The main form of nervous activity is a reflex act. In other words, it is the reflexes that express the purposeful actions of the organism.

Reflex

A reflex is the integral reaction of the body to irritation, which is carried out by the central nervous system. The manifestation of the reflex can be seen in involuntary and voluntary movements, in the functioning of internal organs, in changes in behavior, emotions and sensitivity.

Perception of irritation occurs with the help receptors... These are nerve endings and structures that are sensitive to stimuli.

Each of the receptors perceives certain categories of stimuli - sound, light, cold, pressure, touch, heat, etc. According to these criteria, receptors are divided into types.

How does the reflex manifest itself?

With irritation, excitation occurs in the receptor, and the receptors convert the energy of the stimulus into nerve signals - of an electrical nature.

The received information comes in the form of electrical impulses and follows the fibers of sensitive neurons before contacting other nerve cells. Signals are transmitted to intercalary neurons and then to motor... The signal can also come from sensory neurons to motor neurons.

Neurons enter the central nervous system, the spinal cord and the brain, where they already form the nerve center of the reflex. The transmitted information is processed, as a result of which a control command is created.

After that, the team follows to the executive organ, where the signal causes muscle contraction.

Reflex arc

Reflex arc- this is the anatomical basis of the reflex. It is represented by a chain of nerve cells that provide the conduction of nerve impulses from the receptors to the executive organ.

The chain consists of five links:

1. The receptor for the perception of a stimulus - internal or external. This receptor also produces nerve impulses.

2. Sensory pathway, consisting of processes of sensory neurons. It is through them that nerve signals enter the nerve centers of the brain.

3. Nervous center, which contains intercalary and motor neurons. Interneurons send signals to motor neurons, and the latter form commands.

4. Centrifugal path from motor neuron fibers. Through it, nerve impulses go to the executive organ.

5. Executive or working organ - gland or muscle.

The reflex act can be carried out only with the integrity of all components of the reflex arc.

Reflex ring

After a reflex effect on a certain organ, its receptors are excited, and from them follows information about the state of the organ or about the result achieved. Information enters the central nervous system through sensitive pathways.

Having received information about the state of the organ, the nerve centers amend the actions of the executive body or itself nervous system generally.

Feedback forms a reflex ring through which the reflex act actually takes place.

Nerve networks and circuits

Sensory, intercalary, and motor neurons form neural networks and circuits. They are the structural basis of the reflex act: signals propagate through their serial and parallel connections and reach various nerve centers.

Introduction

1. Reflex theory and its basic principles

2. Reflex - a concept, its role and meaning in the body

3. The reflex principle of the construction of the nervous system. Feedback principle

Conclusion

Literature

Introduction

Human interaction with reality is carried out through the nervous system.

In humans, the nervous system consists of three sections: the central, peripheral and autonomic nervous systems. The nervous system functions as a single and integral system.

The complex, self-regulating activity of the human nervous system is carried out due to the reflex nature of this activity.

This work will reveal the concept of "reflex", its role and significance in the body.

1. Reflex theory and its basic principles

The provisions of the reflex theory developed by I.M.Sechenov. I.P. Pavlov and developed by N.E. Vvedensky. A. A. Ukhtomsky. VM Bekhterev, PK Anokhin and other physiologists, are the scientific and theoretical basis of Soviet physiology and psychology. These theses find their creative development in the research of Soviet physiologists and psychologists.

The reflex theory, which recognizes the reflex essence of the activity of the nervous system, is based on three main principles:

1) the principle of materialistic determinism;

2) the principle of structure;

3) the principle of analysis and synthesis.

The principle of materialistic determinism means that every nervous process in the brain is conditioned (caused) by the action of certain stimuli.

The principle of structure lies in the fact that the differences in the functions of different parts of the nervous system depend on the characteristics of their structure, and the change in the structure of the parts of the nervous system in the process of development is due to changes in functions. Thus, in animals that do not have a brain, higher nervous activity is significantly more primitive than the higher nervous activity of animals that have a brain. In a person in the course historical development the brain has reached a particularly complex structure and perfection, which is associated with his work and social conditions of life, requiring constant verbal communication.

Analysis and Synthesis Principle is expressed as follows. When centripetal impulses enter the central nervous system, excitation occurs in some neurons, in others - inhibition, that is, a physiological analysis occurs. The result is a distinction between specific objects and phenomena of reality and the processes taking place inside the body.

At the same time, during the formation of a conditioned reflex, a temporary neural connection (closure) is established between two foci of excitation, which physiologically expresses a synthesis. The conditioned reflex is the unity of analysis and synthesis.

2. Reflex - a concept, its role and meaning in the body

Reflexes (from the Latin slot reflexus - reflected) are the body's responses to stimulation of receptors. Nerve impulses arise in the receptors, which enter the central nervous system via sensory (centripetal) neurons. There, the information received is processed by intercalary neurons, after which motor (centrifugal) neurons are excited and nerve impulses activate the executive organs - muscles or glands. Intercalary neurons are those whose bodies and processes do not extend beyond the central nervous system. The path along which nerve impulses pass from the receptor to the executive organ is called the reflex arc.

Reflex actions are holistic actions aimed at satisfying a specific need for food, water, safety, etc. They contribute to the survival of an individual or a species as a whole. They are classified into food, water-extracting, defensive, sexual, tentative, nest-building, etc. There are reflexes that establish a certain order (hierarchy) in a herd or flock, and territorial, defining the territory captured by a particular individual or flock.

Distinguish between positive reflexes, when the stimulus causes a certain activity, and negative, inhibitory, in which the activity stops. The latter, for example, includes the passive-defensive reflex in animals, when they freeze when a predator appears, an unfamiliar sound.

Reflexes play an exceptional role in maintaining consistency. internal environment organism, its homeostasis. So, for example, with an increase in blood pressure, a reflex slowdown of cardiac activity and an expansion of the lumen of the arteries occur, so the pressure decreases. With its strong fall, opposite reflexes arise, strengthening and accelerating the contractions of the heart and narrowing the lumen of the arteries, as a result, the pressure rises. It constantly fluctuates around some constant value, which is called a physiological constant. This value is genetically determined.

The famous Soviet physiologist P.K.Anokhin showed that the actions of animals and humans are determined by their needs. For example, the lack of water in the body is first replenished by internal reserves. Reflexes appear that delay the loss of water in the kidneys, the absorption of water from the intestines increases, etc. If this does not lead to the desired result, excitement arises in the centers of the brain that regulate the flow of water, and a feeling of thirst appears. This arousal induces purposeful behavior, seeking water. Thanks to direct connections, nerve impulses going from the brain to the executive organs, the necessary actions are provided (the animal finds and drinks water), and thanks to feedback, nerve impulses going in the opposite direction - from peripheral organs: the oral cavity and stomach - to the brain, informs the latter about the results of the action. Thus, during drinking, the center of water saturation is excited, and when the thirst is satisfied, the corresponding center is inhibited. This is how the controlling function of the central nervous system is carried out.

