Unconditioned reflexes- These are innate, hereditarily transmitted reactions of the body. Conditioned reflexes- these are reactions acquired by the body in the process of individual development on the basis of “life experience”.

Unconditioned reflexes are specific, that is, characteristic of all representatives of a given species. Conditioned reflexes are individual: some representatives of the same species may have them, while others may not.

Unconditioned reflexes are relatively constant; conditioned reflexes are not constant and, depending on certain conditions, they can be developed, consolidated or disappear; This is their property and is reflected in their very name.

Unconditioned reflexes are carried out in response to adequate stimulation applied to one specific receptive field. Conditioned reflexes can be formed to a wide variety of stimuli applied to various receptive fields.

In animals with a developed cerebral cortex, conditioned reflexes are a function of the cerebral cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain. This indicates that in the implementation of unconditioned reflexes, in contrast to conditioned ones, the leading role belongs to the lower parts of the central nervous system- subcortical nuclei, brain stem and spinal cord. 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 a long time after birth, but they necessarily appear under the condition of normal development of the nervous system. Unconditioned reflexes are part of the fund of reflex reactions strengthened in the process of phylogenesis and hereditarily transmitted.

Conditioned reflexes are developed on the basis of unconditioned reflexes. For the formation of a conditioned reflex, a combination in time of some litto change in the external environment or internal state organism, 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 of the body become a stimulus to 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.

In order for the clinking of knives and forks in the dining room or the knocking of a cup from which a dog is fed to cause salivation in the first case in a person, in the second case in a dog, it is necessary to re-coincidence of these sounds with food - reinforcement of stimuli that are initially indifferent to salivary secretion by feeding , i.e., unconditional irritation of the salivary glands. Likewise, the flashing of an electric light bulb in front of a dog’s eyes or the sound of a bell will only cause conditioned reflex flexion of the paw if they are repeatedly accompanied by electrical irritation of the skin of the leg, causing an unconditioned flexion reflex whenever it is used.

Similarly, a child’s crying and his hands pulling away from a burning candle will be observed only if the sight of the candle first coincided at least once with the feeling of a burn. In all the above examples, external agents that are initially relatively indifferent - the clinking of dishes, the sight of a burning candle, the flashing of an electric light bulb, the sound of a bell - become conditioned stimuli if they are reinforced by unconditioned stimuli. Only under this condition the initially indifferent signals outside world become irritants of a certain type of activity.

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.

Unconditioned reflexes are constant innate reactions of the body to certain influences from the external world, carried out through the nervous system and do not require special conditions for their occurrence.

All unconditioned reflexes, according to the degree of complexity and severity of the body’s reactions, are divided into simple and complex; depending on the type of reaction - to food, sexual, defensive, orientation-exploratory, etc.; depending on the animal’s attitude to the stimulus - into biologically positive and biologically negative. Unconditioned reflexes arise mainly under the influence of contact irritation: food unconditioned reflex - when food enters and is exposed to the tongue; defensive - when pain receptors are irritated. However, the emergence of unconditioned reflexes is also possible under the influence of such stimuli as the sound, sight and smell of an object. Thus, the sexual unconditioned reflex occurs under the influence of a specific sexual stimulus (sight, smell and other stimuli emanating from a female or male). The approximate exploratory unconditioned reflex always occurs in response to a sudden, little-known stimulus and usually manifests itself in turning the head and moving the animal towards the stimulus. Its biological meaning lies in the examination of a given stimulus and the entire external environment.

Complex unconditioned reflexes include those that are cyclical in nature and are accompanied by various emotional reactions (see). Such reflexes are often referred to as (see).

Unconditioned reflexes serve as the basis for the formation of conditioned reflexes. Violation or distortion of unconditioned reflexes is usually associated with organic lesions of the brain; the study of unconditioned reflexes is carried out to diagnose a number of diseases of the central nervous system (see Pathological reflexes).

Unconditioned reflexes (specific, innate reflexes) are innate reactions of the body to certain influences of the external or internal environment, carried out through the central nervous system and not requiring special conditions for their occurrence. The term was introduced by I.P. Pavlov and means that the reflex certainly occurs if adequate stimulation is applied to a certain receptor surface. Biological role unconditioned reflexes is that they adapt an animal of a given species in the form of appropriate acts of behavior to constant, habitual environmental factors.

