The nervous system functions due to the interaction of two processes - excitation and inhibition. Both are a form of activity of all neurons.
Excitation is a period of active activity of the body. Outwardly, it can manifest itself as you like: for example, muscle contraction, salivation, students' answers in the lesson, etc. Excitation always gives only electronegative potential in the tissue excitation zone. This is his indicator.
Braking is the exact opposite process. It sounds interesting that inhibition is caused by excitement. With him, nervous excitement temporarily stops or weakens. When braking, the potential is electropositive. Behavioral activity of a person is based on the development of conditioned reflexes (SD), preservation of their connections and transformations. This becomes possible only with the existence of excitation and inhibition.
The predominance of arousal or inhibition creates its own dominant, which can cover vast 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 process of internal active inhibition. In the future, these normal force relationships change (phase states occur) and braking develops.
What is braking for?
If for some reason the vital value of a conditioned stimulus is lost, inhibition cancels its action. It thus protects the cortex cells from the action of stimuli that have become destructive and harmful. The reason for the inhibition is that any neuron has its own working capacity limit, beyond which inhibition will occur. 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. The external is also called innate, passive, unconditional. The internal is active, acquired, conditional, its main feature is an innate character. The inbornness of unconditional inhibition means that for its appearance it is not necessary to specifically develop and stimulate it. The process can occur in any department of the central nervous system, including in the cortex.
The reflex of outrageous inhibition is unconditional, i.e., innate. Its occurrence is not associated with the reflex arc of the inhibitory reflex and is located outside it. Conditional inhibition is developed gradually, in the process of formation of SD. It can occur only in the cerebral cortex.
External braking is divided, in turn, into induction and beyond braking. The internal view includes fading, delayed, differentiating braking and conditional braking.
When external braking occurs
External inhibition arises under the influence of outsiders to the working conditioned reflex of stimuli. 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). In response to it, excitement arises. And only then it slows down the existing SD until this extraneous stimulus ceases to be new and disappears.
Such extraneous stimuli most quickly extinguish and inhibit newly established young UR with weak hardened bonds. Well-developed reflexes are quenched slowly. Extinguishing inhibition can also occur if the conditioned signal stimulus is not reinforced with an unconditioned one.
State expression
Outrageous inhibition in the cerebral cortex is expressed by the onset of sleep. Why is this happening? Attention is weakened by uniformity, and the mental activity of the brain is reduced. M.I. Vinogradov also pointed out that monotony leads to rapid nervous exhaustion.
When beyond braking appears
It develops only with stimuli exceeding the neuron's functional limit — superstrong or several mild stimuli with total activity. This is possible with prolonged exposure. What happens: prolonged nervous excitement violates the existing "law of force", which states that the stronger the conditioned signal, the stronger the arc of the reflex. That is, the process is first boosted. And already further, the conditioned reflex reaction with a further increase in strength gradually goes into decline. After stepping over the limits of the neuron, they turn off, protecting themselves from exhaustion and destruction.
So, such prohibitive braking occurs under the following conditions:
- An ordinary irritant for a long time.
- A strong irritant acts for a short time. Outrageous inhibition can develop with mild irritants. If they act simultaneously, or their frequency increases.
The biological significance of unconditional beyond limiting inhibition comes to the fact that the exhausted brain cells are given a break, rest, which they urgently need, for their subsequent active activity. Nerve cells are conceived by nature as highly intense for activity, but they are also the most rapidly fatiguing.
Examples
Examples of transcendental inhibition: a dog developed, for example, a salivary reflex to a weak sound stimulus, and then gradually began to increase in strength. The nerve cells of the analyzers are excited. Excitation at first increases, the amount of saliva secreted will indicate this. But such an increase is observed only to a certain limit. At some point, even a very strong sound of saliva does not cause, it will not stand out at all.
The ultimate excitement gave way to inhibition - that is what it is. This is an outrageous inhibition of conditioned reflexes. The same picture will be with small stimuli, but for a long time. Long-term irritation leads to fatigue faster. Then the cells of the neurons slow down. An expression of such a process is a dream after experiences. This is a protective reaction of the nervous system.
Another example: a child of 6 years old is involved in a family situation, where his sister accidentally knocked over a pot of boiling water. Clutter rose in the house, screams. The boy was very scared and after a short time of strong crying, he suddenly fell asleep deeply in place and slept all day, although the shock was still in the morning. The nerve cells of the baby's cortex did not tolerate excessive stress - this is also an example of transcendent inhibition.