The discovery of conditioned reflexes by I.P. Pavlov was a great achievement of physiology.

Unconditioned reflexes are innate, inherited by the body reactions to environmental influences. Unconditioned reflexes are characterized by constancy and do not depend on training and special conditions for their occurrence. For example, the body responds to painful irritation with a defensive reaction. There is a wide variety of unconditioned reflexes: defensive, food, orientation, sexual, etc.

The reactions underlying unconditioned reflexes in animals have been developed for millennia in the course of adaptation. different types animals to the environment, in the process of struggle for existence. Gradually, under conditions of long-term evolution, the unconditional reflex reactions necessary to satisfy biological needs and preserve the vital activity of the organism, were consolidated and inherited, and those of the unconditional reflex reactions that lost their value for the life of the organism lost their expediency, on the contrary, disappeared. not recovering.

Under the influence of constant changes in the environment, more durable and more perfect forms of reaction of animals were required, ensuring the adaptation of the organism to the changed conditions of life. During individual development in highly organized animals, a special type of reflexes is formed, which I.P. Pavlov called conditioned.

The conditioned reflexes acquired by the body during life provide a corresponding response of the living organism to changes in the environment and, on this basis, balancing the organism with the environment. Unlike unconditioned reflexes, which are usually carried out by the lower parts of the central nervous system (spinal cord, medulla oblongata, subcortical nodes), conditioned reflexes in highly organized animals and in humans are carried out mainly by the higher part of the central nervous system (cerebral cortex).

Observation of the phenomenon of "psychic secretion" in a dog helped I.P. Pavlov to open a conditioned reflex. An animal, seeing food at a distance, vigorously salivated even before the food was served. This fact has been interpreted in different ways. The essence of "psychic secretion" was explained by IP Pavlov. He found that, firstly, in order for a dog to start salivating at the sight of meat, it had to see and eat it at least once before. And, secondly, any stimulus (for example, the type of food, a bell, the blinking of a light bulb, etc.) is capable of causing salivation, provided that the time of action of this stimulus and the time of feeding coincide. If, for example, feeding was constantly preceded by the knock of the cup in which the food was located, then there always came a moment when the dog began to salivate at just one knock. Reactions that are triggered by stimuli that were previously indifferent. IP Pavlov called conditioned reflex. A conditioned reflex, Pavlov noted, is a physiological phenomenon, since it is associated with the activity of the central nervous system, and at the same time, a psychological one, since it is a reflection in the brain of specific properties of stimuli from the external world.

In Pavlov's experiments, conditioned reflexes in animals were most often developed on the basis of an unconditioned food reflex, when food served as an unconditioned stimulus, and one of the indifferent (indifferent) stimuli (light, sound, etc.) .).

Distinguish between natural conditioned stimuli, which serve as one of the signs of unconditioned stimuli (the smell of food, the squeak of a chicken for a chicken, causing her parental conditioned reflex, a squeak of a mouse for a cat, etc.), and artificial conditioned stimuli that are completely unrelated to unconditional reflex stimuli (for example, a light bulb, on the light of which a salivary reflex was developed in a dog, the ringing of a gong, on which moose gather for feeding, etc.). However, any conditioned reflex has a signal value, and if the conditioned stimulus loses it, then the conditioned reflex gradually fades away.

The presence of a second signaling system in humans leaves a significant imprint on the formation of conditioned reflexes, the development of cortical inhibition, the processes of irradiation and concentration of excitation and inhibition, on the processes of mutual induction, as well as on the nature of analytical and synthetic activity in humans.

Let us consider the features of the formation of conditioned reflexes to simple stimuli. Autonomic, somatomotor, and motor conditioned reflexes to simple stimuli are formed in humans much faster than in animals (especially in children and adolescents) and are characterized by extreme variability. But on the other hand than younger age, the less durable the conditioned reflex is formed and the more combinations are required to strengthen it. In contrast to animals, in humans, a motor conditioned reflex is often formed immediately in a specialized form, i.e. manifests itself only on the stimulus for which it was developed, without arising on similar stimuli.

During the formation and implementation of autonomic and somato-motor conditioned reflexes in a person, such a peculiar phenomenon is often observed: the conditioned reflex formed (and, moreover, very quickly) immediately suddenly disappears - the conditioned stimulus, despite continuing reinforcement, ceases to cause a reflex reaction. Such cases of "non-education" occur the more often, the older the subjects, and in children of the same age they are more common among the most capable and disciplined. Many researchers believe that this delay is due to the involvement of a second signaling system.

In general, the participation of the second signaling system gives a lot of specificity in the development of conditioned reflexes to stimuli of the first signaling system in humans. Various encouraging words or prohibitions, respectively, accelerate or slow down the development of conditioned reflexes in a person. With the help of verbal information that a certain indifferent stimulus will be accompanied by an unconditioned reinforcement known to the subject, it turned out to be possible to develop a conditioned reflex before the combination of these stimuli. So in one of the studies of G.A. Shichko, the subjects received the following information before the start of the experiments: "During the action of the bell, they will give you a cranberry extract." Immediately after the application of the conditioned stimulus (bell), a salivary reaction was observed in some of the subjects, while in others this information accelerated the formation of a conditioned reflex when an indifferent and unconditioned stimulus was combined. In the same way, it was possible to develop a blinking reflex in the subjects after the message that the sound of the metronome would be combined with a stream of air into the eye.

Let us consider the features of the development of conditioned reflexes in humans to complex stimuli. To simultaneous complex stimuli, reflexes are formed the faster the older age... The synthesis of a complex stimulus into a single whole also occurs faster when the separately used components lose their signal value. For example, after the formation of a conditioned motor reflex to the simultaneous action of red, green and yellow lights, 66% of children 11-12 years old had no motor reaction to the isolated use of individual components.

Conditioned reflexes to successive complex stimuli in humans are formed more slowly than to simple stimuli (the slower, the younger the age). Synthesis of a sequential complex of stimuli into a single whole is carried out more slowly than a simultaneous complex, although much faster than in animals. In comparison with animals, differentiation into a sequential complex stimulus is much easier and faster in humans.

In general, all these differences are explained by the presence of a second signaling system. Conditioned reflexes to relationships and temporarily are formed in humans much faster than in animals. For example, when feeding a newborn at certain hours, the appearance of motor and sucking movements was observed already on the 7th day of life a few minutes before the start of feeding, as well as an increase in gas exchange by the hour of eating. In adults, when eating at certain hours, food leukocytosis can be observed at the same hours and without eating. In general, people easily develop various reflexes for a while - food, cardiovascular, and respiratory. For example, when repeating at 5 minute intervals, muscle work(20 squats) the subjects experienced a noticeable increase in systolic pressure. It turned out that after 4-5 experiments at the fifth minute and without work, systolic pressure also increased (AS Dmitriev, R. Ya. Shikhova).

