Conditioned reflexes can be. Congenital and acquired forms of behavior

12.10.2019

"If the animal were not ... exactly adapted to the external world, then it would soon or slowly cease to exist ... It must react to the external world in such a way that its existence is ensured by all its response activities."
I.P. Pavlov.

The adaptation of animals and humans to the changing conditions of existence in the external environment is ensured by the activity of the nervous system and is realized through reflex activity. In the process of evolution, hereditarily fixed reactions (unconditioned reflexes) arose, which unite and coordinate the functions of various organs, carry out the adaptation of the body. In humans and higher animals, in the process of individual life, qualitatively new reflex reactions arise, which IP Pavlov called conditioned reflexes, considering them to be the most perfect form of adaptation.

While relatively simple shapes nervous activity determine the reflex regulation of homeostasis and vegetative functions of the body, higher nervous activity (HNA) provides complex individual forms of behavior in changing living conditions. GNI is implemented due to the dominant influence of the cortex on all underlying structures of the central nervous system. The main processes that dynamically replace each other in the central nervous system are the processes of excitation and inhibition. Depending on their ratio, strength and localization, the control influences of the cortex are built. the functional unit of GNI is the conditioned reflex.

Higher nervous activity is a set of unconditional and conditioned reflexes, as well as higher mental functions that provide adequate behavior in changing natural and social conditions. For the first time, the assumption about the reflex nature of the activity of the higher parts of the brain was made by I.M. Sechenov, which made it possible to extend the reflex principle to human mental activity. The ideas of I.M. Sechenov received experimental confirmation in the works of I.P. Pavlov, who developed a method for objective assessment of the functions of the higher parts of the brain - the method of conditioned reflexes.

IP Pavlov showed that all reflex reactions can be divided into two groups: unconditioned and conditional.

Unconditioned reflexes	Conditioned reflexes
1. Congenital, hereditary reactions, most of them begin to function immediately after birth.	1. Reactions acquired in the process of individual life.
2. They are specific, i.e. common to all members of this species.	2. Customized.
3. Permanent and persist throughout life.	3. Fickle - can appear and disappear.
4. Carried out at the expense of the lower parts of the central nervous system (subcortical nuclei, brain stem, spinal cord).	4. They are predominantly a function of the cerebral cortex.
5. Occur in response to adequate stimuli acting on a specific receptive field.	5. Arise on any stimuli acting on different receptive fields.

Unconditioned reflexes can be simple or complex. Complex innate unconditioned reflex reactions are called instincts. Them characteristic feature is a chain reaction.

Conditioned reflex- this is a complex multicomponent reaction, which is developed on the basis of unconditioned reflexes using a previous indifferent stimulus. It has a signal character, and the body meets the impact of the unconditioned stimulus prepared. For example, in the pre-launch period, there is a redistribution of blood, increased respiration and blood circulation, and when the muscle load begins, the body is already prepared for it.

To develop a conditioned reflex, you must:

Conditioned reflexes are easier to develop in response to influences that are ecologically close to a given animal. In this regard, conditioned reflexes are divided into natural and artificial. Natural conditioned reflexes are developed to agents that, under natural conditions, act together with the stimulus that causes the unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes are artificial, i.e. are produced in response to agents that are not normally associated with the action of an unconditioned stimulus, for example, a food salivary reflex to a bell.

The physiological basis for the emergence of conditioned reflexes is the formation of functional temporary connections in the higher parts of the central nervous system.

Temporary connection- this is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur in the process of the combined action of conditioned and unconditioned stimuli. IP Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and unconditioned reflexes. Excitation from the center of the conditioned reflex can be transmitted to the center of the unconditioned reflex from neuron to neuron.

Consequently, the first way to form a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical. However, when the cortical representation of the conditioned reflex is destroyed, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection takes place between the subcortical center of the conditioned reflex and the cortical center of the unconditioned reflex. With the destruction of the cortical representation of the unconditioned reflex, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can go between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex.

The separation of the cortical centers of the conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of a conditioned reflex.

This indicates that a temporal connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex, and the cortical center of the unconditioned reflex.

There are different opinions on the question of the mechanisms for the formation of a temporary connection. Perhaps the formation of a temporary connection occurs according to the principle of dominance. The focus of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant, therefore it attracts excitation from the focus of conditioned irritation. If the excitation has passed along some nerve circuits, then the next time it will pass along these paths much easier (the phenomenon of "breaking the path"). This is based on: the summation of excitations, a prolonged increase in the excitability of synaptic formations, an increase in the amount of a mediator in synapses, and an increase in the formation of new synapses. All this creates structural prerequisites for facilitating the movement of excitation along certain neural circuits.

Another idea of the mechanism of the formation of a temporary connection is the convergent theory. It is based on the ability of neurons to respond to stimuli of different modalities. According to P.K. Anokhin, conditioned and unconditioned stimuli cause widespread activation of cortical neurons due to the inclusion of the reticular formation. As a result, the ascending signals (conditioned and unconditioned stimuli) overlap, i.e. there is a meeting of these excitations on the same cortical neurons. As a result of the convergence of excitations, temporary connections arise and stabilize between the cortical representations of the conditioned and unconditioned stimuli.

