All reflex reactions of the organism 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 a vegetative, plant life in a relatively constant environment (the mother's body), he suddenly passes into completely new conditions of the air environment with an infinite number of frequently changing stimuli, into the world where he is to 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. Biofile.ru). In the early days, the following can also be noted. Severe skin irritation (an injection, for example) causes a protective withdrawal, the flickering of an object in front of the face - squinting, and a sharp increase in the brightness of the light - constriction of the pupil, etc. These reactions are defensive reflexes.

In addition to protective ones, 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 on an object placed in 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 inborn 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 biological significance of conditioned reflexes is that they make it possible to adapt much better and more accurately to the conditions of existence and to survive in these conditions.

As a result of the formation of conditioned reflexes, the organism reacts not only directly to unconditioned stimuli, but also to the possibility of their action on it; reactions appear some time before unconditioned irritation. By this, the organism turns out to be prepared in advance for the actions that it has to carry out in a given situation. Conditioned reflexes contribute to the finding of food, early avoidance of danger, elimination of harmful influences, etc.

The adaptive meaning of conditioned reflexes is also manifested in the fact that the precedence of conditioned stimulation to the unconditioned one enhances the unconditioned reflex and accelerates its development.

on the topic: "Higher nervous activity"

1. The concept of higher nervous activity 3
2. Characteristics of conditioned reflexes in comparison with unconditioned 5
3. The order of the development of a conditioned reflex 6
4. The meaning of conditioned reflexes 8
5. The importance of conditioned reflexes in the development of diseases in humans 8
6. Inhibition of conditioned reflexes and the value of inhibition 9
7. Types of higher nervous activity (VNI) 10
8. Temperament 11
9. The meaning and knowledge of temperament in working with patients 12

1. The concept of higher nervous activity

Higher nervous activity is the processes taking place in the higher parts of the central nervous system of animals and humans. These processes include a set of conditioned and unconditioned reflexes, as well as "higher" mental functions that ensure adequate behavior of animals and humans in changing environmental and social conditions. Higher nervous activity should be distinguished from the work of the central nervous system by synchronizing the work of various parts of the body with each other. Higher nervous activity is associated with neurophysiological processes taking place in the cerebral cortex and the subcortex closest to it.

Departments of the brain

Continuous improvement of mental processes of higher nervous activity occurs in two ways - empirical and theoretical. Theoretical is carried out in the learning process (assimilation of someone else's experience). The empirical is carried out in the process of life - with direct experience and verification, formed as a result of theoretical training of stereotypes in personal practice.

Higher nervous activity (HND) is the activity of the cerebral cortex and the subcortical structures closest to it, providing the most perfect adaptation (behavior) of highly organized animals and humans to the environment. The higher nervous activity of the central nervous system should be distinguished from the work of the central nervous system by synchronizing the work of various parts of the body with each other.

The term "higher nervous activity" was first introduced into science by I.P. Pavlov, who considered it to be equivalent to the concept of mental activity. I.P. Pavlov identified two main sections in the physiology of higher nervous activity: the physiology of analyzers and the physiology of the conditioned reflex. Later, these sections were supplemented by the doctrine of the second human signaling system.

Thanks to the works of I.P. Pavlova's physiology of higher nervous activity becomes the science of neurophysiological mechanisms of the psyche and behavior, based on the principle of reflex reflection of the external world.

Conditioned reflexes are the foundation of GNI. They arise on the basis of a combination of the action of unconditioned reflexes and conditioned stimuli, which include signals that come to a person through sight, hearing, smell, touch. In humans, the activity of the cerebral cortex has the most developed ability to analyze and synthesize signals from the surrounding and internal environment of the body.

Thinking and consciousness I.P. Pavlov also referred to the elements of GNI. Continuous improvement of higher nervous activity occurs in the learning process (assimilation of someone else's experience).

The first experimental studies on animals are associated with the name of the Roman physician Galen (129–201 AD), in whose opinion mental activity is carried out by the brain and is its function. Galen tested the effect of various medicinal substances on animal organisms, observed their behavior after cutting the nerves going from the sense organs to the brain.

Galen described some of the brain centers that control limb movements, facial expressions, chewing and swallowing. He distinguished between different types of brain activity and for the first time put forward the provisions on congenital and acquired forms of behavior, on voluntary and involuntary muscle reactions. However, due to the poor development of experimental sciences for many centuries, the study of mental processes took place without connection with the morphology and physiology of the brain.

