Human behavior is associated with conditioned-unconditioned reflex activity and represents higher nervous activity, the result of which is a change in the relationship of the organism with the external environment.

Unlike the highest nervous activity lower nervous activity consists of a set of reactions aimed at unifying and integrating 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 cerebral hemispheres and the subcortical formations closest to it.

For the first time, the idea of ​​the reflex nature of brain activity was widely and in detail developed by the founder of Russian physiology I.M. Sechenov in his book “Reflexes of the Brain.” The ideological setting of this classic work is expressed in the original title, changed under the influence of censorship: “An attempt to introduce physiological basis into mental processes." Before 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.

The ideas of I. M. Sechenov received brilliant development in the remarkable works of I. P. Pavlov, who opened the path to 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 underlying parts of the central nervous system - the subcortical nuclei, brain stem, spinal cord - reflex reactions are carried out according to innate, hereditarily fixed nerve pathways, in the cerebral cortex, nerve connections are developed and created in the process of individual life of animals and humans, as a result of a combination of countless irritations 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 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 may 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 be formed in response to a wide variety of stimuli applied to various receptive fields
• are closed at the level of the cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain.
• carried out through functional temporary connections

Conditioned reflexes are developed on the basis without conditioned 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 body, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition does a change in the external environment or internal state the body becomes a stimulus for a conditioned reflex - a conditioned stimulus, or signal. The irritation that causes an unconditioned reflex - unconditioned irritation - must, during the formation of a conditioned reflex, accompany the conditioned irritation and reinforce it.

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

When conditioned and unconditioned stimulation coincide and combine, a connection is established between different neurons in the cerebral cortex and a process of closure occurs between them.

Unconditioned reflexes

• These are innate, hereditary reactions of the body
• are specific, i.e. characteristic of all representatives of a given species
• relatively constant, as a rule, persist throughout life
• carried out in response to adequate stimulation applied to one specific receptive field
• close at level spinal cord and brain stem
• are carried out through a phylogenetically fixed, anatomically expressed reflex arc.

It should be noted, however, that in humans and monkeys, who 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 proven by the fact that its 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 at the time of birth. Many unconditioned reflexes, for example, those associated with locomotion and sexual intercourse, arise in humans and animals through long term after birth, but they necessarily appear subject to normal development of the nervous system.

The entire set of unconditioned and conditioned reflexes formed on their basis is accepted according to their functional significance divided into a number of groups.

1. By receptor
   1. Exteroceptive reflexes
      • visual
      • olfactory
      • flavoring, etc.
   2. Interoreceptive reflexes- reflexes in which the conditioned stimulus is irritation of the receptors of internal organs by a change chemical composition, temperature of internal organs, pressure in hollow organs and vessels
2. By effector trait, i.e. by those effectors that respond to stimulation
   1. autonomic reflexes
      • food
      • cardiovascular
      • respiratory, etc.
   2. somato-motor reflexes- manifested in movements of the whole organism or its individual parts in response to a stimulus
      • defensive
3. According to biological significance
   1. Food
      • reflex act of swallowing
      • reflexive act of chewing
      • reflex act of sucking
      • reflex act of salivation
      • reflex act of secretion of gastric and pancreatic juice, etc.
   2. Defensive- reactions to eliminate damaging and painful stimuli
   3. Genital- reflexes associated with sexual intercourse; This group also includes the so-called parental reflexes associated with feeding and nursing the offspring.
   4. Stato-kinetic and locomotor- reflex reactions of maintaining a certain position and movement of the body in space.
   5. Reflexes for maintaining homeostasis
      • thermoregulation reflex
      • breathing reflex
      • cardiac reflex
      • vascular reflexes that help maintain constancy blood pressure and etc.
   6. Orienting reflex- reflex to novelty. It occurs in response to any fairly quickly occurring fluctuation in the environment and is expressed externally in alertness, listening to a new sound, sniffing, turning the eyes and head, and sometimes the whole body towards the emerging light stimulus, etc. The implementation of this reflex ensures better perception active agent and has important adaptive significance.

