Conditioned reflexes and their meaning.

The conditions of the environment in which humans and animals are found are constantly changing. Since unconditioned reflexes are rather conservative, they cannot ensure every time the adaptation of the body's reactions to these changes. In the process of evolution, animals have developed the ability to form reflexes, which are manifested only under certain conditions, called conditioned reflexes by I.P. Pavlov.

Conditioned reflexes unlike unconditional, they are temporary in nature and can fade away with a change in environmental conditions. Coinciding in their action with unconditioned stimuli, conditioned ones acquire a signaling, warning meaning. They provide humans and animals with an early response to negative or positive stimuli.

Conditioned reflexes are formed on the basis of unconditioned ones. In the process of development of the organism, they subordinate to themselves the function of the unconditioned, adapting them in accordance with the new requirements of the environment. In the formation of conditioned reflexes, certain rules and conditions should be adhered to. The first and main condition is coincidence in time single or multiple action of a conditioned stimulus (indifferent) with an unconditioned stimulus or actions immediately after it. For example, for the formation of a conditioned salivary reflex in dogs to the sound of a bell, it is necessary that this sound precede feeding several times. After such a combination in time of the conditioned and unconditioned stimuli, saliva is released when only the bell is turned on without being accompanied by food. Consequently, the bell became a conditioned stimulus for salivation. In the same way, conditioned reflexes are formed in humans. For example, consumption of lemon causes salivation. This is an unconditioned reflex reaction. Combining several times drinking lemon with turning on the light, only turning on the light will cause salivation. This is a conditioned reflex reaction.

An important condition for the formation of conditioned reflexes is a certain the sequence of stimuli, due to the fact that under the influence of an unconditioned stimulus in the cerebral cortex in the nerve center of this stimulus, a strong focus of excitation is formed. In this case, the excitability of other parts of the cortex decreases, therefore a weak conditioned stimulus will not cause excitation of the corresponding zone of the cortex. For the formation of conditioned reflexes, it is also necessary that the cerebral cortex be free from other types of activity, and the body is in a normal functional state. The action of constant stimuli, the morbid state of the body significantly complicate the formation of conditioned reflexes. Unlike the brain of animals, the human brain is able to form conditioned reflexes not only in response to specific signals, but also to words, numbers, pictures heard or read, which provides the possibility of abstraction and generalization. The latter form the basis of our thinking and consciousness.

The mechanism of formation of conditioned reflexes. The research of I.P. Pavlov established that the formation of conditioned reflexes is based on the establishment of temporary connections in the cerebral cortex between the nerve centers of the unconditioned and conditioned stimuli. Temporary neural connection is formed as a result of the interaction of the processes of excitation and plowing (paving) the path for its conduction, which simultaneously and repeatedly arise in the cortical centers of unconditioned and conditioned stimuli. The formation of temporary connections is characteristic not only of the cerebral cortex, but also of other parts of the central nervous system. This is evidenced by experiments in which simple conditioned reflexes were developed in animals with the bark removed. Reactions such as conditioned reflexes can be developed in animals without a cortex, and even in invertebrates with a very primitive nervous system, such as annelids.

However, for higher animals and humans, the cerebral cortex plays the main role in the formation of temporary connections, although subcortical structures are also important for the formation of conditioned reflexes.

Thus, conditioned reflexes are formed as a result of the mutually coordinated activity of the cortex and subcortical centers; therefore, the structure of the reflex arc of conditioned reflexes has a rather complex character. The role of the cortex and subcortical structures in the formation of various reflexes is not the same. For example, the cortex and subcortex play the same role in the formation of autonomic conditioned reflexes, while the cortex plays the leading role in complex behavioral reactions. However, in these cases, the subcortical centers and the reticular formation contribute to the formation of conditioned reflexes.

The activity of various parts of the central nervous system during the formation of complex behavioral conditioned reflexes is manifested in the fact that the processes of their formation are accompanied by the appearance of orienting reflex reactions. The increased excitability of the cerebral cortex contributes to the closure of temporary nerve connections.

So, conditioned reflexes enable a person to adapt his behavior in accordance with changes in the environment. Conditioned reflexes are formed on the basis of unconditioned ones. The basis of the mechanism for the formation of conditioned reflexes is the establishment of temporary neural connections in the cerebral cortex between the nerve centers of the unconditioned and conditioned stimuli.

