Introduction
1. Reflex theory and its basic principles
2. Reflex - a concept, its role and significance in the body
3. The reflex principle of building 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 paper 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. V. M. Bekhterev, P. K. Anokhin and other physiologists are the scientific and theoretical basis of Soviet physiology and psychology. These propositions 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.
Principle of materialistic determinism means that each nervous process in the brain is determined (caused) by the action of certain stimuli.
Structural principle lies in the fact that the differences in the functions of different parts of the nervous system depend on the features of their structure, and the change in the structure of parts of the nervous system in the process of development is due to a change in functions. Thus, in animals that do not have a brain, the higher nervous activity is much more primitive than the higher nervous activity of animals that have a brain. In humans, in the course of historical development, the brain has reached a particularly complex structure and perfection, which is associated with its labor activity and social living conditions that require constant verbal communication.
Principle of analysis and synthesis is expressed as follows. When centripetal impulses enter the central nervous system, excitation occurs in some neurons, inhibition occurs in others, i.e., a physiological analysis occurs. The result is the distinction between specific objects and phenomena of reality and processes occurring inside the body.
At the same time, during the formation of a conditioned reflex, a temporary nervous connection (closure) is established between the two foci of excitation, which physiologically expresses synthesis. The conditioned reflex is the unity of analysis and synthesis.
2. Reflex - a concept, its role and significance in the body
Reflexes (from the Latin slot reflexus - reflected) are the body's responses to irritation of receptors. In the receptors, nerve impulses arise, which, through the sensory (centripetal) neurons, enter the central nervous system. There, the received information is processed by intercalary neurons, after which motor (centrifugal) neurons are excited and nerve impulses actuate the executive organs - muscles or glands. Intercalary neurons are called neurons, the bodies and processes of which do not go 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, security, etc. They contribute to the survival of an individual or species as a whole. They are classified into food, water-producing, defensive, sexual, orienting, nest-building, etc. There are reflexes that establish a certain order (hierarchy) in a herd or flock, and territorial reflexes that determine the territory captured by one or another individual or flock.
There are positive reflexes, when the stimulus causes a certain activity, and negative, inhibitory, in which the activity stops. The latter, for example, include a passive-defensive reflex in animals, when they freeze at the appearance of a predator, an unfamiliar sound.
Reflexes play an exceptional role in maintaining the constancy of the internal environment of the body, 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 speeding up the contractions of the heart and narrowing the lumen of the arteries, as a result, the pressure rises. It continuously fluctuates around a certain constant value, which is called the 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. There are reflexes 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, excitation occurs in the centers of the brain that regulate the flow of water and a feeling of thirst appears. This arousal causes goal-directed behavior, the search for 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. So, while 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.
A great achievement of physiology was the discovery by IP Pavlov of conditioned reflexes.
Unconditioned reflexes are inborn, 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 pain irritation with a defensive reaction. There is a wide variety of unconditioned reflexes: defensive, food, orientation, sexual, etc.
The reactions that underlie unconditioned reflexes in animals have been developed over thousands of years in the course of adaptation of various animal species to the environment, in the process of struggle for existence. Gradually, under conditions of long evolution, the unconditioned reflex reactions necessary to satisfy the biological needs and preserve the vital activity of the organism were fixed and inherited, and those of the unconditioned 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 a constant change in the environment, more durable and perfect forms of animal response were required to ensure the adaptation of the organism to the changed conditions of life. In the process of individual development, highly organized animals form a special type of reflexes, which IP Pavlov called conditional.
Conditioned reflexes acquired by an organism during its lifetime provide an appropriate response of a living organism to changes in the environment and, on this basis, balance 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 humans are carried out mainly by the higher part of the central nervous system (cerebral cortex).
The observation of the phenomenon of "mental secretion" in a dog helped IP Pavlov to discover the conditioned reflex. The animal, seeing food at a distance, intensively salivated even before the food was served. This fact has been interpreted in different ways. The essence of "mental 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, a flashing light, etc.) can cause 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 a cup in which there was food, then there always came a moment when the dog began to salivate just at one knock. Reactions that are caused by stimuli that were previously indifferent. I. P. Pavlov called conditioned reflex. The conditioned reflex, I. P. 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 the specific properties of stimuli from the outside world.
Conditioned reflexes in animals in the experiments of I. P. Pavlov were most often developed on the basis of an unconditioned food reflex, when food served as an unconditioned stimulus, and one of the stimuli (light, sound, etc.) indifferent (indifferent) to food performed the function of a conditioned stimulus. .).
There are 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, which causes a parental conditioned reflex in it, the squeak of a mouse for a cat, etc.), and artificial conditioned stimuli that are completely unrelated to unconditioned reflex stimuli. (for example, a light bulb, to 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.
3. The reflex principle of the construction of the nervous system The principle of feedback
From the point of view of modern science, the nervous system is a collection of neurons connected by synapses into cell chains that act on the principle of reflection, that is, reflexively. Reflex (from Latin reflexus - “turned back”, “reflected”) - the body's reaction to irritation, carried out with the help of the nervous system. The first ideas about the reflected activity of the brain were expressed in 1649 by the French scientist and philosopher Rene Descartes (1590-1650). He considered reflexes as the simplest movements. However, over time, the concept has expanded.
In 1863, the creator of the Russian school of physiologists, Ivan Mikhailovich Sechenov, uttered a phrase that went down in the history of medicine: "All acts of conscious and unconscious activity are, by way of origin, reflexes." Three years later, he substantiated his claim in the classic Reflexes of the Brain. Another Russian scientist I. P. Pavlov built on the statement of a brilliant compatriot the doctrine of higher nervous activity. The reflexes underlying it, Pavlov divided into unconditional, with which a person is born, and conditional, acquired during life.
The structural basis of any reflex is the reflex arc. The shortest consists of three neurons and functions within the torso. It turns on when the receptors are irritated (from Latin . recipio - “take”); they are sensitive nerve endings or special cells that convert this or that effect (light, sound, etc.) into biopotentials (from the Greek "bios" - "life" plat. potentia - "strength").
Through centripetal - afferent (from Latin affero - “I bring”) fibers, signals arrive at the so-called first (sensitive) neuron located in the spinal ganglion. It is he who passes through himself the initial information, which the brain transforms in a fraction of a second into familiar sensations: touch, prick, warmth ... Along the axon of a sensitive nerve cell, impulses follow to the second neuron - intermediate (intercalary). It is located in the posterior sections, or, as experts say, the posterior horns of the spinal cord; a horizontal section of the spinal cord really looks like the head of a strange animal with four horns.
From here, the signals have a direct road to the anterior horns: to the third - motor - neuron. The axon of the motor cell extends beyond the spinal cord along with other efferent (from Latin effero - “I take out”) fibers as part of the nerve roots and nerves. They transmit commands from the central nervous system to the working organs: the muscle, for example, is ordered to contract, the gland - to secrete juice, the vessels - to expand, etc.
However, the activity of the nervous system is not limited to the “highest decrees”. She not only gives orders, but also strictly monitors their execution - she analyzes signals from receptors located in the organs that work on her instructions. Due to this, the amount of work is adjusted depending on the state of the “subordinates”. In fact, the body is a self-regulating system: it carries out vital activity according to the principle of closed cycles, with feedback on the result achieved. Academician Pyotr Kuzmich Anokhin (1898-1974) came to this conclusion back in 1934, when he combined the theory of reflexes with biological cybernetics.
Sensory and motor neurons are the alpha and omega of a simple reflex arc: it starts with one and ends with another. In complex reflex arcs, ascending and descending cell chains are formed, connected by a cascade of intercalary neurons. This is how extensive bilateral connections are made between the brain and the spinal cord.
The formation of a conditioned reflex connection requires a number of conditions:
1. Multiple coincidence in time of the action of the unconditioned and conditioned stimuli (more precisely, with some precedence of the action of the conditioned stimulus). Sometimes a connection is formed even with a single coincidence of the action of stimuli.
2. Absence of extraneous irritants. The action of an external stimulus during the development of a conditioned reflex leads to inhibition (or even to the cessation) of the conditioned reflex reaction.
3. Great physiological strength (factor of biological significance) of the unconditioned stimulus in comparison with the conditioned stimulus.
4. Active state of the cerebral cortex.
According to modern concepts, nerve impulses are transmitted during the implementation of reflexes along the reflex rings. The reflex ring includes at least 5 links.
It should be noted that the latest research data of scientists (P.K. Anokhin and others) confirm just such an annular reflex scheme, and not a reflex arc scheme that does not fully reveal this complex process. The organism needs to receive information about the results of the action, information about each stage of the ongoing action. Without it, the brain cannot organize purposeful activity, cannot correct the action when any random (interfering) factors intervene in the reaction, cannot stop the activity at the necessary moment, when the result is achieved. This led to the need to move from the idea of an open reflex arc to the idea of a cyclic innervation structure in which there is feedback - from the effector and the object of activity through receptors to the central nervous structures.
