The concept of reflex - unconditioned and conditioned reflexes. Congenital and acquired forms of behavior

UNCONDITIONED REFLEX (specific, innate reflex) - a constant and innate reaction of the body to certain influences of the external world, carried out with the help of the nervous system and does not require special conditions for its occurrence. The term was introduced by I.P. Pavlov while studying the physiology of higher nervous activity. An unconditioned reflex occurs unconditionally if adequate stimulation is applied to a certain receptor surface. In contrast to this unconditionally occurring reflex, I.P. Pavlov discovered a category of reflexes, for the formation of which a number of conditions must be met - a conditioned reflex (see).

A physiological feature of the unconditioned reflex is its relative constancy. An unconditioned reflex always occurs with corresponding external or internal stimulation, manifesting itself on the basis of innate nerve connections. Since the constancy of the corresponding unconditioned reflex is the result of the phylogenetic development of a given animal species, this reflex received the additional name “species reflex”.

The biological and physiological role of the unconditioned reflex is that, thanks to this innate reaction, animals of a given species adapt (in the form of expedient acts of behavior) to the constant factors of existence.

The division of reflexes into two categories - unconditioned and conditioned - corresponds to two forms of nervous activity in animals and humans, which were clearly distinguished by I. P. Pavlov. The totality of the unconditioned reflex constitutes lower nervous activity, while the totality of acquired, or conditioned, reflexes constitutes higher nervous activity (see).

From this definition it follows that the unconditioned reflex, in its physiological meaning, along with the implementation of constant adaptive reactions of the animal in relation to the action of environmental factors, also determines those interactions of nervous processes that in total direct the internal life of the organism. I. P. Pavlov attached especially great importance to this last property of the unconditioned reflex. Thanks to innate nerve connections that ensure the interaction of organs and processes within the body, animals and humans acquire an accurate and stable course of basic vital functions. The principle on the basis of which these interactions and integration of activities within the body are organized is self-regulation of physiological functions (see).

The classification of unconditioned reflexes can be built on the basis of the specific properties of the current stimulus and the biological meaning of the responses. It was on this principle that the classification was built in the laboratory of I. P. Pavlov. In accordance with this, there are several types of unconditioned reflex:

1. Food, the causative agent of which is the action of nutrients on the receptors of the tongue and on the basis of the study of which all the basic laws of higher nervous activity are formulated. Due to the spread of excitation from the receptors of the tongue towards the central nervous system, excitation of branched innate nervous structures occurs, which generally constitute the food center; As a result of such a fixed relationship between the central nervous system and the working peripheral apparatuses, responses of the whole organism are formed in the form of an unconditioned food reflex.

2. Defensive, or, as it is sometimes called, protective reflex. This unconditioned reflex has a number of forms depending on which organ or part of the body is in danger. For example, applying painful stimulation to a limb causes the limb to be withdrawn, which protects it from further destructive effects.

In a laboratory setting, electric current from appropriate devices (Dubois-Reymond induction coil, city current with a corresponding voltage drop, etc.) is usually used as a stimulus that evokes a defensive unconditioned reflex. If air movement directed at the cornea of the eye is used as a stimulus, then the defensive reflex is manifested by closing the eyelids - the so-called blink reflex. If the irritants are potent gaseous substances that pass through the upper respiratory tract, then the protective reflex will be a delay in respiratory excursions of the chest. The most common type of protective reflex in the laboratory of I.P. Pavlov is the acid protective reflex. It is expressed by a strong rejection reaction (vomiting) in response to the infusion of a solution of hydrochloric acid into the animal’s oral cavity.

3. Sexual, which certainly occurs in the form of sexual behavior in response to an adequate sexual stimulus in the form of an individual of the opposite sex.

4. Orienting-exploratory, which is manifested by a rapid movement of the head towards the external stimulus that is acting at the moment. The biological meaning of this reflex consists in a detailed examination of the stimulus that acted and, in general, the external environment in which this stimulus arose. Thanks to the presence of innate pathways of this reflex in the central nervous system, the animal is able to respond expediently to sudden changes in the external world (see Orienting-exploratory reaction).

5. Reflexes from internal organs, reflexes during irritation of muscles and tendons (see Visceral reflexes, Tendon reflexes).

A common property of all unconditioned reflexes is that they can serve as the basis for the formation of acquired, or conditioned, reflexes. Some of the unconditioned reflexes, for example, defensive, lead to the formation of conditioned reactions very quickly, often after just one combination of any external stimulus with painful reinforcement. The ability of other unconditioned reflexes, for example, blinking or knee reflexes, to form temporary connections with an indifferent external stimulus is less pronounced.