All reflex reactions of the body to various stimuli I.P. Pavlov divided into two groups: unconditioned and conditioned.
Unconditioned reflexes are innate reflexes inherited from parents. They are specific, relatively constant and are carried out by the lower parts of the central nervous system - the spinal cord, trunk and subcortical nuclei of the brain.

Unconditioned reflexes (for example, sucking, swallowing, pupillary reflexes, coughing, sneezing, etc.) are retained in animals without cerebral hemispheres. They are formed in response to the action of certain stimuli. So, the reflex of salivation occurs when food irritates the taste buds of the tongue. The resulting excitement in the form of a nerve impulse is carried along the sensory nerves to the medulla oblongata, where the center of salivation is located, from where it is transmitted along the motor nerves to the salivary glands, causing salivation. On the basis of unconditioned reflexes, regulation and coordinated activity of various organs and their systems is carried out, the very existence of the organism is maintained.

In changing environmental conditions, the preservation of the body's vital activity and adaptive behavior is carried out due to the formation of conditioned reflexes with the obligatory participation of the cerebral cortex. They are not congenital, but are formed during life on the basis of unconditioned reflexes under the influence of certain environmental factors. Conditioned reflexes are strictly individual, that is, in some individuals of the species this or that reflex may be present, in others it may be absent.

Unconditioned reflexes. The meaning of unconditioned reflexes

Maintaining the constancy of the internal environment (homeostasis);
- maintaining the integrity of the body (protection from damaging environmental factors);
- reproduction and preservation of the species as a whole.

Unconditioned reflexes and their importance for child development

Birth is a big shock for a child's body. From vegetative, plant existence in a relatively constant environment (the mother's organism), he suddenly passes into completely new conditions of the air environment with an infinite number of frequently changing stimuli, into the world where he will become a rational person.

The life of a child in new conditions is provided by innate mechanisms. It is born with a certain readiness of the nervous system to adapt the body to external conditions. So, immediately after birth, reflexes are switched on, ensuring the work of the main systems of the body (respiration, blood circulation - approx. Site). In the early days, the following can also be noted. Severe irritation of the skin (an injection, for example) causes a protective withdrawal, the flickering of an object in front of the face - closing the eyes, and a sharp increase in the brightness of the light - constriction of the pupil, etc. These reactions are defensive reflexes.

In addition to protective, in newborns, reactions aimed at contact with an irritant can be found. These are indicative reflexes. Observations have established that already in the period from the first to the third day, a strong light source causes the head to turn: in the nursery of a maternity hospital on a sunny day, the heads of most newborns, like sunflowers, are turned towards the light. It has also been proven that already in the first days, newborns tend to follow a slowly moving light source. Orientation and food reflexes are also easily evoked. Touching the corners of the lips, to the cheeks, causes a search reaction in a hungry child: he turns his head towards the stimulus, opens his mouth.
In addition to the above, the child also exhibits several congenital reactions: sucking reflex - the child immediately begins to suck the object put into his mouth; grasping reflex - touching the palm causes a grasping reaction; repulsion (crawling) reflex - when touching the soles of the feet and some other reflexes.

Thus, the child is armed with a certain number of unconditioned reflexes that appear in the very first days after birth. In recent years, scientists have proven that some reflex reactions are manifested even before birth. So, after eighteen weeks, the sucking reflex is formed in the fetus.

Most congenital reactions are necessary for a child to live. They help him to adapt to new conditions of existence. Thanks to these reflexes, a new type of breathing and feeding becomes possible for the newborn. If before birth the fetus develops at the expense of the mother's body (through the walls of the vessels of the placenta - the child's place - nutrients and oxygen enter the blood of the embryo from the mother's blood), then after birth the child's body switches to pulmonary respiration and the so-called oral nutrition (through the mouth and gastrointestinal -intestinal tract). This adjustment occurs reflexively. After the lungs are filled with air, the entire muscle system is involved in rhythmic breathing movements. Breathing is easy and free. Feeding occurs with the help of the sucking reflex. The innate actions included in the sucking reflex are at first still poorly coordinated with each other: the child chokes when sucking, suffocates, his strength quickly runs out. All his activity is aimed at sucking for the sake of saturation. The establishment of the reflex automatism of thermoregulation is also very important: the child's body is getting better and better at adapting to temperature extremes.