This connection (reverse flow of information from the object of activity) is a mandatory element. Without it, the organism would be cut off from the environment in which it lives and to change which its activity is directed, including human activity associated with the use of tools of production. .
theory reflex nerve system
Conclusion
Thus, experiencing the impact of a variety of signals from the outside world and from the body, the cerebral cortex performs a complex analytical and synthetic activity, which consists in decomposing complex signals, stimuli into parts, comparing them with their past experience, highlighting the main, the main, essential and the unification of the elements of this main, essential. This complex analytical and synthetic activity of the cerebral cortex, which determines the breadth, diversity, and activity of feedback neural connections, provides a person with better adaptability to the outside world, to changed living conditions.
Literature
1. Aspiz M.E. - Encyclopedic Dictionary of a Young Biologist. - M.: Pedagogy, 1986. - 352 p.: ill.
2. Volodin V.A. - Encyclopedia for children. T. 18. Man. – M.: Avanta+, 2001. – 464 p.: ill.
3. Grashchenkov N.I., Latash N.P., Feigenberg I.M. – Philosophical questions of the physiology of higher nervous activity and psychology. – M.: 1963. – 370 p.: ill.
4. Kozlov V.I. - Human anatomy. Textbook for students of institutes of physical culture. - M .: "Physical culture and sport", 1978. - 462 p.: ill.
5. Kuzin V.S. – Psychology. - M .: Higher. school, 1982. - 256 p.: ill.
6. Petrovsky B.V. – Popular medical encyclopedia. - M .: "Soviet Encyclopedia", 1979. - 483 p.: ill.
The basis of the activity of the nervous system is reflexes (reflex acts). Reflex It is the body's response to an external or internal stimulus. Numerous reflex acts are divided into unconditional and conditional.
Unconditioned reflexes - These are congenital (inherited) reactions of the body to stimuli carried out with the participation of the spinal cord or brain stem.
Conditioned reflexes - these are temporary reactions of the body acquired on the basis of unconditioned reflexes, carried out with the obligatory participation of the cerebral cortex and forming the basis of higher nervous activity. Higher nervous activity is characterized by the complexity of reflex actions. They are based not just on reactions to a certain stimulus, but on the assessment of numerous afferent signals from the outside world and the internal environment of the body that enter the brain through various sensory pathways (proprioceptive, pain, tactile, visual, auditory, olfactory, etc.), and evaluation of memory cues that store information about past experiences.
It should be noted that, starting to perform a particular type of activity, a person usually predicts its results, i.e. preliminarily forms an afferent representation, and then performs an action, which leads to the appearance of a result. The coincidence or discrepancy between the predicted and real results of the action affects the nature of the accompanying emotional reactions. In the first case they are positive, in the second they are negative.
The morphological basis of any reflex is reflex arc, represented by a chain of neurons that provide the perception of irritation, the transformation of the energy of irritation into a nerve impulse, the conduction of a nerve impulse to the nerve centers, the processing of incoming information and the implementation of a response.
Depending on the complexity of the reflex act, simple and complex reflex arcs are distinguished. As a rule, for the implementation of unconditioned reflexes, simple reflex arcs are formed. Conditioned reflexes are characterized by multi-neuron complex reflex arcs (Fig. 1.5).
Rice. 1.5.
a - simple reflex arc: 1 - receptor (sensitive) neuron; 2 - associative (intercalary) neuron; 3 - effector (motor) neuron; b - complex reflex arc; 1 - afferent path; 2 - associative (intercalary) neuron; 3 - effector (motor) neuron; 4 - receptor (sensitive) neuron; 5 - efferent path; 6 - brain
There are three links in a simple reflex arc - afferent, intercalary (associative) and efferent. The afferent link is represented by a sensitive, or receptor, neuron, which is located in the sensitive node of the spinal nerve and is represented by pseudo-unipolar cells. One process departs from the body of a pseudo-unipolar cell. It soon divides into peripheral and central processes. The peripheral process begins with receptors on the periphery (in the skin, muscles, tendons, articular bags). The area of localization of receptors, the irritation of which leads to the emergence of a certain reflex, is called the reflexogenic zone. Nerve impulses that have arisen as a result of irritation of the receptors move in a centripetal direction, first to the body of the pseudo-unipolar cell, and then along its central process to the spinal cord. The central process of the receptor neuron forms a synaptic ending on the dendrites of the associative (intercalary) neuron.
Associative neuron is an intercalary link of the reflex arc and is a small multipolar cell with a short axon. It receives a nerve impulse with its dendrites or directly on the surface of the body, conducts it along the axon and forms a synaptic ending on the effector neuron.
effector neuron - This is a large multipolar cell, the axon of which leaves the central nervous system and ends with effector endings in the tissues of the working organ (in the striated muscles).
The complication of reflex arcs occurs due to the insertion link. Associative neurons form numerous nuclei (nerve centers) within the spinal cord and brain. Nerve centers are groups of neurons united on the basis of morphofunctional features, carrying out not only the synaptic transmission of nerve impulses from one neuron to another, but also their certain processing.
A two-way connection is established between the nerve center and the working organ during the implementation of any reflex. Reaching the effectors located in the muscle or gland, nerve impulses cause a response to irritation. In this case, the working effect is accompanied by irritation of receptors located in the executive organ. As a result of this, a new stream of impulses enters the nerve center. The presence of feedback allows you to control the correct execution of commands coming from the nerve centers, and to make additional timely correction in the performance of the body's responses.
The presence of a second signaling system in a person 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, the processes of mutual induction, as well as the nature of analytical and synthetic activity in humans.
Consider the features of the formation of conditioned reflexes to simple stimuli. Vegetative, somato-motor 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, the younger the age, the less strong the resulting conditioned reflex is 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. It manifests itself only on the stimulus for which it was developed, without arising on similar stimuli.
During the formation and implementation of vegetative and somato-motor conditioned reflexes, a person often observes such a peculiar phenomenon: the conditioned reflex that has formed (and, moreover, very quickly) suddenly disappears immediately - the conditioned stimulus, despite continued reinforcement, ceases to cause a reflex reaction. Such cases of “non-education” occur more frequently the older the subjects are, and in children of the same age they are more common among the most capable and disciplined. Many researchers believe that this delay is related to the involvement of the 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 humans. With the help of verbal information that a certain indifferent stimulus would be accompanied by an unconditioned reinforcement known to the subject, it turned out to be possible to develop a conditioned reflex before combining 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 operation of the bell, they will give you cranberry extract.” Immediately after the application of the conditioned stimulus (bell), some of the subjects experienced a salivary reaction; in others, this information accelerated the formation of a conditioned reflex when the indifferent and unconditioned stimulus were combined. In the same way, it was possible to develop a blinking reflex in the subjects after being told 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 in humans of conditioned reflexes to complex stimuli. Reflexes to simultaneous complex stimuli are formed the faster, the older the 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 aged 11-12 immediately 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 lower the age). The synthesis of a sequential complex of stimuli into a single whole is slower than a simultaneous complex, although much faster than in animals. In comparison with animals, differentiation to 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 time in humans are formed much faster than in animals. For example, when feeding a newborn at certain hours, already on the 7th day of life, the appearance of motor and sucking movements was observed 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 form various reflexes for time - food, cardiovascular, respiratory. For example, when repeating at intervals of 5 minutes of short-term muscular 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 (A.S. Dmitriev, R. Ya. Shikhova).
In comparison with animals, a person has an immeasurably more developed ability to form conditioned reflexes of a higher order - a person can form conditioned reflexes from the 2nd to the 20th order, and they are formed quickly. For example, in studies on adults using the salivary method, the conditioned reflex of the first order (when a tone was 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 direct and verbal stimuli formed after 2-6 combinations and became stronger after 2-13 combinations (GA Shichko). Influences through the second signal system can have a great influence on the process of formation of conditioned reflexes of a higher order.
So, a characteristic feature of the formation of conditioned reflexes in humans is the active participation in this process of the second signaling system. 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), but also the connections between the cortical points of direct and verbal stimuli, i.e., associative or sensory connections that close without reinforcement, becomes important. . The word, as a generalizing stimulus, is associated with numerous associative links 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 process of formation of a conditioned reflex. So, thanks to the participation of the second signaling system, it becomes possible to quickly (sometimes "from the spot") the formation of conditioned reflexes based on the generalization of a person's previous life experience. And the more developed the second signal system, the richer the life experience of a person, the more pronounced are these specific features of the process of formation of a conditioned reflex in a person.
Features of unconditional braking at person. Like the animals external braking in humans, the stronger the extraneous stimulus and the less strong the conditioned reflex. External inhibition covers 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 primary signal conditional connections.
Extreme braking is common in children, especially in young children, in whom already during the experiment, with the repetition of conditioned stimuli of moderate strength, prohibitive inhibition often develops, which is expressed in a 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, drowsiness. The development of translimiting inhibition is facilitated by the fatigue of cortical cells. Therefore, in everyday human life, this type of inhibition occurs at every step, especially in the evening. Other influences also lead to the development of transboundary inhibition, including various diseases, both acute and chronic. In general, in everyday life, transmarginal 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 (differential, extinction, conditionally inhibitory and delayed). This type of inhibition manifests itself in the same four forms (differential, extinctive, conditioned and retarded) as in animals. In humans, it is produced at different rates, moreover, the faster, the greater the age. 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.
