A reflex is the body's response to internal or external stimulation, carried out and controlled by the central nervous system. The first scientists who developed ideas about what was previously a mystery were our compatriots I.P. Pavlov and I.M. Sechenov.

What are unconditioned reflexes?

An unconditioned reflex is an innate, stereotypical reaction of the body to the influence of the internal or environmental environment, inherited by the offspring from the parents. It remains in a person throughout his life. Reflex arcs pass through the brain and the cerebral cortex does not take part in their formation. The significance of the unconditioned reflex is that it ensures the adaptation of the human body directly to those environmental changes that often accompanied many generations of his ancestors.

What reflexes are unconditioned?

An unconditioned reflex is the main form of activity of the nervous system, an automatic reaction to a stimulus. And since a person is influenced by various factors, the reflexes are different: food, defensive, orientation, sexual... Food include salivation, swallowing and sucking. Defensive actions include coughing, blinking, sneezing, and jerking limbs away from hot objects. Approximate reactions include turning the head and squinting the eyes. Sexual instincts include those associated with reproduction, as well as caring for offspring. The significance of the unconditioned reflex is that it ensures the preservation of the integrity of the body and maintains the constancy of the internal environment. Thanks to him, reproduction occurs. Even in newborn children, one can observe an elementary unconditioned reflex - this is sucking. By the way, it is the most important. The irritant in this case is touching the lips of any object (pacifier, mother's breast, toy or finger). Another important unconditioned reflex is blinking, which occurs when a foreign body approaches the eye or touches the cornea. This reaction belongs to the protective or defensive group. Also observed in children, for example, when exposed to strong light. However, the signs of unconditioned reflexes are most clearly manifested in various animals.

What are conditioned reflexes?

Conditioned reflexes are those acquired by the body during life. They are formed on the basis of inherited ones, subject to exposure to an external stimulus (time, knocking, light, and so on). A striking example is the experiments conducted on dogs by academician I.P. Pavlov. He studied the formation of this type of reflexes in animals and was the developer of a unique method for obtaining them. So, to develop such reactions, the presence of a regular stimulus - a signal - is necessary. It triggers the mechanism, and repeated repetition of the stimulus allows it to develop. In this case, a so-called temporary connection arises between the arcs of the unconditioned reflex and the centers of the analyzers. Now the basic instinct awakens under the influence of fundamentally new external signals. These stimuli from the surrounding world, to which the body was previously indifferent, begin to acquire exceptional, vital importance. Each living creature can develop many different conditioned reflexes during its life, which form the basis of its experience. However, this applies only to this particular individual; this life experience will not be inherited.

An independent category of conditioned reflexes

It is customary to classify into a separate category conditioned reflexes of a motor nature developed throughout life, that is, skills or automated actions. Their meaning is to master new skills, as well as develop new motor forms. For example, over the entire period of his life a person masters many special motor skills that are associated with his profession. They are the basis of our behavior. Thinking, attention, and consciousness are freed up when performing operations that have reached automaticity and become a reality of everyday life. The most successful way to master skills is to systematically perform the exercise, timely correction of noticed errors, and knowledge of the ultimate goal of any task. If the conditioned stimulus is not reinforced by the unconditioned stimulus for some time, it is inhibited. However, it does not disappear completely. If you repeat the action after some time, the reflex will be restored quite quickly. Inhibition can also occur when a stimulus of even greater strength appears.

Compare unconditioned and conditioned reflexes

As mentioned above, these reactions differ in the nature of their occurrence and have different formation mechanisms. In order to understand what the difference is, just compare unconditioned and conditioned reflexes. Thus, the first ones are present in a living creature from birth; throughout life they do not change or disappear. In addition, unconditioned reflexes are the same in all organisms of a particular species. Their significance lies in preparing a living being for constant conditions. The reflex arc of this reaction passes through the brain stem or spinal cord. As an example, here are some (congenital): active secretion of saliva when a lemon enters the mouth; sucking movement of the newborn; coughing, sneezing, withdrawing hands from a hot object. Now let's look at the characteristics of conditioned reactions. They are acquired throughout life, can change or disappear, and, no less important, each organism has its own individual (its own). Their main function is to adapt a living creature to changing conditions. Their temporary connection (reflex centers) is created in the cerebral cortex. An example of a conditioned reflex is the reaction of an animal to a nickname or the reaction of a six-month-old child to a bottle of milk.

Unconditioned reflex diagram

According to the research of academician I.P. Pavlova, the general scheme of unconditioned reflexes is as follows. Certain receptor nerve devices are affected by certain stimuli from the internal or external world of the body. As a result, the resulting irritation transforms the entire process into the so-called phenomenon of nervous excitation. It is transmitted along nerve fibers (as if through wires) to the central nervous system, and from there it goes to a specific working organ, already turning into a specific process at the cellular level of a given part of the body. It turns out that certain stimuli are naturally connected with this or that activity in the same way as cause and effect.

Features of unconditioned reflexes

The characteristics of unconditioned reflexes presented below systematize the material presented above; it will help to finally understand the phenomenon we are considering. So, what are the features of inherited reactions?

Unconditioned instinct and reflex of animals

The exceptional constancy of the nervous connection underlying unconditional instinct is explained by the fact that all animals are born with a nervous system. She is already able to respond appropriately to specific environmental stimuli. For example, a creature may flinch at a sharp sound; he will secrete digestive juice and saliva when food enters his mouth or stomach; it will blink when visually stimulated, and so on. Innate in animals and humans are not only individual unconditioned reflexes, but also much more complex forms of reactions. They are called instincts.