2. Characteristics of conditioned reflexes in comparison with unconditioned

The term "conditioned reflex" IP Pavlov called a reflex reaction that occurs in response to an initially indifferent stimulus in the event that it is several times combined in time with an unconditioned stimulus. The formation of a conditioned reflex is based on either the modification of existing nerve connections, or the formation of new ones.

The conditioned reflex is characterized by the following features:

Flexibility, the ability to change depending on the conditions;

Purchaseability and cancellation;

Signal character (an indifferent stimulus turns into a signal, i.e. it becomes a significant conditioned stimulus);

The implementation of a conditioned reflex by the higher parts of the central nervous system.

The biological role of conditioned reflexes is to expand the range of adaptive capabilities of a living organism. Conditioned reflexes complement unconditioned and allow subtle and flexible

adapt to a variety of environmental conditions (Table 1).

Table 1

The difference between conditioned reflexes and unconditioned

Unconditioned reflexes	Conditioned reflexes
Congenital, reflect the specific characteristics of the organism	Acquired throughout life and reflect the individual characteristics of the body
Individuals relatively constant throughout their life	Are formed, change and can be canceled when they become inadequate to living conditions
Implemented along genetically determined anatomical pathways	Implemented by functionally organizing temporary connections
They are characteristic of all levels of the central nervous system and are carried out mainly by its lower sections (spinal cord, brainstem, subcortical nuclei)	They are realized with the obligatory participation of the cerebral cortex, and therefore its integrity and safety is required, especially in higher mammals
Each reflex has a specific receptive field and its own specific stimuli.	Reflexes can be formed from any receptive field to a variety of stimuli
React to the action of a present stimulus, which can no longer be avoided	They adapt the organism to the action of a stimulus that does not yet exist, it has yet to be experienced, i.e. they have a warning, signal value

3. The order of development of a conditioned reflex

The conditioned reflex connection is not innate, but is formed as a result of learning. A newborn child has only a set of nerve elements for the formation of conditioned reflexes: receptors, ascending and descending nerve pathways, the central sections of sensory analyzers that are in the stage of formation, and the brain, which has unlimited possibilities for combining all these elements.

The formation of conditioned reflexes requires certain conditions:

1) the presence of two stimuli - unconditioned (food, pain stimulus, etc.), "triggering" an unconditioned reflex reaction, and conditioned (signal), preceding the unconditioned;

2) repeated exposure to a conditioned stimulus preceding the unconditioned one;

3) the indifferent nature of the conditioned stimulus (should not be excessive, cause a defensive or any other unconditioned reaction);

4) the unconditioned stimulus should be sufficiently significant and strong, the excitation from it should be more pronounced than from the conditioned stimulus;

5) the formation of a conditioned reflex is impeded by extraneous (distracting) stimuli;

6) the tone of the cerebral cortex should be sufficient for the formation of a temporary connection - the state of fatigue or ill health prevents the formation of a conditioned reflex.

The formation of a classical conditioned reflex consists of three stages:

The first stage is the pregeneralization stage. It is characterized by a pronounced concentration of arousal, primarily in the zones of projections of conditioned and unconditioned stimuli. This stage of concentration of excitement is short-lived, and it is followed by the second stage - the stage of generalization of the conditioned reflex. The stage of generalization is based on the process of diffuse propagation of excitation (irradiation). During this period, conditioned reactions arise both to signal and to other stimuli (the phenomenon of afferent generalization). Also, reactions occur in the intervals between the presentation of the conditioned stimulus - these are intersignal reactions. At the third stage, as only the conditioned stimulus is reinforced, the intersignal reactions fade away, and the conditioned response arises only to the conditioned stimulus. This stage is called the stage of specialization, during which the bioelectric activity of the brain becomes more limited and is associated mainly with the action of a conditioned stimulus. This process ensures the differentiation (fine discrimination) of stimuli and the automation of the conditioned reflex.

4. The meaning of conditioned reflexes

Conditioned reflexes provide a perfect adaptation of the organism to changing living conditions and make behavior plastic. Under the action of a conditioned signal (a signal that causes the corresponding conditioned reflex), the cerebral cortex provides the body with a preliminary preparation for the response to those environmental stimuli that will subsequently have their effect.