The development of the doctrine of unconditioned reflexes is associated with the research of I. M. Sechenov, E. Pfluger, F. Goltz, S. S. Sherrington, V. Magnus, N. E. Vvedensky, A. A. Ukhtomsky, who laid the foundations for the next stage in the development of reflex theory, when it finally became possible to fill with physiological content the concept of a reflex arc, which previously existed as an anatomical and physiological scheme (see Reflexes). The undoubted condition that determined the success of these quests was the full awareness that the nervous system acts as a single whole, and therefore acts as a very complex formation.

The brilliant foresights of I.M. Sechenov about the reflex basis of mental activity of the brain served as a starting point for research, which, developing the doctrine of higher nervous activity, discovered two forms of neuro-reflex activity: unconditioned and conditioned reflexes. Pavlov wrote: “... we must admit the existence of two types of reflex. One reflex is ready-made, with which the animal is born, a purely conductive reflex, and the other reflex is constantly, continuously formed during individual life, with exactly the same pattern, but based on another property of our nervous system - closure. One reflex can be called innate, the other - acquired, and also, accordingly: one - specific, the other - individual. We called the innate, specific, constant, stereotypical unconditional, the other, since it depends on many conditions, constantly fluctuates depending on many conditions, we called conditional...”

The complex dynamics of the interaction of conditioned reflexes (see) and unconditioned reflexes is the basis of the nervous activity of humans and animals. Biological significance unconditioned reflexes, as well as conditioned reflex activity, consists in adapting the body to various kinds of changes in the external and internal environment. Such important acts as self-regulation of functions are based on the adaptive activity of unconditioned reflexes. Accurate adaptation of unconditioned reflexes to qualitative and quantitative characteristics stimulus, especially carefully studied in Pavlov’s laboratories using examples of the work of the digestive glands, made it possible to interpret the problem of the biological expediency of unconditioned reflexes materialistically, bearing in mind the exact correspondence of the function to the nature of the irritation.

The differences between unconditioned and conditioned reflexes are not absolute, but relative. Various experiments, in particular with the destruction of various parts of the brain, allowed Pavlov to create general idea about the anatomical basis of conditioned and unconditioned reflexes: “Higher nervous activity“,” wrote Pavlov, “is composed of the activity of the cerebral hemispheres and the nearest subcortical nodes, representing the combined activity of these two the most important departments central nervous system. These subcortical nodes are... centers of the most important unconditioned reflexes, or instincts: food, defensive, sexual, etc....". Pavlov’s stated views must now be recognized only as a diagram. His doctrine of analyzers (see) allows us to believe that the morphological substrate of unconditioned reflexes actually covers various parts of the brain, including the cerebral hemispheres, meaning the afferent representation of the analyzer from which this unconditioned reflex is evoked. In the mechanism of unconditioned reflexes, an important role belongs to feedback about the results and success of the action performed (P.K. Anokhin).

IN early years During the development of the doctrine of conditioned reflexes, individual students of Pavlov, who studied salivary unconditioned reflexes, asserted their extreme stability and immutability. Subsequent studies showed the one-sidedness of such views. In Pavlov's own laboratory, a number of experimental conditions were found under which unconditioned reflexes changed even during one experiment. Subsequently, facts were presented indicating that it is more correct to talk about the variability of unconditioned reflexes than about their immutability. Important points in this regard are: the interaction of reflexes with each other (both unconditioned reflexes with each other, and unconditioned reflexes with conditioned ones), hormonal and humoral factors of the body, the tone of the nervous system and its functional state. These questions acquire particular importance in connection with the problem of instincts (see), which a number of representatives of the so-called ethology (the science of behavior) try to present as unchanged, independent of the external environment. Sometimes it is difficult to determine specific factors of variability of unconditioned reflexes, especially if it concerns the internal environment of the body (hormonal, humoral or interoceptive factors), and then some scientists fall into the error of speaking about spontaneous variability of unconditioned reflexes. Such adeterministic constructions and idealistic conclusions lead away from the materialistic understanding of the reflex.

I. P. Pavlov repeatedly emphasized the importance of systematization and classification of unconditioned reflexes, which serve as the foundation for the rest of the nervous activity of the body. The existing stereotyped division of reflexes into food, self-preservation, and sexual ones is too general and inaccurate, he pointed out. A detailed systematization and careful description of all individual reflexes are necessary. Speaking about systematization along with classification, Pavlov meant the need for a broad study of individual reflexes or their groups. The task should be recognized as both very important and very difficult, especially since Pavlov did not distinguish such complex reflexes as instincts from the series of unconditioned reflex phenomena. From this point of view, it is especially important to study the already known and find new and complex forms of reflex activity. Here we must pay tribute to this logical direction, which in a number of cases obtains facts of undoubted interest. However, the ideological basis of this trend, which fundamentally denies the reflex nature of instincts, remains completely unacceptable.