An unconditioned reflex, in fact, is not a completely monotonous, template, transfer reaction of an animal to an external stimulus. It is characterized, although elementary, primitive, but still by variability, variability, depending on external conditions (strength, peculiarities of the situation, position of the stimulus). In addition, it is influenced by the internal states of the animal (decreased or increased activity, posture, etc.). So, also I.M. Sechenov, in his experiments with decapitated (spinal) frogs, showed that when the toes of the hind legs of this amphibian are exposed, the opposite motor reaction occurs. From this we can conclude that the unconditioned reflex still has adaptive variability, but within insignificant limits. As a result, we find that the balancing of the organism and the external environment achieved with the help of these reactions can be relatively perfect only in relation to slightly changing factors of the surrounding world. The unconditioned reflex is not able to ensure the animal’s adaptation to new or sharply changing conditions.

As for instincts, sometimes they are expressed in the form of simple actions. For example, the rider, thanks to his sense of smell, finds the larvae of another insect under the bark. It pierces the bark and lays its egg in the found victim. This ends all of its actions that ensure continuation of the family. There are also complex unconditioned reflexes. Instincts of this kind consist of a chain of actions, the totality of which ensures procreation. Examples include birds, ants, bees and other animals.

Species specificity

Unconditioned reflexes (specific) are present in both humans and animals. It should be understood that such reactions will be the same in all representatives of the same species. An example is a turtle. All species of these amphibians retract their heads and limbs into their shell when danger arises. And all the hedgehogs jump and make a hissing sound. In addition, you should know that not all unconditioned reflexes occur at the same time. These reactions vary with age and season. For example, the breeding season or the motor and sucking actions that appear in an 18-week fetus. Thus, unconditioned reactions are a kind of development for conditioned reflexes in humans and animals. For example, as cubs grow older, they transition into the category of synthetic complexes. They increase the body's adaptability to external environmental conditions.

Unconditional inhibition

In the process of life, each organism is regularly exposed - both from the outside and from the inside - to various stimuli. Each of them is capable of causing a corresponding reaction - a reflex. If all of them could be realized, then the life activity of such an organism would become chaotic. However, this does not happen. On the contrary, reactionary activity is characterized by consistency and orderliness. This is explained by the fact that unconditioned reflexes are inhibited in the body. This means that the most important reflex at a particular moment in time delays the secondary ones. Typically, external inhibition can occur at the moment of starting another activity. The new pathogen, being stronger, leads to the attenuation of the old one. And as a result, the previous activity will automatically stop. For example, a dog is eating, and at that moment the doorbell rings. The animal immediately stops eating and runs to meet the newcomer. There is a sharp change in activity, and the dog’s salivation stops at this moment. Some innate reactions also include unconditional inhibition of reflexes. In them, certain pathogens cause the complete cessation of certain actions. For example, the anxious clucking of a hen makes the chicks freeze and hug the ground, and the onset of darkness forces the canary to stop singing.

In addition, there is also a protective It arises as a response to a very strong stimulus that requires the body to take actions that exceed its capabilities. The level of such influence is determined by the frequency of impulses of the nervous system. The more excited a neuron is, the higher the frequency of the stream of nerve impulses it generates. However, if this flow exceeds certain limits, then a process will arise that will begin to interfere with the passage of excitation through the neural circuit. The flow of impulses along the reflex arc of the spinal cord and brain is interrupted, resulting in inhibition that preserves the executive organs from complete exhaustion. What conclusion follows from this? Thanks to the inhibition of unconditioned reflexes, the body selects from all possible options the most adequate one, capable of protecting against excessive activity. This process also contributes to the exercise of so-called biological precautions.

The mechanisms of higher nervous activity in higher animals and humans are associated with the activity of a number of parts of the brain. The main role in these mechanisms belongs to the cerebral cortex. It has been experimentally shown that in higher representatives of the animal world, after complete surgical removal of the cortex, higher nervous activity sharply deteriorates.

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Reflex is the basis of nervous activity. Unconditioned and conditioned reflexes and their role in the life of humans and animals

Table of contents

Introduction

Relevance of the work. Higher nervous activity ensures the individual adaptation of the body to changing conditions of the external and internal environment.

The mechanisms of higher nervous activity in higher animals and humans are associated with the activity of a number of parts of the brain. The main role in these mechanisms belongs to the cerebral cortex. It has been experimentally shown that in higher representatives of the animal world, after complete surgical removal of the cortex, higher nervous activity sharply deteriorates. They lose the ability to subtly adapt to the external environment and exist independently in it.

Reflexes are reactions of the body that occur with the obligatory participation of the nervous system in response to irritation of perceptive nerve endings - receptors.

I.P. Pavlov divided all reflex reactions into two groups: unconditioned and conditioned. They also underlie human behavior.

Unconditioned and conditioned reflexes form the basis of the most complex forms of activity of the organism as a whole - its behavior in the external environment.

Conditioned reflexes are the highest form of adaptation of the body to external conditions.

The study of reflex reactions is relevant in our time.

Goal of the work : study unconditioned and conditioned reflexes and their role in the life of humans and animals.

Job objectives:

Consider the reflex as the basis of nervous activity;

Study unconditioned and conditioned reflexes;

Study the differences between conditioned and unconditioned reflexes;

Study the role of the unconditioned and conditioned reflex in the life of humans and animals.

1 Reflex as the basis of nervous activity

The main form of nervous activity is reflexes. Reflex is the body’s response to irritation from the external or internal environment, carried out through the central nervous system.