Differential inhibition in humans develops faster than in animals, especially in adults. This is due to the active participation of the second signaling system, which begins to play a leading role in the process of differentiation of stimuli from a certain age. Influences through the second signaling system greatly accelerate the formation of differentiations. So, in studies of salivary conditioned reflexes in adults, after information that an extract would be given to blue light, but not to a bell, differentiation to an unreinforced stimulus immediately formed (G. A. Shichko). With age, as the second signal system develops, the ability to differentiate stimuli increases. For example, in terms of the subtlety of perception of various colors and shades, 14-year-old children are 90% superior to 6-year-olds.
The process of extinction in humans proceeds in two phases. At the beginning of extinction after the first non-reinforcements, 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, and in the appearance of intersignal reactions. This phase of increased excitability occurs more often and is more pronounced, the younger the age (it is rare in children 10-12 years old). Influences through the second signal system influence the process of extinction of conditioned reflexes. For example, when studying 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 supply of a conditioned stimulus, the reaction to it disappeared (G. A. Shichko).
The formation of a conditioned brake in a person in a number of 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 cause a conditioned response. This phenomenon indicates an increase in the excitability of the cortex in the process of developing a conditioned brake. In some children, it is so pronounced that it becomes completely impossible to form a conditioned brake. However, for the majority, it manifests itself as a short-term phase, after which the formation of a conditioned brake begins. The development of the conditional brake is significantly affected by the second signal system. For example, in studies of salivary conditioned reflexes, the subject was told that cranberry extract would be given to the sound of a whistle, but not to a metronome in combination with a whistle. After such information, the whistle in combination with the metronome did not cause any reaction, while profuse salivation occurred on one whistle (G. A. Shichko).
Lag braking is the most difficult type of internal inhibition for a person - it is formed 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 the presence of a second signal system in a person, 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 extend to the second signal system, as well as to their interaction. Numerous studies of this issue 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 excitation from the first signaling system to the second was first studied in 1927 in the laboratory of A. G. Ivanov-Smolensky. In these studies, a motor conditioned reflex to a bell was developed in children with food reinforcement, and then the action of various verbal stimuli was recorded in order to identify generalizations. It turned out that only the use of the words “bell”, “ringing” (as well as the demonstration of a sign with the inscription “bell”) immediately evoked 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 radiate from the second signaling system to the first. So, after the formation in children of a motor conditioned reflex to the word “bell”, the same reaction occurs immediately, “from the spot” and to the sound of a call that has never been used before. with reinforcements. The phenomena of elective irradiation of excitation from the first signal 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 signal system to another is manifested in the fact that after the development of a conditioned reflex to a direct stimulus, such a reaction begins to be caused not only by words denoting a conditioned stimulus, but also by any other words.
Elective irradiation of excitation in accordance with the general laws of motion of nervous processes is replaced by the following 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 on the second application), the conditioned reaction ceases to appear on it. The reaction is preserved only to the immediate stimulus to which it was developed, i.e., the conditioned reflex specializes.
Elective irradiation of excitation, i.e. selective generalization of the conditioned reflex and its subsequent specialization proceed differently with different conditioned reflexes - the vegetative reflexes are characterized by a generalization phase, and fast specialization is typical for motor conditioned reflexes. The younger the age, the more common irradiation (especially diffuse) of excitation from the first signal system to the second.
The phenomenon of selective (elective) irradiation of all types of internal inhibition from one signal system to another is also characteristic of man. 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” also acquired an inhibitory effect. If this word was included in the number of stimulus words during the verbal experiment, then a noticeable inhibition of the speech reaction to this word was found. In the next study, children developed a conditioned brake (to a bell), and then it was found that the same inhibition of the conditioned reflex reaction is caused by the addition of the word “bell” to the conditioned stimulus, while other words (for example, “hat”) no such action was taken.
It turned out that for the elective irradiation and the subsequent concentration of inhibition, a high speed is characteristic. For example, extinctive inhibition, which quickly radiated from the first signal system to the second, completely leaves the second signal system after 30–60 s and concentrates at the starting point.
Induction relationship between the first and second signaling systems in humans. For a person, the phenomena of mutual induction between the first and second signal systems are also characteristic. The phenomena of negative induction were revealed in studies (L. B. Gakkel et al.), in which a blinking conditioned reflex to a metronome or a buzzer was developed in a person against the background of solving oral arithmetic problems, which began 5 seconds before the conditioned stimulus was given. It turned out that in many subjects, on the background of solving an arithmetic problem (solving it quickly and correctly), the blinking reflex either did not form at all, or it did form, but it was unstable. For example, in one subject, the reflex did not form even after 21 combinations; when he canceled the solution of the arithmetic problem, he developed a blinking reflex already at the 7th combination. Thus, the simultaneous formation of second-signal and first-signal conditioned connections is complicated by their mutual inhibition according to the law of negative induction.
With age, as the second signal system develops, the negative inductive influence from the second signal system begins to predominate. “The second signaling system, said I.P. Pavlov, is predominant, especially valuable in the higher part of the central nervous system and, therefore, must constantly exert a negative induction on the first signaling system. The second signal system constantly keeps the first signal system under the mute.
Features of the analytical and synthetic activity of the cerebral cortex of the human brain. The analytical and synthetic activity of the human cerebral cortex 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 switching. A higher level of development of the 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, let's cite the data obtained in the laboratory of M. M. Koltsova, which demonstrate a person's high ability to develop a dynamic stereotype and switches. 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 blinking reflex. Such a 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 jet of air into the eye, causing a defensive blinking reaction, and in the other case, with the supply of a food reinforcement (candy), causing a food-procuring movement of the hand. Both the environment of the experiment (different experimental rooms, different times of the day, different experimenters) and individual stimuli (simple and complex, direct and verbal) were used as switches. Studies have shown that conditioned reflex switching is developed 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 operation of the switch). At the same time, the leading factor in the development of a conditioned reflex switch 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 the switch is produced relatively slowly (after 37 combinations), but if it is a familiar word, then the switch is generated much faster - after 16-25 combinations. This is explained by 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 links between words. A specific feature of human analytic-synthetic activity is the participation of verbal stimuli in it, which makes it possible to implement complex behavioral reactions without preliminary development, “from the spot”, based on the generalization of previously acquired life experience. This ability is based on the possibility of forming systems of temporary connections between words.
Such systems include verbal stereotypes. It is their education that provides the possibility of comprehensive interaction and mutual influence between people with the help of the word.
The formation of verbal stereotypes begins in children at the beginning of the second year of life, when, along with the process of turning individual words into independent stimuli, separate phrases are used in communication with the child that organize the child’s behavior (“Let’s go 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 to direct stimuli. The words in this stereotype initially act as simple auditory stimuli with no "signal of signals" meaning. When they are first used 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 may also be attached to this). In the future, individual words begin to acquire a signal value. Thus, the pronunciation of the phrase "Give me a pen" in combination with the movement of the child's hand (at 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 forming verbal stereotypes acquires other features at that stage of a 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. As the degree of integration of the word increases, i.e. as the number of sensory connections of the 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 conditional 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 words-integrators of a higher order, as well as by the words combined by these words-integrators. So, in the studies of G.D. Naroditskaya showed that after the formation of conditioned motor reactions to images of various birds (tits, storks, swallows, etc.), the same reaction arose “from the spot” not only to the words “tit”, “stork”, “swallow” and etc., but also to the generalizing word "bird". If, at the same time, differentiations were developed on the images of various animals (tiger, zebra, antelope, etc.), then the same inhibitory effect “from the spot” was caused not only by the words “tiger”, “zebra”, “antelope”, etc. etc., but also the generalizing word "beast". Generalization can also appear in a more complex form. So, in the experiments of V. D. 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 the sense speak of “good” (for example, “The student is an excellent 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 hers, children developed a salivary conditioned reflex to the word "ten" and a differentiation to the word "eight." It turned out that not only these words, but also a wide variety of speech stimuli, expressing examples of addition, subtraction, multiplication and division, began to evoke one or another reaction “from the spot”. So, if as a result of an arithmetic operation the number 10 was obtained, then a salivary reaction appeared, and if the number was 8, then the reaction was inhibited.
The value of the conditioned reflex. In the process of evolution, living organisms developed a special mechanism that made it possible to respond not only to unconditioned stimuli, but also to a mass of indifferent (indifferent) stimuli coinciding in time with unconditioned stimuli. Thanks to this mechanism, the appearance of indifferent stimuli signals the approach of those agents that are of biological significance; the connections of the organism with the outside world expand, become more perfect, more subtle and allow better adaptation to the diverse and changing conditions of existence. Thus, the acquisition by living organisms of the ability to learn in the process of individual development (and, moreover, without consolidating this experience by inheritance) demonstrates a huge leap in the evolution of living things.
Thanks to the emergence of the ability to form conditioned reflexes in living organisms, it became possible to regulate the activity of internal organs ahead of time, and the arsenal of motor acts acquired in the process of individual development has significantly expanded. Thanks 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 is known, defensive conditioned reflexes help the body prepare in advance for protection and avoid the danger that threatens it). Conditioned reflexes, thus, provide a premature (anticipatory) response of a person and an animal to the inevitability of exposure to an unconditioned stimulus, and in this respect they play a signal role in a behavioral response. Due to the fact that reflexes of a higher order can be developed on the basis of a conditioned reflex of the first order, the system of conditioned reflexes allows the body to deeply and accurately assess the conditions of the external environment and, on this basis, respond in a timely manner by changing behavioral reactions in a particular situation.
