Pavlov identified two types of external and internal.

External (unconditional) inhibition is an innate property of the nervous system associated with the weakening or cessation of behavioral stimuli under the action of stimuli from the external environment. Unconditional braking characteristic of all parts of the nervous system, it does not need to be developed, it appears simultaneously with the onset of the orienting-exploratory, caused by an outsider new, and manifests itself in the weakening or oppression of others. Unconditional (innate) inhibition of SD is also called external, since the cause of its occurrence is outside the reflex arc of the inhibited reflex.

External braking mechanism: an extraneous signal is accompanied by the appearance in the cerebral cortex of a new focus of excitation, which, with an average strength of the stimulus, has a depressing effect on the current conditioned reflex activity by the dominant mechanism. External inhibition contributes to the emergency adaptation of the body to changing conditions of external and internal environment and makes it possible to switch to another activity, if necessary, in accordance with the situation.

Biological significance of external inhibition current conditioned reflex activity is reduced to creating the most favorable conditions for the flow in this moment more important for the body of the orienting-exploratory reflex caused by an emergency stimulus. Conditions are created for an urgent assessment of a new stimulus, for assessing its significance for the organism at a given moment and under given conditions. This is where the most important coordinating, ordering adaptive role of external inhibition in . This type of inhibition is based on negative induction (excitation in a new center causes inhibition in the former one).

There are two main types of unconditional inhibition:

Extinguishing brake , it is connected with the fact that conditioned reflex reactions are inhibited under the action of extraneous stimuli, under the influence of which both conditioned reflex and unconditional reflex reactions arise. In most cases, an orienting reaction occurs, which gradually fades with repeated action. EXAMPLE : A person constantly experiences the effect of a dying brake. The first knock on the door causes an indicative reaction that distracts the working person from his main occupation. But if you repeat this several times, then with each new knock on the door, its irritating effect weakens and, finally, completely disappears. In the life situation of schoolchildren, such a brake also occurs. A student in a new classroom may for some time "forget" a well-known educational material. But as soon as he “looks around”, he disappears, and new conditions cease to be a hindrance to him. Therefore, it is very important that children who are starting school life or continuing it in new conditions, had some time to look around and get used to these conditions, so that new conditions (orienting reactions to the situation, to the appearance of the teacher, etc.) did not prevent them from learning the lesson.

Permanent brake – this is such an additional stimulus that does not lose its inhibitory effect with repetition. This braking is called induction, because. its mechanism is based on negative induction and , and is constant because it always manifests itself, not weakening when it is repeated. A constant brake is important for the body, and therefore requires a person to take decisive measures to eliminate it, therefore, conditioned reflex activity is inhibited. EXAMPLE : . In a person with acute toothache, a small wound on the arm stops hurting, i.e. a stronger pain excitation suppresses a less strong one.

The same applies to unconditional inhibition. Extreme braking , which is based on persistent depolarization of the membrane, leading to the closure of sodium channels. develops with prolonged nervous excitation of the body, protecting against exhaustion, the activity of nerve cells is temporarily turned off, which creates a condition for normal excitability and performance. The main signs of this inhibition are: lethargy, drowsiness, twilight state, loss of consciousness, the extreme option is a state of stupor.

The physiological basis of this inhibition is the irradiation of inhibition through the cerebral cortex and part of the sequential induction (self-induction), in which the process of excitation is mostly replaced by inhibition, and inhibition covers large areas of the brain. Extreme inhibition itself is the physiological basis of distraction and the second (“inhibitory”) phase of student fatigue in the lesson. For the occurrence of this inhibition, the following conditions are necessary: ​​1) the action of an ordinary stimulus for a long time; 2) the action of a stimulus of great strength for a short time.

Limiting inhibition develops during prolonged nervous excitation of the body and under the action of an extremely strong conditioned signal or several weak ones, the strength of which is summed up. In this case, the “law of force” is violated (the stronger the conditioned signal, the stronger the conditioned reflex reaction) - the conditioned reflex reaction begins to decrease with increasing force. This is because cells have a certain limit of efficiency, and stimulation above this limit turns off neurons, thereby protecting them from exhaustion.

This inhibition has a protective value, since it prevents the debilitating effect on the nerve cells of excessively strong and prolonged irritation and protects the cells of the cerebral cortex from exhaustion and destruction. This property indicates that the cells of the cerebral cortex have the ability to protect themselves always and especially when the demands made by irritation cease to correspond to their performance. With excessive irritation or with normal, but prolonged, in the cells of the brain there is an outrageous inhibition. EXAMPLE : In training, when you do an exercise for a long time, then you can no longer do it. O Asking students after long and tiring classes leads to the fact that gradually each new question, instead of an active reaction, will cause oppression. In this state, the child soon ceases to answer even those questions that at the beginning of the lessons did not cause him any difficulties. The biological significance of such a reaction is to provide depleted brain cells with the necessary rest for subsequent vigorous activity.