If you do one exercise for a long time, then it fails. When classes last long and tedious, in the end his students will not answer correctly even to light questions that they first overcame without problems. And this is not laziness. Students at the lecture begin to fall asleep with the monotonous voice of the lecturer or with his loud speech. Such an inertness of cortical processes indicates the development of transcendental inhibition. For this, school students have come up with breaks and breaks between couples.
Sometimes strong emotional outbursts in some people can end with emotional shock, stupor, when they suddenly become constrained and quiet.
In a family with small children, the wife screams for the children to be taken out for a walk, the children jabber, scream and jump around the head of the family. What will happen: he will lie on the sofa and fall asleep. An example of exorbitant braking is the athlete’s starting apathy before speaking at competitions, which will negatively affect the result. By its nature, this inhibition is pessimal. Outrageous braking performs a protective function.
What determines the working capacity of neurons
The excitability limit of neurons is not a constant. This value is changeable. It decreases with fatigue, exhaustion, illness, old age, the effects of poisoning, hypnotization, etc. Excessive 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 prohibitive inhibition: apathy, drowsiness and lethargy, then consciousness is disturbed like twilight, the result is a loss of consciousness or sleep. The extreme expression of inhibition is the state of stupor, areactivity.
Induction braking
Induction inhibition (constant brake), or negative induction - at the moment of the appearance of some activity, a dominant stimulus suddenly arises, it is strong and suppresses the manifestation of current activity, i.e., inductive inhibition is characterized by the termination of the reflex.
An example is the case when a reporter photographs an athlete lifting the barbell and his flash blinds the weightlifter - he stops lifting the barbell at the same time. The teacher’s cry stops the student’s thought for a while - an external brake. That is, in fact, a new, more powerful reflex arose. In the example with the teacher’s shout, the student has a defensive reflex when the student concentrates to overcome the danger, and therefore he is stronger.
Another example: a person had a sore arm and suddenly had a toothache. It will overpower the wound on the arm, because toothache is a stronger dominant.
Such inhibition is called induction (the basis in negative induction), it is constant. This means that it will occur and never weaken, even when repeated.
Dimming brake
Another type of external inhibition arising in the form of inhibition of SD under conditions that lead to the emergence of an indicative reaction. This reaction is temporary, and causal external inhibition at the beginning of the experiment ceases to act later. Therefore, the name is - fading.
Example: a person is busy with something, and knocking on a door first provokes an approximate reaction “who is there”. But if it repeats, a person ceases to respond to it. When it comes to some new conditions, it’s 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 transcendental inhibition is as follows - with a foreign signal in the cerebral cortex, a new focus of excitation appears. And with monotony, the current work of the conditioned reflex inhibits the dominant mechanism. What does it give? The body urgently adapts to environmental and internal conditions and becomes capable of other activities.
Outrageous Inhibition Phases
Phase Q - initial inhibition. So far, the man has stood still waiting for further events. Perhaps the incoming signal will disappear on its own.
Phase Q2 is a phase of active response when a person is active and purposeful, responds to the signal adequately and takes action. Focused.
Phase Q3 - beyond braking, the signal continued, the balance is disturbed, and the excitation is replaced by braking. The person is paralyzed and lethargic. There is no work anymore. It becomes inactive and passive. At the same time, he may start to make gross mistakes or simply “turn off”. This is important to consider, for example, for alarm system developers. Excessively strong signals will cause only a brake for the operator instead of active work and emergency measures.
Outrageous inhibition protects nerve cells from exhaustion. In schoolchildren, such inhibition occurs in the lesson, when the teacher explains the teaching material from the very beginning with a loud voice.
Process physiology
The physiology of transcendental inhibition is compiled by irradiation, spill inhibition in the cerebral cortex. In this case, most of the nerve centers are involved. Excitation is replaced by inhibition in its most extensive areas. Outrageous inhibition itself 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 significance of transcendental and induction (external) inhibition is different: induction is always adaptive, adaptive. It is associated with a person’s response to the strongest external or internal stimulus at a given time, whether it is hunger or pain.
Such adaptation is most important for life. To feel the difference between passive and active braking, here is an example: a kitten easily caught a chick and ate it. A reflex has been developed, he begins to throw at any adult bird in the same hope of catching. This fails and he switches to searching for a different kind of prey. The acquired reflex is actively quenched.
The magnitude of the limit of operability of neurons, even for animals of the same species, does not coincide. Like people. In animals with weak central nervous system, old and castrated animals, it is low. Its decrease was noted in young animals after prolonged training.
So, transcendent inhibition leads to the numbness of the animal, a protective inhibition reaction 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 with such inhibition, even leading to imaginary death. Such animals do not pretend, great fear becomes very stressful, and they really seem to die.