      I. P. Pavlov figuratively called the indicative reaction the “what is it?” reflex. 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 fades away relatively quickly with repeated applications of the same stimulus. This feature of the orientation 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. 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 the reactions (the end of one reflex serves as the trigger for the next) and their dependence on hormonal and metabolic factors. Thus, 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 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 strong electrocutaneous irritation of the limb, along with defensive movements, breathing also increases and increases, cardiac activity accelerates, vocal reactions appear (squealing, barking), the blood system changes (leukocytosis, platelets and etc.). The food reflex also distinguishes between its motor (grasping 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 reaction.

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

Changes in respiration, cardiac activity, and vascular tone that accompany the main components are also important for the animal’s holistic response to a stimulus, but they play, as I. P. Pavlov said, “a purely auxiliary role.” Thus, increased and increased respiration, increased heart rate, increased vascular tone, caused by a conditioned defensive stimulus, contribute to increased metabolic processes in skeletal muscles and thereby create optimal conditions for the implementation of protective motor reactions.

When studying conditioned reflexes, the experimenter often chooses one of its main components as an indicator. That is why they talk about conditioned and unconditioned motor or secretory or vasomotor reflexes. It is necessary, however, to take into account that they represent only individual components of the body’s holistic reaction.

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 body reacts not only directly to unconditioned stimuli, but also to the possibility of their action on it; reactions appear some time before unconditional irritation. In this way, the body is prepared in advance for the actions that it has to carry out in a given situation. Conditioned reflexes contribute to finding food, avoiding danger in advance, eliminating harmful effects and so on.

The adaptive significance of conditioned reflexes is also manifested in the fact that the precedence of conditioned stimulation by an unconditioned one strengthens the unconditioned reflex and accelerates its development.

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

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

A distinction is made between external (unconditioned) inhibition of conditioned reflexes and internal (conditioned) inhibition.

External inhibition of conditioned reflexes occurs 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.

Extremely strong or long-acting extraneous stimuli can cause extreme inhibition of reflexes.

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

Internal inhibition does not occur immediately. As a rule, repeated use of a non-reinforced signal is required.

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, and overstrain cause a weakening of internal inhibition.

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

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

Another type is differentiated (discriminating) inhibition.

A non-reinforced conditioned stimulus causes inhibition in the cortex and is called an inhibitory stimulus. Using the described technique, it was possible to determine the discriminative ability different organs feelings in animals.

The phenomenon of disinhibition. It is known that extraneous stimuli cause inhibition of conditioned reflexes. If an extraneous stimulus occurs during the action of an inhibitory stimulus, for example, during the action of a metronome at 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, causing an orienting reflex, inhibits any other process that occurs in this moment in the centers of the conditioned reflex. If the inhibition process is inhibited, then all this leads to excitation and implementation of the conditioned reflex.

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

The meaning of conditional inhibition very large. Thanks to inhibition, a much better correspondence of the body's reaction to external conditions is achieved, 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 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 the body’s assistants, allowing it to quickly respond to any changes and adapt to them.

Story

The idea of ​​a conditioned reflex was first 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 body's reactions. 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 a 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 became a real revolution in physiology. Scientists have proven that conditioned reflexes are reactions of the body that are acquired throughout life, based on unconditioned reflexes.

Instincts

Certain reflexes of the unconditional type are characteristic of each type of living organism. They are called instincts. Some of them are quite complex. An example of this would be bees making honeycombs or birds making nests. Thanks to the presence of instincts, the body is able to optimally adapt to environmental conditions.

They 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 in response to 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 unconditioned reflexes, and some of them simply disappear.

Classification of instincts

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

Which is the body's reaction to a variety of physical or chemical stimuli. Such reflexes, in turn, can manifest locally (withdrawal of the hand) or be complex (flight 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 further eating it.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.

A comfortable instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- Orienting instinct, when the eyes and head are turned towards the stimulus. This reflex is necessary to preserve life.
- The instinct of freedom, which is especially clearly expressed in the behavior of animals in captivity. They constantly want to break free and often die, refusing water and food.

The emergence of conditioned reflexes

During life, acquired reactions of the body 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 members 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 produced, consolidated, and disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.

The mechanism of the conditioned reflex closes at the level. If it is removed, then only instincts will remain.