It should also be taken into account that the speed of development of conditioned reflexes is directly dependent on the strength of the unconditioned stimulus.

The specificity of unconditioned reflexes lies in the exact correspondence of the body's response to the nature of the stimulus acting on the receptor apparatus. So, for example, when the taste buds of the tongue are irritated by a certain food, the reaction of the salivary glands in terms of the quality of the secretion is in strict accordance with the physical and chemical properties of the food taken. If the food is dry, then watery saliva is released, but if the food is sufficiently moistened, but consists of pieces (for example, bread), the unconditioned salivary reflex will manifest itself in accordance with this quality of food: saliva will contain a large amount of mucous glucoprotein - mucin, which prevents food injury ways.

Fine receptor assessment is associated with a lack of a particular substance in the blood, for example, the so-called calcium starvation in children during the period of bone formation. Since calcium selectively passes through the capillaries of developing bones, eventually its amount becomes below a constant level. This factor is a selective irritant of some specific cells of the hypothalamus, which in turn keeps the tongue receptors in a state of increased excitability. This is how children develop a desire to eat plaster, whitewash and other minerals containing calcium.

Such an appropriate correspondence of the unconditioned reflex to the quality and strength of the stimulus that acts depends on the extremely differentiated effect of nutrients and their combinations on the receptors of the tongue. Receiving these combinations of afferent excitations from the periphery, the central apparatus of the unconditioned reflex sends efferent excitations to the peripheral apparatuses (glands, muscles), leading to the formation of a certain composition of saliva or the occurrence of movements. In fact, the composition of saliva can be easily changed through a relative change in the production of its main ingredients: water, proteins, salts. It follows from this that the central salivary apparatus can vary the quantity and quality of excited elements depending on the quality of excitation coming from the periphery. The correspondence of an unconditioned response to the specificity of the applied stimulation can go very far. I.P. Pavlov developed the idea of the so-called digestive warehouse of certain unconditioned reactions. For example, if you feed an animal a certain type of food for a long time, the digestive juices of its glands (stomach, pancreas, etc.) eventually acquire a certain composition in terms of the amount of water, inorganic salts, and especially the activity of enzymes. Such a “digestive warehouse” cannot but be recognized as an expedient adaptation of innate reflexes to the established constancy of food reinforcement.

At the same time, these examples indicate that the stability, or immutability, of the unconditioned reflex is only relative. There is reason to think that already in the first days after birth, the specific “mood” of the tongue receptors is prepared by the embryonic development of animals, which ensures the successful selection of nutrients and the planned course of unconditioned reactions. So, if the percentage of sodium chloride in the mother's milk that a newborn baby is fed on is increased, then the baby's sucking movements are immediately inhibited, and in some cases the baby actively throws out the formula that has already been taken. This example convinces us that the innate properties of food receptors, as well as the properties of intranervous relationships, most accurately reflect the needs of the newborn.

Methodology for using unconditioned reflexes

Since in the practice of work on higher nervous activity, the unconditioned reflex is a reinforcing factor and the basis for the development of acquired, or conditioned, reflexes, the question of methodological techniques for using the unconditioned reflex becomes especially important. In experiments on conditioned reflexes, the use of an unconditioned food reflex is based on feeding the animal with certain nutrients from an automatically fed feeder. With this method of using an unconditioned stimulus, the direct effect of food on the receptors of the animal’s tongue is inevitably preceded by a number of side irritations of the receptors related to various analyzers (see).

No matter how technically perfect the feeding of the feeder is, it certainly produces some kind of noise or knocking and, therefore, this sound stimulus is the inevitable precursor of the truest unconditioned stimulus, that is, the stimulus of the taste buds of the tongue. To eliminate these defects, a technique was developed for the direct introduction of nutrients into the oral cavity, while irrigation of the taste buds of the tongue, for example, with a sugar solution, is a direct unconditioned stimulus, not complicated by any side agent.

It should be noted, however, that under natural conditions animals and humans never receive food into the oral cavity without preliminary sensations (sight, smell of food, etc.). Therefore, the method of directly introducing food into the mouth has some abnormal conditions and the animal’s reaction to the unusual nature of such a procedure.

In addition to this use of an unconditioned stimulus, there are a number of techniques in which the animal itself receives food with the help of special movements. These include a wide variety of devices with the help of which an animal (rat, dog, monkey) receives food by pressing the corresponding lever or button - the so-called instrumental reflexes.