Interaction different types internal inhibition. Different types of inhibition interact with each other. Two main types of interaction:

disinhibition – one inhibitory process destroys the other. The disinhibition of the inhibited reflex is created by an agent foreign to it and ends with the termination of its action. The release depends on the strength of the external brake. If the external brake is weak, then it leaves the UR unchanged. If the external brake is very strong, then all SDs are completely delayed. With an intermediate force of a conditional brake, the following variants of the result exist:

a) since the release depends on the strength of the developed internal braking, the stronger the internal braking of the SD is developed, the more difficult it is to release it;

Extreme braking

This type of inhibition differs from external and internal in terms of the mechanism of occurrence and physiological significance. It occurs when the strength or duration of the action of the conditioned stimulus is excessively increased, due to the fact that the strength of the stimulus exceeds the efficiency of the cortical cells. This inhibition has a protective value, as it prevents the depletion of nerve cells. In its mechanism, it resembles the phenomenon of "pessimum", which was described by N.E. Vvedensky.

Transmarginal inhibition can be caused not only by the action of a very strong stimulus, but also by the action of a small in strength, but prolonged and uniform in character stimulus. This irritation, constantly acting on the same cortical elements, leads them to exhaustion, and, consequently, is accompanied by the appearance of protective inhibition. Transmarginal inhibition develops more easily with a decrease in working capacity, for example, after a severe infectious disease, stress, and more often develops in older people.

All types of conditioned inhibition are of great importance in human life. Endurance and self-control, accurate recognition of the objects and phenomena around us, and finally, the accuracy and clarity of movements are impossible without braking. There is every reason to believe that inhibition is based not simply on the suppression of conditioned reflexes, but on the development of special inhibitory conditioned reflexes. The central link of such reflexes is the inhibitory nervous connection. The inhibitory conditioned reflex is often called negative as opposed to the positive conditioned reflex.

Inhibition of an undesirable reaction is associated with a large waste of energy. Competing irritations, as well as other causes associated with physical condition organism, can weaken the process of inhibition and lead to disinhibition. During disinhibition, actions are manifested that were previously eliminated by braking processes.

Conclusion

The functioning of the conditioned reflex mechanism is based on two main nervous processes: on the process of excitation and on the process of inhibition. As the conditioned reflex develops and becomes stronger, the role of the inhibitory process increases. Inhibition is a factor contributing to the adaptation of the organism to its surrounding conditions. Inhibition also weakens the processes of excitation in the nervous system and ensures the stability of its work.

In the absence of inhibition, the processes of excitation would increase and accumulate, which would inevitably lead to the destruction of the nervous system and the death of the organism.

PRACTICAL PART

MUSCLE-JOINT SENSITIVITY

The subject sits down at the kinematometer and closes his eyes. The researcher alternately sets the angle, which the subject must subsequently reproduce on the large and small scales of the device. AT

during the performance of this exercise, the following data were obtained (given and performed by the test subject) 48, 52, 45 with a given value of 50 (large scale) 25, 27, 27 with a given value of 25 (small scale) for the first subject and 55, 51 , 54 for a given value of 50 (large scale) 30, 28, 29 for a given value of 30 (small scale) for the second subject.

Based on this, we can say that fine articular-muscular sensitivity is higher, in addition, one of the subjects showed better results, which indicates that his joint-muscular sensitivity is better developed.

TACTILE SENSITIVITY

The subject stretches his arms forward and closes his eyes, opens his palms up, and the researcher simultaneously, without pressure, lowers a weight of 1 to 5 g on the palms of both hands.

By changing the ratio of the weight of the load in the palm of the hand, the researcher determines the minimum difference in the weight of the load that the researcher is able to distinguish. In the course of this exercise, the following data were obtained (the minimum difference in the weight of the load that the subject is able to distinguish) 1 gr. for both test subjects. This is explained by the difference threshold of tactile sensitivity, i.e. the minimum difference in the strength of two stimuli of the same type (weight of cargo on different palms) necessary to change the intensity of sensation.

The difference threshold is measured by a relative value, which shows what part of the initial strength of the stimulus must be added (or reduced) in order to get a barely noticeable sensation of a change in the strength of these stimuli. To feel a minimal increase in the pressure of the load on the hand, an increase in the initial strength of irritation by 1/17 of its initial value is necessary, regardless of the units in which this pressure intensity is expressed.

The subject closes his eyes, and the researcher at the same time, without pressure, lowers the needles of the legs of the compass on his skin. Consistently reducing the distance between the needles of the legs of the compass, the researcher determines the minimum distance between them, which is perceived by the researcher when touched as the impact of two stimuli.

In the course of this exercise, the following data were obtained (the minimum distance between the needles of the legs of the compass, perceived when touched as the impact of two stimuli) 1 mm for both subjects. This is explained by the phenomenon of the spatial threshold of tactile sensitivity, i.e. the minimum distance between two different, but adjacent points, the simultaneous stimulation of which causes two independent, distinct tactile sensations.

Touch sensations occur when a mechanical stimulus causes deformation of the skin surface. When pressure is applied to a small area of ​​skin (less than 1 mm), the greatest deformation occurs precisely at the site of direct application of the stimulus. If pressure is exerted on a large surface (more than 1 mm), then it is distributed unevenly, its least intensity is felt in the depressed parts of the surface, and the greatest along the edges of the depressed area.

ARISTOTLE'S EXPERIENCE

The subject rolls a small ball between the index and middle fingers, while he makes sure that he perceives it as one object. If the subject rolls the same ball between the crossed fingers so that it is between the medial (inner) surface of the index finger and the lateral (outer) surface of the middle finger, he can verify that the perception of the presence of two balls is created. This is due to the phenomenon of the illusion of touch, which can arise under the influence of immediately preceding perceptions. In this case, the fact that the medial surface of the index and the lateral surface of the middle finger under normal conditions can be simultaneously irritated by only two objects. There is an illusion of irritation with two objects, because. in the brain there are two centers of excitation.

