27.06.2019

Excitation of the cerebral cortex. Inhibition in the cerebral cortex. Mechanisms of sleep occurrence

The formation of any conditioned reflex in the form of a coordinated response act requires the excitation of some cortical nerve centers and inhibition of others. After repeated reinforcement of some and non-reinforcement of others, a strictly specialized reflex is developed precisely to the stimulus that was reinforced. So, excitation and inhibition are the basis of the activity of the cerebral cortex.

Two types of inhibition can develop in the cerebral cortex: unconditioned reflex (b/u) and conditioned reflex (u/p) inhibition (Fig. 13.2).

Fig. 13.2.

Inductive (external) inhibition occurs in cases when in the cortex cerebral hemispheres when an already developed conditioned reflex is triggered, a new, fairly strong focus of excitation appears, not associated with the reflex. For example, during breakfast the doorbell rang. As a result of the emerging indicative reaction food reflexes are inhibited. According to the mechanism of its occurrence, this type of inhibition is classified as congenital. A new strong focus of excitation in the cortex from an extraneous stimulus causes inhibition of the conditioned reflex (inductive inhibition according to Pavlov). Unconditioned inhibition is called external because the reason for its occurrence lies outside the structure of the conditioned reflex itself.

Increasing irritation or prolonging its action will lead to a decrease or complete disappearance of the effect. This effect is based on extreme inhibition, which I.P. Pavlov called it protective, since it protects brain cells from excessive consumption of energy resources. This type of inhibition depends on the functional state nervous system, age, typological characteristics, state of the hormonal sphere, etc. The limit of a cell’s endurance in relation to stimuli of varying intensity is called the limit of its performance, and the higher this limit, the easier the cells tolerate the effects of super-strong stimuli. Moreover we're talking about not only about the physical, but also about the informational power (significance) of conditioned signals.

This must be taken into account, for example, when determining the amount of work and the intensity of its implementation, especially when working with children. A child’s brain cannot always withstand an information attack. Overload can lead to fatigue and neuroses. Extreme case extreme braking-numbness that occurs under the influence of a super-strong stimulus. A person can fall into a state of stupor—complete immobility. Such conditions arise not only as a result of a physically strong stimulus (a bomb explosion, for example), but also as a result of severe mental shocks (for example, an unexpected message about a serious illness or death of a loved one).

Conditioned inhibition occurs when the conditioned stimulus ceases to be reinforced by the unconditioned, i.e. gradually loses its starting signal value. Such inhibition does not occur immediately, but develops gradually, is developed according to all the general laws of the conditioned reflex and is changeable and dynamic. Such developed inhibition occurs within the central nerve structures, therefore it is internal (i.e., not induced from the outside, but formed within a given temporary connection).

I.P. Pavlov divided conditioned inhibition into four types: extinction, differentiation, conditioned inhibition and delay.

Extinction inhibition develops if the conditioned reflex is not repeatedly reinforced unconditional stimulus. Some time after extinction, the conditioned reflex can be restored. This will happen if the action of the conditioned stimulus is again reinforced by the unconditioned one.

Extinction inhibition is a very common phenomenon and has a large biological significance. Thanks to it, the body stops responding to signals that have lost their meaning. Extinction can explain the temporary loss of work skills, playing skills musical instruments, fragility of knowledge of educational material if it is not consolidated by repetition. Extinction is the basis of forgetting.

Differential inhibition develops when stimuli that are similar in properties to the reinforced signal are not reinforced. This type of inhibition underlies the discrimination of stimuli. With the help of differential inhibition, from the mass of similar stimuli, the one that is reinforced is isolated, i.e. biologically significant. For example, a mother feeds her child with a silver spoon. The sight of this spoon evokes corresponding food reactions, but for some time the child was given medicine from a plastic spoon of a similar size and shape. The sight of a plastic spoon gradually begins to cause a negative reaction.

Thanks to differential inhibition, they distinguish sounds, noises, colors, shapes, shades of objects, similar houses, people, and choose the one they need from similar objects. Already from the first months of life, the child begins to develop various differentiations. This helps him navigate the outside world and isolate significant signal stimuli from it. Differential inhibition is based on the process of concentration of excitation in nerve centers.

