Ivan Petrovich Pavlov. Conditioned reflex There is no need to prove that I.P. Pavlov was an outstanding scientist. During his long life (1849–1936) he achieved enormous success thanks to great diligence, purposeful work, keen insight, theoretical clarity,

Conditional abbreviations aa-t-RNA - aminoacyl (complex) with transport RNAATP - adenosine triphosphoric acidDNA - deoxyribonucleic acid-RNA (i-RNA) - matrix (information) RNANAD - nicotinamide adenine dinucleotide NADP -

Conventional abbreviations AG - Golgi apparatus ACTH - adrenocorticotropic hormone AMP - adenosine monophosphate ATP - adenosine triphosphate VND - higher nervous activity GABA - β-aminobutyric acid GMP - guanosine monophosphate GTP - guanine triphosphoric acid DVP -

The main form of activity of the nervous system is reflex. All reflexes are usually divided into unconditioned and conditioned.

Classification of unconditioned reflexes.

The question of the classification of unconditioned reflexes still remains open, although the main types of these reactions are well known.

1. Food reflexes. For example, salivation when food enters the oral cavity or the sucking reflex in a newborn baby.

2. Defensive reflexes. Protect the body from various adverse effects. For example, the reflex of withdrawing a hand when a finger is painfully irritated.

3. Approximate reflexes, or “What is it?” reflexes, as I. P. Pavlov called them. A new and unexpected stimulus attracts attention, for example, turning the head towards an unexpected sound. A similar reaction to novelty, which has important adaptive significance, is observed in various animals. It is expressed in alertness and listening, sniffing and examining new objects.

4.Gaming reflexes. For example, children's games of family, hospital, etc., during which children create models of possible life situations and carry out a kind of “preparation” for various life surprises. The unconditional reflex play activity of a child quickly acquires a rich “spectrum” of conditioned reflexes, and therefore play is the most important mechanism for the formation of the child’s psyche.

5.Sexual reflexes.

6. Parental reflexes are associated with the birth and feeding of offspring.

7. Reflexes that ensure movement and balance of the body in space.

8. Reflexes that support constancy of the internal environment of the body.

Complex unconditioned reflexes I.P. Pavlov called instincts, the biological nature of which remains unclear in its details. In a simplified form, instincts can be represented as a complex interconnected series of simple innate reflexes.

Physiological mechanisms of formation of conditioned reflexes

To understand the neural mechanisms of conditioned reflexes, consider such a simple conditioned reflex reaction as increased salivation in a person when he sees a lemon. This natural conditioned reflex. In a person who has never tasted lemon, this object does not cause any reactions other than curiosity (indicative reflex). What physiological connection exists between such functionally distant organs as the eyes and salivary glands? This issue was resolved by I.P. Pavlov.

The connection between the nerve centers that regulate the processes of salivation and analyze visual stimulation arises as follows:

2. If after this a person gets the opportunity to taste the lemon, then a source of excitement arises in the subcortical nerve center salivation and in its cortical representation, located in the frontal lobes of the cerebral hemispheres (cortical food center).

3. Due to the fact that the unconditioned stimulus (the taste of lemon) is stronger than the conditioned stimulus (external signs of lemon), the food source of excitation has a dominant (main) meaning and “attracts” excitation from the visual center.

4. Between two previously unconnected nerve centers, a neural temporal connection, i.e. a kind of temporary “pontoon bridge” connecting two “shores”.

5. Now the excitation arising in the visual center quickly “travels” along the “bridge” of temporary communication to the food center, and from there along the efferent nerve fibers to the salivary glands, causing salivation.

Thus, for the formation of a conditioned reflex, the following are necessary: conditions:

1. The presence of a conditioned stimulus and unconditional reinforcement.

2. The conditioned stimulus must always somewhat precede the unconditional reinforcement.

3. The conditioned stimulus, in terms of the strength of its impact, must be weaker than the unconditioned stimulus (reinforcement).

4. Repetition.

5. A normal (active) functional state of the nervous system is necessary, first of all its leading part - the brain, i.e. the cerebral cortex should be in a state of normal excitability and performance.

Conditioned reflexes formed by combining a conditioned signal with unconditioned reinforcement are called first order reflexes. If the reflex is developed, then it can also become the basis of a new conditioned reflex. It is called second order reflex. Reflexes developed on them - third order reflexes etc. In humans, they are formed on verbal signals, reinforced by the results of joint activities of people.