PUPIL REACTION

The subject becomes facing daylight, and the researcher measures the width of his pupil. Then one eye of the subject is covered with a hand and the width of the pupil of the open eye is measured. Then the closed eye is opened and the width of its pupil is again measured.

During this exercise, the following data were obtained (pupil width) 5 - 7 - 5 mm and 6 - 8 - 6 mm for the first and second subjects, respectively. Thus, the pupil width changed by an average of 2 mm, and the pupillary reaction time did not exceed 1 sec for both subjects. When both eyes were closed for 30 seconds, the pupil width was 5 - 9 - 5 mm and 6 - 10 - 6 mm, respectively, while the pupillary reaction time did not exceed 1 second.

The researcher fixes his gaze on a distant object, and the researcher measures the width of his pupil, then the researcher fixes his gaze on an object 15 cm distant, and the researcher again measures the width of his pupil. During this exercise, the following data were obtained (pupil width) 5 - 3 mm and 6 - 4 mm for the first and second subject, respectively. Thus, the pupil width changed by an average of 2 mm, and the pupillary reaction time did not exceed 1 sec for both subjects.

From the foregoing, it follows that the reaction of the pupil to light in both subjects is at the same level, and the difference in indicators is due to individual differences (in this case, pupil width at rest).

SPHERICAL ABERATION

The subject closes one eye, and brings a pencil close to the other, to such a distance that the image is blurry, then a sheet of paper with a hole 1 mm in diameter is placed between the pencil and the eye, and the object becomes clearly distinguishable. This is explained by the fact that spherical aberration is better expressed for the central beams. During this exercise, the following data were obtained (the distance from the eye to the pencil at the moment when it becomes less clearly distinguishable) 10 cm and 11 cm for the first and second subjects, respectively.

Looking at a pattern of vertical and horizontal lines, the subject fixes his gaze on the vertical and then on the horizontal lines and makes sure that he cannot see the horizontal and vertical lines equally clearly.

The subject looks through a thin grid at the printed text from a distance of 50 cm from the eye, if you fix the letters with your eyes, then the threads of the grid are made less visible, and if you fix the grid with your eyes, then the letters.

From the foregoing, it follows that the subject cannot simultaneously clearly see two objects at different distances due to the fact that the optical system of the eye has spherical aberration, i.e. the focus of the peripheral rays is closer than the focus of the central ones.

DETECTION OF ASTIGMATISM

The subject looks at a pattern consisting of vertical and horizontal lines of the same thickness, while both subjects noted that the vertical lines appear visually more distinct. As the drawing approaches the eye, the horizontal lines become more distinct. In the course of this exercise, the following data were obtained (the distance from the eye to the drawing at the moment when the horizontal lines become clearer) 10 cm and 11 cm for the first and second subjects, respectively. This is explained by the fact that the rays coming from the horizontal lines at the initial position of the pattern were in front of the retina, and when the pattern approached the eye, the convergence points of the rays moved to the retina. When the picture is rotated, the subject's idea of ​​the thickness of the lines is constantly changing according to the change in their position to vertical or horizontal. This is due to the fact that the rays coming from the horizontal and vertical lines are alternately in front of the retina and on the retina.

BLIND SPOT DETECTION

The subject fixes his gaze in the figure in the form of a black rectangle, in the left half of which there is a white circle, and in the right half there is a white cross. Closing the right eye, the subject with his left eye fixes the cross located on the right side of the picture. The drawing is brought closer to the eye until the circle falls out of sight. In the course of this exercise, the following data were obtained (the distance from the eye to the drawing at the moment when it falls out of sight) 11 cm for both subjects.

The subject fixes with his right eye a cross located in the upper left corner of a white sheet of paper. A pencil wrapped in white paper (except for the sharpened tip) moves from the upper right corner towards the cross.

The subject is convinced that at a certain distance from the cross the pencil becomes less distinguishable, but as it approaches the cross further, its image becomes clearer again.

During this exercise, the following data were obtained (distance from the nodal point of the eye to the retina) 18.5 and 18.0 mm for the first and second subjects, respectively, and (diameter of the blind spot) 2.7 mm for both subjects.

This is due to the fact that there is a blind spot on the retina of the eye (the entry point of the neurovascular bundle, the area that does not have sensitive elements), i.e. the area where the image does not appear.

DETERMINATION OF VISUAL ACUITY

The subject fixes his gaze on a drawing consisting of two parallel lines spaced 1 mm apart, then he moves away from the drawing until both lines become visible as one line.

During this exercise, the following data were obtained (the distance from the eye to the drawing, in which two parallel lines are perceived as one) 3 m for both subjects and (angle of view) 0.006 mm for both subjects.

This is due to the fact that two points in space are perceived by the optical system of the eye as separate only if the distance between them is greater than or equal to 5 microns, in our case 6 microns, which indicates a certain decrease in sensitivity. optical system the eyes of both subjects

SEQUENTIAL VISUALS

The subject fixes his gaze on the drawing in the form of a black square for a certain time, and then shifts his gaze to a white wall. The subject is convinced that for some time a subtle image of a black square remains on the wall.

