Human behavior is associated with conditionally unconditioned reflex activity and is a higher nervous activity, the result of which is a change in the relationship between the body and the external environment.

Unlike the highest nervous activity lower nervous activity consists of a set of reactions aimed at unification, integration of functions within the body.

Higher nervous activity manifests itself in the form of complex reflex reactions, carried out with the obligatory participation of the cortex large hemispheres and the subcortical formations closest to it.

For the first time, the idea of ​​the reflex nature of the activity of the brain was widely and in detail developed by the founder of Russian physiology, IM Sechenov, in his book "Reflexes of the Brain". The ideological attitude of this classic work is expressed in the original title changed under the influence of censorship: "An attempt to introduce physiological foundations into mental processes. "Prior to I. M. Sechenov, physiologists and neurologists did not even dare to raise the question of the possibility of an objective, purely physiological analysis mental processes... The latter remained completely at the mercy of subjective psychology.

I.M.Sechenov's ideas were brilliantly developed in the remarkable works of I.P. Pavlov, who opened the way of objective experimental research functions of the cerebral cortex and created a harmonious doctrine of higher nervous activity.

I.P. Pavlov showed that while in the lower parts of the central nervous system - subcortical nuclei, brain stem, spinal cord - reflex reactions are carried out along innate, hereditarily fixed nerve pathways, in the cerebral cortex, nerve connections are produced and created in the process the individual life of animals and humans, as a result of a combination of countless stimuli acting on the body.

The discovery of this fact made it possible to divide the entire set of reflex reactions occurring in the body into two main groups: unconditioned and conditioned reflexes.

Conditioned reflexes

• these are the reactions acquired by the body in the process of individual development based on "life experience"
• are individual: some representatives of the same species may have them, while others do not
• are unstable and depending on certain conditions they can develop, gain a foothold or disappear; this is their property and is reflected in their very name
• can form on a wide variety of stimuli applied to different receptive fields
• are closed at the level of the cortex. After removal of the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain.
• carried out through functional temporary links

Conditioned reflexes are developed on the basis unconditioned reflexes... For the formation of a conditioned reflex, it is necessary to combine the time of any change in the external environment and the internal state of the organism, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition is the change in the external environment or internal state the organism becomes a stimulus for a conditioned reflex - a conditioned stimulus, or signal. Irritation that causes an unconditioned reflex - unconditioned irritation - should accompany the conditioned irritation during the formation of a conditioned reflex, reinforce it.

For the formation of conditioned reflexes, a temporary connection, a closure between the cortical cells that perceive the conditioned stimulus, and the cortical neurons that are part of the arc of the unconditioned reflex, is necessary.

With the coincidence and combination of conditioned and unconditioned stimuli, a connection is established between various neurons in the cortex of the cerebral hemispheres, and a closure process occurs between them.

Unconditioned reflexes

• these are congenital, hereditarily transmitted reactions of the body
• are specific, that is, characteristic of all representatives of a given species
• relatively constant, as a rule, persist throughout life
• carried out in response to adequate stimuli applied to one specific receptive field
• close at the level spinal cord and the brain stem
• are carried out through a phylogenetically fixed, anatomically pronounced reflex arc.

It should be noted, however, that in humans and monkeys, which have a high degree of corticalization of functions, many complex unconditioned reflexes are carried out with the obligatory participation of the cerebral cortex. This is proved by the fact that her lesions in primates lead to pathological disorders of unconditioned reflexes and the disappearance of some of them.

It should also be emphasized that not all unconditioned reflexes appear immediately by the time of birth. Many unconditioned reflexes, for example, those associated with locomotion, sexual intercourse, occur in humans and animals through long term after birth, but they necessarily appear under the condition of the normal development of the nervous system.

The whole set of unconditioned and conditioned reflexes formed on their basis is taken according to their functional value divided into a number of groups.