Irritation of the skin of the plantar part of the foot in humans causes reflex flexion of the foot and toes. This is the plantar reflex. When the quadriceps tendon is struck under the patella, the leg is extended at the knee. It's a knee-jerk reaction. Touching the lips of an infant causes sucking movements in him - the sucking reflex. Illumination of the eye with bright light causes constriction of the pupil - the pupillary reflex. Thanks to reflex activity, the body is able to quickly respond to various changes in the external or internal environment. Reflex reactions are very diverse. They can be conditional or unconditional.

All organs of the body contain nerve endings that are sensitive to stimuli. These are receptors. Receptors vary in structure, location and function. Some receptors look like relatively simply arranged nerve endings, or they are separate elements of complex sensory organs, such as the retina of the eye. 1

Based on their location, receptors are divided into exteroceptors, proprioceptors and interoceptors. Exteroreceptors perceive irritations from the external environment. These include the receptive cells of the retina of the eye, ear, skin receptors, olfactory and taste organs. Interoreceptors are located in the tissues of internal organs (heart, liver, kidneys, blood vessels, etc.) and perceive changes in the internal environment of the body. Proprioceptors are located in the muscles and perceive muscle contractions and stretches, i.e. signal the position and movements of the body.

In the receptors, under the action of appropriate stimuli of a certain strength and duration of action, an excitation process occurs. The resulting excitation from the receptors is transmitted to the central nervous system along centripetal nerve fibers. In the central nervous system, due to intercalary neurons, the reflex turns from a narrow-local act into a holistic activity of the nervous system. In the central nervous system, incoming signals are processed and impulses are transmitted to centrifugal nerve fibers.

The executive organ whose activity changes as a result of the reflex is called an effector. The path along which nerve impulses travel from the receptor to the executive organ is called a reflex arc. This is the material basis of the reflex.

Speaking about the reflex arc, we must keep in mind that any reflex act is carried out with the participation of a large number of neurons. The two- or three-neuron reflex arc is just a diagram. In fact, the reflex occurs when not one, but many receptors located in one or another area of ​​the body are irritated. Nerve impulses during any reflex act, arriving in the central nervous system, spread widely in it, reaching its different parts. Therefore, it is more correct to say that the structural basis of reflex reactions is made up of neural chains of centripetal, central, or intercalary, and centrifugal neurons. Due to the fact that in any reflex act groups of neurons take part, transmitting impulses to various parts of the brain, the entire body is involved in the reflex reaction. Indeed, if you were unexpectedly pricked in the arm by a pin, you would immediately pull it away. This is a reflex reaction. But this will not only reduce the arm muscles. Breathing and the activity of the cardiovascular system will change. You will react with words to an unexpected injection. Almost the entire body was involved in the response. A reflex act is a coordinated reaction of the entire organism. 2

There are both direct and feedback connections between the central nervous system and the working and executive organs. When a stimulus acts on the receptors, a motor reaction occurs. As a result of this reaction, nerve impulses from the effector organs - the muscles - enter the central nervous system. These secondary afferent (centripetal) impulses constantly signal the nerve centers about the state of the motor system, and in response to these signals, new impulses are received from the central nervous system to the muscles, including the next phase of movement or changing movement in accordance with the conditions of activity. This means that there is a circular interaction between regulators (nerve centers) and regulated processes, which gives grounds to speak not of a reflex arc, but of a reflex ring, or reflex chain.

The structure of the reflex ring differs significantly from the structure of the reflex arc, which is essentially open at the periphery. The reflex ring has additional links in the form of receptors of the executive organ, an afferent neuron and a system of interneurons that transmit secondary afferent impulses to the centrifugal neurons of the reflex ring.

Secondary afferent impulses (feedback) are very important in the coordination mechanisms carried out by the nervous system. In patients with impaired muscle sensitivity, movements, especially walking, lose their smoothness and become uncoordinated. The central nervous system in such patients loses control over movements.

Thanks to feedback, we can not only judge the results of actions, but also make amendments to our activities and correct mistakes. Therefore, in order for the body’s activity to be coordinated and provide the desired effect, only direct connections from the brain to the working organ are not enough; feedback connections (working organs - brain), through which impulses travel, signaling the correctness or error of the action being performed, are also important. Physiologists know many examples of self-regulation of functions in the body using feedback: this is the maintenance of blood pressure at a constant level due to impulses entering the central nervous system from receptors of blood vessels, or the importance of impulses from receptors of the lungs and respiratory muscles in the regulation of breathing, etc.

The doctrine of the reflex activity of the central nervous system led to the idea of ​​a nerve center. A nerve center is a collection of neurons in the central nervous system that participate in the implementation of a certain reflex action or the regulation of a particular function.

The nerve center is a complex functional association, “ensembles” of neurons located in various parts of the central nervous system, coordinately involved in the regulation of functions and reflex reactions.

Nerve centers have a number of characteristic properties determined by the characteristics of the conduction of excitation through the synapses of the central nervous system and the structure of the neural circuits that form them.

In the central nervous system, unilateral conduction of excitation is noted. This is due to the characteristics of synapses; transmission of excitation in them is possible only in one direction - from the nerve ending, where the transmitter is released upon excitation, to the postsynaptic membrane. In the opposite direction, the excitatory postsynaptic potential does not propagate. 3

In the synapses of the central nervous system, there is a slow conduction of excitation. It is known that excitation along nerve fibers is carried out quickly. In synapses, the speed of excitation is approximately 200 times lower than the speed of excitation in the nerve fiber. This is due to the fact that when transmitting an impulse through a synapse, time is spent on the release of the transmitter by the nerve ending in response to the incoming impulse; on the diffusion of the transmitter through the synoptic cleft to the postsynaptic membrane; on the occurrence of an excitatory postsynaptic potential under the influence of this mediator.