Compared to animals, humans have an immeasurably more developed ability to form conditioned reflexes. higher order- a person can have conditioned reflexes from the 2nd to the 20th order, and they are formed quickly. For example, in studies on adults using the salivary technique, a first-order conditioned reflex (when the tone is combined with giving cranberry extract) was formed and strengthened after 2-3 combinations. Conditioned reflexes of higher orders (up to the 15th order inclusive) to immediate and verbal stimuli were formed after 2-6 and strengthened after 2-13 combinations (GA Shichko). Influences through the second signaling system can have a great influence on the formation of conditioned reflexes of a higher order.

So, a characteristic feature of the formation of conditioned reflexes in humans is the active participation of the second signal system in this process. Due to this, in the formation of conditioned reflexes, the closure of not only the usual temporary connections (between the cortical point of the conditioned stimulus and the cortical representation of the unconditioned reflex) acquires significance, but also the connections between the cortical points of direct and verbal stimuli, i.e., associative or sensory connections, which are closed without reinforcement. ... The word, as a generalizing stimulus, is connected by numerous associative connections with other sensory areas of the cortex, and through them is connected with various previously developed systems of conditioned reflexes. And these latter can influence the formation of a conditioned reflex. So, thanks to the participation of the second signaling system, the possibility of rapid (sometimes "from the spot") formation of conditioned reflexes arises on the basis of generalization of the previous life experience of a person. And the more developed the second signal system, the richer a person's life experience, the more pronounced these specific features of the process of the formation of a conditioned reflex in a person.

Features of unconditional braking at person. Like animals external braking in humans, the stronger the stronger the external stimulus and the less strong the conditioned reflex. External inhibition encompasses both the first and second signal systems, which, in particular, is expressed in a decrease in the adequacy of reflection in the second signal system of the first signal conditional connections.

Outrageous braking occurs often in children, especially in young children, in whom already during the experiment, with the repetition of conditioned stimuli of moderate strength, transcendental inhibition often develops, which is expressed in the lengthening of the latent period, in a decrease in the magnitude of the conditioned reflex, as well as in the appearance of a feeling of fatigue, headache, sleepiness. The development of transcendental inhibition is facilitated by fatigue of cortical cells. Therefore, in the everyday life of a person, this type of inhibition is found at every step, especially in evening time... Other influences also lead to the development of transcendental inhibition, including various diseases- both acute and chronic. In general, in Everyday life transcendental inhibition provides rest and restoration of the working capacity of cortical cells tired during the day, and also helps to restore the functional properties of neurons in various diseases.

Features of internal inhibition in humans (differentiation, extinguishing, conditionally inhibitory and delayed). This type of inhibition is manifested in the same four forms (differentiation, extinguishing, conditional inhibition, and retardation) as in animals. In humans, it is produced at different rates, moreover, the faster the older the person. In adults, the rate and strength of the formation of internal inhibition is greater than in children, but with the onset of old age they begin to decrease more and more.

Differentiating inhibition in humans, in comparison with animals, develops faster, especially in adults. It's connected with active participation the second signal system, starting from a certain age, to play a leading role in the process of differentiation of stimuli. Actions through the second signaling system greatly accelerate the formation of differentiations. Thus, in studies of salivary conditioned reflexes in adults, after information that an extract would be given to blue light and not to a call, differentiation to an unreinforced stimulus was immediately formed (G.A. Shichko). With age, as the second signaling system develops, the ability to differentiate stimuli increases. For example, according to the subtlety of perception different colors and shades 14-year-olds outperform 6-year-olds by 90%.

The process of extinction in humans occurs in two phases. At the beginning of extinction after the first non-reinforcement, many children experience a short-term increase in excitability, which is expressed in a shortening of the latent period, in an increase in the strength of the conditioned reaction, in the appearance of intersignal reactions. This phase of increased excitability occurs the more often and the more pronounced the younger the age (in children 10-12 years old, it is rare). Actions through the second signaling system affect the process of extinction of conditioned reflexes. For example, in the study of salivary conditioned reflexes, the subject was told that in the future the conditioned stimulus would not be reinforced by the unconditioned one. With the subsequent application of the conditioned stimulus, the reaction to it disappeared (G. A. Shichko).

The formation of a conditioned brake in humans in some cases passes through the stage of secondary conditioned reflexes. This is manifested in the fact that after two or three applications of the inhibitory combination (conditioned signal + additional agent), this agent itself begins to induce a conditioned response. This phenomenon indicates an increase in the excitability of the cortex during the development of a conditioned brake. In some children, it is so strongly pronounced that it becomes completely impossible to form a conditional brake. However, in the majority, it manifests itself in the form of a short-term phase, after which the formation of a conditional brake begins. The second signaling system significantly affects the development of the conditional brake. For example, in studies of salivary conditioned reflexes, the subject was told that cranberry extract would be given to the sound of the whistle, but not to the metronome in combination with the whistle. After such information, the whistle in combination with the metronome did not cause any reaction, while one whistle produced profuse salivation (G.A. Shichko).

Retarded braking is the most difficult type of internal inhibition for a person - it forms slowly, especially in children and adolescents. With age, the formation of delayed inhibition proceeds more easily and faster, which is associated with the increasing role of the second signaling system in this process.

Features of irradiation and mutual induction of nervous processes in humans (selective and diffuse irradiation). I.P. Pavlov, noting that a person has a second signal system, pointed out that the basic laws established in the work of the first signal system, including the law of irradiation and concentration of nervous processes and the law of their mutual induction, should apply to the second signal system, as well as to their interaction. Numerous studies of this issue have confirmed the point of view of I.P. Pavlova.

First of all, the phenomenon of irradiation of nervous processes from one signal system to another was established, including the phenomenon of selective (elective) and diffuse irradiation.

The phenomenon of selective irradiation of excitement from the first signaling system to the second was first investigated in 1927 in the laboratory of A.G. Ivanov-Smolensky. In these studies, a motor conditioned reflex to a call with food reinforcement was developed in children, and then the action of various verbal stimuli was written in order to identify generalization. It turned out that only the use of the words "bell", "rings" (as well as the demonstration of a sign with the inscription "bell") immediately caused a motor reaction in children, while other words (for example, "window") did not cause such a reaction. At the same time, it was shown that the excitation process can selectively irradiate from the second signaling system to the first. So, after the formation of a motor conditioned reflex in children to the word "bell", the same reaction occurs immediately, "from the spot" and to the sound of a bell, which had never been used before. with reinforcements. The phenomena of elective irradiation of excitation from the first signaling system to the second and back were noticed during the formation of cardiac, vascular, respiratory, salivary, photochemical and other vegetative conditioned reflexes.

The phenomenon of diffuse irradiation of excitation from one signaling system to another manifests itself in the fact that after the development of a conditioned reflex to a direct stimulus, such a reaction begins to be elicited not only by words denoting a conditioned stimulus, but also by any other words.