The unconditioned reflex pure form"may appear one or more times after the birth of the animal, and then quite a short time“overgrows” with conditioned and other unconditioned reflexes. All this makes it very difficult to classify unconditioned reflexes. Until now, it has not been possible to find a single principle for their classification. For example, A.D. Slonim based his classification on the principle of balancing the organism with the external environment and maintaining a constant composition of its internal environment. In addition, he identified groups of reflexes that do not ensure the preservation of an individual, but are important for the preservation of the species. The classification of unconditioned reflexes and instincts proposed by N. A. Rozhansky is extensive. It is based on biological and environmental characteristics and the dual (positive and negative) manifestation of the reflex. Unfortunately, Rozhansky’s classification suffers from a subjective assessment of the essence of the reflex, which is reflected in the names of some reflexes.

Systematization and classification of unconditioned reflexes should provide for their ecological specialization. Given the ecological adequacy of the stimuli and the biological training of the effector, a very subtle differentiation of unconditioned reflexes appears. The speed, strength, and the very possibility of forming a conditioned reflex depend not so much on the physical or chemical characteristics of the stimulus, but on the ecological adequacy of the stimulus and the unconditioned reflex.

The problem of the emergence and development of unconditioned reflexes is of great interest. I. P. Pavlov, A. A. Ukhtomsky, K. M. Bykov, P. K. Anokhin and others believed that unconditioned reflexes arise as conditioned, and subsequently become fixed in evolution and become innate.

Pavlov pointed out that new emerging reflexes, while maintaining the same living conditions in a number of successive generations, apparently continuously transform into permanent ones. This is probably one of the operating mechanisms for the development of an animal organism. Without recognizing this position, it is impossible to imagine the evolution of nervous activity. Nature cannot allow such wastefulness, said Pavlov, that each new generation would have to start everything from the very beginning. Transitional forms of reflexes that occupied an intermediate position between conditioned and unconditioned were found with great biological adequacy of the stimuli (V.I. Klimova, V.V. Orlov, A.I. Oparin, etc.). These conditioned reflexes did not fade away. See also Higher nervous activity.

Each person, as well as all living organisms, has a number of vital needs: food, water, comfortable conditions. Everyone has instincts of self-preservation and continuation of their kind. All mechanisms aimed at satisfying these needs are laid down at the genetic level and appear simultaneously with the birth of the organism. These are innate reflexes that help to survive.

The concept of an unconditioned reflex

The word reflex itself is not something new and unfamiliar for each of us. Everyone has heard it in their life, and quite many times. This term was introduced into biology by I.P. Pavlov, who devoted a lot of time to studying the nervous system.

According to the scientist, unconditioned reflexes arise under the influence of irritating factors on the receptors (for example, withdrawing a hand from a hot object). They contribute to the body’s adaptation to those conditions that remain practically unchanged.

This is the so-called product historical experience previous generations, which is why it is also called the species reflex.

We live in a changing environment; it requires constant adaptations, which cannot in any way be provided for by genetic experience. Unconditioned reflexes of a person are constantly either inhibited, then modified or arise again, under the influence of those stimuli that surround us everywhere.

Thus, already familiar stimuli acquire the qualities of biologically significant signals, and the formation of conditioned reflexes occurs, which form the basis of our individual experience. This is what Pavlov called higher nervous activity.

Properties of unconditioned reflexes

The characteristics of unconditioned reflexes include several mandatory points:

1. Congenital reflexes are inherited.
2. They appear equally in all individuals of a given species.
3. For a response to occur, the influence of a certain factor is necessary, for example, for the sucking reflex it is irritation of the lips of a newborn.
4. The area of ​​perception of the stimulus always remains constant.
5. Unconditioned reflexes have a constant reflex arc.
6. They persist throughout life, with some exceptions in newborns.

The meaning of reflexes

All our interaction with the environment is built at the level of reflex responses. Unconditioned and conditioned reflexes play an important role in the existence of the organism.