1. By receptor evidence
   1. Exteroreceptive reflexes
      • visual
      • olfactory
      • flavoring, etc.
   2. Interoreceptive reflexes- reflexes, in which the conditioned stimulus is irritation of the receptors of internal organs by changes in the chemical composition, temperature of internal organs, pressure in hollow organs and vessels
2. By effector trait, i.e. by those effectors that respond to irritation
   1. vegetative reflexes
      • food
      • cardiovascular
      • respiratory, etc.
   2. somato-motor reflexes- manifested in the movements of the whole organism or its individual parts on the action of an irritant
      • defensive
3. By biological value
   1. Food
      • reflex swallowing
      • reflex chewing
      • reflex sucking act
      • reflex act of salivation
      • reflex act of secretion of gastric and pancreatic juice, etc.
   2. Defensive- elimination reactions from damaging and painful irritations
   3. Sexual- reflexes associated with sexual intercourse; this group also includes the so-called parental reflexes associated with the feeding and nursing of the offspring.
   4. Stato-kinetic and locomotor- reflex reactions of maintaining a certain position and movement of the body in space.
   5. Reflexes of maintaining homeostasis
      • thermoregulation reflex
      • respiratory reflex
      • heart reflex
      • vascular reflexes that help maintain consistency blood pressure and etc.
   6. Orientation reflex- a reflex to novelty. It arises in response to any rapidly occurring fluctuation of the environment and is expressed outwardly in alertness, listening to a new sound, sniffing, turning the eyes and head, and sometimes the whole body towards the light stimulus that has appeared, etc. The implementation of this reflex provides the best perception of the acting agent and has an important adaptive value.

      IP Pavlov figuratively called the orienting reaction the reflex "what is it?" This reaction is innate and does not disappear when complete removal cerebral cortex in animals; it is also observed in children with underdeveloped cerebral hemispheres - anencephals.

The difference between the orienting reflex and other unconditioned reflex reactions is that it dies out relatively quickly with repeated applications of the same stimulus. This feature of the orienting reflex depends on the influence of the cerebral cortex on it.

The above classification of reflex reactions is very close to the classification of various instincts, which are also divided into food, sexual, parental, and defensive ones. This is understandable due to the fact that, according to I.P. Pavlov, instincts are complex unconditioned reflexes. Their distinctive features is the chain nature of reactions (the end of one reflex serves as the causative agent of the next) and their dependence on hormonal and metabolic factors. So, the emergence of sexual and parental instincts is associated with cyclical changes in the functioning of the gonads, and the food instinct depends on those metabolic changes that develop in the absence of food. One of the features of instinctive reactions is also the fact that they are characterized by many properties of the dominant.

The reflex component is a reaction to irritation (movement, secretion, change in breathing, etc.).

Most unconditioned reflexes are complex reactions that include several components. So, for example, with an unconditioned defensive reflex caused in a dog by a strong electrocutaneous irritation of the limb, along with protective movements, there is also an increase and increase in respiration, an acceleration of cardiac activity, voice reactions appear (screeching, barking), the blood system changes (leukocytosis, platelets and etc.). The food reflex also distinguishes between its motor (seizure of food, chewing, swallowing), secretory, respiratory, cardiovascular and other components.

Conditioned reflexes, as a rule, reproduce the structure of the unconditioned reflex, since the conditioned stimulus excites the same nerve centers as the unconditioned one. Therefore, the composition of the components of the conditioned reflex is similar to the composition of the components of the unconditioned response.

Among the components of a conditioned reflex, there are main reflexes specific for a given type, and secondary components. In the defensive reflex, the main one is the motor component, in the food reflex - the motor and secretory.

Changes in respiration, cardiac activity, vascular tone accompanying the main components are also important for the integral reaction of the animal to the stimulus, but they play, as IP Pavlov said, "a purely service role." Thus, increased and increased respiration, increased heart rate, increased vascular tone caused by a conditioned defensive stimulus, enhance metabolic processes in skeletal muscles and thereby create optimal conditions for the implementation of protective motor reactions.

In the study of conditioned reflexes, the experimenter often chooses one of its main components as an indicator. Therefore, they talk about conditioned and unconditioned motor or secretory or vasomotor reflexes. However, it must be borne in mind that they are only separate components of the integral reaction of the organism.

The biological significance of conditioned reflexes is that they make it possible to adapt much better and more accurately to the conditions of existence and to survive in these conditions.

As a result of the formation of conditioned reflexes, the organism reacts not only directly to unconditioned stimuli, but also to the possibility of their action on it; reactions appear some time before unconditioned irritation. By this, the organism turns out to be prepared in advance for the actions that it has to carry out in a given situation. Conditioned reflexes contribute to the finding of food, early avoidance of danger, elimination harmful effects etc.

The adaptive meaning of conditioned reflexes is also manifested in the fact that the precedence of conditioned stimulation to the unconditioned one enhances the unconditioned reflex and accelerates its development.