Electoral irradiation of excitement in accordance with general laws movement of nervous processes is replaced by the subsequent the concentration of the excitation process at the starting point. Therefore, if the verbal stimulus, which caused the conditioned reaction by the mechanism of elective irradiation, is not reinforced, then after a while (sometimes for the second application) the conditioned reaction ceases to appear. The reaction is retained only to the immediate stimulus for which it was developed, that is, the conditioned reflex is specialized.

Elective irradiation of arousal, i.e. selective generalization of the conditioned reflex and its subsequent specialization proceed differently with different conditioned reflexes - the generalization phase is characteristic of autonomic reflexes, and rapid specialization is typical for motor conditioned reflexes. The younger the age, the more often there is irradiation (especially diffuse) of excitation from the first signaling system to the second.

The phenomenon of selective (elective) irradiation of all types of internal inhibition from one signaling system to another is also characteristic of humans. So, in children 9-10 years old, a motor reflex was developed with food reinforcement to a flash of blue light and differentiation to green light. It turned out that verbal designations of both positive and differentiating stimuli began to cause the same effect: the words "blue light" caused a conditioned motor reaction, and the words "green light" - inhibition of the reaction. In another study, after extinction of the conditioned motor reflex to a bell, the word “bell” acquired an inhibitory effect. If this word was included in the number of stimulating words during a verbal experiment, then a noticeable suppression of the speech reaction to this word was found. V next study children developed a conditioned brake (to the bell), and then it was found that the same inhibition of the conditioned reflex reaction also causes the word “bell” to be attached to the conditioned stimulus, while other words (for example, “cap”) do not provided.

It turned out that elective irradiation and the subsequent concentration of inhibition are characterized by a high speed. For example, extinguishing inhibition, which quickly radiated from the first signaling system to the second, leaves the second signaling system completely after 30-60 s and concentrates at the starting point.

Induction relationship between the first and second signaling systems in humans. Phenomena of mutual induction between the first and second signaling systems are also characteristic of humans. The phenomena of negative induction were identified in studies (L.B. Gakkel et al.), In which a person developed a blinking conditioned reflex to a metronome or a buzzer against the background of solving oral arithmetic problems, which began 5 seconds before giving the conditioned stimulus. It turned out that in many subjects, against the background of solving an arithmetic problem (solved quickly and correctly), the blink reflex either did not form at all, or it did form, but it was unstable. For example, in one subject the reflex was not formed even after 21 combinations; when the solution of the arithmetic problem was canceled, the blinking reflex was developed in him already at the 7th combination. Thus, the simultaneous formation of second-signal and first-signal conditional connections is complicated by their mutual inhibition according to the law of negative induction.

With age, as the second signaling system develops, the negative inductive influence from the second signaling system begins to prevail. “The second signaling system, said IP Pavlov, is predominant, especially valuable in the higher part of the central nervous system and, thus, must constantly exert negative induction on the first signaling system. The second signaling system constantly keeps the first signaling system under silence. "

Features of analytical and synthetic activity of the cerebral cortex of the human brain. The analytical and synthetic activity of the cerebral cortex of the human brain is characterized, in comparison with animals, by an immeasurably higher level of development. This is evidenced by the rapid development of various conditioned reflexes and differentiations, the easier and faster formation of complex conditioned reflex reactions, including conditioned reflexes to complex stimuli, to the ratio of stimuli, to time, conditioned reflexes of a higher order, etc., as well as a high ability to the formation of stereotypes and switchings. A higher level of development of analytical and synthetic activity of the human cerebral cortex is due to the presence of a second signaling system. It is the participation of the word that gives specific features to the process of formation of systems of temporary connections. To illustrate, we present the data obtained in the laboratory of M. M. Koltsova, which demonstrate the high ability of a person to develop a dynamic stereotype and switchings. A dynamic stereotype was developed in children 4-5 years old with the use of four stimuli in a certain sequence (beep - bell - M-120 - whistle); each sequence was combined with the action of a jet of air into the eye, causing an unconditioned blink reflex. This stereotype was formed after 6-12 combinations, when the entire chain of conditioned reflexes could be reproduced by using only the first stimulus. Conditioned reflex switching was studied in children aged 5-6 years. To do this, the same conditioned stimulus was combined under different conditions with different reinforcements: in one case, with the supply of a stream of air into the eye, causing a defensive blinking reaction, and in the other case, with the supply of food reinforcement (candy), causing food-procuring movement of the hand. Both the experimental setting (different experimental rooms, different times of the day, different experimenters) and individual stimuli (simple and complex, immediate and verbal) were used as switches. Studies have shown that conditioned reflex switching is produced in humans much faster than in animals. If in animals this required several dozen combinations, then in children 5-6 years old - from 4 to 29 combinations (depending on the nature and method of action of the switch). In this case, the leading in the development of conditioned reflex switching is the formation of so-called sensory connections, which is facilitated by the use of verbal stimuli as switching signals. For example, if the switch is a word unfamiliar to the child, then switching is developed relatively slowly (after 37 combinations), but if it is a familiar word, then switching is developed much faster - after 16-25 combinations. This is due to the fact that the word, in the process of becoming a second-signal stimulus, is associated with numerous and strong sensory connections with other stimuli (both direct and verbal). Thanks to this, the word, on the one hand, acquires a generalizing meaning, and on the other hand, it acquires the ability, when combined with other stimuli, to form strong sensory connections. It is for this reason that faster and more durable systems of temporary connections are formed with the participation of verbal stimuli.

Consider the formation of systems of temporary connections between words. Specific feature analytic-synthetic human activity is the participation of verbal stimuli in it, due to which it becomes possible to carry out complex behavioral reactions without preliminary elaboration, "from the spot", on the basis of generalization of previously acquired life experience. This ability is based on the possibility of forming systems of temporary connections between words.

These systems include verbal stereotypes. It is their education that provides the opportunity for all-round interaction and mutual influence between people with the help of words.

The formation of verbal stereotypes begins in children at the beginning of the second year of life, when, along with the process of converting individual words into independent stimuli in communication with the child, separate phrases are used that organize the child's behavior ("Let's go to eat", "Open your mouth", "Give me a pen" and etc.). Such phrases at this age become units of speech for the child. Verbal stereotypes are formed according to the same patterns as dynamic stereotypes for immediate stimuli. Words in this stereotype initially act as simple auditory stimuli that do not have the meaning of "signal cues". The first time they are applied in a certain sequence (for example, in the phrase "Give me a pen"), sensory connections are formed between the words of the phrase based on kinesthetic reinforcement during the articulation of these words (in other cases, food reinforcement can also be added to this). Subsequently, individual words begin to acquire a signal meaning. Thus, the pronunciation of the phrase "Give me a pen" in combination with the movement of the child's hand (first passive and then active) will lead to the fact that the word "pen", and later the words "me" and "give" will become signals of certain reactions. With the acquisition of signal meaning by words, sensory connections are fixed between them.