In the central nervous system, the rhythm of impulses entering it is transformed into its own rhythm. In this case, both a decrease in the frequency of impulses entering it and an increase in their frequency may occur. In response to a single stimulation of a centripetal neuron, the central nervous system sends a series of impulses along the centrifugal neuron, following each other at a certain interval. Rhythm transformation is associated with the characteristics of the transmission of excitation through synapses. Nerve centers are characterized by the phenomenon of summation of excitation. This property was first described by I.M. Sechenov in 1863. It was found that weak stimulations do not cause a visible reflex reaction of the central nervous system. A reflex response can only be caused by a stimulus that has reached a threshold strength. But if a weak stimulus acts simultaneously on several receptor areas (for example, several areas of the skin) or a weak stimulus acts on the receptor repeatedly (for a long time), then the reflex response will arise due to folding, i.e. summation, excitement.

This phenomenon is based on the process of summation of excitatory postsynaptic potentials on the body of neurons. As a rule, the portion of the transmitter released by the nerve ending in response to a single impulse is too small to cause an excitatory postsynaptic potential sufficient to depolarize the nerve cell membrane. Such depolarization is possible either in the case of simultaneous excitation of several synapses located on the neuron body, or when a series of nerve impulses arrive at the same synapse, following each other with a short interval. In this case, postsynaptic potentials are summed with each other, and at the moment when the total potential reaches a threshold value, a propagating action potential arises. The reflex reaction does not stop immediately after the cessation of the stimulus, and for some period of time, exciting impulses continue to flow to the working organ (effector) from the central nervous system. This is an aftereffect. The aftereffect is usually longer, the stronger the irritation and the longer it acts on the receptors. Unlike isolated nerve fibers, nerve centers are easily fatigued. Fatigue of the nerve centers manifests itself in a gradual decrease and ultimately complete cessation of the reflex response with prolonged stimulation of the receptor. It is believed that fatigue of the nerve centers is associated with a disruption in the transmission of excitation in interneuron synapses. In this case, there is a decrease in the reserves of the synthesized transmitter in the nerve endings and a decrease in the sensitivity of the postsynaptic membrane to the transmitter. 4

After excitation of the central nervous system by rhythmic stimulation, the next stimulation causes a greater effect, or a smaller force of subsequent stimulation is required to maintain the previous level of response. This property of nerve centers is called prototyping. The facilitating effect during penetration is explained by the fact that with the first stimuli of irritation, the transmitter vesicles move closer to the presynaptic membrane and with subsequent irritation, the transmitter is more quickly released into the synaptic cleft.

2 Unconditioned reflexes

Unconditioned reflexes are innate reactions to certain influences of external agents, carried out with the help of the nervous system. The term “unconditioned reflex” was introduced by I.P. Pavlov.

The characteristic features of unconditioned reflexes are their relative constancy, innateness and species specificity, as well as the fact that they serve as the basis and reinforcing factor for the formation of conditioned reflexes. The totality of B. r. constitutes the so-called lower nervous activity of animals, conditioned higher nervous activity.

Unconditioned reflexes are divided into simple (food, defensive, sexual, visceral, tendon) and complex reflexes (instincts, emotions). Some researchers to B. r. also include indicative (orientative-exploratory) reflexes. The instinctive activity of animals (instincts) includes several stages of animal behavior, and the individual stages of its implementation are sequentially connected with each other like a chain reflex.

The question of the mechanisms of closure of unconditioned reflexes has not been studied enough. According to the teachings of I.P. Pavlov about the cortical representation of B. r., each unconditional stimulation, along with the inclusion of subcortical structures, causes excitation of nerve cells in the cerebral cortex. Studies of cortical processes using electrophysiological methods have shown that an unconditioned stimulus comes to the cerebral cortex in the form of a generalized flow of ascending excitations. 5

Based on the provisions of I.P. Pavlov about the nerve center as a morphofunctional set of nerve formations located in various parts of the central nervous system, the concept of the structural and functional architecture of unconditioned reflexes was developed. The central part of the unconditioned reflex arc does not pass through any one part of the central nervous system, but is multi-story and multi-branched. Each branch passes through an important part of the nervous system: the spinal cord, medulla oblongata, midbrain, and cerebral cortex. The higher branch, in the form of the cortical representation of one or another unconditioned reflex, serves as the basis for the formation of conditioned reflexes. Evolutionarily more primitive species of animals are characterized by simple unconditioned reflexes and instincts, for example, in animals in which the role of acquired, individually developed reactions is still relatively small and innate, albeit complex forms of behavior predominate, dominance of tendon and labyrinthine reflexes is observed. With the increasing complexity of the structural organization of the central nervous system and the progressive development of the cerebral cortex, complex unconditioned reflexes and, in particular, emotions acquire a significant role.

The study of unconditioned reflexes is important for the clinic. Thus, in conditions of pathology of the central nervous system, unconditioned reflexes may appear, characteristic of the early stages of onto- and phylogenesis (sucking, grasping, Babinsky, Bekhterev, etc. reflexes), which can be considered as rudimentary functions, i.e. functions that existed previously, but were suppressed during the process of phylogenesis by the higher parts of the central nervous system. When the pyramidal tracts are damaged, these functions are restored due to the resulting disconnection between the phylogenetically ancient and later developed parts of the central nervous system.