Differences between conditioned reflexes and unconditioned ones. Unconditioned reflexes are innate reactions of the body, they were formed and fixed in the process of evolution and are inherited. Conditioned reflexes arise, are fixed, fade away during life and are individual. Unconditioned reflexes are species-specific, that is, they are found in all individuals of a given species. Conditioned reflexes may be developed in some individuals of a given species, while others may be absent; they are individual. Unconditioned reflexes do not require special conditions for their occurrence; they necessarily arise if adequate stimuli act on certain receptors. Conditioned reflexes require special conditions for their formation; they can be formed to any stimuli (of optimal strength and duration) from any receptive field. Unconditioned reflexes are relatively constant, persistent, unchanging 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 brain stem. Conditioned reflexes can be formed in response to any signals perceived by the body and are predominantly a function of the cerebral cortex, implemented with the participation of subcortical structures.

Unconditioned reflexes can ensure the existence of the organism only at the very early stage of life. The adaptation of the organism to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life. Conditioned reflexes are changeable. In the process of life, some conditioned reflexes, losing their meaning, fade away, others are developed.

Biological significance of conditioned reflexes. An organism is born with a certain fund of unconditioned reflexes. They provide him with the maintenance of life in relatively constant conditions of existence. These include unconditioned reflexes: food (chewing, sucking, swallowing, separation of 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 (reflexes associated with sexual intercourse, feeding and caring for offspring), thermoregulatory, respiratory, cardiac, vascular reflexes that maintain the constancy of the internal environment of the body (homeostasis), etc.

Conditioned reflexes provide a more perfect adaptation of the body to changing conditions of life. They help to find food by smell, timely escape from danger, orientation in time and space. Conditioned reflex separation of saliva, gastric, pancreatic juices in appearance, smell, meal time creates Better conditions to digest food before it enters the body. An increase in gas exchange and an increase in pulmonary ventilation before the start of work, only at the sight of the environment in which the work is performed, contributes to greater endurance and better performance of the body during muscle activity.

Under the action of a conditioned signal, the cerebral cortex provides the body with a preliminary preparation for responding to those environmental stimuli that will have their effect in the future. Therefore, the activity of the cerebral cortex is a signal.

Conditions for the formation of a conditioned reflex. Conditioned reflexes are developed on the basis of unconditioned ones. The conditioned reflex is so named by I.P. Pavlov because certain conditions are needed for its formation. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or a certain change in the internal state of the organism. In the laboratory of I.P. Pavlov, a flashing light bulb, a bell, gurgling water, skin irritation, taste, olfactory stimuli, the sound of dishes, the sight of a burning candle, etc. were used as conditioned stimuli. Conditioned reflexes are developed for a while in a person subject to the work regime meals at the same time, a constant bedtime.

A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex. In this way, conditioned reflexes of the second order are formed, then it is necessary to reinforce the indifferent stimulus with a conditioned stimulus of the first order. It was possible to form conditioned reflexes of the third and fourth orders in the experiment. These reflexes are usually unstable. The children managed to develop reflexes of the sixth order.

The possibility of developing conditioned reflexes is hampered or completely excluded by strong extraneous stimuli, illness, etc.

In order to develop a conditioned reflex, the conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that causes an unconditioned reflex. The ringing of knives in the dining room will cause salivation in a person only if this ringing was reinforced by food one or more times. The ringing of knives and forks in our case is a conditioned stimulus, and the unconditioned stimulus that causes a salivary unconditioned reflex is food. The sight of a burning candle can become a signal for a child to withdraw his hand only if at least once the sight of a candle coincided with the pain of a burn. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).

The mechanism of formation of a conditioned reflex. According to the ideas of IP Pavlov, the formation of a conditioned reflex is associated with the establishment of a temporary connection between two groups of cortical cells: between those who perceive conditioned and those who perceive unconditioned stimulation. This connection becomes stronger, the more often both parts of the cortex are simultaneously excited. After several combinations, the connection is so strong that under the action of only one conditioned stimulus, excitation also occurs in the second focus (Fig. 15).

Initially, an indifferent stimulus, if it is new and unexpected, causes a general generalized reaction of the body - an orienting reflex, which I.P. Pavlov called research or the “what is it?” reflex. Any stimulus, if it is used for the first time, causes a motor reaction (general startle, turning of the eyes, ears towards the stimulus), increased breathing, heartbeat, generalized changes in the electrical activity of the brain - the alpha rhythm is replaced by rapid fluctuations (beta rhythm). These reactions reflect the general generalized excitation. When the stimulus is repeated, if it does not become a signal for a certain activity, the orienting reflex fades. For example, if a dog hears a bell for the first time, it will give a general orienting reaction to it, but it will not salivate. Let's back up the sounding bell with food. In this case, two foci of excitation will appear in the cerebral cortex - one in the auditory zone, and the other in the food center (these are areas of the cortex that are excited under the influence of the smell, taste of food). After several reinforcements of the call with food in the cerebral cortex, a temporary connection will arise (close) between the two foci of excitation.