In the course of this exercise, the following data were obtained (the time during which the image of a black square is stored on a white wall) is less than 1 second for both subjects.

This phenomenon is explained by the property of the nervous system to maintain excitation for some time after the cessation of the irritating factor.

FIELDS OF VISION

The subject fixes his gaze on any object, while with one of his eyes he looks through a paper cone with a narrow hole. The subject is convinced that visually the object seems to be perforated.

This is explained by the fact that the field of view of one eye is illuminated relatively stronger than the field of view of the other eye, the object attached to the cone is visible, but a small part of the field of view of the eye attached to the cone is illuminated even more, so the subject sees a hole in the object.

SIMULATED DEAFNESS

The subject reads a book aloud. After he has read a few sentences, the researcher taps a box of lead pieces against his ear. The researcher can make sure that the subject after that began to read louder. This does not happen in a deaf person. This experience is based on the fact that a person, with the help of an auditory analyzer, controls the intensity and correctness of his speech (semantic stress, emotional coloring). In a noisy environment, a person increases the intensity of speech to a level at which others will hear it. A deaf person cannot exercise such control over his speech. I did this experience not only in the audience at the last session, but also at work, conducting a therapeutic reception of a convict with second-degree sensorineural hearing loss.

USE OF DISPOSABLE DIAPERS. Pampers, Hages and others. Pros and cons.

The disposable diaper is a useful and necessary invention. It makes life easier not for the child, but for his parents. Nights without sleep and endless washing of diapers are a thing of the past. When going on a trip, you don’t have to take with you huge piles of diapers, undershirts and diapers cut from old diapers, scarves, gauze ...

A disposable diaper is a must have. On a walk, on the road, at a party, you don’t need to change your child’s clothes, the soft absorbent layer absorbs everything, and the tight-fitting elastic bands prevent leakage. The drawings that appear will show you when you need to change the diaper ... but it's all advertising! Yes, disposable diapers are really needed, but at certain times and in certain cases.

Behind the brilliance and beauty of advertising, we do not notice those disadvantages that are very important. The diaper is made of polymeric materials that can cause allergies in the child's body. The film that prevents leakage also prevents the skin from breathing, so diaper rash can occur quite easily. And most importantly, the use of a disposable diaper can cause a lot of problems at the age at which the child needs to be potty trained, at the age when the child must learn to control himself and restrain urination and defecation.

A disposable diaper is a necessary and useful thing, but when used correctly.

From a survey conducted on the site's forum www.lyamino.moy.su it turned out that:

6 people have a positive attitude towards disposable diapers

5 people - negative

2 people said they didn't care.

No one responded to the proposed answer option “other” and the opportunity to write their opinion.

This type of inhibition differs from external and internal in terms of the mechanism of occurrence and physiological significance. It occurs when the strength or duration of the action of the conditioned stimulus is excessively increased, due to the fact that the strength of the stimulus exceeds the efficiency of the cortical cells. This inhibition has a protective value, as it prevents the depletion of nerve cells. In its mechanism, it resembles the phenomenon of "pessimum", which was described by N.E. Vvedensky.

Transmarginal inhibition can be caused not only by the action of a very strong stimulus, but also by the action of a small in strength, but prolonged and uniform in character stimulus. This irritation, constantly acting on the same cortical elements, leads them to exhaustion, and, consequently, is accompanied by the appearance of protective inhibition. Transmarginal inhibition develops more easily with a decrease in working capacity, for example, after a severe infectious disease, stress, and more often develops in older people.

30. Functional states of the body (wakefulness, sleep, etc.) x Physiology of sleep

"Who knows the secret of sleep, knows the secret of the brain." M. Jouvet.

Dream- a physiological state, which is characterized by the loss of active mental connections of the subject with the world around him. Sleep is vital for higher animals and humans. For a long time, it was believed that sleep is a rest necessary to restore the energy of brain cells after active wakefulness. However, it turned out that brain activity during sleep is often higher than during wakefulness. It was found that the activity of neurons in a number of brain structures during sleep increases significantly; sleep is an active physiological process.

Reflex reactions during sleep are reduced. A sleeping person does not respond to many external influences, unless they are of excessive strength. Sleep is characterized by phase changes in GNI, which are especially pronounced during the transition from wakefulness to sleep (equalizing, paradoxical, ultraparadoxical and narcotic phases). In the narcotic phase, animals cease to respond with a conditioned reflex reaction to any conditioned stimuli. Sleep is accompanied by a number of characteristic changes in vegetative parameters and bioelectrical activity of the brain.

The state of wakefulness is characterized by low-amplitude high-frequency EEG activity (beta rhythm). When the eyes are closed, this activity is replaced by an alpha rhythm, a person falls asleep. During this period, awakening occurs quite easily. After a while, "spindles" begin to appear. Approximately 30 min later, the "spindles" stage is replaced by the stage of high-amplitude slow theta waves. Awakening to this stage is difficult, it is accompanied by a number of changes in vegetative parameters: the heart rate decreases, blood pressure, body temperature, etc.