The set of unconditioned reflexes that provide complex forms of animal behavior is called instinct. For example, bird migration, caring for offspring, construction of dams by beavers. However, unconditioned reflexes alone are not enough for the body to adapt to changing environmental conditions. Such adaptations are carried out thanks to reflexes, which I. P. Pavlov called conditioned in 1903. 6

Instincts are very strong. Complex forms of behavior associated with their manifestation often indicate their high adaptive significance. For example, puppies from the hunting dog breed, without prior training in hunting conditions, exhibit many nuances in behavior that are characteristic of trained animals.

During the growth and development of the organism, the system of unconditioned reflex connections still turns out to be limited, inert, and unable to provide sufficiently mobile adaptation reactions corresponding to fluctuations in the external and internal environment. More perfect adaptation of the body to constantly changing conditions of existence occurs thanks to conditioned reflex, i.e., individually acquired, reactions. Conditioned reflex mechanisms of the brain are related to all types of activity of the body (to somatic and vegetative functions, to behavior), providing adaptive reactions aimed at maintaining the integrity and stability of the “organism-environment” system. I. P. Pavlov called a conditioned reflex a temporary connection between a stimulus and a response activity that occurs in the body under certain conditions. Therefore, in the literature, instead of the term “conditioned reflex,” the term “temporary connection” is often used, which includes more complex manifestations of animal and human activity, representing entire systems of reflexes and behavioral acts.

3 Conditioned reflexes

Conditioned reflexes are individually acquired complex adaptive reactions of the animal and human body that arise under certain conditions (hence the name) based on the formation of a temporary connection between a conditioned (signal) stimulus and an unconditioned reflex act that reinforces this stimulus. They are carried out by the higher parts of the central nervous system - the cerebral cortex and subcortical formations; are formed in the process of ontogenesis on the basis of unconditioned reflexes. 7

Conditioned reflexes can be formed to any stimulation of any receptor fields. (A conditioned food reflex can be developed to stimulate visual, auditory, skin and other receptors).

There are natural and artificial conditioned reflexes. Natural ones are produced in response to natural signals that accompany an unconditioned stimulus (the sight and smell of food; the sight and sounds made by a predator; a start command for an athlete). Natural conditioned reflexes are developed in natural conditions and, as a rule, remain throughout life. In the experiment, artificial conditioned reflexes are developed in response to signals not related to the stimulus (light, bell, etc.). 8

Certain conditions are necessary for the formation of conditioned reflexes. It is important that the indifferent stimulus, which then becomes conditioned, precedes (by 15 s) or coincides with the action of the unconditioned. If an indifferent stimulus acts long before the unconditioned one, or if the unconditioned stimulus is given first and then the conditioned stimulus, then the conditioned reflex is not developed. Conditioned reflexes are formed and reinforced only after a sufficient number of repeated combinations. The rate of formation and stability of a conditioned reflex depend on the intensity of the unconditioned reaction (food conditioned reflexes are developed faster in a hungry animal). The formation of conditioned reflexes is also influenced by the strength of the conditioned stimulus: reflexes are more difficult to develop to weak signals than to stronger ones. Under natural conditions, reflexes are most often formed in response to signals that simultaneously or sequentially irritate various receptors. Such conditioned reflexes are called complex. In an experiment, with the sequential presentation of several signals, conditioned reflexes of the first, second and subsequent orders are developed.

A conditioned reflex is formed due to the emergence of a functional temporary connection between the center in the cerebral cortex that perceives the conditioned signal and the center of the cortical representation of the unconditioned reflex. Cortical representation of the unconditioned reflex these are the nerve cells in the cortex that are involved in its execution. For example, the arc of the unconditioned salivary reflex passes through the center in the medulla oblongata. When the neurons of the medulla oblongata are excited, the impulses propagate along the ascending pathways, reach the neurons of the cortical representation in the frontal lobe, activate them and return along the reverse pathways to the center of the unconditioned reflex. If the functioning of the cortical representation is disrupted, salivation becomes weak, less accurate and quickly stops. With simultaneous irritation of the hearing organ, signals arrive at the hearing center of the temporal lobe and activate it. Thus, two groups of excited neurons appear simultaneously in the cerebral cortex: neurons of the cortical representation of the salivary reflex and the hearing center. Thanks to this, a new functional connection is formed between them, which is reinforced as it is repeated.

4 Differences between conditioned and unconditioned reflexes

Unconditioned reflexes are innate reactions of the body, they were formed and consolidated in the process of evolution and are inherited. Conditioned reflexes arise, become consolidated, and fade away throughout life and are individual. Unconditioned reflexes are specific, i.e. they are found in all individuals of a given species. Conditioned reflexes can be developed in some individuals of a given species, while in others they may be absent. Unconditioned reflexes do not require special conditions for their occurrence; they certainly occur if certain receptors are acted upon by adequate stimuli. Conditioned reflexes require special conditions for their formation; they can be formed in response to any stimuli (of optimal strength and duration) from any receptive field.

Unconditioned reflexes are relatively constant, stoic, unchanging and persist throughout life. Conditioned reflexes are changeable and more mobile. 9

The implementation of unconditioned reflexes involves mainly the subcortical parts of the central nervous system. These reflexes can be carried out in higher animals even after the removal of their cerebral cortex. Although it was possible to show that after removal of the cerebral cortex the nature and course of unconditioned reflex reactions changes, this gave grounds to talk about the cortical representation of the unconditioned reflex. Conditioned reflexes in higher animals are a function of the cerebral cortex.

The change of unconditioned reflexes for each person, depending on age, is just as programmed as the replacement of baby teeth with permanent ones. This is due to several reasons.