In the course of further research, facts were obtained indicating that the closure of the temporary connection occurs not only along the horizontal fibers (bark - bark). Gray matter incisions were used to separate different areas of the cortex in dogs, but this did not prevent the formation of temporary connections between the cells of these areas. This gave grounds to believe that the pathways cortex - subcortex - cortex also play an important role in establishing temporary connections. In this case, centripetal impulses from a conditioned stimulus through the thalamus and a nonspecific system (hippocampus, reticular formation) enter the corresponding zone of the cortex. Here they are processed and reach the subcortical formations along the descending paths, from where the impulses come again to the cortex, but already in the zone of representation of the unconditioned reflex.

What happens in the neurons involved in the formation of a temporary connection? There are different points of view on this matter. One of them assigns the main role to morphological changes in the endings of the nerve processes.

Another point of view on the mechanism of the conditioned reflex is based on the principle of dominant A. A. Ukhtomsky. In the nervous system at each moment of time there are dominant foci of excitation - dominant foci. The dominant focus tends to attract to itself the excitation that enters other nerve centers, and thereby intensify. For example, during hunger, a persistent focus with increased excitability appears in the corresponding parts of the central nervous system - a food dominant. If a hungry puppy is allowed to lap milk and at the same time begins to irritate the paw with an electric current, then the puppy does not withdraw the paw, but begins to lap with even greater intensity. In a well-fed puppy, stimulation of the paw with an electric current causes a reaction of its withdrawal.

It is believed that during the formation of a conditioned reflex, the focus of persistent excitation that arose in the center of the unconditioned reflex "attracts" the excitation that arose in the center of the conditioned stimulus to itself. As these two excitations combine, a temporary connection is formed.

Many researchers believe that changes in protein synthesis play a leading role in fixing the temporal connection; specific protein substances associated with the imprinting of a temporal connection are described. The formation of a temporary connection is associated with the mechanisms of storage of traces of excitation. However, the mechanisms of memory cannot be reduced to the mechanisms of “belt connection.

There are data on the possibility of saving traces at the level of single neurons. Cases of imprinting from a single action of an external stimulus are well known. This gives reason to believe that the closure of a temporary connection is one of the mechanisms of memory.

Inhibition of conditioned reflexes. Conditioned reflexes are plastic. They can persist for a long time, or they can slow down. Two types of inhibition of conditioned reflexes are described - internal and external.

Unconditional, or external, inhibition. This type of inhibition occurs when a new, sufficiently strong focus of excitation arises in the cerebral cortex during the implementation of the conditioned reflex, which is not associated with this conditioned reflex. If a dog has developed a conditioned salivary reflex to the sound of a bell, then turning on a bright light at the sound of a bell in this dog inhibits the previously developed salivation reflex. This inhibition is based on the phenomenon of negative induction: a new strong focus of excitation in the cortex from extraneous stimulation causes a decrease in excitability in the areas of the cerebral cortex associated with the implementation of the conditioned reflex, and, as a result of this phenomenon, inhibition of the conditioned reflex occurs. Sometimes this inhibition of conditioned reflexes is called induction inhibition.

Induction inhibition does not require development (that is why it belongs to unconditioned inhibition) and develops immediately as soon as an external stimulus, extraneous for a given conditioned reflex, acts.

External braking also includes limiting braking. It manifests itself with an excessive increase in the strength or duration of the action of the conditioned stimulus. In this case, the conditioned reflex weakens or completely disappears. This inhibition is of protective importance, since it protects nerve cells from stimuli of too great strength or duration, which could disrupt their activity.

Conditional, or internal, inhibition. Internal inhibition, in contrast to external inhibition, develops within the arc of the conditioned reflex, i.e., in those nervous structures that are involved in the implementation of this reflex.

If external inhibition occurs immediately, as soon as the inhibitory agent has acted, then internal inhibition must be developed, it occurs under certain conditions, and this sometimes takes a long time.

One of the types of internal inhibition is extinction. It develops if many times the conditioned reflex is not reinforced by an unconditioned stimulus.

Some time after extinction, the conditioned reflex can be restored. This will happen if we again reinforce the action of the conditioned stimulus with an unconditioned one.

Fragile conditioned reflexes are restored with difficulty. Fading can explain the temporary loss of labor skill, the skill of playing musical instruments.

Decay is much slower in children than in adults. That is why it is difficult to wean children from bad habits. Fading is at the root of forgetting.

The extinction of conditioned reflexes is of great biological importance. Thanks to him, the body stops responding to signals that have lost their meaning. No matter how many unnecessary, superfluous movements a person would make during writing, labor operations, sports exercises without fading inhibition!

The delay of conditioned reflexes also refers to internal inhibition. It develops if the reinforcement of the conditioned stimulus by the unconditioned stimulus is set aside in time. Usually, when developing a conditioned reflex, they turn on a conditioned stimulus-signal (for example, a bell), and after 1-5 seconds they give food (unconditioned reinforcement). When the reflex is developed, immediately after turning on the bell, without giving food, saliva already begins to flow. Now let's do this: turn on the bell, and gradually move the food reinforcement in time up to 2-3 minutes after the start of the bell. After several (sometimes very multiple) combinations of a sounding bell with a delayed food reinforcement, a delay develops: the bell turns on, and saliva will now flow not immediately, but 2-3 minutes after the bell is turned on. Due to non-reinforcement for 2-3 minutes of the conditioned stimulus (bell) by the unconditioned stimulus (food), the conditioned stimulus acquires inhibitory significance during the time of non-reinforcement.