The stage of theta waves is replaced by the stage of high-amplitude infraslow delta waves. Delta sleep is a period of deep sleep. Heart rate, blood pressure, body temperature in this phase reach their minimum values. The slow-wave stage of sleep lasts 1-1.5 hours and is replaced by the appearance on the EEG of low-amplitude high-frequency activity characteristic of the state of wakefulness (beta rhythm), which is called paradoxical or fast-wave sleep. Thus, the entire period of sleep is divided into two states that alternate 6-7 times during the night: slow-wave (orthodox) sleep and fast-wave (paradoxical) sleep. If you wake up a person in the phase of paradoxical sleep, then he reports dreams. A person, waking up in a phase of non-REM sleep, usually does not remember dreams. If a person during sleep is selectively deprived of only the paradoxical phase of sleep, for example, waking him up as soon as he enters this phase, this leads to significant disturbances in mental activity.

sleep theories. The humoral theory, as the cause of sleep, considers substances that appear in the blood during prolonged wakefulness. The proof of this theory is an experiment in which an awake dog was transfused with the blood of an animal deprived of sleep during the day. The recipient animal immediately fell asleep. At present, it has been possible to identify some hypnogenic substances, for example, a peptide that induces delta sleep. But humoral factors cannot be considered as the absolute cause of sleep. This is evidenced by observations of the behavior of two pairs of unseparated twins. In them, the division of the nervous system occurred completely, and the circulatory systems had many anastomoses. These twins could sleep in different time: one girl, for example, could sleep, while the other was awake.

Subcortical and cortical theories of sleep. With various tumor or infectious lesions of subcortical, especially stem, brain formations, patients have various sleep disorders - from insomnia to prolonged lethargic sleep, which indicates the presence of subcortical sleep centers. When the posterior structures of the subthalamus and hypothalamus were stimulated, the animals fell asleep, and after the stimulation ceased, they woke up, which indicates the presence of sleep centers in these structures.

In the laboratory of I.P. Pavlov, it was found that during prolonged development of fine differential inhibition, animals often fell asleep. Therefore, the scientist considered sleep as a consequence of the processes of internal inhibition, as a deep, spilled inhibition that spread to both hemispheres and the nearest subcortex (cortical theory of sleep).

However, a number of facts could not explain either the cortical or subcortical theories of sleep. Observations of patients who lacked almost all types of sensitivity showed that such patients fall into a state of sleep as soon as the flow of information from the active sense organs is interrupted. For example, in one patient, of all the sense organs, only one eye was preserved, the closure of which plunged the patient into a state of sleep. Many questions about the organization of sleep processes were explained with the discovery of ascending activating influences of the reticular formation of the brain stem on the cerebral cortex. It was experimentally proved that sleep occurs in all cases of elimination of the ascending activating influences of the reticular formation on the cerebral cortex. The descending influences of the cerebral cortex on subcortical formations were established. In the waking state, in the presence of ascending activating influences of the reticular formation on the cerebral cortex, neurons in the frontal cortex inhibit the activity of neurons in the sleep center of the posterior hypothalamus. In the state of sleep, when the ascending activating influences of the reticular formation on the cerebral cortex decrease, the inhibitory influences of the frontal cortex on the hypothalamic sleep centers decrease.

There are reciprocal relationships between the limbic-hypothalamic and reticular structures of the brain. When the limbic-hypothalamic structures of the brain are excited, inhibition of the structures of the reticular formation of the brain stem is observed and vice versa. During wakefulness, due to afferent flows from the sense organs, the structures of the reticular formation are activated, which have an upward activating effect on the cerebral cortex. At the same time, the neurons of the frontal cortex have a descending inhibitory effect on the sleep centers of the posterior hypothalamus, which eliminates the blocking effects of the hypothalamic sleep centers on the reticular formation of the midbrain. With a decrease in the flow of sensory information, the ascending activating influences of the reticular formation on the cerebral cortex decrease. As a result, the inhibitory effects of the frontal cortex on the neurons of the sleep center of the posterior hypothalamus are eliminated, which begin to inhibit the reticular formation of the brain stem even more actively. In conditions of blockade of all ascending activating influences of subcortical formations on the cerebral cortex, a slow-wave stage of sleep is observed.

The hypothalamic centers, due to connections with the limbic structures of the brain, can exert ascending activating influences on the cerebral cortex in the absence of influences from the reticular formation of the brain stem. These mechanisms make up the cortical-subcortical theory of sleep (P.K. Anokhin), which made it possible to explain all types of sleep and its disorders. It proceeds from the fact that the state of sleep is associated with the most important mechanism - a decrease in the ascending activating influences of the reticular formation on the cerebral cortex. The sleep of non-cortical animals and newborns is explained by the weak severity of the descending influences of the frontal cortex on the hypothalamic sleep centers, which under these conditions are in an active state and have an inhibitory effect on the neurons of the reticular formation of the brain stem.

The sleep of a newborn is periodically interrupted only by the excitation of the hunger center located in lateral nuclei hypothalamus, which inhibits the activity of the sleep center. In this case, conditions are created for the ascending activating influences of the reticular formation to enter the cortex. This theory explains many sleep disorders. Insomnia, for example, often occurs as a result of overexcitation of the cortex under the influence of smoking, intense creative work before bedtime. At the same time, the descending inhibitory influences of the neurons of the frontal cortex on the hypothalamic sleep centers are enhanced and the mechanism of their blocking action on the reticular formation of the brain stem is suppressed. Prolonged sleep can be observed when the centers of the posterior hypothalamus are irritated by a vascular or tumor pathological process. Excited cells of the sleep center continuously have a blocking effect on the neurons of the reticular formation of the brain stem.