The methodological features of reinforcement with an unconditioned stimulus have an undoubted influence on the experimental results obtained, and, therefore, the assessment of the results should be made taking into account the type of unconditioned reflex. This especially applies to the comparative assessment of the food and defensive unconditioned reflex.

While reinforcement with a food unconditioned stimulus is a factor of positive biological significance for an animal (I.P. Pavlov), on the contrary, reinforcement with a painful stimulus is a stimulus for a biologically negative unconditioned reaction. It follows that “non-reinforcement” of a well-established conditioned reflex with an unconditioned stimulus in both cases will have the opposite biological sign. While non-reinforcement of a conditioned stimulus with food leads to a negative and often aggressive reaction in the experimental animal, on the contrary, non-reinforcement of a conditioned signal with electric current leads to a completely distinct biological positive reaction. These features of the animal’s attitude to the non-reinforcement of a conditioned reflex by one or another unconditioned stimulus can be clearly identified by such a vegetative component as breathing.

Composition and localization of unconditioned reflexes

The development of experimental technology has made it possible to study the physiological composition and localization of the unconditioned food reflex in the central nervous system. For this purpose, the very effect of an unconditioned food stimulus on the receptors of the tongue was studied. An unconditioned stimulus, regardless of its nutritional properties and consistency, primarily irritates the tactile receptors of the tongue. This is the fastest type of excitation that is part of unconditioned stimulation. Tactile receptors produce the fastest and highest-amplitude type of nerve impulses, which first spread along the lingual nerve to the medulla oblongata, and only after a few fractions of a second (0.3 seconds) nerve impulses from temperature and chemical stimulation of the tongue receptors arrive there. This feature of the unconditioned stimulus, manifested in the sequential excitation of various receptors of the tongue, has enormous physiological significance: conditions are created in the central nervous system for signaling with each previous stream of impulses about subsequent stimuli. Thanks to such relationships and characteristics of tactile excitation, depending on the mechanical qualities of a given food, in response only to these excitations, salivation can occur before the chemical qualities of the food act.

Special experiments carried out on dogs and studies of the behavior of newborn children have shown that such relationships between individual parameters of the unconditioned stimulus are used in the adaptive behavior of the newborn.

For example, in the first days after birth, the decisive stimulus for a child’s food intake is its chemical qualities. However, after a few weeks, the leading role passes to the mechanical properties of food.

In the lives of adults, information about the tactile parameters of food is faster than information about chemical parameters in the brain. Thanks to this pattern, the sensation of “porridge”, “sugar”, etc. is born before the chemical signal arrives in the brain. According to the teachings of I.P. Pavlov on the cortical representation of the unconditioned reflex, each unconditioned irritation, along with the inclusion of the subcortical apparatuses, has its own representation in the cerebral cortex. Based on the above data, as well as oscillographic and electroencephalographic analysis of the spread of unconditioned excitation, it was established that it does not have a single point or focus in the cerebral cortex. Each of the fragments of unconditional excitation (tactile, temperature, chemical) is addressed to different points of the cerebral cortex, and only the almost simultaneous stimulation of these points of the cerebral cortex establishes a systemic connection between them. These new data correspond to I. P. Pavlov’s ideas about the structure of the nerve center, but require a change in existing ideas about the “cortical point” of the unconditioned stimulus.

Studies of cortical processes using electrical devices have shown that an unconditioned stimulus comes to the cerebral cortex in the form of a very generalized flow of ascending excitations, and, obviously, to every cell of the cortex. This means that not a single excitation of the sensory organs that preceded the unconditioned stimulus can “escape” its convergence with the unconditioned excitation. These properties of the unconditioned stimulus strengthen the idea of “convergent closure” of the conditioned reflex.

Cortical representations of unconditioned reactions are cellular complexes that take an active part in the formation of a conditioned reflex, that is, in the closing functions of the cerebral cortex. By its nature, the cortical representation of the unconditioned reflex must be afferent in nature. As is known, I.P. Pavlov considered the cerebral cortex “an isolated afferent section of the central nervous system.”

Complex unconditioned reflexes. I.P. Pavlov identified a special category of unconditioned reflex, into which he included innate activities that are cyclical and behavioral in nature - emotions, instincts and other manifestations of complex acts of innate activity of animals and humans.