A conditioned stimulus can be any change in the environmental and internal environment of the body; bell, electric light, tactile skin stimulation, etc. Food reinforcement and pain stimulation are used as unconditioned stimuli (reinforcers).

The development of conditioned reflexes with such unconditional reinforcement occurs most quickly. In other words, powerful factors contributing to the formation of conditioned reflex activity are reward and punishment.

Classifications of conditioned reflexes

Due to their large number, it is difficult.

According to the location of the receptor:

1. exteroceptive- conditioned reflexes formed when exteroceptors are stimulated;

2. interoceptive - reflexes formed by irritation of receptors located in internal organs;

3. proprioceptive, arising from irritation of muscle receptors.

By the nature of the receptor:

1. natural- conditioned reflexes formed by the action of natural unconditioned stimuli on receptors;

2. artificial- under the influence of indifferent stimuli. For example, the release of saliva in a child at the sight of his favorite sweets is a natural conditioned reflex (the release of saliva when the oral cavity is irritated by some food is an unconditioned reflex), and the release of saliva that occurs in a hungry child at the sight of dinnerware is an artificial reflex.

By action sign:

1. If the manifestation of a conditioned reflex is associated with motor or secretory reactions, then such reflexes are called positive.

2. Conditioned reflexes without external motor and secretory effects are called negative or braking.

By the nature of the response:

1. motor;

2. vegetative are formed from internal organs - heart, lungs, etc. Impulses from them, penetrating the cerebral cortex, are immediately inhibited, not reaching our consciousness, due to this we do not feel their location in a state of health. And in case of illness, we know exactly where the diseased organ is located.

Reflexes occupy a special place for a while, the formation of which is associated with regularly repeated stimuli at the same time, for example, food intake. That is why, by the time of eating, the functional activity of the digestive organs increases, which has a biological meaning. Temporary reflexes belong to the group of so-called trace conditioned reflexes. These reflexes are developed if unconditional reinforcement is given 10 - 20 seconds after the final action of the conditioned stimulus. In some cases, it is possible to develop trace reflexes even after a 1-2 minute pause.

Reflexes are important imitation, which, according to L.A. Orbels are also a type of conditioned reflex. To develop them, it is enough to be a “spectator” of the experiment. For example, if you develop some kind of conditioned reflex in one person in full view of another, then the “viewer” also forms corresponding temporary connections. In children, imitative reflexes play an important role in the formation of motor skills, speech and social behavior, and in adults in the acquisition of labor skills.

There are also extrapolation reflexes - the ability of humans and animals to foresee situations that are favorable or unfavorable for life.

Conditioned reflex- this is an acquired reflex characteristic of an individual (individual). They arise during the life of an individual and are not fixed genetically (not inherited). They appear under certain conditions and disappear in their absence. They are formed on the basis of unconditioned reflexes with the participation of higher parts of the brain. Conditioned reflex reactions depend on past experience, on the specific conditions in which the conditioned reflex is formed.

The study of conditioned reflexes is associated primarily with the name of I. P. Pavlov and the students of his school. They showed that a new conditioned stimulus can trigger a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if a dog is allowed to sniff meat, then gastric juice is released (this is an unconditioned reflex). If, simultaneously with the appearance of meat, a bell rings, then the dog’s nervous system associates this sound with food, and gastric juice will be released in response to the bell, even if the meat is not presented. This phenomenon was discovered independently by Edwin Twitmyer at approximately the same time as in the laboratory of I. P. Pavlov. Conditioned reflexes are the basis acquired behavior. These are the simplest programs. The world around us is constantly changing, so only those who quickly and expediently respond to these changes can live successfully in it. As we gain life experience, a system of conditioned reflex connections develops in the cerebral cortex. Such a system is called dynamic stereotype. It underlies many habits and skills. For example, having learned to skate or bicycle, we subsequently no longer think about how we should move so as not to fall.

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Human Anatomy: Conditioned Reflexes

Conditioned reflexes

Higher nervous activity

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Formation of a conditioned reflex

To do this you need:

• The presence of 2 stimuli: an unconditioned stimulus and an indifferent (neutral) stimulus, which then becomes a conditioned signal;
• Certain strength of stimuli. The unconditioned stimulus must be so strong as to cause dominant excitation in the central nervous system. The indifferent stimulus must be familiar so as not to cause a pronounced orienting reflex.
• A repeated combination of stimuli over time, with the indifferent stimulus acting first, then the unconditioned stimulus. Subsequently, the action of the two stimuli continues and ends simultaneously. A conditioned reflex will occur if an indifferent stimulus becomes a conditioned stimulus, that is, it signals the action of an unconditioned stimulus.
• Constancy of the environment - the development of a conditioned reflex requires constancy of the properties of the conditioned signal.