Continuous, more subtle differentiation of the phenomena of the surrounding world constitutes important part a person’s thinking determines the possibility of learning. By differentiating verbal stimuli, their particular features necessary for the formation of new concepts are revealed.

IN independent species conditioned inhibition I.P. Pavlov identified a conditioned inhibitor, which is formed when a combination of a positive conditioned signal and an indifferent stimulus is not reinforced. The additional stimulus at the first moment of its application in combination with a positive signal causes an orienting reflex and inhibition of the conditioned reaction (induction inhibition), then turns into indifferent stimulus and finally, a conditioned inhibitor develops. If an additional stimulus has acquired these properties, then being attached to any other positive signal, it inhibits the conditioned reflex corresponding to this signal. So, having seen delicious sandwiches, we want to try them, but, much to our disappointment, we notice that a green fly, a carrier of infection, has landed on one of them. This causes an inhibition reaction of the food reflex.

This type of inhibition also allows for more flexible behavior depending on the action. various factors environment and the needs of the body, it underlies the ability to stop or not carry out actions in response to prohibitions. Examples of stimuli that cause a conditioned inhibitory reaction are the words “no”, “you can’t”, “stop”, “don’t do something”, etc. From this it is clear that the development of a conditioned brake plays a role important role in the formation of discipline, human behavior, and his ability to obey requirements and laws.

Delay inhibition. When developing this type of inhibition, reinforcement by the corresponding unconditioned reflex is not canceled as in previous types of inhibition, but is significantly delayed from the beginning of the action of the conditioned stimulus. Only the last period of action of the conditioned signal is reinforced, and the long period of its action preceding it is deprived of reinforcement. It is this period that is accompanied by inhibition of retardation. After its expiration, inhibition stops and is replaced by excitation - the so-called reflex phase. So, for athletes with the commands “Attention!”, “To the start!” all body functions are activated, as during the load itself, however, due to delayed braking, the athlete remains motionless at the start. When this inhibition is underdeveloped, he often makes false starts.

In children, delay is developed with great difficulty. The first grader impatiently reaches out his hand, waves it, and gets up from his desk. He knows the answer and wants the teacher to notice him. Only to the elder school age Children develop such qualities as endurance, the ability to restrain their desires, and willpower. The basis of these qualities is inhibition of delay.

Despite the apparent difference, all types of internal conditioned reflex inhibitions have a common similarity, which lies in the fact that they are all developed during repeated exposure to a conditioned reflex stimulus without reinforcement. Inhibitory and excitatory reflexes also have similarities. It lies in the fact that both conditioned reflexes are developed and are signal ones, but with some, excitation develops in the cerebral cortex - these reflexes are called positive; while others are based on inhibition, and they are called negative.

So, braking as one of the types nervous processes It has important in the life of the organism. It does two important functions: protective and corrective.

The protective (protective) role of inhibition is to change the excitatory process to another, more economical one - inhibition. When exposed to extremely strong stimuli, inhibition protects nerve cells from overstrain and exhaustion. Great importance has extreme inhibition in cell protection.

The corrective role of inhibition is to bring the reactions and reflexes performed by the body adequately in time and space into accordance with the conditions environment. So, if the developed conditioned reflex has ceased to be reinforced by the unconditioned one, and the conditioned stimulus continues to turn on and cause a significant reaction, in this case the body seems to be making a mistake. Its activities do not correspond to environmental conditions and are therefore uneconomical. This will continue until the conditioned reflex fades away, and the conditioned stimulus causes inhibition. Extinction inhibition corrects the activity of the cerebral cortex in accordance with changed environmental conditions.

Caffeine is one of the foods that generates so much controversy. Facilities mass media focus a lot of attention on this issue, since caffeine has many faces and is the main active substance. We propose to find out whether caffeine is harmful to human health.