The behavior of animals is different forms of external, mainly motor activity, aimed at establishing vital links between the body and the environment. Animal behavior consists of conditioned, unconditioned reflexes and instincts. Instincts include complex unconditioned reactions that, being innate, appear only at certain periods of life (for example, the instinct for nesting or feeding offspring). Instincts play a leading role in the behavior of lower animals. However, the higher an animal is on the evolutionary level, the more complex and varied its behavior, the more perfect and subtle it adapts to the environment, and the greater the role of conditioned reflexes in its behavior.

The environment in which animals exist is highly variable. Adaptation to the conditions of this environment by means of conditioned reflexes will be subtle and accurate only if these reflexes are also changeable, that is, conditioned reflexes unnecessary in new environmental conditions will disappear, and new ones are formed instead. The disappearance of conditioned reflexes occurs due to the processes of inhibition.

Distinguish between external (unconditioned) inhibition of conditioned reflexes and internal (conditioned) inhibition.

External inhibition of conditioned reflexes arises under the influence of extraneous stimuli that cause a new reflex reaction. This inhibition is called external because it develops as a result of processes occurring in areas of the cortex that are not involved in the implementation of this conditioned reflex.

Superstrong or long-acting extraneous stimuli can cause transcendental inhibition of reflexes.

Internal inhibition of conditioned reflexes occurs in the absence of reinforcement of the received signal by an unconditioned stimulus.

In this case, internal inhibition does not occur immediately. Requires, as a rule, multiple use of an unsupported signal.

The fact that this is inhibition of the conditioned reflex, and not its destruction, is evidenced by the restoration of the reflex the next day, when the inhibition has passed. Various diseases, overwork, overstrain causes a weakening of internal inhibition.

If the conditioned reflex is extinguished (not reinforced with food) for several days in a row, then it may disappear altogether.

There are several types of internal inhibition. The form of inhibition considered above is called extinguishing inhibition. This inhibition underlies the disappearance of unnecessary conditioned reflexes.

Another type is differential (discriminatory) inhibition.

An unreinforced conditioned stimulus causes inhibition in the cortex and is called an inhibitory stimulus. With the help of the described technique, it was possible to determine the distinctive ability of different sense organs in animals.

The phenomenon of disinhibition. It is known that extraneous stimuli cause inhibition of conditioned reflexes. If an extraneous stimulus arises during the action of an inhibitory stimulus, for example, when the metronome is operated with a frequency of 100 times per minute, as in the previous case, then this will cause the opposite reaction - saliva will flow. I.P. Pavlov called this phenomenon disinhibition and explained it by the fact that an extraneous stimulus, inducing an orientation reflex, inhibits any other process that is currently taking place in the centers of the conditioned reflex. If the process of inhibition is inhibited, then all this leads to the excitation and implementation of a conditioned reflex.

The phenomenon of disinhibition also indicates the inhibitory nature of the processes of discrimination and extinction of conditioned reflexes.

Conditional inhibition value very large. Thanks to inhibition, a much better correspondence of the organism's reaction to external conditions is achieved, and its adaptation to the environment is more perfect. The combination of two forms of a single nervous process - excitation and inhibition - and their interaction make it possible for the body to navigate in different difficult situations, are the conditions for the analysis and synthesis of stimuli.

Conditioned reflexes are the reactions of the whole organism or any part of it to external or internal stimuli. They manifest themselves through the disappearance, weakening or strengthening of certain activities.

Conditioned reflexes are helpers of the body that allow it to quickly respond to any changes and adapt to them.

History

For the first time, the idea of ​​a conditioned reflex was put forward by the French philosopher and scientist R. Descartes. Somewhat later, the Russian physiologist I. Sechenov created and experimentally proved new theory concerning the reactions of the body. For the first time in the history of physiology, it was concluded that conditioned reflexes are a mechanism that is activated not only. The entire nervous system is involved in its work. This allows the body to maintain its connection with the environment.

Studied by Pavlov. This outstanding Russian scientist was able to explain the mechanism of action of the cerebral cortex and cerebral hemispheres. At the beginning of the 20th century, he created the theory of conditioned reflexes. This scientific work has become a real revolution in physiology. Scientists have proven that conditioned reflexes are the body's reactions that are acquired throughout life, based on unconditioned reflexes.

Instincts

Certain reflexes of the unconditioned type are characteristic for each type of living organism. They are called instincts. Some of them are quite complex. Examples of this are bees that make honeycombs, or birds that make nests. Thanks to the presence of instincts, the body is able to optimally adapt to environmental conditions.