By the time of birth, not all parts of the nervous system are functioning. Some nerve centers are formed later. Thus, more ancient systems (for example, the extrapyramidal) mature earlier than the pyramidal system, with which voluntary movements and actions are associated. The reflexes of the extrapyramidal system include the Babinski reflex and the Robinson reflex. If an adult draws a dashed line along the sole of the foot, he will bend his toes, and a child will straighten them - they form a figure reminiscent of a fan. Any touch to the child’s palm causes the hand to be clenched into a fist. In premature babies it can be so severe that some babies can support their weight if they are allowed to grab a stick with their hands and then lift the stick with the baby.

The second reason for the change in reflexes is related to the ecological adaptability of organisms to the capabilities that a child has at a given age. When the child begins to hold his head up, then when it “falls” (and this happens whenever the child gets tired), the head turns to the side, and he does not bury his mouth and nose in the bed. Otherwise, the child could suffocate. After voluntary movements become available to the child, this reflex fades away.

Sexual reflexes also do not appear immediately; they largely depend on age.

At the birth of a person or any land mammal, a certain chain of reflexes that constitute instinct follows: birth accumulation of carbon dioxide in the blood of the newborn inhalation.

In hippopotamuses, which usually give birth to their young in water, the chain of reflexes is somewhat different: birth accumulation of carbon dioxide in the blood ascent to the surface inhalation. Ignorance of this caused the death of a baby hippopotamus born in captivity. The staff of this zoo were very concerned that the newborn cub did not appear from the water for a long time. They decided to release the water to save him, but in doing so they killed the cub. He was not allowed to float up and breathing became impossible. In other words, the chain of reflexes was broken and the middle link was crossed out.

In one row there are images of the heads of adult animals, and in the second - the heads of their young. Students must answer the question which row is their favorite.

Practice has shown that cubs evoke more sympathy.

Signal stimuli of pups that evoke parental reflexes. On the right are adult forms of the same animal species and humans.

5 The role of unconditioned and conditioned reflexes in the life of humans and animals

Unconditioned reflexes, together with conditioned ones, ensure the adaptability of organisms to living conditions.

Examples of unconditioned reflexes are: food, defensive, sexual, self-regulation of the functions of organs and systems, pain, swallowing, vomiting, sneezing, coughing, blinking, etc. In the first moments after birth, the child is able to breathe, feed by sucking, etc. 10

The ability to use predominantly the right or left hand is also an unconditioned reflex. The so-called instincts are nothing more than complex complexes of various reflexes. Some unconditioned reflexes are used in medicine to determine the state of people's health: knee, Achilles, abdominal, blinking, plantar, sucking, etc. Of these, the knee reflex is probably known to everyone who has been to a neurologist. The doctor hits the muscle tendon below the patella with a special hammer. At the same time, the lower leg is extended at the knee joint. The Achilles reflex is induced in the same way: a blow to the Achilles tendon causes plantar flexion of the foot. Abdominal reflexes manifest themselves in the form of displacements of the abdominal wall in response to line irritations of the abdominal skin. The blink reflex is manifested by contraction of the orbicularis oculi muscles when illuminated or the sudden appearance of an object in the field of view. Based on these and other reflexes, the doctor judges the state of the nervous system.

During life, innate reflexes can change and become difficult to recognize. It should be noted that in humans, unlike animals, unconditioned reflexes manifest themselves with the participation of the cerebral cortex.

The reflex activity of the nervous system, consisting of unconditioned and conditioned reflexes, determines the entire variety of body functions, including memory, thinking and behavior.

The perfect adaptation of the organism to the environment is carried out through the formation and disappearance of various conditioned reflexes. Variability, conditioning by factors of the external and internal environment of the body and the temporality of conditioned reflexes are of extremely important biological significance, ensuring the flexibility and accuracy of the body’s adaptation to a changing environment. The signaling nature of conditioned reflex activity allows the body, based on one, often distant precursors - conditioned stimuli, to strive in advance for favorable conditions for its existence and avoid unfavorable ones, and also immeasurably expands the perception of objects and events of the surrounding world and the range of activity. The role of unconditioned reflexes in V. n. d. lies not only in the fact that on their basis all conditioned reflexes are ultimately developed, but also in the fact that unconditioned reflexes, especially their complex forms, act as a concentrated expression of the hereditarily fixed experience of previous generations, as a manifestation of genetic memory. 11

The relative importance of conditioned and unconditioned reflexes in V. n. d. changes in the process of historical development of the animal world. In the behavior of invertebrates and lower vertebrates, innate forms of nervous activity prevail over acquired ones; During the evolution of animals, acquired forms of nervous activity gradually gain predominance, becoming the dominant forms of nervous activity. e. Moreover, these forms themselves undergo significant changes: conditioned reflexes continuously become more complex and improved, their composition is constantly enriched, conditioned reflex activity as a whole becomes an increasingly more advanced and active means of adaptation to the environment, i.e., it ensures the possibility of the organism’s existence in all a wider range of environmental conditions.

conclusions

Changing environmental conditions require constant adaptation of the body to them. Such reactions in humans are ensured by the reflex activity of the nervous system. In the process of evolution, firmly fixed, inherited reflexes arose that provide the adaptive capabilities of the organism, unite and coordinate its functions. I. P. Pavlov called these reflexes unconditional. Unconditioned reflexes are innate reactions of the body, fixed and carried out with the help of the nervous system. They are fully formed by the time of birth, carried out by a reflex arc ready at the time of birth, and are characteristic of all representatives of this species. Unconditioned reflexes are constant and stable throughout life, carried out with the participation of the spinal cord, brain stem and subcortical nuclei. The biological role of these reflexes is that they ensure the functioning of the body immediately after birth, and subsequently are the main one for the development of conditioned reflexes. Examples of unconditioned reflexes include sucking in newborns, blinking, salivation when food enters the mouth, etc.