The process of the formation of verbal stereotypes at that stage of the child's development (usually, from the end of the 2nd year of life), when words become integrators of the second and then of a higher order, acquires other features. As the degree of integration of the word increases, i.e. As the number of sensory connections of a word with other stimuli increases, connections of this word with other members of the verbal stereotype are more and more easily formed (and with less participation of unconditional reinforcement), and these connections become more and more strong. In turn, the formation of systems of conditioned connections between words raises generalization in the higher nervous activity of a person to a higher level. For example, a conditioned reaction formed to one or another immediate stimulus is caused not only by the word denoting this stimulus, but also by integrator words of a higher order, as well as by the words combined by these integrator words. So, in the studies of G.D. Naroditskaya showed that after the formation of conditioned motor reactions to images of various birds (titmouse, stork, swallow, etc.), the same reaction arose "from the spot" not only to the words "titmouse", "stork", "swallow" and etc., but also on the generalizing word "bird". If at the same time differentiations were developed on the images of various animals (tiger, zebra, antelope, etc.), then not only the words “tiger”, “zebra”, “antelope”, etc., caused the same inhibitory effect “from the spot”. etc., but also the generalizing word "beast". Generalization can manifest itself in a more complex form. Thus, in the experiments of VD Volkova, children of 13 years old developed a salivary conditioned reflex to the word "good" and differentiation to the word "bad." It turned out that from the very first application they began to cause a salivary reaction and all phrases that in their meaning speak of “good” (for example, “The student is a great student”). Phrases that speak of "bad" (for example, "The student broke the glass"), caused "from the spot" inhibition of the salivary reaction. In another study of her, children developed a conditioned salivary reflex to the word "ten" and differentiation to the word "eight". It turned out that not only these words, but also the most diverse speech stimuli expressing examples for addition, subtraction, multiplication and division, began to cause one or another reaction from the spot. So, if, as a result of the arithmetic operation, the number 10 was obtained, then a salivary reaction appeared, and if the number was 8, then the reaction was inhibited.

The meaning of the conditioned reflex... In the process of evolution, living organisms have developed a special mechanism that made it possible to respond not only to unconditioned stimuli, but also to a mass of indifferent (indifferent) stimuli that coincide in time with unconditioned stimuli. Thanks to this mechanism, the appearance of indifferent stimuli signals the approach of those agents that have biological significance; the body's connections with the outside world expand, become more perfect, more subtle and allow better adaptation to diverse and changeable conditions of existence. Thus, the acquisition by living organisms of the ability to learn in the process of individual development (moreover, without consolidating this experience by inheritance) demonstrates a huge leap in the evolution of living things.

Due to the emergence of the ability to form conditioned reflexes in living organisms, the possibility of early regulation of the activity of internal organs arose, the arsenal of motor acts acquired in the process of individual development has significantly expanded. Due to the formation of conditioned reflexes, many indifferent stimuli acquire the role of a warning factor signaling the onset of upcoming events, including those dangerous for the body (as you know, defensive conditioned reflexes help the body prepare in advance for defense and avoid the danger that threatens it). Conditional reflexes, thus, provide a premature (anticipatory) response of humans and animals to the inevitability of the impact of an unconditioned stimulus, and in this respect they play a signaling role in the behavioral response. Due to the fact that on the basis of the conditioned reflex of the first order, reflexes of a higher order can be developed, the system of conditioned reflexes allows the body to deeply and accurately assess the conditions external environment and on this basis respond in a timely manner by changing behavioral reactions in a specific situation.

The conditioned reflex was the basis of higher nervous activity, i.e. the basis of human and animal behavior. The appearance in evolution of the ability to develop a conditioned reflex created the precondition for the emergence of consciousness, thinking and speech. The conditioned reflex mechanism underlies the formation of any acquired skill, the basis of the learning process, including motor, sensory, intellectual (reading, writing, thinking) skills and abilities. Based on the development of simple conditioned reflexes, a dynamic stereotype is formed, which forms the basis of professional skills and many habits of a person. Thus, with the participation of conditioned reflexes, a person cognizes the environment and actively reconstructs it.

Although conditioned reflexes are not inherited, it is with their direct participation (including through imitative reflexes) that a large amount of information is transmitted from one generation to another in animals and humans.

Thanks to conditioned reflexes in humans, it is possible social adaptation... With the help of techniques based on the formation of conditioned reflexes, it is possible to carry out preventive and therapeutic work.

At the same time, it should be borne in mind that conditioned reflexes can underlie the formation of harmful needs and habits undesirable for human health, as well as pathological conditioned reflexes such as conditioned reflex spasm of the coronary vessels, which, along with pain reactions, can lead to the development of myocardial infarction.

I.P. Pavlova on neuroses. Experimental neuroses. Neuroses - these are functional disorders of the GNI, which can turn into profound disorders of mental activity, i.e. into psychosis. I.P. Pavlov came to the idea of ​​neuroses by chance, observing the behavior of experimental animals that survived the flood in Leningrad. The animals seem to have "lost their minds." Neuroses were expressed in sleep disturbance, in the inability to reproduce already developed reflexes or to develop new ones, in a violation of behavior, which in animals with choleric features was in the nature of overexcitation, and in animals with melancholic features - the character of drowsiness, apathy. Even after the restoration of conditioned reflexes, they could not respond normally to strong stimuli, especially those associated with the shock experienced. In general, I.P. Pavlov and his co-workers came to the conclusion that experimental neurosis is a long-term disturbance of GNI that develops in animals under emotional (psychogenic) influences due to overstrain of excitatory or inhibitory nervous processes or their mobility.

Later, in the laboratories of I.P. Pavlov, methods were developed that allow to induce neurosis in animals, i.e. simulate a neurotic state, as well as cure it.

1. Overstrain of the excitatory process by the action of "superstrong" stimuli. For this purpose, a particularly strong stimulus was used in the experiment (similar to that which took place in dogs that survived the 1924 flood in Leningrad).

2. Overvoltage of the braking process. It was achieved through the persistent development of subtle differentiations, i.e. distinguishing very close, similar, hardly distinguishable stimuli, as well as by delaying the action of inhibitory stimuli or by delaying reinforcement for a long time.

3. Overexertion of the mobility of nervous processes. It was achieved by rather rapid and frequent alterations of the signal value of positive and negative conditioned stimuli or by an emergency breaking of stereotypes.

4. Collision of excitation and inhibition, or "collision" of nervous processes. This type of IRR disturbance in experimental animals arose due to alteration of a complex dynamic stereotype, as well as due to too rapid change or simultaneous action of stimuli of opposite signal value. By the way, the first experimental neuroses in the laboratory of I.P. Pavlov were obtained precisely in this way during the development of a conditioned food reflex to a signal of a painful stimulus causing a defensive reaction. Later, in the laboratory of I.P. Pavlova enjoyed different ways, including the use of a feeder under current, which is closed by the dog's muzzle, placing dummy snakes in monkey feeders, etc. Studies on dogs have shown that it is easier to cause a neurotic breakdown in a weak and unrestrained type of nervous system, and in the first case, the excitatory process suffers more often, and in the second, the inhibitory process. These data are also confirmed by observations of people with manifestations of neurosis.