Formation and biological significance of conditioned reflexes

Conditioned reflexes are formed as a result of a combination of an unconditioned reflex with the action of a conditioned stimulus. For this, two conditions must be met:

1) the action of the conditioned stimulus must necessarily somewhat precede the action of the unconditioned stimulus;

2) the conditioned stimulus must be repeatedly reinforced by the action of the unconditioned stimulus.

The mechanism of formation of a conditioned reflex is to establish a temporary connection (closure) between two foci of excitation in the mayor of the brain. For the considered example, such foci are the centers of salivation and hearing.
The arc of a conditioned reflex, in contrast to that of an unconditioned reflex, is significantly complicated and includes receptors that perceive conditioned stimulation, a sensory nerve that conducts excitation to the brain, a section of the cortex associated with the center of an unconditioned reflex, a motor nerve and a working organ.

Conditioned reflexes in higher animals, and especially in humans, are constantly developed. This phenomenon is explained by the dynamism of the external environment, to the constantly changing conditions of which the nervous system must quickly adapt.
Thus, if unconditioned reflexes provide only a strictly limited orientation in the environment, then conditioned reflexes provide a universal orientation.

The biological significance of conditioned reflexes in the life of humans and animals is enormous, since they provide their adaptive behavior - they allow one to accurately navigate in space and time, find food (by sight, smell), avoid danger, and eliminate influences harmful to the body. With age, the number of conditioned reflexes increases, the experience of behavior is acquired, thanks to which the adult organism turns out to be better adapted to the environment than the child's.

The adaptability of organisms to their environment is the result of evolution.

1) traits of adaptability to the habitat of fish and birds.

2) evidence of the relativity of adaptive characters in the given conditions of existence.

· Body shape. The streamlined body shape helps with movement in water and in the air.

· The shape of the body is similar to the environment.

· Covering coloration similar to the environment.

· Warning coloration, characteristic of poisonous or stinging insects.

· Mimicry. The similarity of defenseless animals to animals with warning coloration.

· Protective formations in the form of needles, thorns, scalding hairs.

· Adaptive behavior that scares off the approach of the enemy.

· Caring for offspring.

Adaptation to the environment is useful only in the conditions in which it was historically formed.

Example: a mole has adaptations to life in the soil, but on the surface it is helpless. Jellyfish are adapted to life in HO, but those washed up on the shore die.

3) What biological consequences can the acquisition of new adaptive traits by populations and species lead to?

The emergence of new species and populations

Complication or simplification of the organization of living organisms

Complete extinction of species and populations

1) reflex- This is the body's response to irritations of the central nervous system caused by the environment.

Conditioned reflexes - these are reflexes that are acquired throughout life and are strictly individual.

Unconditioned reflexes - these are reflexes that are inherited from parents and persist throughout life.

2) reflex principle of the nervous system.

Perception of irritation from the external environment by receptors, the emergence of nerve impulses in them

They are transmitted through sensitive neurons to the spinal cord of the central nervous system

In the nerve center, the signal is switched to the motor neuron associated with the working muscle

The reflex arc is the path along which nerve impulses travel when a reflex is exercised.

Example: a person touches a hot kettle. The nerve impulse is transmitted to the nerve center. There he switches to a motor neuron, as a result of which the person withdraws his hand.

3) the role of reflexes in the life of humans and animals.

Perception of environmental stimuli and reaction in response to them.

LECTURE 2. PHYSIOLOGY OF HIGHER NERVOUS ACTIVITY. INTEGRATED BRAIN ACTIVITY AND SYSTEM ORGANIZATION OF ADAPTIVE BEHAVIORAL REACTIONS. TEACHING I.P. PAVLOVA ON TYPES OF HIGHER NERVOUS ACTIVITY

Higher nervous activity and its age characteristics. Conditioned and unconditioned reflexes.

1. Differences between conditioned and unconditioned reflexes:

Unconditioned reflexes- innate reactions of the organism, they were formed and fixed in the process of evolution and are inherited.

Conditioned reflexes arise, consolidate, fade away during life and are individual.