Conditioned reflexes are acquired during the individual development of the organism throughout life based on interaction with the environment. Conditioned reflexes are changeable; they can arise, become stronger, or be lost if the need for them disappears. Conditioned reflexes are individual; a reflex may be present in some individuals of a species and absent in others. These reflexes are mobile; they can be formed, if necessary, when any receptor apparatus is irritated. Conditioned reflexes are developed with the participation of the cerebral cortex.

The biological role of the conditioned reflex is to expand the range of adaptive capabilities of the body to a wide variety of conditions. Conditioned reflexes form the basis of training, education, development of speech and thinking in a child, skills in labor, social and creative activities of a person.

List of used literature

1. Asratyan E. A., Essays on the physiology of conditioned reflexes, M., 2006.
2. Belenkov N. Yu., Conditioned reflex and subcortical formations of the brain, M., 2005.
3. Beritov I. S., Structure and functions of the cerebral cortex, M., 2005.
4. Kogan A. B., Electrophysiological study of the central mechanisms of some complex reflexes, M., 2004.
5. Konorski Yu., Integrative brain activity, trans. from English, M., 2004.
6. Livanov M. N., Spatial organization of brain processes, M., 2002.
7. Milner P., Physiological Psychology, trans. With. English, M., 2003.
8. Pavlov I. P., Complete. collection tr., vol. 3, M. L., 2006.
9. Electrical activity of the brain during the formation of simple forms of temporary connection, M., 2006.

1 Anokhin P.K., Biology and neurophysiology of the conditioned reflex, M., 2006.

2 Dmitriev A. S., Physiology of higher nervous activity, M., 2006.

3 Voronin L.G., Course of lectures on the physiology of higher nervous activity. M. 2006.

4 Physiology of higher nervous activity, part 12, L., 2004.

5 Voronin L.G., Course of lectures on the physiology of higher nervous activity. M. 2006.

6 Physiology of higher nervous activity, part 12, L., 2004.

7 Rudenko L.P., Functional organization of elementary and complex forms of conditioned reflex activity, M., 2004.

8 Dmitriev A. S., Physiology of higher nervous activity, M., 2006.

9 Voronin L.G., Course of lectures on the physiology of higher nervous activity. M. 2006.

10 Physiology of higher nervous activity, part 12, L., 2004.

11 Anokhin P.K., Biology and neurophysiology of the conditioned reflex, M., 2006.

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Unconditioned reflexes provide the body with maintaining vital functions in relatively constant conditions of existence.

Basic unconditioned reflexes:

• · food(chewing, sucking, swallowing, secretion of saliva, gastric juice, etc.),
• · defensive(pulling a hand away from a hot object, coughing, sneezing, blinking),
• · sexual and etc.

Conditioned reflexes provide the body with a more perfect adaptation to changing conditions of existence.

They are developed on the basis of unconditional ones. An example of the formation of a conditioned reflex reaction would be the combination of a sound stimulus (for example, a bell) with feeding an animal. After a number of repetitions of this combination, the animal will experience salivation that occurs at the sound of the bell, even in the absence of food presentation.

Inhibition processes. Along with excitation, inhibition is of great importance for the reflex reaction. In some cases, the excitation of one neuron is not only not transmitted to another, but even inhibits it, that is, causes inhibition. Inhibition does not allow excitation to spread indefinitely in the nervous system. The relationship between excitation and inhibition ensures the coordinated functioning of all organs and the body as a whole.

To ensure adequate behavior, not only the ability to form conditioned reflexes is required, but also the ability to eliminate conditioned reflex reactions, the need for which has disappeared. This is ensured by braking processes.

Inhibition of conditioned reflexes can be unconditioned (external and transcendental) and conditioned (internal).

• · External inhibition occurs if, at the moment of action of the conditioned signal, an extraneous stimulus begins to act.
• · Excessive inhibition is observed when the intensity of the conditioned signal exceeds a certain limit. In both cases, the conditioned reaction is inhibited.
• · Internal inhibition manifests itself in the extinction of a conditioned reflex over time if it is not reinforced by the action of unconditioned reflexes (that is, if the conditions for its development are not repeated).

There are different classifications of conditioned reflexes.

Formation and inhibition of conditioned reflexes. The main conditions for the formation of conditioned reflexes include:

• · repeated combination of a previously indifferent (neutral) stimulus (sound, light, tactile, etc.) with the action of a reinforcing unconditioned (or well-developed conditioned) stimulus;
• · slight precedence in time of the indifferent stimulus in relation to the reinforcing stimulus;
• · sufficient excitability of the unconditioned reaction (active state of the cerebral cortex);
• · absence of extraneous irritation or other activity during the development of the reflex.

Features of human higher nervous activity. Conditioned reflex activity is common to both higher animals and humans. Both humans and animals have the first signaling system - the analysis and synthesis of specific signals, objects and phenomena of the external world. In addition, a person develops a second signaling system - speech, writing, abstract thinking. Its emergence is associated with collective work activity and life in society. Words are signals of the second signaling system. The second signaling system is socially conditioned - outside of society, without communication with other people, it is not formed. Some animals are capable of making sounds. However, a word for a person is not just a combination of certain sounds, but, first of all, its meaning, the meaning contained in it. With the help of words, people are able to exchange thoughts. Speech and writing allow a person to accumulate and pass on experience from generation to generation. The appearance of speech led to the emergence of abstract thinking - thinking with the help of abstract concepts abstracted from specific objects and phenomena.