Sometimes during sleep, the so-called partial wakefulness is observed, which is explained by the presence of certain channels of reverberation of excitations between the subcortical structures and the cerebral cortex during sleep against the background of a decrease in the ascending activating influences of the reticular formation on the cerebral cortex. For example, a nursing mother may sleep soundly and not respond to strong sounds, but she quickly wakes up even with the slightest movement of the baby. In the case of pathological changes in one or another organ, increased impulses from it can determine the nature of dreams and be a kind of harbinger of a disease, the subjective signs of which are not yet perceived in the waking state.

Pharmacological sleep is inadequate in its mechanisms to natural sleep. Sleeping pills limit the activity of various brain structures - the reticular formation, the hypothalamic region, the cerebral cortex. This leads to a violation of the natural mechanisms of the formation of sleep stages, a violation of the process of memory consolidation, processing and assimilation of information.

Nervous activity is carried out as a result of the interaction of two main nervous processes - excitation and inhibition.

Excitation- a nervous process that brings the body into an active state. Externally, excitation is manifested, for example, in the contraction of a group of muscles or in the release of a secret. A more accurate indicator of excitation is the occurrence of an electronegative potential a in the excited area of ​​\u200b\u200bthe tissue.

Braking- a nervous process leading to a temporary cessation or weakening of the active state of the body. When braking, an electropositive potential occurs. The formation of conditioned reflexes, their connection, preservation and transformation are possible only when excitation interacts with inhibition.

In order to form a conditioned reflex to a certain stimulus, all reflexes to other stimuli that continuously act on the organism must be temporarily delayed. The process of inhibition also cancels the action of the conditioned stimulus if it has temporarily lost its vital significance. Finally, inhibition protects the nerve cells of the cortex from the destructive action of harmful stimuli.

Distinguish inhibition unconditional, or passive, and conditional, or active.

A feature of unconditioned inhibition is its innate nature. It does not require special development and is characteristic of all parts of the central nervous system. Conditioned inhibition, which is also called internal, occurs gradually in the process of formation of conditioned reflexes. It is peculiar only to the cerebral cortex.

To unconditional inhibition include external and transcendental inhibition, the conditional (internal) include extinction, differential, delay braking and the so-called conditional brake.

External braking arises under the influence of extraneous stimuli to the formed conditioned reflex. A stimulus foreign to experience, especially a new and strong one, evokes an orienting reflex, and the excitation related to this reflex inhibits the conditioned reflex being developed until the foreign stimulus disappears or loses its novelty. In order to avoid the inhibitory effect of extraneous stimuli, special conditions are created for some laboratory experiments - isolated soundproof chambers.

It has been observed that young, weakly strengthened conditioned reflexes are most easily inhibited under the influence of extraneous stimuli.

The latest studies of the orienting reflex (E. N. Sokolov and others) prove its complex nature. It has been found that orienting reflexes not only inhibit the formation of conditioned reflexes, but are also a necessary condition for their formation. Any stimulus at the beginning of its action causes an orientation reaction of the organism, which increases the sensitivity of the corresponding analyzers. An indifferent stimulus, i.e., one that has lost the character of novelty under the given conditions of experience, does not evoke an orienting reaction until the moment its action is combined with reinforcement. From the moment of the combination, each appearance of the conditioned stimulus will evoke an orienting reaction to itself, which increases the sensitivity of the analyzer and contributes to the formation of a conditioned connection.

Similar to external braking is inhibition, called negative induction.

Transmarginal inhibition occurs under the influence of super-strong, excessively prolonged and other harmful conditioned and unconditioned stimuli that exceed the limit of nerve cell performance. Transmarginal inhibition plays a protective role, as it protects nerve cells from unbearable stresses.

Let's give examples. At the dog produce a salivary reflex to a weak sound stimulus, and then gradually increase its strength. Accordingly, the strength of excitation in the nerve cells of the analyzers also increases, as can be judged by the intensity of salivation. However, this is observed up to a certain limit. At some point in the action of a very strong sound stimulus, a sharp drop in salivation occurs. The excitation of the limiting force is immediately replaced by deceleration. The same is observed with continuous and excessively prolonged action of the stimulus. Nerve cells, which differ from other cells in the body by a high intensity of activity, quickly get tired. With their continuous and prolonged irritation, fatigue develops faster, and the nerve cells go into a state of inhibition. Sleep occurs as a protective reaction of the nervous system from excessive stress.

There was such a case. A six-year-old child witnessed a difficult scene in the family: his sister accidentally knocked over a pot of boiling water on herself. There was a commotion in the house. The boy's fright was so strong that, after several minutes of desperate crying, he suddenly fell into a deep sleep and slept for several hours, although the incident occurred in the morning. The nerve cells of the cortex could not bear the excessive stress.

Strong emotional outbursts in some people reach the so-called "emotional shock", that is, sudden stiffness. The physiological basis of such a shock is also transcendental inhibition.

The excitability limit of nerve cells is not constant. It decreases due to prolonged fatigue, illness, the effects of toxic substances on the body. In addition, they matter individual characteristics people, the type of their higher nervous activity.

The simplest type of conditioned inhibition is the extinction of conditioned reflexes.