Unconditioned reflexes necessarily arise if adequate stimuli act on certain receptors.

Conditioned reflexes for their formation require special conditions; they can be formed to any stimuli (of optimal strength and duration) from any receptive field.

Unconditioned reflexes are relatively constant, stable, unchanged and persist throughout life.

Conditioned reflexes are changeable and more mobile.

Unconditioned reflexes can be carried out at the level of the spinal cord and brainstem.

Conditioned reflexes are a function of the cerebral cortex, realized with the participation of subcortical structures.

Unconditioned reflexes can ensure the existence of an organism only at the earliest stage of life.

The adaptation of the organism to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life.

Conditioned reflexes are variable. In the process of life, some conditioned reflexes, losing their meaning, fade away, others are developed.

1. The biological significance of unconditioned reflexes.

An organism is born with a certain set of unconditioned reflexes. They ensure the maintenance of the body's vital activity in relatively constant conditions of existence. These include unconditioned reflexes:

food- chewing, sucking, swallowing, separating saliva, gastric juice, etc.,

defensive- pulling the hand away from a hot object, coughing, sneezing, blinking when a jet of air enters the eye, etc.,

sexual reflexes- the implementation of sexual intercourse, feeding and caring for the offspring,

thermoregulatory,

respiratory,

cardiovascular,

maintaining the constancy of the internal environment of the body(homeostasis), etc.

1. The biological significance of conditioned reflexes.

Conditioned reflexes provide a more perfect adaptation of the body to changing living conditions. They help to find food by smell, timely avoidance of danger, orientation in time and space.

1. Conditions for the formation of a conditioned reflex.

Conditioned reflexes are developed on the basis of unconditioned ones. For the formation of a conditioned reflex, certain conditions are required. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or the internal environment of the organism.

for example :

in the laboratory of IP Pavlov, the flashing of an electric light bulb, a bell, the gurgling of water, skin irritation, gustatory and olfactory stimuli, the clink of dishes, the appearance of a burning candle, etc., were used as conditioned stimuli;

Conditioned reflexes are temporarily developed in a person while observing the work schedule, eating at the same time, and a constant time of going to bed.

To develop a conditioned reflex, a conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that causes an unconditioned reflex. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).

A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex - these are conditioned reflexes of the second order, then the indifferent stimulus must be reinforced with a conditioned stimulus of the first order.

for example :

The clanging of knives in the dining room will cause a person to salivate only if this clinking has been reinforced with food one or more times. The ringing of knives and forks in our case is a conditioned stimulus, and food is the unconditioned stimulus that causes the unconditioned salivary reflex.

The sight of a burning candle can be a signal to pull away the child's hand only if at least once the sight of the candle coincides with the pain of the burn.

2. Reflex - a concept, its role and meaning in the body

Reflexes (from the Latin slot reflexus - reflected) are the body's responses to stimulation of receptors. Nerve impulses arise in the receptors, which enter the central nervous system through sensory (centripetal) neurons. There, the information received is processed by intercalary neurons, after which motor (centrifugal) neurons are excited and nerve impulses activate the executive organs - muscles or glands. Intercalary neurons are called, the bodies and processes of which do not go beyond the central nervous system. The path along which nerve impulses pass from the receptor to the executive organ is called the reflex arc.

Reflex actions are holistic actions aimed at satisfying a specific need for food, water, safety, etc. They contribute to the survival of an individual or a species as a whole. They are classified into food, water-extracting, defensive, sexual, tentative, nest-building, etc. There are reflexes that establish a certain order (hierarchy) in a herd or flock, and territorial, defining the territory captured by a particular individual or flock.

Distinguish between positive reflexes, when the stimulus causes a certain activity, and negative, inhibitory, in which the activity stops. The latter, for example, includes the passive-defensive reflex in animals, when they freeze when a predator appears, an unfamiliar sound.

Reflexes play an exceptional role in maintaining the constancy of the internal environment of the body, its homeostasis. So, for example, with an increase in blood pressure, a reflex slowdown of cardiac activity and an expansion of the lumen of the arteries occur, so the pressure decreases. With its strong fall, opposite reflexes arise, strengthening and accelerating the contractions of the heart and narrowing the lumen of the arteries, as a result, the pressure rises. It constantly fluctuates around a certain constant value, which is called a physiological constant. This value is genetically determined.