Delay creates conditions for better orientation of the animal in the surrounding world. The wolf does not immediately rush to the hare, seeing him at a considerable distance. He waits for the hare to approach. From the moment when the wolf saw the hare, until the time when the hare approached the wolf, the process of internal inhibition takes place in the cerebral cortex of the wolf: motor and food conditioned reflexes are inhibited. If this did not happen, the wolf would often be left without prey, breaking into the chase as soon as he sees the hare. The developed delay provides the wolf with prey.

Delay in children is developed with great difficulty under the influence of education and training. Remember how impatiently the first grader stretches his hand, waving it, getting up from his desk so that the teacher notices him. And only by the senior school age (and even then not always) we note endurance, the ability to restrain our desires, willpower.

Similar sound, olfactory and other stimuli can signal completely different events. Only an accurate analysis of these similar stimuli provides biologically appropriate responses of the animal. The analysis of stimuli consists in distinguishing, separating different signals, differentiating similar interactions on the organism. In the laboratory of I.P. Pavlov, for example, it was possible to develop such a differentiation: 100 beats of a metronome per minute were reinforced with food, and 96 beats were not reinforced. After several repetitions, the dog distinguished 100 beats of the metronome from 96: saliva flowed for 100 beats, and saliva did not separate for 96 beats. The inhibition that develops at the same time suppresses the reflex reaction to unreinforced stimuli. Differentiation is one of the types of conditioned (internal) inhibition.

Thanks to differential inhibition, signal-significant signs of the stimulus can be distinguished from the many sounds, objects, faces, etc. that surround us. Differentiation is developed in children from the first months of life.

dynamic stereotype. The external world acts on the organism not by single stimuli, but usually by a system of simultaneous and successive stimuli. If this system is often repeated in this order, then this leads to the formation of a dynamic stereotype.

A dynamic stereotype is a sequential chain of conditioned reflex acts that are carried out in a strictly defined order fixed in time and are the result of a complex systemic reaction of the body to a complex of conditioned stimuli. Thanks to the formation of chain conditioned reflexes, each previous activity of the organism becomes a conditioned stimulus - a signal for the next one. Thus, the previous activity prepares the body for the next one. A manifestation of a dynamic stereotype is a conditioned reflex to time, which contributes to the optimal activity of the body with the correct daily routine. For example, eating at certain hours ensures a good appetite and normal digestion; Consistent adherence to bedtime helps children and adolescents fall asleep quickly and, thus, sleep longer; the implementation of educational work and labor activity always at the same hours leads to faster development of the body and better assimilation of knowledge, skills, and abilities.

A stereotype is difficult to develop, but if it is developed, then maintaining it does not require significant stress on cortical activity, and many actions become automatic. ;d The dynamic stereotype is the basis for the formation of habits in a person, the formation of a certain sequence in labor operations, the acquisition of skills and abilities.

Walking, running, jumping, skiing, playing the piano, eating with a spoon, fork, knife, writing - all these are skills based on the formation of dynamic stereotypes in the cerebral cortex.

The formation of a dynamic stereotype underlies the daily routine of each person. Stereotypes persist for many years and form the basis of human behavior. Stereotypes that have arisen in early childhood are very difficult to change. Recall how difficult it is to “retrain” a child if he has learned to hold a pen incorrectly when writing, to sit at a table incorrectly, etc. The difficulty of reshaping stereotypes makes one pay special attention to the correct methods of raising and teaching children from the first years of life.

The dynamic stereotype is one of the manifestations of the systemic organization of higher cortical functions aimed at ensuring stable reactions of the body.

Continuation. See No. 34, 35, 36/2004

Congenital and acquired forms of behavior

Lessons on the topic: "Physiology of higher nervous activity"

Table. Comparison of unconditioned and conditioned reflexes

Signs of comparison	Unconditioned reflexes	Conditioned reflexes
Inheritance	congenital, passed down from parents to offspring	Acquired by the body during life, not inherited
Species specificity		Individual
Stimulus	Occurs in response to an unconditioned stimulus	Carried out in response to any irritation perceived by the body; are formed on the basis of unconditioned reflexes
Meaning in life	Life without them is usually impossible.	Contribute to the survival of the organism in constantly changing environmental conditions
The duration of the reflex arc	Have ready and permanent reflex arcs	They do not have ready-made and permanent reflex arcs; their arcs are temporary and form under certain conditions
reflex centers	They are carried out at the level of the spinal cord, brain stem and subcortical nuclei, i.e. reflex arcs pass through the lower floors of the central nervous system	They are carried out due to the activity of the cerebral cortex, i.e. reflex arcs pass through the cerebral cortex

Lesson 5
Generalization of knowledge of the topic “Acquired forms of behavior. Conditioned reflex"

Equipment: tables, diagrams and drawings illustrating the acquired forms of behavior, the mechanisms for the development of conditioned reflexes.

DURING THE CLASSES

I. Knowledge Test

Card work

1. The advantage of behavior that is formed as a result of learning is that it:

a) quickly carried out;
b) is carried out the same way every time;
c) provides answers in changing environmental conditions;
d) carried out correctly the first time;
e) does not occupy a place in the genetic program of the organism.