Are congenital. They are inherited. In addition, they are classified as species, since they are characteristic of all representatives of a certain species. Instincts are permanent and persist throughout life. They manifest themselves on adequate stimuli that are applied to a specific single receptive field. Physiologically unconditioned reflexes are closed in the brainstem and at the level of the spinal cord. They manifest themselves through anatomically expressed

As for monkeys and humans, the implementation of most of the complex unconditioned reflexes is impossible without the participation of the cerebral cortex. When its integrity is violated, pathological changes in unconditioned reflexes occur, and some of them simply disappear.

Classification of instincts

Unconditioned reflexes are very strong. Only under certain conditions, when their manifestation becomes optional, they can disappear. For example, a canary domesticated about three hundred years ago does not currently have the instinct to build nests. There are the following types of unconditioned reflexes:

Which is the body's response to a variety of physical or chemical stimuli. Such reflexes, in turn, can manifest themselves locally (withdrawal of the hand) or be complex (escape from danger).
- Food instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of sequential actions - from searching for prey to attacking it and then eating it.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.

Comfortable instinct for keeping the body clean (bathing, scratching, shaking, etc.).
- An orienting instinct, when the eyes and head turn in the direction of the stimulus. This reflex is needed to preserve life.
- The instinct of freedom, which is especially pronounced in the behavior of animals in captivity. They constantly want to break free and often die, refusing food and water.

The emergence of conditioned reflexes

Throughout life, the acquired reactions of the organism are added to the inherited instincts. They are called conditioned reflexes. They are acquired by the body as a result of individual development. The basis for obtaining conditioned reflexes is life experience... Unlike instincts, these reactions are individual. They may be present in some representatives of the species and absent in others. In addition, a conditioned reflex is a reaction that may not persist throughout life. Under certain conditions, it is developed, fixed, disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.

The conditioned reflex mechanism closes at the level. If you remove it, then only instincts will remain.

The formation of conditioned reflexes occurs on the basis of unconditioned ones. For the implementation of this process, it is necessary to fulfill a certain condition. In this case, any change in the external environment should be combined in time with the internal state of the organism and perceived by the cerebral cortex with a simultaneous unconditioned reaction of the organism. Only in this case does a conditioned stimulus or signal appear, contributing to the emergence of a conditioned reflex.

Examples of

For the appearance of such a reaction of the body as the release of saliva when knives and forks are ringing, as well as when a cup for feeding an animal (in humans and in a dog, respectively), a sine qua non is the repeated coincidence of these sounds with the process of providing food.

In the same way, the sound of a bell or the turning on of a light bulb will cause the dog's paw to bend if these phenomena occur repeatedly accompanied by electrical stimulation of the animal's leg, as a result of which an unconditioned flexion reflex appears.

A conditioned reflex is the withdrawal of the child's hands from the fire and subsequent crying. However, these phenomena will take place only if the type of fire, even once, coincided with the receipt of a burn.

Components of reactions

The body's response to irritation is a change in respiration, secretion, movement, etc. As a rule, unconditioned reflexes are rather complex reactions. That is why they include several components at once. For example, the defensive reflex is accompanied not only by defensive movements, but also by increased respiration, acceleration of the activity of the heart muscle, and a change in the composition of the blood. In this case, voice reactions may appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.

Conditional reactions usually reproduce the structure of unconditioned ones. This occurs due to the excitation of the same nerve centers by stimuli.

Classification of conditioned reflexes

The body's acquired responses to various stimuli are classified by type. Some of the existing classifications have great value when solving not only theoretical, but also practical problems. One of the areas of application of this knowledge is sports activity.

Natural and artificial reactions of the body

There are conditioned reflexes that arise under the action of signals characteristic of the permanent properties of unconditioned stimuli. An example of this is the sight and smell of food. These conditioned reflexes are natural. They are characterized by speed of production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be sustained throughout life. In this case, the importance of the conditioned reflex is especially great at the very first stages of the life of the organism, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature change, light, etc. In natural conditions, they are not irritants. It is these reactions that are called artificial. They are produced slowly and disappear quickly in the absence of reinforcement. For example, artificial conditioned reflexes of a person are reactions to the sound of a bell, touching the skin, weakening or increasing lighting, etc.