The formation of conditioned reflexes occurs on the basis of unconditioned ones. To carry out this process, a certain condition must be met. In this case, any change in the external environment must be combined in time with the internal state of the body and perceived by the cerebral cortex with a simultaneously carried out unconditional reaction of the body. Only in this case does a conditioned stimulus or signal appear that contributes to the emergence of a conditioned reflex.

Examples

For the body’s reaction to occur, such as the release of saliva when knives and forks clink, as well as when an animal’s feeding cup is knocked (in humans and dogs, respectively), an indispensable condition 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 flex if these phenomena have repeatedly occurred accompanied by electrical stimulation of the animal's leg, as a result of which an unconditioned type of flexion reflex appears.

The conditioned reflex is the child's hands being pulled away from the fire and subsequent crying. However, these phenomena will only occur if the type of fire, even once, coincides with a burn.

Reaction components

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

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

Classification of conditioned reflexes

The responses acquired by the body to various stimuli are divided into types. 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 activities.

Natural and artificial reactions of the body

There are conditioned reflexes that arise under the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the sight and smell of food. Such conditioned reflexes are natural. They are characterized by rapid production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The importance of the conditioned reflex is especially great in the very first stages of an organism’s life, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature changes, light, etc. Under natural conditions, they are not irritants. It is precisely such reactions that are called artificial. They are developed slowly and, in the absence of reinforcement, quickly disappear. For example, artificial conditioned human reflexes are reactions to the sound of a bell, touching the skin, weakening or increasing lighting, etc.

First and highest order

There are types of conditioned reflexes that are formed on the basis of unconditioned ones. These are first order reactions. There are also higher categories. Thus, reactions that are developed on the basis of already existing conditioned reflexes are classified as higher-order reactions. How do they arise? When developing such conditioned reflexes, the indifferent signal is reinforced with well-learned conditioned stimuli.

For example, irritation in the form of a bell is constantly reinforced by food. In this case, a first-order conditioned reflex is developed. 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 influence the activity of the body. Such reactions are considered positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the body, then the reactions are classified as negative. For the process of adaptation to constantly changing environmental conditions, both one and the second species are of great importance.

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

Education mechanism

Conditioned reflexes occur 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 a conditioned stimulus is somewhat ahead of the action of instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditional;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli producing a distracting effect is met.

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

Inhibition of conditioned reactions

In order to ensure adequate behavior of the organism and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. An action in the opposite direction will be required. This is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not necessary. According to the theory developed by Pavlov, there are certain types cortical inhibition. The first of these is 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 processes taking place in those areas of the cortex that do not take part in the implementation. reflex activity. For example, an extraneous smell, sound, or change in lighting before the onset of the food reflex can reduce it or contribute to its complete disappearance. A new stimulus acts as an inhibitor for a conditioned response.

Eating reflexes can also be eliminated by painful stimuli. Inhibition of the body's reaction is facilitated by bladder overflow, vomiting, internal inflammatory processes etc. All of them suppress food reflexes.

Internal inhibition

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

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.

Types of internal braking

Several types of elimination of the body's reaction to stimuli are classified. Thus, the basis for the disappearance of conditioned reflexes, which are simply not needed under given specific conditions, is extinctive inhibition. There is another variety this phenomenon. This is discriminative or differentiated inhibition. Thus, an animal can distinguish the number of metronome beats at which food will be brought to it. This happens when this conditioned reflex is previously developed. The animal distinguishes between stimuli. The basis of this reaction is internal inhibition.

The value of eliminating reactions

Conditioned inhibition plays a significant role in the life of the body. Thanks to it, the process of adaptation to the environment occurs much better. The ability to navigate in a variety of complex 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 body reactions that have signaling value. For example, an animal, knowing in advance that danger is approaching, organizes its behavior in a certain way.

The process of developing conditioned reflexes that relate to to the highest 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 he cannot disobey general laws biology. In this regard, it can be studied objectively. However, it is worth keeping in mind that activities human brain has qualitative specificity and a fundamental difference from the work of the animal’s brain.

Age anatomy and physiology Antonova Olga Aleksandrovna

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