The conditioned reflex was the basis of higher nervous activity, i.e. basis of human and animal behavior. The appearance in evolution of the ability to develop a conditioned reflex created the prerequisite 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 human habits. 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) in animals and humans that a large amount of information is transmitted from one generation to another.
Thanks to conditioned reflexes, social adaptation is possible in a person. 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 that are 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.
Presentation by I.P. Pavlova about neuroses. Experimental neuroses. neuroses - these are functional disorders of the GNI, which can turn into deep disorders of mental activity, i.e. into psychosis. I.P. Pavlov arrived at the concept of neuroses by accident, observing the behavior of experimental animals that survived the flood in Leningrad. 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 traits had the character of overexcitation, and in animals with melancholic features - the character of drowsiness, apathy. Even after the restoration of conditioned reflexes, they could not normally respond to strong stimuli, especially those associated with the experienced shock. In general, I.P. Pavlov and his collaborators came to the conclusion that experimental neurosis is a long-term disturbance of the GNI that develops in animals under emotional (psychogenic) influences due to an overstrain of the excitatory or inhibitory nervous processes or their mobility.
Later in the laboratories of I.P. Pavlova, methods were developed to cause neurosis in animals, i.e. to simulate a neurotic state, and also to cure it.
1. Overvoltage 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 occurred in dogs that survived the 1924 flood in Leningrad).
2. Overvoltage of the braking process. It was achieved by persistent development of subtle differentiations, i.e. discrimination of very close, similar, difficult to distinguish stimuli, as well as by delaying the action of inhibitory stimuli or due to a long delay in reinforcement.
3. Overvoltage of the mobility of nervous processes. It was achieved by rather quick and frequent alterations of the signal value of positive and negative conditioned stimuli or by an emergency breaking of stereotypes.
4. Clash of excitation and inhibition, or "collision" of nervous processes. This type of HNI disturbance in experimental animals arose due to the alteration of a complex dynamic stereotype, as well as by too rapid a 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 when developing a conditioned food reflex to a signal of a painful stimulus that causes a defensive reaction. Later in the laboratory of I.P. Pavlova were used in various ways, including the use of a feeder under current, which is closed by the muzzle of a dog, putting models of snakes in the feeders of monkeys, etc. Studies on dogs have shown that a neurotic breakdown is easier to induce in a weak and uncontrolled type of nervous system, and in the first case, the excitatory process suffers more often, and in the second, the inhibitory one. These data are also confirmed by observations of people who have a manifestation of neurosis.
Experimental neurosis is characterized by a violation of adaptive behavior, sleep, chaotic conditioned reflexes, the appearance of phase states (with equalizing and paradoxical phases), pathological inertia of nervous processes, and 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, atony of the stomach 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, and the activity of the kidneys and other systems is disrupted.
Modeling neuroses, in the laboratories of I.P. Pavlova were looking for ways to correct these conditions. The effective methods were the refusal to experiment with animals, changing the environment, long 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 excitation. Mixtures containing a mixture of bromine and caffeine in certain proportions succeeded in restoring the balance of excitation and inhibition, which is characteristic of the normal state of VID. 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 preventing and treating 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).
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Introduction
1. Reflex activity
2. Anatomical and physiological mechanism of reflex activity
3. Unconditioned reflexes
4. Features of unconditioned reflexes
Conclusion
List of used literature
Introduction
Activity is understood as the activity of the subject, aimed at changing the world, at the production or generation of a certain objectified product of material or spiritual culture. Human activity appears first as a practical, material activity. Then theoretical activity is separated from it. Any activity usually consists of a series of acts - actions or deeds based on certain motives or motives and aimed at a specific goal. Since under different conditions this goal can be achieved in different ways (operations) or ways (methods), the action acts as a solution to the problem.
The activity of the subject is always associated with some need. Being an expression of the subject's need for something, the need causes his search activity, in which the plasticity of activity is manifested - its assimilation to the properties of objects that exist independently of it. In this subordination to the object, likening it, lies the determinism of human activity by the external world. In the process of this assimilation, the need “gropes” for its object, objectifies it, turns it into a specific motive of activity. In the future, the activity of the subject is no longer directed by the object itself, but by its image, which arises in the search situation in the process of assimilation of human activity to the properties of the object.
The concept of activity is necessarily connected with the concept of motive. There is no activity without a motive: unmotivated activity is an activity that is not devoid of a motive, but an activity with a subjectively and objectively hidden motive. Activities are usually carried out by some set of actions that are subject to particular goals that can be distinguished from the general goal. The role of a common goal is performed by a conscious motive.
Activity is the main way, the only effective way to be a person; a person by his activity continues himself in other people. A produced object is, on the one hand, an object of activity, and on the other hand, a means by which a person asserts himself in the world, because this object is produced for other people.
Activity is generated by the meeting of a need with resistance, an obstacle. The objectivity of activity lies in the objective nature of the resistance offered to the subject by the environment, the world of objects in which he has to act. But a person lives and acts not only in the world of objects, but also in the social environment. To the objective resistance to the satisfaction of needs, social resistance is added in the form of norms, rules, prohibitions, etc. Consequently, human activity is as social as it is objective.
Is all human activity an activity? The criterion of activity (behavior) was put forward by P.Ya. Galperin. He believes that actions that are controlled by the subject on the basis of orientation in terms of the image are acts of behavior, and where there is no orientation of actions on the basis of the image, there is no behavior, there is only the reaction of the organism (automatism). If there is no resistance to the satisfaction of the need at all, neither orientation nor activity is needed. When it is impossible to automatically satisfy the need for the force of social and objective resistance, there is a need for an active orientation, for activity.
An activity is carried out to satisfy a need. Depending on what needs and how this object is satisfied, it acquires one or another meaning for the subject. The source of meaning is the satisfaction of the need, presented to the subject in the form of an anticipated emotional state associated with the process of satisfying the need.
1. Reflex activity
Man is by nature active. He is the creator and creator, regardless of what kind of work he does. Without activity, expressed in activity, it is impossible to reveal the richness of a person's spiritual life: the depth of the mind and feelings, the power of imagination and will, abilities and character traits.
Activity is a social category. Animals can only live, which manifests itself as a biological adaptation of the body to the requirements of the environment. A person is characterized by a conscious isolation of himself from nature, knowledge of its laws and a conscious impact on it. A person as a person sets goals for himself, is aware of the motives that prompt him to be active.
The principle of the unity of consciousness and activity, formulated by Soviet psychologists, generalizes a number of theoretical propositions. The content of consciousness is primarily those objects or aspects of cognizable activity that are included in the activity. Thus, the content and structure of consciousness are associated with activity. Activity, as the most important characteristic of the mental reflection of the personality, is laid down and realized in objective activity and then becomes the mental quality of a person. Being formed in activity, consciousness manifests itself in it. By answering and completing the task, the teacher judges the level of knowledge of the student. Analyzing the educational activity of a student, the teacher makes a conclusion about his abilities, about the features of thinking and memory. By deeds and deeds, the nature of the relationship, feelings, strong-willed and other qualities of the personality are determined. The subject of psychological study is personality in activity. reflex physiological unconditional person
Any type of activity is associated with movements, regardless of whether it is the musculoskeletal movement of the hand when writing, when performing a labor operation by a machine operator, or the movement of the speech apparatus when pronouncing words. Movement is a physiological function of a living organism. Motor, or motor, function in humans appears very early. The first movements are observed during the intrauterine period of development, in the embryo. The newborn screams and makes chaotic movements with his hands and feet, he also has congenital complexes of complex movements; for example, sucking, grasping reflexes.
The congenital movements of an infant are not objectively directed and are stereotyped. As studies in childhood psychology show, accidental contact of an irritant with the surface of the palm of a newborn causes a stereotypical grasping movement. This is the initial unconditionally reflex connection between sensation and movement without reflecting the specifics of the influencing object. Significant changes in the nature of the grasping reflex occur at the age of 2.5 to 4 months. They are caused by the development of the senses, primarily vision and touch, as well as the improvement of motor skills and motor sensations. Prolonged contact with the object, carried out in a grasping reflex, occurs under the control of vision. Due to this, a system of visual-motor connections is formed based on tactile reinforcement. The grasping reflex disintegrates, giving way to conditioned reflex movements corresponding to the characteristics of the object.
On a physiological basis, all human movements can be divided into two groups: congenital (unconditioned reflex) and acquired (conditioned reflex). The vast majority of movements, including even such an elementary act common with animals as movement in space, a person acquires in life experience, that is, most of his movements are conditioned reflexes. Only a very small number of movements (shouting, blinking) are innate. The motor development of the child is associated with the transformation of the unconditioned reflex regulation of movements into a system of conditioned reflex connections.
2. Anatomical and physiological mechanism of reflex activity
The main mechanism of nervous activity, both in the lowest and in the most complex organisms, is the reflex . A reflex is the response of the body to irritations of the external or internal environment. Reflexes differ in the following features: they always begin with a nervous excitation caused by some stimulus in one or another receptor, and end with a certain reaction of the body (for example, movement or secretion).