2. For experiments on the study of conditioned reflexes, two dogs were taken. One of them was given a drink a large number of water. Then the research began. Initially, conditioned reflexes were carried out normally in both dogs. But after a while, the conditioned reflexes disappeared in the dog that drank water. There were no random external influences. What is the reason for the inhibition of conditioned reflexes?

3. As you know, a conditioned reflex can be developed to the action of almost any indifferent stimulus. One dog in the laboratory of I.P. Pavlova could not develop a conditioned reflex to the gurgling of water. Try to explain the lack of result in this case.

4. It is known that the strength (biological significance) of the conditioned stimulus should not exceed the strength of the unconditioned stimulus. Otherwise, the conditioned reflex cannot be developed. Therefore, it is very difficult to develop, for example, a conditioned food reflex to painful stimulation (the action of a current). However, in the laboratory of I.P. Pavlov in the famous experiments of Erofeeva managed to develop such a conditioned reflex. Under the action of the current (conditioned stimulus), the dog salivated, it licked its lips and wagged its tail. How was this achieved?

5. During one of the concerts, the listener suddenly started having pains in the region of the heart. Moreover, the beginning of pain coincided with the performance of one of Chopin's nocturnes. Since then, every time a man heard this music, his heart ached. Explain this pattern.

Oral knowledge test on questions

1. Learning and its methods (addiction, trial and error).
2. Imprinting and its characteristics.
3. Methodology for the development of conditioned reflexes.
4. Mechanisms for the development of conditioned reflexes
5. General properties and classification of conditioned reflexes.
6. Rational activity of animals.
7. Dynamic stereotype and its meaning.

Checking the filling of the table "Comparison of unconditioned and conditioned reflexes"

The children had to fill in the table as homework after the previous lesson.

Biological dictation

The teacher reads out the characteristics of the reflexes under the numbers, and the students, working on the options, write down the numbers of the correct answers: Option I - unconditioned reflexes, Option II - conditioned reflexes.

1. Are inherited.
2. Not inherited.
3. Reflex centers are located in the subcortical nuclei, the brain stem and spinal cord.
4. Reflex centers are located in the cerebral cortex.
5. There is no species specificity; each individual of the species has its own reflexes.
6. Species specificity - these reflexes are characteristic of all individuals of a certain species.
7. Persistently persist throughout life.
8. Change (new reflexes arise, and old ones fade away).
9. The reasons for the formation of reflexes are events that are vital for the whole species.
10. The causes of reflexes are signals that arise on the basis of personal past experience and warn of an important event.

Answers: I option - 1, 3, 6, 7, 9; II option - 2, 4, 5, 8, 10.

Laboratory work number 2.
"The development of conditioned reflexes in humans on the basis of unconditioned reflexes"

Equipment: rubber pear for air injection, metronome.

WORKING PROCESS

1. Turn on the metronome at a rhythm of 120 beats per minute and, on the second or third beat, press the pear, directing a stream of air into the eye of the subject.

2. Repeat the steps described in paragraph 1 until the flashing is stable (at least 2-3 times in a row) ahead of pressing the pear.

3. After the blinking reflex has been developed, turn on the metronome without directing the air stream to the eye. What do you observe while doing this? Make a conclusion.

What reflex was developed in the subject in the course of the actions you performed? What plays the role of unconditioned and conditioned stimuli in the developed reflex? What is the difference between the arcs of the unconditioned blinking and conditioned blinking reflexes?

Homework

Repeat the material on the mechanisms of development of conditioned reflexes in animals and humans.

Lesson 6-7.
Congenital and acquired inhibition, their types and characteristics

Equipment: tables, diagrams and drawings illustrating the mechanisms for the development of conditioned reflexes, different kinds congenital and acquired inhibition.

DURING THE CLASSES

I. Knowledge Test

Card work

1. Thanks to what innate nervous mechanisms can an animal distinguish good food from spoiled food? What role do neurons and their synapses play in these processes?

2. What facts can prove that instinct is a chain of interconnected unconditioned reflexes? How do instincts interact with acquired conditioned reflexes?

3. infant smacks his lips at the sight of a bottle of kefir; a person salivates at the sight of a cut lemon; wanting to know what time it is, the person looks at the hand where he usually wears a watch, although he forgot it at home. Explain the described phenomena.

Test knowledge check

Choose the correct answers to the given statements.

1. This is an unconditioned stimulus.
2. It is an indifferent stimulus.
3. This is an unconditioned reflex.
4. This is a conditioned reflex.
5. This is a combination of an indifferent stimulus with an unconditioned one.
6. Without these stimuli, the conditioned salivary reflex is not formed.
7. An irritant that excites the visual cortex.
8. An irritant that excites the taste zone of the cortex.
9. Under this condition, a temporary connection is formed between the visual and gustatory zones of the cortex.

Answer options

A. Turning on the light before the experiments without feeding.
B. Food in the mouth.
B. Turning on the light during feeding.
D. Salivation of food in the mouth.
D. Salivation in the light of a light bulb.

Answers: 1 - B, 2 - A, 3 - D, 4 - D, 5 - C, 6 - C, 7 - A, 8 - B, 9 - C.

II. Learning new material

1. Excitation and inhibition - the main processes of nervous activity

As you already know, the regulatory function of the central nervous system is carried out using two processes - excitation and inhibition.