Experimental neurosis is characterized by impaired adaptive behavior, sleep, chaotic conditioned reflexes, the appearance of phase states (with equalizing and paradoxical phases), pathological inertia of nervous processes, as well as disorders of autonomic functions (this reflects the functional connection of the cerebral cortex and internal organs). In particular, with neuroses, the acidity of gastric juice increases, stomach atony sets in, the secretion of bile and pancreatic juice increases without a corresponding change in blood supply, a persistent increase in blood pressure is observed, the activity of the kidneys and other systems is disrupted.

Modeling neuroses, in the laboratories of I.P. Pavlova, they were looking for ways to correct these conditions. Effective methods were the refusal to experiment with animals, changing the environment, prolonged rest, normalization of sleep, the use of pharmacological drugs. At the same time, bromine derivatives were used to restore inhibition, and caffeine preparations were used to restore arousal. Potions containing in certain ratios a mixture of bromine and caffeine, it was possible to restore the balance of excitation and inhibition, characteristic of the normal state of the VIS. Thus, it was shown that the effectiveness of pharmacological agents depends on the state of the central nervous system and the nature of the neurotic breakdown.

Currently, experimental neurosis is widely used as a model for studying the mechanisms of pathogenesis, as well as the possibilities of prevention and treatment of neurotic conditions, and in general, the study of experimental neuroses gave impetus to the development of such a direction in medicine as cortico-visceral pathology (K.M.Bykov, M. . K. Petrova).

Physiology alone holds in its hands the key to a truly scientific analysis of mental phenomena.

I. M. Sechenov

4.1. Reflex as the main form of activity of the nervous system

The structure of the nervous system and the totality of the processes taking place in it make it possible to perform regulatory and control functions that provide:

1. Rapid coordination of body functions.

2. Coordination of the state of the organism with different conditions environment.

3. Unification of individual organs and systems of the body into a single whole.

The control apparatus in higher animals and humans is represented by a reflex mechanism, which manifests itself in all parts of the nervous system and is the main form of activity of the nervous system. The first ideas about the reflex principle of the activity of the nervous system, that is, about the principle of "reflection" and the concept reflex were introduced by R. Descartes in the 17th century. But due to the lack of scientific information about the structure and function of the nervous system, his ideas about the mechanism of the reflex were speculative and mechanistic. So, Descartes explained the motor reaction in response to external influence by the fact that under the influence of any stimulus on the sense organs, "nerve threads" are pulled, going along the "neural tubes" to the brain. The tension of the threads leads to the opening of "valves" through which the "animal spirit" emerges from the brain, rushing along the nerves to the muscles and inflating them.

Currently reflex called any reaction organism, arising from the action of an irritant from the external or internal environment and carried out with the obligatory participation of the central nervous system. Any reflex is based on the sequential propagation of an excitation wave through the elements of the nervous system, which forms the so-called reflex arc (fig. 4.1).

Rice. 4.1. Scheme of the reflex arc of the spinal reflex:

1 - receptor; 2 - sensitive nerve cell; 3 - sensitive posterior root; 4 - central (contact) part of the reflex arc; 5 - motor neuron; 6 - efferent (motor) nerve fiber; 7 - muscle; 8 - spinal cord

To understand how the reflex is carried out and what a reflex arc is, consider how the hand is pulled back when a hot object is exposed to it. At this moment in the receptors - sensitive nerve endings - excitement arises, which, according to afferent(centripetal) fiber is transmitted to the sensitive nerve cell. From it, along the axon, excitation is transmitted to the central nervous system to intercalary neurons, in which complex processes of processing the received information take place. After this, the excitation will be transmitted to the motor nerve cells and along their axon ( efferent, centrifugal fiber) will go to the muscles, which, by contracting, will cause the arm to withdraw.

According to the theory of I.P. Pavlov, the reflex arc of any reflex consists of three parts: analyzer, contact and executive.

Analyzer part includes a receptor, afferent fiber and a sensory nerve cell. The function of the receptor is to perceive irritation and process (transform) it into a nerve impulse.

Receptors are specific: they are adapted to the perception of a certain stimulus. Rirritant - it is a factor with a certain amount of energy, which, when applied to the tissue, is capable of causing its excitement. So, the effect of chemical energy is perceived chemoreceptors, thermal - thermoreceptors, mechanical - mechanoreceptors, electromagnetic oscillations with a certain wavelength (light) - photoreceptors etc. In relation to receptors, all stimuli can be divided into adequate and inadequate. Adequate for this type of receptor is the stimulus to the perception of which they are adapted. The threshold intensity of an adequate stimulus is much lower than that of an inadequate one. So, the sensation of light under the action of a light stimulus occurs when its power is 10 -17 -10 -18 W. But a mechanical, inadequate effect on the eyeball also causes the sensation of a flash of light. In this case, the power of the stimulus should be at least 10 -4 W, ie, 13-14 orders of magnitude higher than the power of the adequate stimulus.

In addition, stimuli are classified according to the strength or magnitude of the applied energy. By strength, the following types of stimuli are distinguished:

a) subthreshold - weak stimuli that do not cause a visible response;

b) threshold - minimal stimuli, causing a minimal response;

c) suprathreshold - stimuli of different strength, causing a reaction corresponding to their strength;

d) maximum - strong stimuli that cause the maximum possible reaction.

Depending on the location of the receptors, they can be divided into two groups: exterO- and interoreceptors... The former are excited by various factors of the external environment, the latter are sensitive to fluctuations in the parameters of the internal environment. And finally, there are the so-called proprioceptors(own receptors), which perceive changes in the state of muscles, ligaments and tendons.

Contact part the reflex arc is represented by intercalary neurons of the spinal cord or brain.

In the simplest case, the reflex arc includes only two neurons, and impulses are transmitted from centripetal to centrifugal nerve fiber... More often, excitation in the central nervous system passes through a number of interneurons. The more complex the reflex, the more associative cells are included in the contact part of the reflex arc.

It should be noted the existence of the so-called "reflex arcs with a humoral link." Such arcs differ in that information from the central nervous system, which causes a change in the state of the working organ, is transmitted not through nerve conductors, but through the humoral route, through the release of hormones into the blood.

Executive link The reflex arc consists of an effector neuron and an executive organ, or effector. These organs include muscles and glands. Effectors are characterized by the fact that when excited, they perform specific work that can be measured: muscles contract, glands secrete a secret.

However, the reflex act does not end with the activities of the executive body. Each effector has its own sensitive receptor devices, which, in turn, signal to the central nervous system about the work they have done. The information from the receptors, the excitation of which is caused by the reflex, is compared with the flow of impulses coming from the receptors of the executive organ. Thanks to this comparison, the response of the organism is refined. The connection of the receptors of the working organ with the central nervous system is called "feedback". Therefore, it is more correct to talk not about a reflex arc, but about reflex ring .