Reflex activity is a complex analyzing and synthesizing work of the cerebral cortex, the essence of which is the differentiation of numerous stimuli and the establishment of various connections between them.
The analysis of stimuli is performed by complex nerve analyzer organs. Each analyzer consists of three parts:
1) peripheral perceiving organ (receptor);
2) conductive afferent, i.e. the centripetal pathway, along which nervous excitation is transmitted from the periphery to the center;
3) cortical part of the analyzer (central link).
The transmission of nervous excitation from the receptors first to the central parts of the nervous system, and then from them to the efferent, i.e. centrifugal, paths back to the receptors for the response that takes place during the reflex, is carried out along the reflex arc. The reflex arc (reflex ring) consists of a receptor, an afferent nerve, a central link, an efferent nerve, and an effector (muscle or gland).
The initial analysis of stimuli takes place in the receptors and in the lower parts of the brain. It has an elementary character and is determined by the degree of perfection of one or another receptor. The highest and most subtle analysis of stimuli is carried out by the cortex of the cerebral hemispheres, which is a combination of the brain endings of all analyzers.
In the course of reflex activity, a process of differential inhibition is also carried out, during which excitations caused by unreinforced conditioned stimuli gradually fade away, while excitations remain that strictly correspond to the main, reinforced conditioned stimulus. Thanks to differential inhibition, a very fine differentiation of stimuli is achieved. Because of this, the formation of conditioned reflexes to complex stimuli is possible.
In this case, the conditioned reflex is caused only by the action of the complex of stimuli as a whole and is not caused by the action of any one of the stimuli included in the complex.
3. Unconditioned reflexes
Unconditioned reflexes were singled out in a special category to designate the specific reactions of the body to internal and external stimuli, carried out on the basis of innate neural connections, i.e. reflecting the phylogenetic experience of adaptation to the conditions of existence. Unconditioned reflexes are relatively constant, stereotyped in response to adequate stimulation of a certain receptive field, and serve as the basis for the formation of numerous conditioned reflexes associated with individual experience. Unconditioned reflexes provide coordinated activity aimed at maintaining the constancy of many parameters of the internal environment, the interaction of the organism with the external environment, the coordinated activity of somatic, visceral and vegetative reactions.
However, optimal adaptation to the changing conditions of the external and internal environments of the body is achieved with the help of conditioned reflexes, due to which stimuli that are indifferent to a certain activity acquire the quality of biologically significant signals.
4. Features of unconditioned reflexes
Several classifications of unconditioned reflexes have been proposed in accordance with the nature of the stimuli that cause them, their biological role, levels of control (connection with certain parts of the central nervous system), and the sequence in a particular adaptive act. The authors of these classifications reflected in them their scientific interests and methodological guidelines. I.P. Pavlov described food, defensive, orienting, parental and children's reactions, subdivided into more fractional reflexes. So, food reflexes associated with the activity of the food center include search, extraction, capture, taste testing of food, secretion of saliva and digestive juices in the gastrointestinal tract, and its motor activity.
In the works of I.P. Pavlova, there are also indications of the following unconditioned reflexes: food (positive and negative), indicative, collecting, goals, caution, freedom, exploratory, self-preserving (positive and negative), aggressive, watchdog, submission, sexual (male and female), game, parental, nesting, migratory, social, drinking.
ON THE. Rozhansky singled out 24 reflexes included in the following six groups: general activity, exchange, interanimal relations, continuation of the species and reproduction, ecological and non-behavioral reflexes of the subcortical-stem parts of the brain. This classification almost does not affect the vegetative sphere of regulation, which plays an important role in the implementation of behavioral acts.
A broader classification is based on the study of the adaptive aspects of unconditional reflex activity. The representative of the ecological and physiological direction A.D. Slonim proposed to divide unconditioned reflexes into three groups of reactions associated with maintaining the constancy of the internal environment, changes in the external environment, and the preservation of the species.
The above classifications provide not only a description of behavior, but also the elucidation of the underlying physiological mechanisms. The latter is of less interest to ethologists, who also study behavior in an environment adequate for the animal.
Here is an example of the classification of behavior types proposed by the German ethologist G. Tembrok: behavior determined by metabolism and consisting of food production and eating, urination and defecation, food storage, rest and sleep, stretching; comfortable behavior; defensive behavior; behavior associated with reproduction, consisting of the protection of the territory, mating, caring for offspring; social (group) behavior; construction of nests, burrows and shelters.
Although in many respects such a division is close to the above classifications of physiologists N.A. Rozhansky and A.D. Slonim, it tends to a greater extent to an external description of innately fixed stereotypes of behavior.
For P.V. Simonov, the classifying principle of grouping the most complex unconditioned reflexes were the ideas of V.I. Vernadsky and A.A. Ukhtomsky about the development by living beings of different levels of organization in the geo-, bio-, and for a person also in the socio- and noosphere (intellectual development of the world). P.V. Simonov singled out the following unconditioned reflexes: vital, role-playing (zoosocial) and self-development. The vital unconditioned reflexes include food, drink, sleep regulation, defensive (including the “biological caution” reflex), the reflex of saving strength, and many others. They do not require the participation of another individual, and the impossibility of their implementation leads to physical death. Role (zoosocial) unconditioned reflexes, on the contrary, are manifested in the process of interaction with other individuals of a given species. Unconditional self-development reflexes reflect exploratory behavior, reflexes of freedom, imitation and play.
The Polish neurophysiologist Yu. Konorski divided the unconditioned reflexes according to their biological role into conservation ones, associated with the entry into the body and the removal of everything necessary from it; restorative (sleep) aimed at preserving the species (copulation, pregnancy, caring for offspring), and protective ensuring the removal of the entire body or its individual parts from the scope of a harmful or dangerous stimulus for the body (withdrawal and retreat reflexes) or associated with the elimination of harmful agents that got on the surface of the body or inside the body, the destruction or neutralization of harmful agents (offensive reflexes).
Conservative attraction reflexes are directed directly at the object (food, sexual partner), protective reflexes are directed in the direction opposite to the harmful stimulus. By the order of the sequence of phases, this classification is supplemented by an indication of preparatory (drive, motivational) and executive (consumer) reflexes associated with the final actions, unconditioned reflexes.
So, based on this classification, it is possible to single out preparatory food unconditioned reflexes that underlie the formation of states of hunger and satiety. These include reactions that occur when the chemical composition of the blood changes, changes in metabolism, strengthening or weakening of interoceptive signaling (mainly from the receptors of the stomach, intestines and liver).
The initiation and termination of food arousal are determined by nerve and humoral signals perceived by specialized receptors in the hypothalamic region. Many other brain structures are also involved in the formation of states of hunger and satiety. Food motivation depends on internal stimuli and on stimuli emanating from the external environment. Against the background of the dominant hunger motivation, motor restlessness arises and some sensory systems (in particular, taste and smell) are activated. After food enters the oral cavity, preparatory reflexes are inhibited and executive food reflexes begin to be realized: chewing food, salivation, swallowing a formed food bolus, coordinated contractions of the esophagus and stomach, secretion of gastric and pancreatic juices, changes in metabolic reactions, etc.
Equally complex are the preparatory and executive unconditioned reflexes associated with sexual or defensive behavior. At the same time, it should be borne in mind that in the process of ontogenesis, preparatory and executive unconditioned reflexes are modified under the influence of external and internal stimuli, therefore, conditioned reflexes begin to play a primary role in coordinated adaptive activity.
As can be seen, the reflex control of body functions is carried out by mechanisms of varying complexity. This allowed I.P. Pavlov to divide unconditioned reflexes according to the anatomical principle: simple (spinal), complicated (medulla oblongata), complex (midbrain) and complex (the nearest subcortex and cerebral cortex). At the same time, I.P. Pavlov pointed to the systemic nature of the regulation of physiological processes, which he considered using the example of the organization of a "food center" - a functional set of structures located at different levels of the brain.
The position on systemicity as the main principle of the brain was formulated by A.A. Ukhtomsky in his doctrine of the dominant - the functional association of various nerve centers based on increased excitability. These ideas were developed by P.K. Anokhin, according to which the functional systems dynamically combine the nervous elements of different levels of the CNS, providing certain adaptive effects.
Thus, it is possible to classify unconditioned reflex and conditioned reflex activity on the basis of anatomical and functional approaches, between which there are no fundamental contradictions. In recent decades, with the help of stereotaxic techniques, it has been possible to determine the participation in specialized unconditional reflex activity of many parts of the brain (hypothalamus, amygdala, hippocampus, striopallidar system, etc.). The obtained data expanded the understanding of the organization of various forms of behavior.
The development of the theory of automatic regulation has led to the need to consider the organization of innate and acquired behavior in terms of ideas about the information and control activity of the brain. Six levels of its organization were distinguished (A.B. Kogan and others): elementary, coordination, integrative, most complex unconditioned reflexes, elementary conditioned reflexes, and complex forms of higher nervous (mental) activity.
Elementary unconditioned reflexes are simple responses of local significance, implemented in accordance with a rigidly determined program of their segmental centers. They are carried out through one main channel (centripetal, central and centrifugal links). The role of feedback (mostly negative) in the correction of elementary unconditioned reflexes is small. Examples of such a reflex are pulling the burned leg away from the fire or blinking when a mote enters the eye.