Conversation with students on questions

What is arousal?

What is braking?

Why is the process of excitation called the active state of the nervous tissue?

What causes the excitation of the motor centers?

By what process can we imagine them mentally without doing anything?

What processes are responsible for complex coordinated actions, such as walking?

Thus, excitation- this is an active state of the nervous tissue in response to the action of various stimuli of sufficient strength. In a state of excitation, neurons generate electrical impulses. Braking- is active nervous process leading to inhibition of excitation.

2. general characteristics cortical inhibition

Excitation and inhibition of I.P. Pavlov called the true creators of nervous activity.

Excitation participates in the formation of conditioned reflexes and in their implementation. The role of inhibition is more complex and varied. It is the process of inhibition that makes conditioned reflexes a mechanism for subtle, precise, and perfect adaptation to the environment.

According to I.P. Pavlov, two forms of inhibition are characteristic of the cortex: unconditional and conditional. Unconditional inhibition does not require development, it is inherent in the body from birth (reflex holding of the breath with a sharp smell of ammonia, inhibition in the triceps muscle of the shoulder during the action of the biceps, etc.). Conditional inhibition is developed in the process of individual experience.

There are the following types of braking. Unconditional braking: transcendental (protective); external; inborn reflexes. Conditional braking: fading; differentiation; delayed.

3. Types of unconditioned (innate) inhibition and their characteristics

In the process of vital activity, the body is constantly exposed to one or another irritation from the outside or from the inside. Each of these stimuli can cause a corresponding reflex. If all these reflexes could be realized, then the activity of the organism would be chaotic. However, this does not happen. On the contrary, reflex activity is characterized by coherence and orderliness: with the help of unconditional inhibition, the most important reflex for the organism at a given moment delays all other, secondary, reflexes for the duration of its implementation.

Depending on the causes underlying the processes of inhibition, the following types of unconditional inhibition are distinguished.

beyond, or protective, braking occurs in response to very strong stimuli that require the body to act beyond its capabilities. The strength of irritation is determined by the frequency of nerve impulses. The stronger the neuron is excited, the greater the frequency of the flow of nerve impulses it generates. But if this flow exceeds known limits, processes arise that prevent the passage of excitation along the chain of neurons. The flow of nerve impulses following the reflex arc is interrupted, and inhibition sets in, which protects the executive organs from exhaustion.

Cause of external braking is outside the structures of the inhibitory reflex, it comes from another reflex. This type of inhibition occurs whenever a new activity begins. The new excitation, being stronger, causes inhibition of the old. As a result, the previous activity is automatically terminated. For example, a dog has developed a strong conditioned reflex to light, and the lecturer wants to demonstrate it to the audience. The experiment fails - there is no reflex. An unfamiliar environment, the noise of a crowded audience - new signals that completely turn off the conditioned reflex activity, a new excitation arises in the cortex. If the dog is brought into the audience several times, then the new signals, which turned out to be biologically indifferent, fade away, and the conditioned reflexes are carried out without hindrance.

To be continued

Age anatomy and physiology Antonova Olga Alexandrovna

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

Reflexes are the body's responses to external and internal stimuli. Reflexes are unconditional and conditional.

Unconditioned reflexes are congenital, permanent, hereditarily transmitted reactions characteristic of representatives of this type of organism. The unconditioned include pupillary, knee, Achilles and other reflexes. Some unconditioned reflexes are carried out only at a certain age, for example, during the breeding season, and when normal development nervous system. Such reflexes include sucking and motor reflexes, which are already present in an 18-week-old fetus.

Unconditioned reflexes are the basis for the development of conditioned reflexes in animals and humans. In children, as they grow older, they turn into synthetic complexes of reflexes that increase the adaptability of the body to environmental conditions.

Conditioned reflexes are adaptive reactions of the body, which are temporary and strictly individual. They occur in one or more representatives of a species that have been subjected to training (training) or exposure to the environment. The development of conditioned reflexes occurs gradually, in the presence of certain environmental conditions, for example, the repetition of a conditioned stimulus. If the conditions for the development of reflexes are constant from generation to generation, then conditioned reflexes can become unconditioned and be inherited in a number of generations. An example of such a reflex is the opening of the beak by blind and fledgling chicks in response to the shaking of the nest by a bird that comes to feed them.

Conducted by I.P. Pavlov, numerous experiments have shown that the basis for the development of conditioned reflexes are impulses coming through afferent fibers from extero- or interoreceptors. For their formation, the following conditions are necessary:

a) the action of an indifferent (in the future conditioned) stimulus must be earlier than the action of an unconditioned stimulus (for a defensive motor reflex, the minimum time difference is 0.1 s). In a different sequence, the reflex is not developed or is very weak and quickly fades;

b) the action of the conditioned stimulus for some time must be combined with the action of the unconditioned stimulus, i.e., the conditioned stimulus is reinforced by the unconditioned one. This combination of stimuli should be repeated several times.

In addition, a prerequisite for the development of a conditioned reflex is the normal function of the cerebral cortex, the absence of disease processes in the body and extraneous stimuli. Otherwise, in addition to the developed reinforced reflex, there will also be an orienting reflex, or a reflex of the internal organs (intestines, bladder, etc.).