The conditioned stimulus should somewhat precede the unconditioned stimulus, that is, signal about it. With the formation of a conditioned reflex, a temporary connection arises between the centers of the analyzer of the conditioned stimulus and the center of the unconditioned reflex. Pavlov called the conditioned reflex a temporary connection, because this reflex appears only while the conditions under which it was formed are in effect. Conditioned reflexes are the basis of skills, habits, training, education, development of speech and thinking in a child, labor, social and creative activities.

Conditioned reflexes can arise or disappear if the signal is incorrect. However, if the need for a reflex does not disappear, it can exist for a lifetime.

1. The importance of conditioned reflexes in the development of diseases in humans

Such famous scientists as C. Sherrington and R. Magnus proved that reflexes can be quite complex, involving entire organ systems in their implementation. Examples of such reflexes are walking, setting the head, eyes and body in space.

It has been shown that the reflex principle underlies all

processes in the body associated with the maintenance of vital activity (respiration, blood circulation, digestion, etc.), motor

activity, perception processes, etc.

The individual characteristics of the manifestation of higher nervous activity depend on the character, temperament, intelligence, attention, memory, and other properties of the organism and psyche. Disorder of human higher nervous activity (neurosis) is caused by unfavorable conditions of the external environment (biological and social), physical and mental stress and is accompanied by dysfunctions of various organs and systems.

6. Inhibition of conditioned reflexes and the meaning of inhibition

Inhibition is the activation of inhibitory neurons, which leads to a decrease in excitation in the centers of an already developed conditioned reflex. Inhibition of conditioned reflex activity is manifested in the form of external, or unconditioned, inhibition and in the form of internal, or conditioned, inhibition.

External unconditioned inhibition of conditioned reflexes is an innate genetically programmed inhibition of one conditioned reflex by other conditioned or unconditioned ones. There are two types of external braking: transcendental and induction.

1. Extreme inhibition of conditioned reflexes (UR) develops either with a strong stimulus, or with a weak functioning of the nervous system. The transcendental inhibition has a protective meaning.

2. Induction inhibition of UR is observed when a new stimulus is applied after the development of UR or together with a known stimulus.

The biological significance of external inhibition lies in the fact that the body delays its reaction to secondary events and focuses its activity on the most important at the moment.

Internal, or conditioned, inhibition is inhibition that occurs within the reflex arc in case of non-reinforcement of the conditioned reflex. The biological significance of internal inhibition lies in the fact that if conditioned-reflex reactions to generated signals cannot provide the adaptive behavior necessary in a given situation, especially when the situation changes, then such signals are gradually canceled while maintaining those that turn out to be more valuable.

There are three types of internal inhibition of the conditioned reflex: differentiation, extinguishing and delayed inhibition.

1. As a result of differential inhibition, a person begins to distinguish stimuli that are similar in their parameters, and reacts only to biologically significant ones.

2. Extinguishing inhibition occurs when, during a conditioned reflex, the effect on the organism of the conditioned stimulus is not reinforced by the influence of the unconditioned stimulus. Due to extinction, the body ceases to respond to signals that have lost their meaning. Fading helps to get rid of unnecessary unnecessary movements.

3. Delayed inhibition occurs if the developed conditioned reflex is pushed back in time from the unconditioned stimulus that reinforces it. Delay in children is developed with great difficulty under the influence of education and training. Delay is the basis of endurance, willpower, the ability to restrain one's desires.

7. Types of higher nervous activity (VNI)

Balance of nervous processes is a balance of the processes of excitation and inhibition, which creates the basis for a more balanced behavior.

Additional properties of nervous processes were identified.

Dynamism is the ability of brain structures to quickly generate nervous processes during the formation of conditioned reactions. The dynamism of nervous processes is the basis of learning.

Lability is the rate of onset and termination of nervous processes. This property allows you to make movements with a high frequency, quickly and clearly starting and ending the movement.

Activity - characterizes the individual level of activation of nervous processes and underlies the processes of memorization and reproduction.

Different types of GNI are formed on the basis of various combinations of the three main properties of nervous processes. In the classification of I.P. Pavlov, four main types of GNI are distinguished, differing in adaptability to external conditions:

1) a strong, unbalanced ("unrestrained") type is characterized by a high strength of excitation processes that prevail over inhibition. This is a person with a high level of activity, quick-tempered, energetic, irritable, addicted, with strong, quickly emerging emotions that are vividly reflected in speech, gestures and facial expressions;

2) a strong, balanced, mobile (labile or "live") type is characterized by strong balanced processes of excitation and inhibition with the ability to easily replace one process with another. These people are energetic, with great self-control, decisive, able to quickly navigate in a new environment, mobile, impressionable, vividly expressing their emotions;

3) a strong, balanced, inert (calm) type is distinguished by the presence of strong processes of excitation and inhibition, their balance, but at the same time low mobility of nervous processes. These are very hard-working, able to restrain themselves, calm people, but slow, with a weak manifestation of feelings, it is difficult to switch from one type of activity to another, committed to their habits;

4) the weak type is characterized by weak excitation processes and easily arising inhibitory reactions. These are weak-willed, dull, dreary people, with high emotional vulnerability, suspicious, prone to gloomy thoughts, to a depressed mood, they are fearful, often succumb to other people's influence.

