental inhibition comes down to the fact that exhausted brain cells are provided with a respite, rest, which they badly need, for their subsequent vigorous activity. Nerve cells are designed by nature to be the most intense for activity, but they are also the fastest to tire.
Examples
Examples of extreme inhibition: a dog developed, for example, a salivary reflex to a weak sound stimulus, and then began to gradually increase it in strength. The nerve cells of the analyzers are excited. Excitation first increases, this will be indicated by the amount of saliva secreted. But such an increase is observed only up to a certain limit. At some point, even a very strong sound does not cause saliva, it will notstand out completely.
Ultimate excitation has been replaced by inhibition - that's what it is. This is an extreme inhibition of conditioned reflexes. The same picture will be under the action of small stimuli, but for a long time. Prolonged irritation quickly leads to fatigue. Then neuron cells slow down. An expression of such a process is sleep after experiences. This is a defensive reaction of the nervous system.
Another example: a 6-year-old child is involved in a family situation where his sister accidentally knocked over a pot of boiling water on herself. There was a commotion in the house, screams. The boy was very frightened and after a short time of strong crying he suddenly fell deeply asleep on the spot and slept all day, although the shock was still in the morning. The nerve cells of the baby's cortex could not endure excessive stress - this is also an example of transcendental inhibition.
If you do one exercise for a long time, then it doesn't work anymore. When classes are long and tedious, at the end his students will not answer correctly even easy questions that they had no problem overcoming at first. And it's not laziness. Students at a lecture begin to fall asleep when the lecturer's monotonous voice or when he speaks loudly. Such inertness of cortical processes speaks of the development of limiting inhibition. For this, breaks and breaks between couples for students were invented at school.
Sometimes strong emotional outbursts in some people can end in emotional shock, a stupor, when they suddenly become constrained and quiet.
In a family with small children, the wifeshouting demands to take the children out for a walk, the children make noise, shout and jump around the head of the family. What will happen: he will lie down on the sofa and fall asleep. An example of extreme inhibition can be the starting apathy of an athlete before competing in competitions, which will negatively affect the result. By its nature, this inhibition is pessimal. Overlimiting braking performs a protective function.
What determines the performance of neurons
The excitability limit of neurons is not a constant. This value is variable. It decreases with overwork, exhaustion, illness, old age, the effect of poisoning, hypnotization, etc. Limiting inhibition also depends on the functional state of the central nervous system, on the temperament and type of the human nervous system, its balance of hormones, etc. That is, the strength of the stimulus for each person individual.
Types of external braking
The main signs of transcendent inhibition: apathy, drowsiness and lethargy, then consciousness is disturbed by the type of twilight, the result is loss of consciousness or sleep. The extreme expression of inhibition is the state of stupor, unresponsiveness.
Induction braking
Induction inhibition (permanent brake), or negative induction - at the moment of manifestation of any activity, a dominant stimulus suddenly appears, it is strong and suppresses the manifestation of the current activity, i.e., induction inhibition is characterized by the cessation of the reflex.
An example would bethe case when a reporter photographs an athlete lifting the barbell and his flash blinds the weightlifter - he stops lifting the barbell at the same moment. The shout of the teacher for a while stops the student's thought - an external brake. That is, in fact, a new, already stronger reflex has arisen. In the example of the teacher shouting, the student has a defensive reflex when the student focuses to overcome danger, and therefore is stronger.
Another example: a person had a pain in his arm and suddenly got a toothache. She will overcome the wound on her arm, because toothache is a stronger dominant.
Such inhibition is called inductive (based on negative induction), it is permanent. This means that it will rise and never subside, even with repetition.
Failing brake
Another kind of external inhibition that occurs in the form of SD suppression under conditions that lead to the emergence of an orienting reaction. This reaction is temporary, and the causal external inhibition at the beginning of the experiment ceases to operate later. Therefore, the name is - fading.
Example: a person is busy with something, and a knock on the door first causes him an indicative reaction "who is there." But if it is repeated, the person stops responding to it. When getting into some new conditions, it is difficult for a person to find his bearings at first, but, getting used to it, he no longer slows down when doing work.
Development mechanism
The mechanism of extreme braking is as follows - withan extraneous signal in the cerebral cortex appears a new focus of excitation. And it, with monotony, depresses the current work of the conditioned reflex according to the mechanism of the dominant. What does it give? The body urgently adapts to the conditions of the environment and the internal environment and becomes capable of other activities.
Phases of extreme braking
Phase Q – initial deceleration. The man so far only froze in anticipation of further events. The received signal may disappear by itself.
Phase Q2 is the phase of active response, when a person is active and purposeful, responds to the signal adequately and takes action. Focused.
Phase Q3 - extreme inhibition, the signal continued, the balance was disturbed, and the excitation was replaced by inhibition. The person is paralyzed and lethargic. There are no more jobs. It becomes inactive and passive. At the same time, he may begin to make blunders or simply “turn off”. This is important to consider, for example, for developers of alarm systems. Excessively strong signals will only cause the operator to brake instead of actively working and taking emergency action.
Outrageous inhibition protects nerve cells from exhaustion. For schoolchildren, such inhibition occurs in the lesson when the teacher explains the educational material from the very beginning in a too loud voice.
Physiology of the process
Physiology of transboundary inhibition is formed by irradiation, spillage in the cerebral cortex of inhibition. In this case, most of the nerve centers are involved. Excitation is replaced by inhibition in its most extensive areas. The very transcendentinhibition is the physiological basis of the initial distraction, and then the inhibitory phase of fatigue, for example, in students in a lesson.
External braking value
The meaning of transcendental and induction (external) braking is different: induction is always adaptive, adaptive. It is related to a person's response to the strongest external or internal stimulus at a given time, whether it be hunger or pain.
Such adaptation is most important for life. To feel the difference between passive and active inhibition, here is an example: a kitten easily caught a chick and ate it. A reflex has developed, he begins to throw himself at any adult bird in the same hope of catching it. This fails - and he switches to the search for prey of a different kind. The acquired reflex is actively extinguished.
The value of the limit of neuron performance even for animals of the same species does not match. As do people. In animals with a weak central nervous system, old and castrated animals, it is low. Its decrease was also noted in young animals after prolonged training.
So, transcendental inhibition leads to a numbness of the animal, the protective reaction of inhibition makes it invisible in case of danger - this is the biological meaning of this process. It also happens in animals that the brain turns off almost completely during such inhibition, even leading to imaginary death. Such animals do not pretend, the strongest fear becomes the strongest stress, and they really seem to die.