In the process of evolution, a division occurred between those aimed at the survival of the species and those responsible for adaptability to constantly changing conditions.

Congenital reflexes begin to appear in utero, and their role boils down to the following:

• Maintaining internal environment indicators at a constant level.
• Preserving the integrity of the body.
• Preservation of a species through reproduction.

The role of innate reactions immediately after birth is great; they ensure the survival of the baby in completely new conditions.

The body lives surrounded external factors, which are constantly changing and need to be adapted to. This is where higher nervous activity in the form of conditioned reflexes comes to the fore.

For the body they have the following meaning:

• We will improve the mechanisms of its interaction with the environment.
• The processes of contact between the body and the external environment are clarified and complicated.
• Conditioned reflexes are an indispensable basis for the processes of learning, education and behavior.

Thus, unconditioned and conditioned reflexes are aimed at maintaining the integrity of a living organism and the constancy of the internal environment, as well as effective interaction with the outside world. Between themselves they can be combined into complex reflex acts that have a certain biological orientation.

Classification of unconditioned reflexes

Hereditary reactions of the body, despite their innateness, can differ greatly from each other. It is not at all surprising that the classification can be different, depending on the approach.

Pavlov also divided all unconditioned reflexes into:

• Simple (the scientist included the sucking reflex among them).
• Complex (sweating).
• The most complex unconditioned reflexes. A variety of examples can be given: food reactions, defensive reactions, sexual reactions.

Currently, many adhere to a classification based on the meaning of reflexes. Depending on this, they are divided into several groups:

The first group of reactions has two characteristics:

1. If they are not satisfied, this will lead to the death of the body.
2. Satisfaction does not require the presence of another individual of the same species.

The third group also has its own characteristic features:

1. Self-development reflexes have nothing to do with the body’s adaptation to a given situation. They are aimed at the future.
2. They are completely independent and do not stem from other needs.

We can also divide them according to their level of complexity, then the following groups will appear before us:

1. Simple reflexes. These are the body's normal responses to external stimuli. For example, withdrawing your hand from a hot object or blinking when a speck gets into your eye.
2. Reflex acts.
3. Behavioral reactions.
4. Instincts.
5. Imprinting.

Each group has its own characteristics and differences.

Reflex acts

Almost all reflex acts are aimed at ensuring the vital functions of the body, so they are always reliable in their manifestation and cannot be corrected.

These include:

• Breath.
• Swallowing.
• Vomiting.

In order to stop a reflex act, you simply need to remove the stimulus that causes it. This can be practiced when training animals. If you want to natural needs did not distract you from training, then before this you need to walk the dog, this will eliminate the irritant that can provoke a reflex act.

Behavioral reactions

This type of unconditioned reflex can be well demonstrated in animals. Behavioral reactions include:

• The dog's desire to carry and pick up objects. Retrieval reaction.
• Showing aggression at the sight of a stranger. Active defensive reaction.
• Finding objects by smell. Olfactory-search reaction.

It is worth noting that a behavioral reaction does not mean that the animal will certainly behave this way. What is meant? For example, a dog that has a strong active-defensive reaction from birth, but is physically weak, most likely will not show such aggression.

These reflexes can determine the animal's actions, but they can be controlled. They should also be taken into account when training: if an animal completely lacks an olfactory-search reaction, then it is unlikely that it will be possible to train it as a search dog.

Instincts

There are more complex shapes, in which unconditioned reflexes appear. Instincts come into play here. This is a whole chain of reflex acts that follow each other and are inextricably interconnected.

All instincts are associated with changing internal needs.

When a child is just born, his lungs practically do not function. The connection between him and his mother is interrupted by cutting the umbilical cord, and carbon dioxide accumulates in the blood. It begins its humoral effect on the respiratory center, and instinctive inhalation occurs. The child begins to breathe independently, and the first cry of the baby is a sign of this.

Instincts are a powerful stimulant in human life. They may well motivate success in a certain field of activity. When we stop controlling ourselves, instincts begin to guide us. As you yourself understand, there are several of them.

Most scientists are of the opinion that there are three basic instincts:

1. Self-preservation and survival.
2. Continuation of the family.
3. Leadership instinct.

All of them can generate new needs:

• In safety.
• In material prosperity.
• Looking for a sexual partner.
• In caring for children.
• In influencing others.

We could go on and on about the types of human instincts, but, unlike animals, we can control them. For this purpose, nature has endowed us with reason. Animals survive only due to instincts, but for this we are also given knowledge.