Grade 8 textbook

Higher nervous activity

Higher nervous activity (HND) is understood as all those nervous processes that underlie human behavior, ensuring the adaptation of each person to rapidly changing and often very difficult and unfavorable conditions of existence. The material basis of higher nervous activity is the brain. It is in the brain that all information about what is happening in the world around us flows down. Based on a very fast and accurate analysis of this information, the brain makes decisions that lead to changes in the activity of the body's systems, ensuring the optimal (best under these conditions) human interaction with environment maintaining the constancy of his internal environment.

Reflex activity of the nervous system

The thought that mental activity carried out with the participation of the nervous system, arose in ancient times, but how this happens for a very long time remained unclear. Even now, it cannot be said that the mechanisms of the brain are fully disclosed.

The first scientist to prove the participation of the nervous system in the formation of human behavior was the Roman physician Galen (2nd century AD). He discovered that the brain and spinal cord are connected to all other organs by nerves, and that a break in the nerve that connects the brain and muscle leads to paralysis. Galen also proved that when the nerves coming from the senses are cut, the body ceases to perceive stimuli.

The origin of brain physiology as a science is associated with the works of the French mathematician and philosopher René Descartes (17th century). It was he who laid down the idea of ​​the reflex principle of the body's work. True, the term "reflex" itself was proposed in the 18th century. by the Czech scientist I. Prochazka. Descartes believed that the activity of the brain, like that of the entire human body, is based on the same principles as the basis of the operation of the simplest mechanisms: clocks, mills, bellows, etc. Explaining simple human movements from a completely materialistic standpoint, R. Descartes recognized the presence of a soul in him, which governs the complex and varied behavior of a person.

What is a reflex? A reflex is the most correct, most common response of the body to external stimuli, which is carried out through the nervous system. For example, a child touched a hot stove with his hand, and mi newly felt pain. Only correct solution, which the brain always accepts in this situation, is to pull back the hand in order not to get burned.

For more high level the doctrine of the reflex principle of the body's activity was developed by the great Russian physiologist Ivan Mikhailovich Sechenov (1829-1905). The main work of his life - the book "Reflexes of the Brain" - was published in 1863. In it, the scientist proved that the reflex is a universal form of interaction of the organism with the environment, that is, the reflex character is not only involuntary, but also voluntary - conscious movement. They begin with irritation of any sense organs and continue in the brain in the form of certain neural phenomena that lead to the launch of behavioral programs. IM Sechenov was the first to describe inhibitory processes developing in the central nervous system. In a frog with destroyed cerebral hemispheres, the scientist studied the reaction to irritation of the hind leg with an acid solution: in response to a painful stimulus, the leg flexed. Sechenov found that if a crystal of salt was previously applied to the surface of the midbrain in an experiment, the time to a response would increase. Based on this, he concluded that reflexes can be inhibited by some kind of strong influences. A very important conclusion made by scientists at the end of the 19th - beginning of the 20th centuries was the conclusion that any response of the body to a stimulus is always expressed by movement. Any sensation, consciously or unconsciously, is accompanied by a motor response. By the way, it is precisely on the fact that any reflex ends with muscle contraction or relaxation (i.e., movement), and the work of lie detectors is based, capturing the smallest, unconscious movements of an agitated, alarmed person.

The assumptions and conclusions of I.M.Sechenov were revolutionary for their time, and not all scientists at that time immediately understood and accepted them. Experimental evidence of the truth of Sechenov's ideas was obtained by the great Russian physiologist Ivan Petrovich Pavlov (1849 1936). It was he who introduced the term "higher nervous activity" into the scientific language. He believed that higher nervous activity is equivalent to the concept of "mental activity".

Indeed, both sciences — physiology of GNI and psychology — study the activity of the brain; they are united by a number common methods research. At the same time, the physiology of GNI and psychology investigate different sides work of the brain: physiology of VND - the mechanisms of activity of the whole brain, its individual structures and neurons, connections between structures and their influence on each other, as well as mechanisms of behavior; psychology - the results of the work of the central nervous system, manifested in the form of images, ideas, representations and other mental manifestations. The scientific research of psychologists and physiologists of GNI has always been interdependent. In recent decades, there has even been new science- psychophysiology, the main task of which is to study the physiological foundations of mental activity.

All reflexes that arise in the body of an animal or a person, I.P. Pavlov subdivided into unconditioned and conditioned.

Unconditioned reflexes. Unconditioned reflexes ensure the adaptation of the body to constant environmental conditions. In other words, it is the body's response to strictly defined external stimuli. All animals of the same species have a similar set of unconditioned reflexes. Therefore, unconditioned reflexes are classified as species characteristics.

An example of unconditioned reflexes is the onset of a cough when foreign bodies enter the respiratory tract, withdrawal of the hand when pricked on the thorns of a rose.

Already in a newborn child, unconditioned reflexes are observed. This is understandable, because it is impossible to live without them, and there is no time to learn: breathing, eating, avoiding dangerous influences is necessary from the very first moments of life. One of the important reflexes of newborns is the sucking reflex - an unconditioned food reflex. An example of a protective unconditioned reflex is constriction of the pupil in bright light.

The role of unconditioned reflexes in the life of those creatures whose existence lasts only a few days, or even only one day, is especially important. For example, the female of one of the species of large solitary wasps emerges from the pupa in the spring and lives only for a few weeks. During this time, she must have time to meet the male, catch the prey (spider), dig a hole, drag the spider into the hole, lay eggs. She does all these actions several times during her life. The wasp emerges from the pupa as an "adult" and is immediately ready to carry out its activity. This does not mean that she is incapable of learning. She, for example, can and should remember the location of her mink.

More complex forms of behavior - instincts - are a chain of sequentially related reflex reactions that follow one after another. Here, each individual reaction serves as a signal for the next. The presence of such a chain of reflexes allows organisms to adapt to a particular situation, the environment.

A striking example of instinctive activity is the behavior of ants, bees, birds when building a nest, etc.

The situation is different in highly organized vertebrates. For example, a wolf cub is born blind and completely helpless. Of course, at birth he has a number of unconditioned reflexes, but they are not enough for a fulfilling life... In order to adapt to existence in constantly changing conditions, it is necessary to develop a wide range of conditioned reflexes. Conditioned reflexes, developed as a superstructure over innate reflexes, greatly increase the body's chances of survival.

Conditioned reflexes. Conditioned reflexes are the reactions acquired during the life of each person or animal, with the help of which the organism adapts to the changing influences of the environment. For the formation of a conditioned reflex, the presence of two stimuli is necessary: ​​a conditioned (indifferent, signal, indifferent to the generated reaction) and an unconditioned, causing a certain unconditioned reflex. The conditioned signal (a flash of light, the sound of a bell, etc.) should be somewhat ahead of the time of the unconditional reinforcement. Usually a conditioned reflex is developed after several combinations of conditioned and unconditioned stimuli, but in some cases, one presentation of the conditioned and unconditioned stimuli is enough for a conditioned reflex to form.