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

The concept of an unconditioned reflex

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

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

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

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

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

Properties of unconditioned reflexes

The characteristics of unconditioned reflexes include several mandatory points:

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

The meaning of reflexes

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

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

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

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

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

The body lives surrounded by external factors that are constantly changing, and it is necessary to adapt to them. This is where higher nervous activity in the form of conditioned reflexes comes to the fore.

For the body they have the following meaning:

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

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

Classification of unconditioned reflexes

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

Pavlov also divided all unconditioned reflexes into:

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

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

The first group of reactions has two characteristics:

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

The third group also has its own characteristic features:

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

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

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

Each group has its own characteristics and differences.

Reflex acts

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

These include:

• Breath.
• Swallowing.
• Vomiting.

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

Behavioral reactions

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

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

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

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

Instincts

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

All instincts are associated with changing internal needs.

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

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

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

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

All of them can generate new needs:

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

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

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

Imprint

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

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

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

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

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

Congenital reflexes of an infant

After birth, the baby goes through a complex developmental path that consists of several stages. The degree and speed of mastery of various skills will directly depend on the state of the nervous system. The main indicator of its maturity are the unconditioned reflexes of the newborn.

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

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

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

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

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

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

Oral segmental reflexes

This type of reflexes includes:

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

Spinal motor automatisms

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

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

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

Differences between conditioned and unconditioned reflexes

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

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

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

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

Unconditioned reflexes (for example, sucking, swallowing, pupillary reflexes, coughing, sneezing, etc.) are preserved in animals without cerebral hemispheres. They are formed in response to certain stimuli. Thus, the salivation reflex occurs when the taste buds of the tongue are irritated by food. The resulting excitation 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 through the motor nerves to the salivary glands, causing salivation. On the basis of unconditioned reflexes, the regulation and coordinated activity of different organs and their systems is carried out, and the very existence of the organism is supported.

In changing environmental conditions, the preservation of the vital activity of the organism and adaptive behavior is carried out through 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 a species one or another reflex may be present, while in others it may be absent.

Unconditioned reflexes. The meaning of unconditioned reflexes

Maintaining a constant 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 great shock to a child's body. From a vegetative, plant existence in a relatively constant environment (the mother’s body), he suddenly moves into completely new conditions of the air environment with an endless number of frequently changing stimuli, into a world where he has to become a rational person.

A child’s life in new conditions is ensured by innate mechanisms. He is born with a certain readiness of the nervous system to adapt the body to external conditions. So, immediately after birth, reflexes are activated, ensuring the functioning of the main systems of the body (breathing, blood circulation - note biofile.ru). In the first days, you can also note the following. Severe skin irritation (an injection, for example) causes a protective withdrawal, the flashing of an object in front of the face causes squinting, and a sharp increase in the brightness of the light causes constriction of the pupil, etc. These reactions are protective reflexes.

In addition to protective ones, reactions aimed at contact with an irritant can be found in newborns. These are orientation 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 children's room of the 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. Orienting food reflexes are also easily evoked. Touching the corners of the lips or the cheeks causes a searching reaction in a hungry child: he turns his head towards the stimulus and opens his mouth.
In addition to those listed, the child exhibits several more innate reactions: sucking reflex - the child immediately begins to suck on an object placed in his mouth; clinging reflex - touching the palm causes a grasping reaction; repulsion reflex (crawling) - when touching the soles of the feet and some other reflexes.

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

Most of the innate reactions are necessary for the child to live. They help him 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 blood vessels of the placenta - the child's place - nutrients and oxygen enter the blood of the fetus from the mother's blood), then after birth the child's body switches to pulmonary respiration and so-called oral nutrition (through the mouth and gastrointestinal tract). -intestinal tract). This adaptation occurs reflexively. After the lungs are filled with air, an entire system of muscles is involved in rhythmic breathing movements. Breathing is easy and free. Feeding occurs using the sucking reflex. The innate actions included in the sucking reflex are, at first, poorly coordinated with each other: when sucking, the child chokes, suffocates, and quickly runs out of strength. All his activity is aimed at sucking for the sake of saturation. The establishment of reflex automaticity of thermoregulation is also very important: the child’s body adapts better and better to temperature changes.

Education 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. To do 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 for the formation of a conditioned reflex consists of establishing a temporary connection (closure) between two foci of excitation in the mayor of the brain. For the example considered, such foci are the centers of salivation and hearing.
The arc of the conditioned reflex, in contrast to that of the unconditioned reflex, is significantly more 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 the 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 strictly limited orientation in the environment, then conditioned reflexes provide universal orientation.

The biological significance of conditioned reflexes in the life of humans and animals is enormous, since they ensure their adaptive behavior - they allow them 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, behavioral experience is acquired, thanks to which an adult organism turns out to be better adapted to the environment than a 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 body reacts not only directly to unconditioned stimuli, but also to the possibility of their action on it; reactions appear some time before unconditional irritation. In this way, the body is prepared in advance for the actions that it has to carry out in a given situation. Conditioned reflexes contribute to finding food, avoiding danger in advance, eliminating harmful influences, etc.

The adaptive significance of conditioned reflexes is also manifested in the fact that the precedence of conditioned stimulation by an unconditioned one strengthens the unconditioned reflex and accelerates its development.