Coordinating unconditioned reflexes are also carried out at the segmental level, but unlike elementary reflexes, they include a number of cycles, although stereotyped, but allowing correction based on negative and positive feedbacks. An example of a simple coordination reflex is the antagonistic reflex, which coordinates contractions of the flexor and extensor muscles.
Integrative unconditioned reflexes - the synthesis of coordinated motor acts with their vegetative provision into complex reactions of a certain biological significance. They ensure the maintenance of homeostasis and carry out the correction of elementary and coordination reflexes. The implementation of integrative reflexes is determined by suprasegmental mechanisms (mainly the lower parts of the brainstem, structures of the medulla oblongata, middle and diencephalon, cerebellum). If for the implementation of elementary and coordination reflexes it is mainly physical properties and local application of the stimulus that matter, then integrative reflexes provide integral responses of the organism (the simplest behavioral acts with their vegetative components).
The mechanisms of nervous regulation of different levels are closely intertwined, so their separation is conditional. Even in a spinal animal, several reflex arcs are involved in the realization of an elementary reflex. More I.M. Sechenov discovered that in the frog, the inefficiency of removing the damaging stimulus with the paw leads to the involvement of new motor coordinations in the reaction. The motor response is determined by the initial state of the reflex apparatus. In a decapitated frog, irritation of the skin of the foot causes its flexion, while in a bent frog, extension. The non-standard implementation of congenital reflex programs, which is manifested even after the removal of the suprasegmental parts of the central nervous system, is much more pronounced in the absence of a violation of its integrity.
The complexity of the organization of innate reactions can be traced on the example of the salivary unconditioned reflex, which was considered to be relatively simple. In reality, it is associated with various receptors (taste, tactile, pain), fibers of several nerves (trigeminal, facial, glossopharyngeal, vagus), many parts of the central nervous system (medulla oblongata, hypothalamus, amygdala, cerebral cortex). Salivation is associated with eating behavior, cardiovascular, respiratory, endocrine, thermoregulatory functions.
The unconditioned reflex secretion of saliva depends not only on the adequate stimulus that causes it, but also on many external and internal factors. An increase in ambient temperature leads to the release of a large amount of "thermoregulatory" saliva with a low content of organic substances. The amount of saliva depends on the level of food arousal, the availability of water, the content of salt in food, hormonal levels, and many other factors.
Thus, it would seem that relatively simple innate reactions are actually included in the systemic integration of complex mechanisms that determine the maintenance of homeostasis and the relationship of the organism with the external environment. Such integration is extremely flexible, and in accordance with the principle of dominance, the same reactions can be included in complexes associated with the satisfaction of various needs of the organism. For example, the salivary reflex may be associated with thermoregulation, feeding or defensive behavior.
In the implementation of integrative unconditioned reflexes, which are complexes of coordinated movements with their vegetative support, suprasegmental mechanisms play a leading role. A complex feedback system corrects elementary, coordination and integrative reactions that are combined into a single system. It is inseparable from the central mechanisms of instinctive reactions associated with the subcortical-stem parts of the brain. The cortex of the cerebral hemispheres also plays a certain role in the realization of instinctive reactions.
It can be seen that the division of levels of unconditional reflex activity proposed by different authors is relative. The schematic nature of any of its classifications can be traced on the example of one of the fundamental unconditioned reflexes - indicative. It includes three groups of phenomena (L.G. Voronin). Its first form, designated I.P. Pavlov as a “what is it?” reflex, includes many elementary and coordinated reactions - pupil dilation, lowering the thresholds of sensitivity to a range of sensory stimuli, contraction and relaxation of the muscles of the eye, ear, turning the head and torso towards the source of irritation, sniffing it, changing the electrical brain activity (depression, blockade of the alpha rhythm and the occurrence of more frequent fluctuations), the appearance of a galvanic skin reaction, deepening of breathing, dilation of the blood vessels of the head and narrowing of the vessels of the extremities, initial slowdown and subsequent increase in heart rate and a number of other changes in the vegetative sphere of the body .
The second form of the orienting reflex is associated with specialized search movements and depends on motivational-need characteristics, i.e. prevailing dominant, and from external stimuli.
The third form of the orienting reflex manifests itself in the form of an exploratory reaction, not necessarily associated with the satisfaction of the current needs of the organism, i.e. based on curiosity.
In foreign literature, psychological concepts are used to describe the orienting reflex - attention, setting in the conditions of expectation of a stimulus, reaction of surprise, alertness, fright, anxiety, vigilance. From the point of view of a neurophysiologist, the orienting reflex is a multicomponent non-specific reaction of the body to "novelty", aimed at increasing the ability of analyzers to differentiate a new phenomenon. It is characterized by the effect of extinction and independence from the modality and direction of changes in the O.A. stimulus. Kostandov).
The orienting-exploratory reflex is an integral part of orienting-exploratory behavior, which, being innate, is nevertheless practically inseparable from conditioned reflex activity. This also applies to many other forms of behavior. Therefore, one of the most difficult questions in the physiology of behavior is the separation of congenital and acquired reactions.
In an adult individual, innate activity usually does not manifest itself in its pure form, it is modified by conditioned reflexes that form in the process of ontogenesis. Thus, unconditioned reflexes are modified in accordance with individual adaptation to the characteristics of existence. Even at the earliest stages of postnatal life, and for some aspects of life even in the prenatal period, congenital reactions "acquire" conditioned reflex elements. In this case, genetically determined positive reactions can be transformed into negative ones. So, at the earliest stages of life, the preferred sweet taste can become rejected if it is combined with a painful state of the body (discomfort) at least once.
Another difficulty in differentiating innate and acquired reactions is related to the improvement of unconditional reflex activity in the process of individual development. In addition, when interacting with conditioned reflexes, unconditioned reflexes “ripen” in the process of postnatal life (L.A. Orbeli).
Modification of innate forms of behavior in the process of individual development may depend not only on learning, but also on many indirect influences that ultimately affect unconditional reflex activity. In some cases, it is determined by the environmental temperature at which the development of the organism occurs, nutritional conditions, and stressful influences.
Behavior is usually regarded as innate if it is not possible to detect the influence of training or other factors on it in ontogeny. These influences are attempted to be identified through experiments using certain types of deprivation (eg isolation from peers, rearing in the dark, etc.). Such a method is not always effective, since deprivation, firstly, cannot exclude all environmental influences, and secondly, it causes a number of general changes in the state of the organism. In particular, depending on the stimuli affecting the developing organism (enriched and depleted environment), DNA synthesis in neurons, neurotransmitter balance and many other components that affect the implementation of behavioral acts are regulated.
The body's responses are not the result of straightforward developmental processes leading directly from the gene to the behavior of an adult animal and only in some cases are changed by external influences. In reality, there is a complex interweaving of causal relationships, when each part of the body can interact with its other parts and the external environment (R. Hynd).
The range of variability of the most complex unconditioned reflexes, depending on the conditions of existence at an early age, is not the same for different types of activity. Some innate movement complexes are extremely stable and cannot be changed by environmental influences, while others are more plastic. Fixed sequences of movements that do not depend on training are described. They are well traced in insects and birds. So, burrowing wasps of one species build nests with the help of stereotyped movements, the patterned movements of domestic roosters when caring for chickens.
Fixed complexes of movements are also characteristic of highly developed animals, including humans. Scanning movements of the head of babies are characteristic, making it easier to find the nipple. Other complexes of movements associated with sucking are stereotypically manifested. These reflexes mature even in the prenatal period of development, which has been established in observations of premature babies. The grasping reflex, facial expressions of the child and many other manifestations of innate activity do not depend on learning. Observations on representatives of many animal species show that an adequate choice of food can be made without the help of parents, i.e. does not always require prior training. A negative reaction to height is manifested in monkeys who have never met it.
At the same time, many of the most complex unconditioned reflexes are modified in the process of development or require a period of training for their manifestation. In chicks, the formation of singing is determined not only by innate characteristics, but also by the conditions of feeding by birds of their own or another species (A.N. Promptov). Isolation from peers of rat pups or puppies leads to irreversible changes in subsequent "social" communication. The isolation of monkeys sharply disrupts their subsequent sexual and maternal behavior.
The difficulties that arise in separating genetically determined behavioral acts from those developed in the course of life are aggravated by the fact that some innate forms of behavior appear at relatively late stages of development, when the animal has some experience and conditioned reflex stereotypes have already been formed.
This happens, in particular, with sexual behavior, the readiness for the manifestation of which occurs at a certain age against the background of hormonal changes. However, the effectiveness of mating in many species is also determined by individual experience acquired before reaching puberty as a result of communication with peers. For example, in adult male cichlid fish reared in isolation, courtship behavior is addressed not only to females but also to males. Similar changes have been observed in birds, rodents, and monkeys. Communication with relatives affects sexual behavior in different ways, changing the readiness for mating, reactivity to appropriate stimuli, accuracy of movements, and various reactions directly or indirectly associated with reproduction. It should be borne in mind that specific (in this example, sexual) behavior can be modified in adults on the basis of nonspecific behavior in relation to it, which manifests itself at earlier stages of ontogenesis.