It arises as a result of their non-reinforcement. If the conditioned stimulus of the developed conditioned reflex is given several times in a row at short intervals without combining it with the unconditioned one, then the conditioned reflex will gradually disappear, fade away. Thus, a repeatedly given light signal, to which a salivary reflex was developed in a dog without reinforcement, instead of excitation, begins to cause inhibition. Pigeons flock to the feeder as long as there are grains in it; in the absence of food, their arrivals become less and less frequent, until they stop altogether. A child taught to wash his hands on his own, in the absence of control, gradually ceases to fulfill this hygienic requirement.

The extinction of conditioned reflexes underlies the forgetting caused by the absence of repetitions.

The following patterns of extinction have been established: young, weakly strengthened conditioned reflexes are easily extinguished; extinction develops the faster, the more often the conditioned stimulus is applied without reinforcement; conditioned reflexes formed on the basis of strong reinforcing stimuli fade slowly; the extinction of one conditioned reflex entails the weakening of others similar to the fading and fragile conditioned reflexes, etc. It is useful to use these patterns in the process of teaching students and in organizing independent work on the acquisition of knowledge and skills.

Decay is not destruction conditioned reflexes. A faded reflex can be quickly restored by repeated reinforcement. As regards well-strengthened and then quenched reflections, the facts of their spontaneous recovery are known. The positive value of extinction is that it cancels those temporary connections in the cortex that turned out to be unnecessary in the future, which makes it possible to replace them with others.

At a certain stimulus, at first, other homogeneous stimuli also cause a positive reaction, although their action is not combined with an unconditioned stimulus. So, when a dog develops a conditioned salivary reflex to a tone of a certain pitch, at first saliva flows to other tones. This phenomenon is called generalization. However, if the main tone is systematically reinforced with an unconditioned stimulus, and a similar sound (or sounds) is systematically left without reinforcement, then differentiation occurs, the distinction between these sounds: a reinforced tone will cause a positive reflex (excitation), and an unreinforced tone will cause a negative reflex (inhibition). It has been established that the greater the similarity between homogeneous stimuli, the more difficult their differentiation is. For its formation, a large number of repetitions of experience is required.

Differential braking

Together with some other physiological mechanisms, it underlies all kinds of discrimination, analysis both in animals and in humans: discrimination of sounds, colors, smells, shapes and sizes of objects, movements. In addition, a person has the distinction of words, concepts, thoughts, actions.

Under natural conditions, a young animal at the beginning of its life performs many actions that are not justified by the situation, weakly distinguishing similar objects and influences. Then, gradually, generalized reactions are replaced by more accurate differentiated reactions based on a more subtle distinction between objects and phenomena of the external world. “Although the owner feeds the puppy, he runs up to strangers. They put him in a box with a soft bedding, and he climbs onto the bed. Having put a sparrow to flight, he begins to chase chickens around the yard ... ”Not so with an adult dog. She subtly distinguishes even the intonations of her master's voice. “Having heard gentle notes, she runs up to him, and when irritation sounds in the owner’s voice, she goes away” (A. B. Kogan). Children starting to study at school, at first, do not distinguish similar sounds of speech - voiced and deaf, hard and soft consonants, so some children say “teeth” instead of the word “teeth”, “suba” instead of “fur coat”, etc. They confuse and letters, numbers, grammatical and arithmetic signs, geometric shapes. Learning in the learning process scientific concepts, rules, laws, students often confuse similar either in verbal expression (for example, the source and tributary of the river, participle and gerund, repression and depression) or in content (for example, strength and tension electric current; weight and body weight; metaphor and comparison; bisector and median; monsoons and trade winds). Sometimes a large number of specially selected exercises are required to teach students to accurately distinguish between similar concepts, rules, laws, etc.

During the experimental formation of a conditioned reflex

Usually during experimental the formation of a conditioned reflex the conditioned stimulus is given 1-5 seconds before the onset of the action of the unconditioned stimulus, then both stimuli act together. However, if gradually from experience to experience we increase the time interval between the isolated action of the conditioned stimulus and the joint action of both stimuli, then an interesting result can be observed. After several repetitions of the experiment, the conditioned stimulus (for example, light) will cause an inhibitory process for some time, and the conditioned reflex will appear with a delay. This is the inhibition of delay. And the longer the time of the isolated action of the conditioned stimulus during the development of the conditioned reflex, the longer the process of inhibition will be. Biologically, this is very expedient: the conditioned response is timed exactly at the time when it should occur in response to reinforcement.

In animals, retardation inhibition lasts within 1 to 3 minutes of the isolated action of the conditioned stimulus. Conditioned reflexes obtained in this way are called delayed. And if the unconditioned stimulus is given only after the cessation of the conditioned stimulus and there is no coincidence, then a trace conditioned reflex is formed. A conditioned reaction does not arise to a present stimulus, but to a trace from it.

Lag braking is the physiological basis of various delayed reactions, which play an important role in the adaptive activity of animals and in practical activities of people. Not every planned action can be immediately implemented. Sometimes it is necessary to delay the action until a certain time, to have patience, endurance. One of the physiological mechanisms of delayed responses is the inhibition of delay at the level of secondary signal connections.

Delay inhibition is developed with great difficulty in excitable individuals.