The mechanism of formation of a conditioned reflex. The active conditioned stimulus always causes a weak focus of excitation in the corresponding zone of the cerebral cortex. The attached unconditioned stimulus creates a second, stronger focus of excitation in the corresponding subcortical nuclei and a section of the cerebral cortex, which diverts the impulses of the first (conditioned), weaker stimulus. As a result, a temporary connection arises between the centers of excitation of the cerebral cortex, with each repetition (i.e. reinforcement) this connection becomes stronger. The conditioned stimulus turns into a signal of a conditioned reflex.

To develop a conditioned reflex in a person, secretory, blinking or motor techniques with verbal reinforcement are used; in animals - secretory and motor techniques with food reinforcement.

The studies of I.P. Pavlov on the development of a conditioned reflex in dogs. For example, the task is to develop a reflex in a dog according to the salivation method, that is, to cause salivation to a light stimulus, reinforced by food - an unconditioned stimulus. First, the light is turned on, to which the dog reacts with an orienting reaction (turns its head, ears, etc.). Pavlov called this reaction the “what is it?” reflex. Then the dog is given food - an unconditioned stimulus (reinforcement). This is done several times. As a result, the orienting reaction appears less and less often, and then completely disappears. In response to impulses that enter the cortex from two foci of excitation (in the visual zone and in the food center), the temporal connection between them is strengthened, as a result, the dog's saliva is released to the light stimulus even without reinforcement. This happens because the trace of the movement of a weak impulse towards a strong one remains in the cerebral cortex. The newly formed reflex (its arc) retains the ability to reproduce the conduction of excitation, i.e., to carry out a conditioned reflex.

The signal for the conditioned reflex can also be the trace left by the impulses of the present stimulus. For example, if you act on a conditioned stimulus for 10 seconds, and then a minute after it stops giving food, then the light itself will not cause a conditioned reflex separation of saliva, but a few seconds after it stops, a conditioned reflex will appear. Such a conditioned reflex is called a follow-up reflex. Trace conditioned reflexes develop with great intensity in children from the second year of life, contributing to the development of speech and thinking.

To develop a conditioned reflex, you need a conditioned stimulus of sufficient strength and high excitability of the cells of the cerebral cortex. In addition, the strength of the unconditioned stimulus must be sufficient, otherwise the unconditioned reflex will go out under the influence of a stronger conditioned stimulus. In this case, the cells of the cerebral cortex should be free from third-party stimuli. Compliance with these conditions accelerates the development of a conditioned reflex.

Classification of conditioned reflexes. Depending on the method of development, conditioned reflexes are divided into: secretory, motor, vascular, reflexes-changes during internal organs and etc.

The reflex, which is developed by reinforcing the conditioned stimulus with an unconditioned one, is called the first-order conditioned reflex. Based on it, you can develop a new reflex. For example, by combining a light signal with feeding, a dog has developed a strong conditioned salivation reflex. If you give a call (sound stimulus) before the light signal, then after several repetitions of this combination, the dog begins to salivate in response to the sound signal. This will be a second-order reflex, or a secondary reflex, reinforced not by an unconditioned stimulus, but by a first-order conditioned reflex.

In practice, it has been established that it is not possible to develop conditioned reflexes of other orders on the basis of a secondary conditioned food reflex in dogs. In children, it was possible to develop a sixth-order conditioned reflex.

To develop conditioned reflexes of higher orders, you need to “turn on” a new indifferent stimulus 10–15 s before the start of the action of the conditioned stimulus of the previously developed reflex. If the intervals are shorter, then a new reflex will not appear, and the one developed before will fade away, because inhibition will develop in the cerebral cortex.

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Conventions and abbreviations AN - Academy of Sciences. - English ATP - adenosine triphosphate, cc. - century, centurieshigh. – height – grammg., years. - year, godyga - hectare deep. - depth arr. - mainly Greek - Greek diam. - dia. – DNA length –

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Conditional abbreviations AG - Golgi apparatus ACTH - adrenocorticotropic hormoneAMP - adenosine monophosphate ATP - adenosine triphosphate GNI - higher nervous activity GABA - ?-aminobutyric acidGMP - guanosine monophosphate GTP - guanine triphosphoric acid

Our nervous system- this is a complex mechanism for the interaction of neurons that send impulses to the brain, and it, in turn, controls all organs and ensures their work. This process of interaction is possible due to the presence in a person of the main inseparable acquired and innate forms of adaptation - conditional and unconditional reactions. A reflex is a conscious response of the body to certain conditions or stimuli. Such well-coordinated work of nerve endings helps us interact with the outside world. A person is born with a set of simple skills - this is called An example of such behavior: the ability of an infant to suck on its mother's breast, swallow food, blink.

and animal

As soon as a living being is born, he needs certain skills that will help ensure his life. The body actively adapts to the surrounding world, that is, it develops a whole range of purposeful motor skills. This mechanism is called species behavior. Each living organism has its own set of reactions and innate reflexes, which is inherited and does not change throughout life. But the behavior itself is distinguished by the method of its implementation and application in life: congenital and acquired forms.