The mechanism of formation of conditioned reflexes

At action of an indifferent stimulus excitation occurs in the corresponding receptors, and impulses from them enter the brain section of the analyzer. When exposed to an unconditioned stimulus, specific excitation of the corresponding receptors occurs, and impulses through the subcortical centers go to the cerebral cortex (cortical representation of the center of the unconditioned reflex, which is the dominant focus). Thus, two foci of excitation simultaneously arise in the cerebral cortex: In the cerebral cortex, a temporary reflex connection is formed between two foci of excitation according to the dominant principle. When a temporary connection occurs, the isolated action of a conditioned stimulus causes an unconditioned reaction. In accordance with Pavlov's theory, the consolidation of temporary reflex communication occurs at the level of the cerebral cortex, and it is based on the principle of dominance.

Types of conditioned reflexes

There are many classifications of conditioned reflexes:

• If the classification is based on unconditioned reflexes, then we distinguish between food, protective, orientation, etc.
• If the classification is based on the receptors on which the stimuli act, exteroceptive, interoceptive and proprioceptive conditioned reflexes are distinguished.
• Depending on the structure of the used conditioned stimulus, simple and complex (complex) conditioned reflexes are distinguished.
  In real conditions of the functioning of the body, as a rule, the conditioned signals are not individual, single stimuli, but their temporal and spatial complexes. And then the conditioned stimulus is a complex of environmental signals.
• There are conditioned reflexes of the first, second, third, etc. order. When a conditioned stimulus is reinforced by an unconditioned one, a first-order conditioned reflex is formed. A second-order conditioned reflex is formed if a conditioned stimulus is reinforced by a conditioned stimulus to which a conditioned reflex was previously developed.
• Natural reflexes are formed in response to stimuli that are natural, accompanying properties of the unconditional stimulus on the basis of which they are developed. Natural conditioned reflexes, compared to artificial ones, are easier to form and more durable.

Notes

Ivan Petrovich Pavlov's school conducted vivisector experiments not only on dogs, but also on people. Street children aged 6–15 years were used as laboratory material. These were tough experiments, but they were the ones that made it possible to understand the nature of human thinking. These experiments were carried out in the children's clinic of the 1st LMI, in the Filatov hospital, in the hospital named after. Rauchfus, in the Department of Experimental Pediatrics of the IEM, as well as in several orphanages. are essential information. In two works by N. I. Krasnogorsky, “Development of the doctrine of the physiological activity of the brain in children” (L., 1939) and “Higher nervous activity of the child” (L., 1958), Professor Mayorov, who was the official chronicler of the Pavlovian school, melancholy noted: “ Some of our employees expanded the range of experimental objects and began studying conditioned reflexes in other animal species; in fish, ascidians, birds, lower apes, as well as children" (F. P. Mayorov, "History of the doctrine of conditioned reflexes." M., 1954). "laboratory material" of a group of Pavlov's students (Prof. N. I. Krasnogorsky , A.G. Ivanov-Smolensky, I. Balakirev, M.M. Koltsova, I. Kanaev) became homeless children. Full understanding at all levels was ensured by the Cheka.A. A. Yushchenko in his work “Conditional Reflexes of a Child” (1928 All this is confirmed by protocols, photographs and the documentary “Mechanics of the Brain” (another title is “Behavior of Animals and Humans”; directed by V. Pudovkin, camera by A. Golovnya, production film factory "Mezhrabprom-Rus", 1926)

Conditioned and unconditioned reflexes are characteristic of the entire animal world.

In biology, they are considered as the result of a long evolutionary process and represent the response of the central nervous system to external environmental influences.

They provide a very quick response to a particular stimulus, thereby significantly saving the resources of the nervous system.

Classification of reflexes

In modern science, such reactions are described using several classifications that describe their features in different ways.

So, they come in the following types:

1. Conditional and unconditional - depending on how they are formed.
2. Exteroceptive (from “extra” - external) - reactions of external receptors of the skin, hearing, smell and vision. Interoreceptive (from “intero” - inside) - reactions of internal organs and systems. Proprioceptive (from “proprio” - special) - reactions associated with the sensation of one’s own body in space and formed by the interaction of muscles, tendons and joints. This is a classification based on receptor type.
3. Based on the type of effectors (zones of reflex response to information collected by receptors), they are divided into: motor and autonomic.
4. Classification based on specific biological role. There are species aimed at protection, nutrition, orientation in the environment and reproduction.
5. Monosynaptic and polysynaptic - depending on the complexity of the neural structure.
6. Based on the type of influence, excitatory and inhibitory reflexes are distinguished.
7. And based on where the reflex arcs are located, they are divided into cerebral (various parts of the brain are included) and spinal (neurons of the spinal cord are included).