The famous Soviet physiologist P.K.Anokhin showed that the actions of animals and humans are determined by their needs. For example, the lack of water in the body is first replenished by internal reserves. Reflexes appear that delay the loss of water in the kidneys, the absorption of water from the intestines increases, etc. If this does not lead to the desired result, excitement occurs in the centers of the brain that regulate the flow of water, and a feeling of thirst appears. This excitement causes purposeful behavior, the search for water. Thanks to direct connections, nerve impulses going from the brain to the executive organs, the necessary actions are provided (the animal finds and drinks water), and thanks to feedback, nerve impulses going in the opposite direction - from peripheral organs: the oral cavity and stomach - to the brain, informs the latter about the results of the action. Thus, during drinking, the center of water saturation is excited, and when the thirst is satisfied, the corresponding center is inhibited. This is how the controlling function of the central nervous system is carried out.

The discovery of conditioned reflexes by I.P. Pavlov was a great achievement of physiology.

Unconditioned reflexes are innate, inherited by the body reactions to environmental influences. Unconditioned reflexes are characterized by constancy and do not depend on training and special conditions for their occurrence. For example, the body responds to painful irritation with a defensive reaction. There is a wide variety of unconditioned reflexes: defensive, food, orientation, sexual, etc.

The reactions underlying unconditioned reflexes in animals have been developed for thousands of years in the course of adaptation of various animal species to the environment, in the process of struggle for existence. Gradually, under conditions of long-term evolution, the unconditional reflex reactions necessary to satisfy biological needs and preserve the vital activity of the organism were consolidated and inherited, and those of the unconditional reflex reactions that lost their value for the life of the organism lost their expediency, on the contrary, disappeared. not recovering.

Under the influence of constant changes in the environment, more durable and more perfect forms of reaction of animals were required, ensuring the adaptation of the organism to the changed conditions of life. In the process of individual development in highly organized animals, a special type of reflexes is formed, which I.P. Pavlov called conditional.

The conditioned reflexes acquired by the body during life provide a corresponding response of the living organism to changes in the environment and, on this basis, balancing the organism with the environment. Unlike unconditioned reflexes, which are usually carried out by the lower parts of the central nervous system (spinal cord, medulla oblongata, subcortical nodes), conditioned reflexes in highly organized animals and in humans are carried out mainly by the higher part of the central nervous system (cerebral cortex).

Observation of the phenomenon of "psychic secretion" in a dog helped IP Pavlov to open a conditioned reflex. The animal, seeing food at a distance, vigorously salivated even before the food was served. This fact has been interpreted in different ways. The essence of "psychic secretion" was explained by IP Pavlov. He found that, firstly, in order for a dog to start salivating at the sight of meat, it had to see and eat it at least once before. And, secondly, any stimulus (for example, the type of food, a bell, the blinking of a light bulb, etc.) is capable of causing salivation, provided that the time of action of this stimulus and the time of feeding coincide. If, for example, feeding was constantly preceded by the knock of the cup in which the food was located, then there always came a moment when the dog began to salivate at just one knock. Reactions caused by stimuli that were previously indifferent. IP Pavlov called conditioned reflex. A conditioned reflex, Pavlov noted, is a physiological phenomenon, since it is associated with the activity of the central nervous system, and at the same time, a psychological one, since it is a reflection in the brain of specific properties of stimuli from the external world.

In Pavlov's experiments, conditioned reflexes in animals were most often developed on the basis of an unconditioned food reflex, when food served as an unconditioned stimulus, and one of the indifferent (indifferent) stimuli (light, sound, etc.) .).

Distinguish between natural conditioned stimuli, which serve as one of the signs of unconditioned stimuli (the smell of food, the squeak of a chicken for a chicken, causing her parental conditioned reflex, a squeak of a mouse for a cat, etc.), and artificial conditioned stimuli that are completely unrelated to unconditioned reflex stimuli (for example, a light bulb, on the light of which a salivary reflex was developed in a dog, the ringing of a gong, on which moose gather for feeding, etc.). However, any conditioned reflex has a signal value, and if the conditioned stimulus loses it, then the conditioned reflex gradually fades away.

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