It has also been established that the stronger the conditioned stimulus, the more difficult lag inhibition is generated. It is well known how difficult it is for a small child to restrain himself not to take a delicacy in front of his eyes until the moment when the elders allow, for example, before the end of dinner. The sight of a juicy apple or a sweet cake is a very strong conditioned stimulus. It is easier for the child if the treat is removed for the time being. Inhibition of delay also occurs with difficulty with a strong unconditioned stimulus. It is difficult for a hungry person to wait for the set time for lunch. Prolonged exercise in developing the inhibition of retardation facilitates its occurrence.

If a conditioned stimulus, to which a positive conditioned reflex has been developed, to give simultaneously with some other additional stimulus and this combination is not reinforced, then conditioned inhibition occurs. The role of the conditioned brake here belongs to an additional stimulus.

So, a dog has developed a positive conditioned reflex to the sound of a metronome of a certain frequency. If then gurgling is added to the beat of the metronome and this combination of two stimuli is not reinforced by an unconditioned reflex, then conditioned inhibition will occur (in the narrow sense of the word). The beat of a metronome given under new conditions (together with gurgling) temporarily loses its signal value, and the conditioned reflex to it is inhibited. An additional irritant - gurgling - acts as a conditioned brake.

Any external agent can become a conditioned brake to signal stimuli.

Thus, the slightest change in environment changes the signal role of the conditioned stimulus, which indicates the finest adaptation of the organism to the conditions of its existence.

Here example of natural conditional inhibition. The sniffer dog is taught to take food only from the hands of its owner and does not touch it if someone else feeds it: the sight and smell of food cease to be a conditioned stimulus in other conditions. The role of a conditional brake here is played by the sight and smell of an outsider.

While raising children, we instill in them the skills and abilities to change their behavior depending on specific conditions, to temporarily delay those actions that are considered inappropriate in a certain situation. One of the physiological mechanisms of such delayed responses is conditioned inhibition. It is useful to know that stimuli acting as a conditional brake can have a negative effect on a person, reduce his performance. So, if an inexperienced teacher once greatly frightened a child with a cry or a threat of punishment, then the student subsequently for a long time cannot work calmly and productively: the appearance and voice of the teacher become a conditional brake for him.

Any kind of internal inhibition is an active process of delay, suppression of conditioned reflexes.

It is easy to verify this if at the moment internal inhibition to act on the animal with a stimulus foreign to experience, which under other conditions is an external brake. External inhibition meets with internal and disinhibition occurs: the signal stimulus again causes a temporarily delayed conditioned reflex.

Partial braking the cortex can go into general inhibition, sleep. This process has three phases: leveling, paradoxical and ultraparadoxical. In the equalizing phase, strong stimuli are equalized in their action with weak ones. In the paradoxical phase, strong stimuli have less effect than weak stimuli. In the ultraparadoxical phase irritants, which previously caused a positive reaction of the body, now do not cause it at all, and the stimuli that caused an inhibitory reaction now give a positive one.

Name the types of inhibition of conditioned reflexes and explain the reasons for their occurrence and the main differences. What is the significance of the inhibition of conditioned reflexes for the organism?

Explanation.

1. Types of inhibition of conditioned reflexes: external (unconditioned) inhibition and internal (conditioned) inhibition.

2. The reasons for their occurrence and the main differences:

External (unconditioned) inhibition - arises according to the principle of an unconditioned reflex - develops as a result of the action of a new external strong stimulus, which leads to the emergence of a new external relatively strong stimulus, which leads to the emergence of a new focus of excitation in the cortex and this focus causes inhibition of the old one.

Peculiarities:

Unconditional inhibition is an innate form of inhibition; it is inherent in all individuals of a given species;

It doesn't take time for it to occur;

It can develop in any part of the central nervous system.

Internal (conditioned) inhibition - is carried out according to the principle of a conditioned reflex.

Conditional inhibition occurs when the conditioned signal is not reinforced. In the cerebral cortex, a temporary reflex connection ceases to be carried out - a gradual extinction of the response is observed.

Peculiarities:

This is an individual reaction of the body acquired during life;

Requires certain conditions, for its implementation it is necessary to develop;

It develops in the neurons of the cerebral cortex.

An example of external inhibition: salivation to light stops with a sharp, sudden, strong sound.

An example of internal inhibition: salivation to light fades and disappears if it is not reinforced by feeding.

3. Significance for the organism of inhibition of conditioned reflexes:

inhibition of conditioned reflexes ensures that conditioned reflexes correspond to the conditions of existence and at the same time delays conditioned reflexes that have no or have lost their significance for life.

a more detailed analysis and synthesis of information is carried out - along with conditioned reflexes, they ensure the adaptation of the body to changing environmental conditions.

Provides (together with excitation) the normal activity of all organs and the body as a whole. It has a protective value (primarily for the nerve cells of the cerebral cortex), protecting nervous system from excitement.

Note (not specified in the criteria).

External (unconditioned inhibition) - transcendental inhibition: the conditioned reflex obeys the law of the strength of stimulation (with an increase in the strength of the stimulus to a certain limit, the response increases). With a further increase in the strength of the stimulus, conditioned reflexes are inhibited. Mechanism: the conditioned reflex sharply increases the strength and exceeds the threshold of performance of the neurons of the cerebral cortex. As a result, in the brain section of the analyzer there is an outrageous inhibition. Meaning: Protects the neurons of the cerebral cortex from exhaustion.

Conditioned inhibition - differential value - accurate discrimination of close stimuli. Mechanism: differentiation of stimuli occurs in the neurons of the brain analyzer.