For example, if you turn on the light bulb several times before giving the dog food, then, starting at some point, the dog will go to the feeder and saliva every time the light is turned on, even before the food is presented to it. Here, light becomes a conditioned stimulus, signaling that the body must prepare for an unconditioned reflex food reaction. A temporary functional connection is formed between the stimulus (the light of the bulb) and the food reaction. The conditioned reflex is developed in the learning process, and the connection between the sensory (in our case, the visual) system and the effector organs that ensure the implementation of the food reflex is formed on the basis of the combination of the conditioned stimulus and its unconditioned reinforcement with food. So, for the successful development of a conditioned reflex, three conditions must be met. First, the conditioned stimulus (in our example, light) must precede unconditioned reinforcement (in our example, food). Second, the biological significance of the conditioned stimulus should be less than that of unconditioned reinforcement. For example, for a female of any mammal, the cry of her young is obviously a stronger irritant than food reinforcement. Thirdly, the strength of both conditioned and unconditioned stimuli must have a certain value (the law of strength), since very weak and very strong stimuli do not lead to the development of a stable conditioned reflex.

A conditioned stimulus can be any event that occurred in the life of a person or animal, which several times coincided with the action of reinforcement.

The brain, capable of developing conditioned reflexes, considers conditioned stimuli as signals indicating the imminent appearance of reinforcement. Thus, an animal with only unconditioned reflexes can only eat food that it accidentally stumbles upon. An animal, on the other hand, capable of developing conditioned reflexes, associates a previously indifferent smell or sound with the presence of food nearby. And these irritants become a clue that makes him look for prey more actively. For example, pigeons can sit quietly on the eaves and windowsills of some architectural landmark, but as soon as a bus with tourists approaches them, the birds will immediately begin to descend to the ground, expecting to be fed. Thus, the sight of the bus, and especially of tourists, is a conditioned irritant for pigeons, saying that they need to take a comfortable seat and start fighting with rivals for food.

As a result, an animal capable of rapidly developing conditioned reflexes will more successfully obtain food than one that lives using only a set of innate unconditioned reflexes.

Braking. If unconditioned reflexes are practically not inhibited during life, then developed conditioned reflexes can lose their significance when the conditions for the existence of an organism change. The extinction of conditioned reflexes is called inhibition.

Distinguish between external and internal inhibition of conditioned reflexes. If, under the influence of a new strong external stimulus, a focus of strong excitation arises in the brain, then the previously developed conditioned reflex connection does not work. For example, a conditioned alimentary reflex in a dog is inhibited by a strong noise, fright, the action of a painful stimulus on it, etc. This type of braking is called external. If the reflex of salivation developed for the bell is not reinforced by feeding, then gradually the sound ceases to play the role of a conditioned stimulus; the reflex will begin to fade and will soon slow down. The temporary connection between the two centers of excitation in the cortex will collapse. This type of inhibition of conditioned reflexes is called internal.

Skills. In an independent category of conditioned reflexes, motor conditioned reflexes developed during life, i.e., skills, or automated actions, are distinguished. A person learns to walk, swim, ride a bicycle, type on a computer keyboard. Learning takes time and perseverance. However, gradually, when the skills are already fixed, they are performed automatically, without mind control.

During his life, a person masters many special motor skills associated with his profession (working on a machine, driving a car, playing a musical instrument).

Skills are good for a person because it saves time and energy. Consciousness and thinking are freed from the control of operations that have become automated and become skills in everyday life.

Works by A. A. Ukhtomsky and P. K. Anokhin

At every moment of life, many external and internal stimuli act on a person - some of them are very important, while others can be neglected at the moment. After all, the body cannot provide the simultaneous realization of many reflexes. You shouldn't even try to satisfy the need for food while running away from the dog. You have to choose one thing. According to the great Russian physiologist Prince A.A.Ukhtomsky, a single focus of excitation temporarily dominates in the brain, as a result of which the fulfillment of one vital reflex at the given moment is ensured. A. A. Ukhtomsky called this focus of excitement the dominant (from the Latin "dominance" - dominant). Dominants constantly replace each other as the main needs at some point are satisfied and new ones arise. If the need for food after a hearty dinner has passed, the need for sleep may arise, and a completely different dominant will appear in the brain, aimed at finding a sofa and a pillow. The dominant focus inhibits the work of neighboring nerve centers and, as it were, subordinates them to itself: when you want to eat, your sense of smell and taste are exacerbated, and when you want to sleep, the sensitivity of the sense organs weakens. The dominant lies at the heart of such mental processes, as attention, will, and makes a person's behavior active and selectively aimed at meeting the most important needs.

Since the organism of an animal or a person cannot simultaneously fully respond to several different stimuli, it is necessary to establish something like a "queue". Academician P.K.Anokhin believed that in order to satisfy the most important need at the moment, various systems and the organs are combined into a so-called "functional system", consisting of many sensitive and working links. This functional system "works" until the desired result is achieved. For example, feeling hungry, a person is full. Now the same systems that were involved in the search, production, absorption of food can unite into a different functional system and participate in the satisfaction of other needs.

Sometimes the previously developed conditioned reflexes persist for a long time, even if they no longer receive unconditioned reinforcement.

• In the English cavalry of the middle of the XIX century. horses have been taught for years to attack in close formation. Even if the rider was knocked out of the saddle, his horse had to gallop in a general formation side by side with other horses and make a U-turn with them. During Crimean War in one of the attacks, the cavalry unit suffered very heavy losses. But the surviving part of the horses, turning around and supporting the formation as possible, went to their starting position, saving those few wounded cavalrymen who were able to stay in the saddles. As a token of gratitude, these horses were sent from Crimea to England and kept there in excellent conditions without forcing you to walk under the saddle. But every morning, as soon as the stable doors opened, the horses ran out onto the field and lined up. Then the leader of the herd gave a signal with a neigh, and the line of horses rushed in perfect order across the entire field. At the edge of the field, the line unfolded and returned in the same order to the stable. And this was repeated from day to day ... This is an example of a conditioned reflex that persisted long time without unconditional reinforcement.

Test your knowledge

1. What are the merits of I.M.Sechenov and I.P. Pavlov in the development of the doctrine of higher nervous activity?
2. What is an unconditioned reflex?
3. What unconditioned reflexes do you know?
4. What underlies innate behavior?
5. How does a conditioned reflex differ from an unconditioned one?
6. What is instinct?
7. What conditions are necessary for the development of a conditioned reflex?
8. What forms of behavior can be attributed to acquired?
9. Why can a conditioned reflex fade over time?
10. What is the essence of conditioned inhibition?

Think

As a result, the conditioned reflex fades away? What is the biological meaning of this phenomenon?

The reflex is the cornerstone of nervous activity. Distinguish between congenital and acquired behavior. They are based on unconditioned and conditioned reflexes. Complex shape acquired behavior is rational activity, it is the beginning of thinking. Conditioned reflexes can fade away. Distinguish between unconditional and conditional inhibition.