People use natural caffeine as part of a drink or as part of medical supplies in synthesized form. Its main task is to stimulate the processes of excitation of the cerebral cortex, reports Joinfo.ua.
You will also be interested to know which five foods are harmful to human health.
The effectiveness of caffeine consumption is as follows:
- increased physical and mental activity;
- general endurance;
- progressive achievement of results;
- improvement of intellectual abilities;
- invigorating effect and lack of fatigue;
- an excellent antidepressant;
- for the prevention of numerous diseases;
- as a result of numerical studies, it has been proven that caffeine improves reproductive function men.
Be careful because exhaustion nerve cells, depends on the dose of caffeine consumed. In this aspect, extract individual approach. It is the vector of the amount of caffeine intake that is the stumbling block regarding its use in the medical environment.
Doctors about caffeine
Medicine demarcates age category regarding caffeine consumption. Young people have a state of health that allows them to drink a cup of coffee as a pleasure, regardless of its strength. But older people are careful about this, since it mainly concerns them blood pressure. A short-term rapid pulsation as a result of increased blood circulation is also possible. Possible provocation of a jump. The same factor is considered positive for of cardio-vascular system, pressure fluctuations protect against premature strokes.

And yet, frequent caffeine consumption is directly related to mental health person. Unmotivated aggression, frequent psychoses are the result of use large quantity caffeine
More troubles...
But regarding microelements, their absorption and leaching also depends on the consumption of caffeine. It interferes with the absorption of microelements such as calcium, sodium, iron, potassium, vitamins B1 and B6. The list can be continued. As a result, the following problems arise: teeth become fragile, they deteriorate due to a lack of calcium, which is washed out of the body. Back pain occurs and osteochondrosis develops. You may also be irritable and have a headache.
Let's pay attention to the dangers of caffeine for children's health and pregnant women. For them, caffeine causes partial harm because it interferes with the full development of the fetus. This applies to low weight, teeth and growth of the unborn child.

But for children it is important to consume foods such as chocolate and Coca-Cola. They also contain caffeine. By frequently consuming them, your children are harming their health. They are more whiny and aggressive, they have inappropriate behavior and frequent mood swings.
With systematic use, nerve cells are depleted, resulting in dependence on the product.
There is no general consensus regarding caffeine consumption.
Consume caffeine in moderation and early in the day. Be objective. Remember that your health depends on the dose of caffeine consumed.

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Publishing house "Enlightenment", M., 1973.

Presented with minor abbreviations

In the cerebral cortex of humans (and animals), two opposing nervous processes constantly occur: excitation and inhibition. Excitation occurs when any objects or phenomena, acting on the senses, cause irritations that are transmitted to the brain. This focus of excitation does not remain unchanged and motionless. Usually it radiates (spreads) and moves along the cerebral cortex.
At the same time, the opposite process occurs in the cortex - inhibition, which actively delays, inhibits or limits the excited area, causing its concentration, concentration in a narrower focus.
Excitation and inhibition are closely related. This connection is expressed, in particular, in the fact that if excitation appears in one part of the brain, then inhibition begins to appear around it. This phenomenon is called negative induction. Excitation occurs around the focus of inhibition in the cerebral cortex. This process is called positive induction of neural processes. (The name was given by Pavlov by analogy with the phenomenon of induction in physics.)
Inhibition can also occur as a result of fatigue. I.P. Pavlov believed that if this inhibition covers a significant part of the cerebral cortex and underlying parts of the brain, then the person falls into sleep. Such inhibition, according to Pavlov, protects the nerve cells of the brain from exhaustion and provides them with the necessary rest, at the same time restoring the strength of the entire body.
Sometimes during sleep, the inhibitory process does not involve the entire cortex of the cerebral hemispheres; some small areas of it remain somewhat excited. These are a kind of “guard points,” as Pavlov called them. Thus, a mother is fast asleep at the bedside of her child, but as soon as he moves or says a word in his sleep, she immediately wakes up.
There is also a type of sleepy state, the so-called hypnosis. With it, inhibition has a special character and, according to I.P. Pavlov, also turns out to be partial, not involving the entire cortex. This state can be induced artificially by putting a person to sleep through verbal suggestion (“you want to sleep, you are sleeping”), as well as through quiet hand movements in front of the person being hypnotized (so-called “passes”).
At the same time, some part of the brain remains excited in the cerebral cortex, thanks to which the euthanized person hears the words of the hypnotist. Since most of the cerebral cortex is in a state of inhibition, the hypnotized person cannot act independently and obeys the person who put him to sleep and does what he is ordered.
According to the latest research, during wakefulness, only a certain part of the nerve cells of the brain are excited, and the rest is in a state of inhibition. During sleep, cells seem to change roles: those that were excited are now resting. But excited areas also remain, thanks to which the brain of a sleeping person performs the functions necessary for the body.