What is a conditioned reflex

This is a term denoting a reflex formed as a result of the fact that simultaneously for a long time a stimulus that does not cause any reaction is presented with a stimulus that causes some specific unconditioned reflex. That is, the reflex response eventually extends to an initially indifferent stimulus.

Where are the centers of conditioned reflexes located?

Since this is a more complex product of the nervous system, the central part of the neural arc of conditioned reflexes is located in the brain, specifically in the cerebral cortex.

Examples of conditioned reflexes

The most striking and classic example is Pavlov’s dog. The dogs were presented with a piece of meat (this caused the secretion of gastric juice and salivation) along with the inclusion of a lamp. As a result, after a while, the process of activating digestion started when the lamp was turned on.

A familiar example from life is the feeling of cheerfulness from the smell of coffee. Caffeine does not yet have a direct effect on the nervous system. He is outside the body - in a circle. But the feeling of vigor is triggered only by the smell.

Many mechanical actions and habits are also examples. We rearranged the furniture in the room, and the hand reaches in the direction where the closet used to be. Or a cat who runs to the bowl when he hears the rustling of a box of food.

The difference between unconditioned reflexes and conditioned ones

They differ in that unconditional ones are innate. They are the same for all animals of one species or another, as they are inherited. They are quite unchanged throughout the life of a person or animal. From birth and always occur in response to receptor irritation, and are not produced.

Conditional ones are acquired throughout life, with experience in interaction with the environment. Therefore, they are quite individual - depending on the conditions under which it was formed. They are unstable throughout life and can fade away if they do not receive reinforcement.

Conditioned and unconditioned reflexes - comparison table

The difference between instincts and unconditioned reflexes

Instinct, like reflex, is a biologically significant form of animal behavior. Only the second is a simple short response to a stimulus, and instinct is a more complex activity that has a specific biological goal.

The unconditioned reflex is always triggered. But instinct is only in a state of biological readiness of the body to trigger this or that behavior. For example, mating behavior in birds is triggered only during a certain period of the year when chick survival may be maximum.

What is not typical for unconditioned reflexes?

In short, they cannot change during life. They do not differ between different animals of the same species. They cannot disappear or stop appearing in response to a stimulus.

When conditioned reflexes fade

Extinction occurs as a result of the fact that the stimulus (stimulus) ceases to coincide in time of presentation with the stimulus that caused the reaction. Need reinforcements. Otherwise, without reinforcement, they lose their biological significance and fade away.

Unconditioned reflexes of the brain

These include the following types: blinking, swallowing, vomiting, orientation, maintaining balance associated with hunger and satiety, braking movement in inertia (for example, during a push).

The disruption or disappearance of any type of these reflexes can be a signal of serious disturbances in brain function.

Pulling your hand away from a hot object is an example of which reflex

An example of a painful reaction is pulling your hand away from a hot kettle. This is an unconditional look, the body's response to dangerous environmental influences.

Blink reflex - conditioned or unconditioned

The blink reaction is an unconditional type. It occurs as a result of dry eye and to protect against mechanical damage. All animals and humans have it.

Salivation in a person at the sight of a lemon - what is the reflex?

This is a conditional view. It is formed due to the fact that the rich taste of lemon provokes salivation so often and strongly that simply looking at it (and even remembering it) triggers a response.

How to develop a conditioned reflex in a person

In humans, unlike animals, the conditioned appearance is developed faster. But for all, the mechanism is the same - joint presentation of stimuli. One, causing an unconditioned reflex, and the other, an indifferent one.

For example, for a teenager who falls off a bicycle while listening to some specific music, later unpleasant feelings that arise while listening to the same music can become the acquisition of a conditioned reflex.

What is the role of conditioned reflexes in the life of an animal

They enable an animal with rigid, unchanging unconditioned reactions and instincts to adapt to conditions that are constantly changing.

At the level of the entire species, this is the ability to live in the largest possible areas with different weather conditions, with different levels of food supply. In general, they provide the ability to react flexibly and adapt to the environment.

Conclusion

Unconditioned and conditioned responses are extremely important for the survival of an animal. But it is in interaction that they allow us to adapt, reproduce and raise the healthiest offspring possible.