Don't let your instincts get the better of you, learn to manage them and become the master of your life.

Imprint

This form of unconditioned reflex is also called imprinting. There are periods in the life of every individual when the entire surrounding environment is imprinted on the brain. For each species, this time period may be different: for some it lasts several hours, and for others it lasts several years.

Remember how easily young children master foreign speech skills. While schoolchildren put a lot of effort into this.

It is thanks to imprinting that all babies recognize their parents and distinguish individuals of their species. For example, after the birth of a baby, a zebra spends several hours alone with it in a secluded place. This is exactly the time that is necessary for the cub to learn to recognize its mother and not confuse her with other females in the herd.

This phenomenon was discovered by Konrad Lorenz. He conducted an experiment with newborn ducklings. Immediately after the hatching of the latter, he presented them with various objects, which they followed like a mother. They even perceived him as a mother, and followed him on his heels.

Everyone knows the example of hatchery chickens. Compared to their relatives, they are practically tame and are not afraid of humans, because from birth they see him in front of them.

Congenital reflexes of an infant

After its birth, the baby goes through difficult path development, which consists of several stages. The degree and speed of mastery of various skills will directly depend on the state of the nervous system. The main indicator of its maturity is the unconditioned reflexes of the newborn.

The presence of them in the baby is checked immediately after birth, and the doctor makes a conclusion about the degree of development of the nervous system.

From the huge number of hereditary reactions, the following can be distinguished:

1. Kussmaul search reflex. When the area around the mouth is irritated, the child turns his head towards the irritant. The reflex usually fades by 3 months.
2. Sucking. If you place your finger in the baby's mouth, he begins to perform sucking movements. Immediately after feeding, this reflex fades away and becomes more active after some time.
3. Palmo-oral. If you press on the child's palm, he opens his mouth slightly.
4. Grasping reflex. If you put your finger in the baby’s palm and lightly press it, a reflexive squeezing and holding occurs.
5. The inferior grasp reflex is caused by light pressure on the front of the sole. The toes flex.
6. Crawling reflex. When lying on the stomach, pressure on the soles of the feet causes a crawling movement forward.
7. Protective. If you lay a newborn on his stomach, he tries to raise his head and turns it to the side.
8. Support reflex. If you take the baby under the armpits and place him on something, he will reflexively straighten his legs and rest on his entire foot.

The unconditioned reflexes of a newborn can go on for a long time. Each of them symbolizes the degree of development of certain parts of the nervous system. After an examination by a neurologist in the maternity hospital, a preliminary diagnosis of some diseases can be made.

From the point of view of their significance for the baby, the mentioned reflexes can be divided into two groups:

1. Segmental motor automatisms. They are provided by segments of the brain stem and spinal cord.
2. Posotonic automatisms. Provide regulation muscle tone. The centers are located in the midbrain and medulla oblongata.

Oral segmental reflexes

This type of reflexes includes:

• Sucking. Appears during the first year of life.
• Search. Extinction occurs at 3-4 months.
• Proboscis reflex. If you hit a baby on the lips with your finger, he pulls them out into his proboscis. After 3 months, extinction occurs.
• The hand-mouth reflex is a good indicator of the development of the nervous system. If it does not appear or is very weak, then we can talk about damage to the central nervous system.

Spinal motor automatisms

Many unconditioned reflexes belong to this group. Examples include the following:

• Moro reflex. When a reaction is caused, for example, by hitting the table near the baby's head, the latter's arms are spread to the sides. Appears up to 4-5 months.
• Automatic gait reflex. When supported and slightly tilted forward, the baby makes stepping movements. After 1.5 months it begins to fade.
• Galant reflex. If you run your finger along the paravertebral line from the shoulder to the buttocks, the body bends towards the stimulus.

Unconditioned reflexes are assessed on a scale: satisfactory, increased, decreased, absent.

Differences between conditioned and unconditioned reflexes

Sechenov also argued that in the conditions in which the body lives, innate reactions are completely insufficient for survival; the development of new reflexes is required. They will help the body adapt to changing conditions.

How do unconditioned reflexes differ from conditioned reflexes? The table demonstrates this well.

Despite the obvious difference between conditioned reflexes and unconditioned ones, together these reactions ensure the survival and preservation of the species in nature.

Age anatomy and physiology Antonova Olga Aleksandrovna

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