Hormonal changes during puberty can also change the nature of the response to various biologically significant stimuli, which, in turn, is reflected in the implementation of previously developed conditioned reflexes. This pattern was traced on the example of conditioned reflex gustatory aversions - a negative attitude towards innately indifferent or preferred gustatory stimuli, combined with a painful condition. Aversion to a sweet taste, once combined with poisoning, is equally pronounced in immature rat pups of both sexes. As females mature, the motivation to consume sweet tasting substances associated with an increase in estrogen levels increases and the aversion developed towards them decreases accordingly. In males, their rejection continues to be significant, since androgens do not change this motivation.
The maturation of the central nervous system in the process of ontogenesis and the accompanying changes in the balance of biologically active substances in the internal environment of the body are extremely important for the manifestation of various innate forms of behavior and the conditioned reflex activity developed on their basis. Certain stages of postnatal life have their own characteristics of the interaction of unconditioned and conditioned reflex activity.
For example, during the first three years of life, puppies develop a food-procuring conditioned reflex to natural or ecologically inappropriate odor stimuli when they are combined with feeding once. From the 4th to the 10th day of life, the ability to develop this reflex disappears and reappears on the 11th–12th day, and starting from this period, learning already requires a multiple combination of conditioned and unconditioned stimuli.
Many reactions are formed in the first hours or days of life in birds and mammals with a single combination of stimulation of various sense organs with innate elements of behavior - following a moving object and other purposeful motor acts. This form of learning, called imprinting, takes place over a sensitive period lasting from 6–8 hours to 4–5 days. Close to being imprinted are natural conditioned reflexes, which are also formed very quickly at a certain stage of ontogenetic development and fade away extremely slowly.
Complex forms of behavior are observed immediately after the transition to postnatal life, which makes it possible to classify them as innate reactions. The process of their ripening cannot be traced "in its pure form", since they are modified due to external influences. The existence of imprinting phenomena and natural conditioned reflexes makes it difficult to differentiate between congenital and postnatal ontogenesis behavioral acts.
There is reason to believe that the implementation of some innate reactions is associated with stimuli to which the body is exposed in prenatal life. Thus, in puppies, the preference for the smell of the mother is formed at the end of the antenatal period.
Some innate reactions do not appear immediately after birth, but at one of the subsequent stages of development. If at this time the animal does not encounter a specific stimulus, in the future the ability to respond to it without special training does not appear. In this case, errors are possible in classifying some reactions as congenital or developed. For example, it has long been believed that dogs raised from the period of transition to the definitive diet on a bread and milk diet do not respond with an innate positive reaction to the smell of meat. The first experiments on these animals were carried out only at the age of 7 months. It turned out, however, that on the 16th - 21st day of a puppy's life, this ability manifests itself. If there is no adequate stimulus, it gradually slows down and is absent in older puppies who encounter the smell of meat for the first time.
The manifestation of some complex forms of behavior, although determined by the genetic program, can be modulated to some extent by external factors. Thus, a decrease in the temperature of the external environment significantly reduces the level of play activity of the young of some mammals, although it causes its specific irritant - contact with peers.
Many examples can be cited that confirm the role of environmental factors in the modification of innate forms of behavior. However, it would be a mistake to contrast the importance of genetic and environmental factors in the development of behavior. All forms of interaction of the organism with the environment, including behavioral ones, are determined by the genetic program and are subject to external influences to one degree or another. The genetic program also determines the range of these influences, i.e. the so-called reaction rate. For some characters, it is strictly fixed, which well illustrates the lack of plasticity in the implementation of certain functions in insects (flight, emergence from a larva or cocoon, sexual behavior).
There are strictly programmed instinctive actions. For example, a female spider during the construction of a cocoon produces complexes of stereotyped movements, even if the web thread is not produced. She then lays eggs in a non-existent hole, which fall to the ground, and continues her activity to mimic building a cocoon that doesn't really exist. In this case, the reaction rate is extremely narrow, and instinctive actions do not depend on signals about their effectiveness. For a number of other traits, it is much wider, and the adaptive variability of instinctive actions was also found in insects, which manifests itself, in particular, during the restoration of destroyed dwellings in conditions different from natural ones.
The genetic conditioning of behavior is manifested in the gradual formation of certain behavioral acts in the process of early ontogenesis. The ratio of congenital and acquired components in the reaction of an attack on a victim in kittens has been studied in detail. At first, only instinctive motor stereotypes appear, gradually, in the process of training, which takes place in conditions of contact with the mother and peers, they are refined and enriched with the movements formed in the learning process.
The initial use of innate movement complexes associated with food activity has been described in puppies of the first days of life during the development of intracerebral self-stimulation of “reward zones” (positive emotiogenic system). Gradually, the repertoire of movements is enriched with less stereotyped, developed complexes, and they are adjacent to the innate stereotypes of motor activity. Obviously, the instinctive commanding acts, on the basis of which a new system of purposeful activity is built, are not necessarily eliminated during its formation.
Difficult is the question of the indispensable reflex basis of each behavioral act.
The idea of its obligation led I.P. Pavlov to the identification of the concepts of complex unconditional reactions and instincts. In many cases, it was possible to detect external and internal stimuli, which are the impetus for the deployment of a chain of patterned reactions, but it is not always possible to identify them, which suggests that a number of forms of instinctive activity manifest themselves spontaneously. Endogenous processes in the central nervous system determine the performance of a number of instinctive acts without visible fluctuations in the state of the external and internal environment. An important role is played by circadian and other rhythms, which are not determined by the physiological state of the body and various stimuli, although they can shift under their influence.
Autonomous oscillatory processes in various brain structures are described, which determine periodic changes in the behavior of animals isolated from relatives and deprived of sight and hearing. Many genetically encoded reactions are determined by changes in the internal environment of the organism. For example, in Siamese mutant cats deaf from birth, the excitation associated with the cycle of sexual activity manifests itself both in behavioral acts (lordosis, etc.) and in specific sound signals. Certain signals are emitted by these animals in a state of hunger and defensive behavior.
Some norms of reactions in the absence of feedback are suppressed. So, deaf and blind people lack some expressive movements (including sound) associated with auditory or visual perception, respectively. Those born blind smile less with age than those who are sighted or blind later in life. However, a number of expressive movements manifest themselves regardless of the usefulness of the sensory systems. An analysis of the expressive movements of children born blind and deaf, recorded on film, showed that their motor skills of laughter are exactly the same as in healthy ones (I. Eibl-Eibesfeldt).
Instinctive movement complexes are usually closely related to signals from the external and internal environments of the body, although they can be determined by autonomous processes in the central nervous system. However, it is not always possible to identify them.
The denial of the reflex nature of instinctive acts has led some researchers to define them as innate, internally organized and spontaneous (W. Thorpe). W. Craig suggested that instinct is associated with the accumulation of "specific energy of action", which is released by the resolving situation. At the same time, instinctive actions that reflect internal needs include the search (preparatory) and final phases.
An example is the activity of a predator in tracking down and eating prey. At the first stage, there is an undirected search, then, in accordance with the stimuli emanating from the victim, the search becomes directed, after which a series of behavioral acts follows (sneaking or chasing, jumping, killing the victim, dismembering it into pieces). The second stage (eating the victim) is the final (consumatory) stage and proceeds more stereotypically than the first. W. Craig attached great importance to drives and impulses, believing that the final stage of instinctive action suppresses them.
Conclusion
Lower nervous activity is called unconditioned reflex, and its individual reactions are called unconditioned reflexes. Unconditioned reflexes, formed over millions of years of evolution, are the same for all representatives of a given animal species and depend little on the momentary conditions for the existence of a particular organism.
Unconditioned reflexes allow us to solve the most important biological problems in reliable, time-tested methods and solve them successfully, provided that environmental factors remain generally the same as they were millions of years ago. With a sharp change in these conditions, the unconditioned reflex becomes a poor helper. For example, hedgehogs are characterized by a defensive unconditioned reflex: curl up into a ball and expose thorns. For many millennia, he rescued them, but in the second half of the 20th century, according to zoologists, this reflex brought them to the brink of extinction, because. hedgehogs that come out at night on roads that keep heat for a long time to warm themselves, when a car approaches, they do not run away, but try to defend themselves with the same thorns as of old and, of course, die under the wheels.
This means that an attempt to adapt to dramatically changed conditions with the help of unconditionally reflex behavior can lead the organism to death. Moreover, since all representatives of a given biological species have the same unconditioned reflexes, with a sharp change in climate or other factors, not one organism, but many individuals may die. In unicellular organisms, worms, mollusks and arthropods, for example, the death of a large number of individuals is compensated for by a huge reproduction rate.
Higher animals and man adapt themselves to the changed conditions quite differently. In these species, on the basis of lower nervous activity, new mechanisms of adaptation were formed - higher nervous activity. With its help, living organisms acquired the ability to respond not only to the direct action of biologically significant agents (food, sexual, defensive), but also to their distant signs, revealing from the chaos of the environment the links in time between a biologically important phenomenon and the events that naturally precede it.