According to the initial opinion of I.P. Pavlov, complex unconditioned reflexes are a function of the “proximal subcortex”. This general expression refers to the thalamus, hypothalamus and other parts of the interstitial and midbrain. However, later, with the development of ideas about the cortical representations of the unconditioned reflex, this point of view was transferred to the concept of complex unconditioned reflexes. Thus, a complex unconditioned reflex, for example, an emotional discharge, has a specific subcortical part, but at the same time the very course of this complex unconditioned reflex at each individual stage has a representation in the cerebral cortex. This point of view of I.P. Pavlov was confirmed by research in recent years using the neurography method. It has been shown that a number of cortical areas, for example, the orbital cortex, the limbic area, are directly related to the emotional manifestations of animals and humans.

According to I.P. Pavlov, complex unconditioned reflexes (emotions) represent a “blind force” or “the main source of strength” for cortical cells. The propositions expressed by I. P. Pavlov about complex unconditioned reflexes and their role in the formation of conditioned reflexes at that time were only at the stage of the most general development, and only in connection with the discovery of the physiological characteristics of the hypothalamus, the reticular formation of the brain stem, did a more in-depth study of this problems.

From the point of view of I.P. Pavlov, the instinctive activity of animals, which includes several different stages of animal behavior, is also a complex unconditioned reflex. The features of this type of unconditioned reflex are that the individual stages of performing any instinctive action are connected with each other according to the principle of a chain reflex; however, it was later shown that each such stage of behavior must necessarily have a reverse afferentation) from the results of the action itself, that is, carry out the process of comparing the actually obtained result with the previously predicted one. Only after this can the next stage of behavior be formed.

In the process of studying the unconditioned pain reflex, it was revealed that pain excitation undergoes significant transformations at the level of the brain stem and hypothalamus. From these structures, unconditioned excitation generally covers all areas of the cerebral cortex simultaneously. Thus, along with the mobilization in the cerebral cortex of systemic connections that are characteristic of a given unconditional excitation and form the basis of the cortical representation of the unconditioned reflex, unconditioned stimulation also produces a generalized effect on the entire cerebral cortex. In electroencephalographic analysis of cortical activity, this generalized effect of an unconditioned stimulus on the cerebral cortex manifests itself in the form of desynchronization of cortical wave electrical activity. The conduction of unconditioned painful excitation to the cerebral cortex can be blocked at the level of the brain stem using a special substance - aminazine. After the introduction of this substance into the blood, even a strong damaging (nociceptive) unconditioned excitation (hot water burn) does not reach the cerebral cortex and does not change its electrical activity.

Development of unconditioned reflexes in the embryonic period

The innate nature of the unconditioned reflex is especially clearly revealed in studies of the embryonic development of animals and humans. At different stages of embryogenesis, each stage of the structural and functional formation of the unconditioned reflex can be traced. The vital functional systems of a newborn are completely consolidated at the time of birth. Individual parts of a sometimes complex unconditioned reflex, such as the sucking reflex, involve different parts of the body, often at a considerable distance from each other. Nevertheless, they are selectively united by various connections and gradually form a functional whole. The study of the maturation of the unconditioned reflex in embryogenesis makes it possible to understand the constant and relatively unchangeable adaptive effect of the unconditioned reflex upon application of the corresponding stimulus. This property of an unconditioned reflex is associated with the formation of interneuronal relationships based on morphogenetic and genetic patterns.

The maturation of the unconditioned reflex in the embryonic period is not the same for all animals. Since the maturation of the functional systems of the embryo has the most important biological meaning in preserving the life of a newborn of a given species of animal, then, depending on the characteristics of the conditions of existence of each species of animal, the nature of structural maturation and the final formation of the unconditioned reflex will exactly correspond to the characteristics of the given species.

For example, the structural design of spinal coordination reflexes turns out to be different in birds that, after hatching from an egg, immediately become completely independent (chicken), and in birds that, after hatching from an egg, are helpless for a long time and are in the care of their parents (rook). While a chick stands on its feet immediately after hatching and uses them completely freely every other day, in a rook, on the contrary, the forelimbs, that is, the wings, come into action first.

This selective growth of the nervous structures of the unconditioned reflex occurs even more clearly in the development of the human fetus. The very first and clearly visible motor reaction of the human fetus is the grasping reflex; it is detected already in the 4th month of intrauterine life and is caused by the application of any hard object to the palm of the fetus. Morphological analysis of all links of this reflex convinces us that, before it is revealed, a number of nerve structures differentiate into mature neurons and unite with each other. Myelination of the nerve trunks related to the finger flexors begins and ends earlier than this process unfolds in the nerve trunks of other muscles.