8. Temperament

These types of GNI correspond to the classical description of temperaments created by Hippocrates, an ancient Greek physician who lived almost 2.5 millennia before IP Pavlov (Table 2).

table 2

Correlation of types of higher nervous activity and temperaments according to Hippocrates

Temperaments according to Hippocrates		Equilibrium	Mobility
		Unbalanced, with a predominance of arousal process
Sanguine		Balanced	Mobile
Phlegmatic person		Balanced	Inert
Melancholic

However, usually the combination of properties of the nervous system is more diverse, and therefore such "pure" types of GNI are rarely seen in life. Even IP Pavlov noted that between the main types there are "intermediate, transitional types, and they must be known in order to navigate in human behavior."

Any work with people is inextricably linked with the process and problems of communication, it permeates the professional activities of health workers at any level. The individual characteristics of the patient's psyche in the context of therapeutic relationships and interactions come into contact with the psychological properties of a medical worker. The purpose of this contact is to provide assistance to the patient.

Clash of interests is the source of conflicts, but the factors that provoke conflict are extremely varied. These can include the character-logical characteristics of a person: decreased self-criticism, prejudice and envy, greed, selfishness, the desire to subordinate others to oneself; his mood, well-being, intelligence, knowledge and ignorance of human psychology, psychology of communication, etc.

As a result, everything that makes up the interpersonal situation of communication can act as a conflict-generating factor, a barrier in communication, and create a complex psychological situation.

The likelihood of conflicts increases when:

Incompatibilities of characters and psychological types;

The presence of a choleric temperament;

Lack of three qualities: the ability to be critical of oneself, tolerance of others, and trust in others.

Calmness and understanding, restraint and tolerance, responsiveness and culture of behavior of a medical worker will positively affect the established relationship with the patient, and form his trust in doctors and medicine.

List of used literature:

1. Batuev AS Higher nervous activity: Textbook. for universities on specials. "Biology", "Psychology". - M .: Higher. shk., 1991. - 256 p.

2. Human anatomy: a textbook for students of institutions providing education in the specialty "Nursing" / E.S. Okolokulak, K.M. Kovalevich, Yu.M. Kiselevsky. Edited by E.S. Okolokulaka. - Grodno: GrSMU, 2008 .-- 424 p.

3. Smirnov V.M., Budylina S.M. Physiology of sensory systems and higher nervous activity. / Moscow, "Academa", 2003.

4. Physiology of higher nervous activity / H.H. Danilova, A.L. Krylov. - Rostov n / a: "Phoenix", 2005. - 478, p.

5. Physiology of higher nervous activity: a textbook for students. institutions of higher. prof. education / V. V. Shulgovsky. - 3rd ed., Rev. - M .: Publishing Center "Academy", 2014. - 384 p.

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

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

1. Differences between conditioned and unconditioned reflexes:

· Unconditioned reflexes- congenital 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 variable 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.

· 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.

The biological significance of unconditioned reflexes.

An organism is born with a certain set of unconditioned reflexes. They ensure the maintenance of the vital activity of the organism 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.

The biological significance of conditioned reflexes.

Conditioned reflexes and their meaning.

The environmental conditions 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 and can fade away with changes in environmental conditions. Coinciding in their action with unconditioned stimuli, conditioned stimuli 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. When conditioned reflexes are formed, 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 drinking lemon several times 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 very primitive nervous systems, 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 is rather complex. 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.

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 via 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 those whose bodies and processes do not extend 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 some 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 arises in the centers of the brain that regulate the flow of water, and a feeling of thirst appears. This arousal induces purposeful behavior, seeking 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 evolution, the unconditional reflex reactions necessary to satisfy biological needs and preserve the vital activity of the organism, were fixed 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 I.P. Pavlov to open a conditioned reflex. An 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 that are triggered 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 unconditional 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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