Bibliography
1. Smirnov V.M., Budylina S.M. Physiology of sensory systems and higher nervous activity - M., 2003.
2. Smironov V.M. Neurophysiology and GNI of children and adolescents. - M., 2000
3. Uryvaev Yu.V. Higher functions of the brain. - M., 1996
4. Anokhin P.K. Biology and neurophysiology of the conditioned reflex. - M.: Medicine, 1968
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Introduction
1. Reflex theory and its basic principles
2. Reflex - a concept, its role and significance in the body
3. The reflex principle of building 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 paper 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. V. M. Bekhterev, P. K. Anokhin and other physiologists are the scientific and theoretical basis of Soviet physiology and psychology. These propositions 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.
Principle of materialistic determinism means that each nervous process in the brain is determined (caused) by the action of certain stimuli.
Structural principle lies in the fact that the differences in the functions of different parts of the nervous system depend on the features of their structure, and the change in the structure of parts of the nervous system in the process of development is due to a change in functions. Thus, in animals that do not have a brain, the higher nervous activity is much more primitive than the higher nervous activity of animals that have a brain. In humans, in the course of historical development, the brain has reached a particularly complex structure and perfection, which is associated with its labor activity and social living conditions that require constant verbal communication.
At the same time, during the formation of a conditioned reflex, a temporary nervous connection (closure) is established between the two foci of excitation, which physiologically expresses synthesis. The conditioned reflex is the unity of analysis and synthesis.
2. Reflex - a concept, its role and significance in the body
Reflexes (from the Latin slot reflexus - reflected) are the body's responses to irritation of receptors. In the receptors, nerve impulses arise, which, through the sensory (centripetal) neurons, enter the central nervous system. There, the received information is processed by intercalary neurons, after which motor (centrifugal) neurons are excited and nerve impulses actuate the executive organs - muscles or glands. Intercalary neurons are called neurons, the bodies and processes of which do not go 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, security, etc. They contribute to the survival of an individual or species as a whole. They are classified into food, water-producing, defensive, sexual, orienting, nest-building, etc. There are reflexes that establish a certain order (hierarchy) in a herd or flock, and territorial reflexes that determine the territory captured by one or another individual or flock.
There are positive reflexes, when the stimulus causes a certain activity, and negative, inhibitory, in which the activity stops. The latter, for example, include a passive-defensive reflex in animals, when they freeze at the appearance of a predator, an unfamiliar sound.
Reflexes play an exceptional role in maintaining the constancy of the internal environment of the body, 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 speeding up the contractions of the heart and narrowing the lumen of the arteries, as a result, the pressure rises. It continuously fluctuates around a certain constant value, which is called the 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. There are reflexes 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, excitation occurs in the centers of the brain that regulate the flow of water and a feeling of thirst appears. This arousal causes goal-directed behavior, the search for 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. So, while 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.
A great achievement of physiology was the discovery by IP Pavlov of conditioned reflexes.
Unconditioned reflexes are inborn, 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 pain irritation with a defensive reaction. There is a wide variety of unconditioned reflexes: defensive, food, orientation, sexual, etc.
The reactions that underlie unconditioned reflexes in animals have been developed over thousands of years in the course of adaptation of various animal species to the environment, in the process of struggle for existence. Gradually, under conditions of long evolution, the unconditioned reflex reactions necessary to satisfy the biological needs and preserve the vital activity of the organism were fixed and inherited, and those of the unconditioned 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 a constant change in the environment, more durable and perfect forms of animal response were required to ensure the adaptation of the organism to the changed conditions of life. In the process of individual development, highly organized animals form a special type of reflexes, which IP Pavlov called conditional.
Conditioned reflexes acquired by an organism during its lifetime provide an appropriate response of a living organism to changes in the environment and, on this basis, balance 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 humans are carried out mainly by the higher part of the central nervous system (cerebral cortex).
The observation of the phenomenon of "mental secretion" in a dog helped IP Pavlov to discover the conditioned reflex. The animal, seeing food at a distance, intensively salivated even before the food was served. This fact has been interpreted in different ways. The essence of "mental 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, a flashing light, etc.) can cause 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 a cup in which there was food, then there always came a moment when the dog began to salivate just at one knock. Reactions that are caused by stimuli that were previously indifferent. I. P. Pavlov called conditioned reflex. The conditioned reflex, I. P. 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 the specific properties of stimuli from the outside world.
Conditioned reflexes in animals in the experiments of I. P. Pavlov were most often developed on the basis of an unconditioned food reflex, when food served as an unconditioned stimulus, and one of the stimuli (light, sound, etc.) indifferent (indifferent) to food performed the function of a conditioned stimulus. .).
There are 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, which causes a parental conditioned reflex in it, the squeak of a mouse for a cat, etc.), and artificial conditioned stimuli that are completely unrelated to unconditioned reflex stimuli. (for example, a light bulb, to 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.
3. The reflex principle of the construction of the nervous system The principle of feedback
From the point of view of modern science, the nervous system is a collection of neurons connected by synapses into cell chains that act on the principle of reflection, that is, reflexively. Reflex (from Latin reflexus - “turned back”, “reflected”) - the body's reaction to irritation, carried out with the help of the nervous system. The first ideas about the reflected activity of the brain were expressed in 1649 by the French scientist and philosopher Rene Descartes (1590-1650). He considered reflexes as the simplest movements. However, over time, the concept has expanded.
In 1863, the creator of the Russian school of physiologists, Ivan Mikhailovich Sechenov, uttered a phrase that went down in the history of medicine: "All acts of conscious and unconscious activity are, by way of origin, reflexes." Three years later, he substantiated his claim in the classic Reflexes of the Brain. Another Russian scientist I. P. Pavlov built on the statement of a brilliant compatriot the doctrine of higher nervous activity. The reflexes underlying it, Pavlov divided into unconditional, with which a person is born, and conditional, acquired during life.
Through centripetal - afferent (from Latin affero - “I bring”) fibers, signals arrive at the so-called first (sensitive) neuron located in the spinal ganglion. It is he who passes through himself the initial information, which the brain transforms in a fraction of a second into familiar sensations: touch, prick, warmth ... Along the axon of a sensitive nerve cell, impulses follow to the second neuron - intermediate (intercalary). It is located in the posterior sections, or, as experts say, the posterior horns of the spinal cord; a horizontal section of the spinal cord really looks like the head of a strange animal with four horns.
From here, the signals have a direct road to the anterior horns: to the third - motor - neuron. The axon of the motor cell extends beyond the spinal cord along with other efferent (from Latin effero - “I take out”) fibers as part of the nerve roots and nerves. They transmit commands from the central nervous system to the working organs: the muscle, for example, is ordered to contract, the gland - to secrete juice, the vessels - to expand, etc.
However, the activity of the nervous system is not limited to the “highest decrees”. She not only gives orders, but also strictly monitors their execution - she analyzes signals from receptors located in the organs that work on her instructions. Due to this, the amount of work is adjusted depending on the state of the “subordinates”. In fact, the body is a self-regulating system: it carries out vital activity according to the principle of closed cycles, with feedback on the result achieved. Academician Pyotr Kuzmich Anokhin (1898-1974) came to this conclusion back in 1934, when he combined the theory of reflexes with biological cybernetics.
Sensory and motor neurons are the alpha and omega of a simple reflex arc: it starts with one and ends with another. In complex reflex arcs, ascending and descending cell chains are formed, connected by a cascade of intercalary neurons. This is how extensive bilateral connections are made between the brain and the spinal cord.
The formation of a conditioned reflex connection requires a number of conditions:
1. Multiple coincidence in time of the action of the unconditioned and conditioned stimuli (more precisely, with some precedence of the action of the conditioned stimulus). Sometimes a connection is formed even with a single coincidence of the action of stimuli.
2. Absence of extraneous irritants. The action of an external stimulus during the development of a conditioned reflex leads to inhibition (or even to the cessation) of the conditioned reflex reaction.
3. Great physiological strength (factor of biological significance) of the unconditioned stimulus in comparison with the conditioned stimulus.
4. Active state of the cerebral cortex.
According to modern concepts, nerve impulses are transmitted during the implementation of reflexes along the reflex rings. The reflex ring includes at least 5 links.
It should be noted that the latest research data of scientists (P.K. Anokhin and others) confirm just such an annular reflex scheme, and not a reflex arc scheme that does not fully reveal this complex process. The organism needs to receive information about the results of the action, information about each stage of the ongoing action. Without it, the brain cannot organize purposeful activity, cannot correct the action when any random (interfering) factors intervene in the reaction, cannot stop the activity at the necessary moment, when the result is achieved. This led to the need to move from the idea of an open reflex arc to the idea of a cyclic innervation structure in which there is feedback - from the effector and the object of activity through receptors to the central nervous structures.
This connection (reverse flow of information from the object of activity) is a mandatory element. Without it, the organism would be cut off from the environment in which it lives and to change which its activity is directed, including human activity associated with the use of tools of production. .
theory reflex nerve system
Conclusion
Thus, experiencing the impact of a variety of signals from the outside world and from the body, the cerebral cortex performs a complex analytical and synthetic activity, which consists in decomposing complex signals, stimuli into parts, comparing them with their past experience, highlighting the main, the main, essential and the unification of the elements of this main, essential. This complex analytical and synthetic activity of the cerebral cortex, which determines the breadth, diversity, and activity of feedback neural connections, provides a person with better adaptability to the outside world, to changed living conditions.
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