First and highest order

There are such types of conditioned reflexes that are formed on the basis of unconditioned ones. These are first-order reactions. There are also higher categories... So, reactions that are developed on the basis of already existing conditioned reflexes are referred to as reactions of a higher order. How do they arise? When such conditioned reflexes are developed, the indifferent signal is reinforced by well-mastered conditioned stimuli.

For example, ringing annoyances are constantly reinforced by food. In this case, the development of a conditioned reflex of the first order occurs. On its basis, a reaction to another stimulus, for example, to light, can be fixed. This will become a second order conditioned reflex.

Positive and negative reactions

Conditioned reflexes can affect the body's activity. Such reactions are classified as positive. The manifestation of these conditioned reflexes can be secretory or motor functions... If the body is not active, then the reactions are classified as negative. For the process of adaptation to the constantly changing conditions of the environment of existence, both one and the second species are of great importance.

At the same time, there is a close relationship between them, since with the manifestation of one type of activity, the other is certainly oppressed. For example, when the command “Attention!” Sounds, the muscles are in a certain position. In this case, motor reactions are inhibited (running, walking, etc.).

Formation mechanism

Conditioned reflexes arise with the simultaneous action of a conditioned stimulus and an unconditioned reflex. In this case, certain conditions must be met:

The unconditioned reflex is biologically stronger;
- the manifestation of the conditioned stimulus is somewhat ahead of the action of the instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditioned;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli that produces a distracting effect is observed.

The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (closure) with each other. In this case, irritation is perceived by cortical neurons, which are part of the arc of an unconditioned reflex.

Inhibition of conditioned reactions

In order to ensure adequate behavior of the organism and for better adaptation to the surrounding conditions, the development of conditioned reflexes alone will not be enough. An opposite action will be required. It is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not needed. According to the theory developed by Pavlov, there are certain types cortical inhibition. The first is the unconditional. It appears as a response to the action of some extraneous stimulus. There is also internal inhibition. It is called conditional.

External braking

This reaction received this name due to the fact that its development is facilitated by the processes taking place in those parts of the cortex that do not take part in the implementation reflex activity... For example, a foreign smell, sound, or change in lighting before the onset of a food reflex can reduce it or contribute to its complete disappearance. The new stimulus acts as a brake on the conditioned reaction.

Food reflexes can be eliminated by painful stimuli. The inhibition of the body's reaction is facilitated by overflow of the bladder, vomiting, internal inflammatory processes etc. All of them inhibit food reflexes.

Internal braking

It occurs when the received signal is not supported by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, a light bulb is periodically turned on in front of the eyes of an animal during the day without bringing food. It has been experimentally proven that saliva production will decrease every time. As a result, the reaction will die out completely. However, the reflex will not disappear without a trace. It will simply slow down. This has also been proven experimentally.

The conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the body's reaction to this stimulus will subsequently disappear forever.

Varieties of internal inhibition

Several types of elimination of the body's response to stimuli are classified. So, the basis for the disappearance of conditioned reflexes, which in given specific conditions are simply not needed, is extinguishing inhibition. There is another variety this phenomenon... This is discriminatory or differentiated inhibition. So, the animal can distinguish the number of metronome beats at which food is brought to it. This happens when this conditioned reflex has been previously worked out. The animal distinguishes between stimuli. This reaction is based on internal inhibition.

The value of eliminating reactions

Conditioned inhibition plays a significant role in the vital activity of the organism. Thanks to him, the process of adapting to the environment is much better. The possibility of orientation in a variety of difficult situations is provided by a combination of excitation and inhibition, which are two forms of a single nervous process.

Conclusion

There are an infinite number of conditioned reflexes. They are the factor that determines the behavior of a living organism. With the help of conditioned reflexes, animals and humans adapt to their environment.

There are many indirect signs of the body's reactions that have a signaling value. For example, an animal, knowing in advance about the approach of danger, builds its behavior in a certain way.

The process of developing conditioned reflexes that relate to higher order, is a synthesis of temporary connections.

The basic principles and patterns manifested in the formation of not only complex, but also elementary reactions are the same for all living organisms. This leads to an important conclusion for philosophy and natural sciences that it cannot but obey the general laws of biology. In this regard, it can be objectively studied. However, it should be borne in mind that the activity human brain possesses qualitative specificity and fundamental difference from the work of the animal's brain.

Age anatomy and physiology Olga Antonova

6.2. Conditioned and unconditioned reflexes. I.P. Pavlov