In a number of athletes, the increase in excitability of the cerebral cortex can be so great that responses begin to generalize, excessive muscle tension appears, and a certain degree of disinhibition of the nerve centers occurs. More often, these phenomena occur in unprepared athletes. The figure shows electromyograms of athletes of the 3rd category, which reveal on the 4th day of arrival in the middle mountains the vagueness of “volleys” of excitation impulses, residual impulses in pauses between tensions.

The trainer can control the degree of excitability of the central nervous system using physical exercise and short-term ascents to high altitudes. Training work performed at a calm pace and with uniform speed, reduces the excitability of the cerebral cortex in those athletes who are in a state of excessive arousal. Short-term ascents to high altitudes can enhance the positive effect of mountain climate on functional state central nervous system.

Reducing the time when altering the signal value of stimuli, reducing the number of errors during the action of positive and negative stimuli, shortening latent period with the development of tension and relaxation skeletal muscles(LVH and LVR), increasing the number of movements per unit of time, i.e. increasing a person’s ability to quickly alternate muscle tension and relaxation, accelerating the process of adaptation of the visual analyzer to varying degrees illumination indicates an increase in the mobility of nervous processes. In doing so, we proceeded from the position put forward by B. M. Teplov (1956) that mobility in the broad sense of the word should be understood as all those aspects of the work of the nervous system to which the category of speed is applicable. At proper organization motor mode, training sessions enhance positive influence on the mobility of nervous processes.

The convergence of the values of LBH and LBP, the duration of “volleys” of excitation impulses and pauses between them, and the reduction in the number of errors during the action of positive and negative stimuli indicate an improvement in the balance of inhibitory-excitatory processes. Thus, training sessions in mid-mountain conditions in most cases quickly increase the mobility and balance of nervous processes, and have a beneficial effect on the properties of the nervous system, which is the most reliable indicator of nervous activity. However, in in some cases There was a violation of the ratio of inhibitory-excitatory processes. Athletes complained about poor muscle relaxation and the appearance of muscle rigidity. In these cases, the athletes did not adapt well to muscular activity, and special organization of their motor regime was required.

Electromyograms at arbitrary voltages
biceps brachii muscle of athletes
3rd category I-va and T-va

A - in the city of Frunze; B - at an altitude of 2100 m.

The study of the analyzer activity of the cerebral cortex showed that, in general, the conditions of mid-mountain conditions significantly impaired the functions of visual, motor and vestibular analyzers they don't call. During the initial period of acclimatization, the motor analyzer is most susceptible to adverse effects. At the same time, a significant proportion of athletes with an increase in height show an increase in visual acuity and field of vision, speed of adaptation to different conditions illumination, proprioceptive sensitivity is heightened, stability increases vestibular apparatus. These changes most often occur after the first 5-7 days of staying in the mountains and may indicate an improvement in the state of the athletes’ higher nervous activity and their readiness to begin performing heavy physical activity.

Thus, the results of our research on the influence of mid-mountain climate and physical work on the higher nervous activity of athletes is confirmed by the fact that the cerebral cortex is sensitive to a relatively small decrease in the partial pressure of oxygen (119-125 mm Hg) in atmospheric air. The direction of these changes largely determines the development of adaptation to muscular activity in the middle mountains.

"Srednegorye and sports training»,
D.A.Alipov, D.O.Omurzakov