Unconditioned reflexes

Scientists say that an innate form of behavior is an unconditioned reflex. An example of such manifestations has been observed since the birth of a person: sneezing, coughing, swallowing saliva, blinking. The transfer of such information is carried out by inheritance of the parent program by centers that are responsible for reactions to stimuli. These centers are located in the brain stem or spinal cord. Unconditioned reflexes help a person quickly and accurately respond to changes in the external environment and homeostasis. Such reactions have a clear demarcation depending on biological needs.

Food.
Approximate.
Protective.
Sexual.

Depending on the species, living beings have different reactions to the world, but all mammals, including humans, have a sucking skill. If you attach an infant or a young animal to the mother's nipple, a reaction will immediately occur in the brain and the feeding process will begin. This is the unconditioned reflex. Examples of eating behavior are inherited in all creatures that receive nutrients from mother's milk.

Defense reactions

These types of reactions to external stimuli are inherited and are called natural instincts. Evolution has laid in us the need to protect ourselves and take care of our safety in order to survive. Therefore, we have learned to instinctively respond to danger, this is an unconditioned reflex. Example: Have you noticed how the head deviates if someone raises a fist over it? When you touch a hot surface, your hand withdraws. This behavior is also called hardly a person in their right mind will try to jump from a height or eat unfamiliar berries in the forest. The brain immediately starts the process of processing information that will make it clear whether it is worth risking your life. And even if it seems to you that you don’t even think about it, the instinct immediately works.

Try to bring your finger to the baby's palm, and he will immediately try to grab it. Such reflexes have been developed over the centuries, however, now such a skill is not really needed by a child. Even among primitive people, the baby clung to the mother, and so she endured him. There are also unconscious innate reactions, which are explained by the connection of several groups of neurons. For example, if you hit the knee with a hammer, it will twitch - an example of a two-neuron reflex. In this case, two neurons come into contact and send a signal to the brain, causing it to respond to an external stimulus.

Delayed reactions

However, not all unconditioned reflexes appear immediately after birth. Some arise as needed. For example, a newborn baby practically does not know how to navigate in space, but after about a couple of weeks he begins to react to external stimuli - this is an unconditioned reflex. Example: the child begins to distinguish the voice of the mother, loud sounds, bright colors. All these factors attract his attention - an indicative skill begins to form. involuntary attention is Starting point in the formation of an assessment of stimuli: the baby begins to understand that when the mother speaks to him and approaches him, most likely, she will take him in her arms or feed him. That is, a person forms a complex form of behavior. His crying will draw attention to him, and he uses this reaction consciously.

sexual reflex

But this reflex belongs to the unconscious and unconditioned, it is aimed at procreation. It occurs during puberty, that is, only when the body is ready for procreation. Scientists say that this reflex is one of the strongest, it determines the complex behavior of a living organism and subsequently triggers the instinct to protect its offspring. Despite the fact that all these reactions are inherently human, they are launched in a certain order.

Conditioned reflexes

In addition to the instinctive reactions that we have at birth, a person needs many other skills in order to better adapt to the world around him. Acquired behavior is formed both in animals and in humans throughout life, this phenomenon is called "conditioned reflexes". Examples: at the sight of food, salivation occurs, while observing the diet, there is a feeling of hunger at a certain time of the day. Such a phenomenon is formed by a temporary connection between the center or vision) and the center of the unconditioned reflex. An external stimulus becomes a signal for a certain action. Visual images, sounds, smells are able to form stable connections and give rise to new reflexes. When someone sees a lemon, salivation may begin, and with a sharp smell or contemplation of an unpleasant picture, nausea occurs - these are examples of conditioned reflexes in humans. Note that these reactions can be individual for each living organism, temporary connections are formed in the cerebral cortex and send a signal when an external stimulus occurs.

Throughout life, conditioned responses can come and go. Everything depends on For example, in childhood, a child reacts to the sight of a bottle of milk, realizing that this is food. But when the baby grows up, this object will not form an image of food for him, he will react to a spoon and a plate.

Heredity

As we have already found out, unconditioned reflexes are inherited in every species of living beings. But conditioned reactions affect only the complex behavior of a person, but are not transmitted to descendants. Each organism "adjusts" to a particular situation and the reality surrounding it. Examples of innate reflexes that do not disappear throughout life: eating, swallowing, reaction to the taste of the product. Conditioned stimuli change constantly depending on our preferences and age: in childhood, at the sight of a toy, the baby experiences joyful emotions; in the process of growing up, the reaction is caused, for example, by visual images of a film.

Animal reactions

Animals, like humans, have both unconditioned innate reactions and acquired reflexes throughout their lives. In addition to the instinct of self-preservation and the production of food, living beings also adapt to environment. They develop a reaction to the nickname (pets), with repeated repetition, an attention reflex appears.

Numerous experiments have shown that it is possible to instill in a pet many reactions to external stimuli. For example, if at each feeding you call the dog with a bell or a certain signal, he will have a strong perception of the situation, and he will immediately react. In the process of training, rewarding a pet for an executed command with a favorite treat forms a conditioned reaction, walking a dog and the type of leash signals an imminent walk where he should relieve himself are examples of reflexes in animals.

Summary

The nervous system constantly sends a lot of signals to our brain, they form the behavior of humans and animals. The constant activity of neurons allows us to perform habitual actions and respond to external stimuli, helping to better adapt to the world around us.