Phylogenetic development of unconditioned reflexes

According to the well-known position of I.P. Pavlov, unconditioned reflexes are a consequence of the consolidation by natural selection and heredity of those reactions acquired over thousands of years that correspond to repeated environmental factors and are useful for a given species.

There is reason to assert that the most rapid and successful adaptations of the organism may depend on favorable mutations, which are subsequently selected by natural selection and are already inherited.

Bibliography: Anokhin P.K. Biology and neurophysiology of the conditioned reflex, M., 1968, bibliogr.; Afferent link of interoceptive reflexes, ed. I. A. Bulygina, M., 1964; Vedyaev F. P. Subcortical mechanisms of complex motor reflexes, JI., 1965, bibliogr.; Vinogradova O. S. Orienting reflex and its neurophysiological mechanisms, M., 1961, bibliogr.; Groysman S. D. and Dekush P. G. An attempt at a quantitative study of intestinal reflexes, Pat. physiol. and Experiment, ter., v. 3, p. 51, 1974, bibliogr.; Orbeli JI. A. Questions of higher nervous activity, p. 146, M.-JI., 1949; Pavlov I.P. Complete works, vol. 1-6, M., 1951 - 1952; Petukhov B. N. Closure after loss of basic unconditioned reflexes, Proceedings Center, Institute of Improvements. doctors, vol. 81, p. 54, M., 1965, bibliogr.; S a l h e nko I. N. Hidden periods of myotatic reflexes that ensure motor interactions of people, Physiol. human, vol. 1, Jvft 2, p. 317, 197 5, bibliography; Sechenov I. M. Reflexes of the brain, M., 1961; Slonim A.D. Fundamentals of general economic physiology of mammals, p. 72, M,-JI., 1961, bibliogr.; Human Physiology, ed. E. B. Babsky, p. 592, M., 1972; Frankstein S.I. Respiratory reflexes and mechanisms of shortness of breath, M., 1974, bibliogr.; Sh u s t i n N. A. Analysis of unconditioned reflexes in the light of the doctrine of the dominant, Physiol, journal. USSR, vol. 61, JSft 6, p. 855, 1975, bibliogr.; Human reflexes, pathophysiology of motor systems, ed. by J. E. Desment, Basel a. o., 1973; Mechanisms of orienting reactions in man, ed. by I. Ruttkay-Nedecky a. o., Bratislava, 1967.

Our nervous system is a complex mechanism of interaction between neurons that send impulses to the brain, and it, in turn, controls all organs and ensures their functioning. This process of interaction is possible due to the presence in humans of basic, inextricable acquired and innate forms of adaptation - conditioned and unconditioned reactions. A reflex is a conscious response of the body to certain conditions or stimuli. Such coordinated work of nerve endings helps us interact with the world around us. A person is born with a set of simple skills - this is called an example of such behavior: the ability of a baby to suckle at the mother's breast, swallow food, blink.

and animal

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

Unconditioned reflexes

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

Food.
Approximate.
Protective.
Sexual

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

Defensive reactions

These types of reactions to external stimuli are inherited and are called natural instincts. Evolution has given us the need to protect ourselves and take care of our safety in order to survive. Therefore, we have learned to instinctively react to danger; this is an unconditioned reflex. Example: Have you ever noticed how your head tilts when someone raises a fist over it? When you touch a hot surface, your hand jerks back. This behavior is also called unlikely that a person in his right mind would try to jump from a height or eat unfamiliar berries in the forest. The brain immediately starts the process of processing information that will make it clear whether it is worth risking your life. And even if it seems to you that you are not thinking about it, instinct immediately kicks in.

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

Delayed reactions

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

Sexual reflex

But this reflex is unconscious and unconditional, it is aimed at procreation. It occurs during puberty, that is, only when the body is ready for procreation. Scientists say that this reflex is one of the most powerful; it determines the complex behavior of a living organism and subsequently triggers the instinct to protect its offspring. Despite the fact that all these reactions are initially characteristic of humans, they are triggered in a certain order.

Conditioned reflexes

In addition to the instinctive reactions that we have at birth, a person needs many other skills to better adapt to the world around him. Acquired behavior is formed in both animals and people throughout life; this phenomenon is called “conditioned reflexes”. Examples: when you see food, salivation occurs; when you follow a diet, you feel hungry at a certain time of the day. This phenomenon is formed by a temporary connection between the center or vision) and the center of the unconditioned reflex. An external stimulus becomes a signal for a specific action. Visual images, sounds, smells can form lasting connections and give rise to new reflexes. When someone sees a lemon, salivation may begin, and when a strong smell or contemplation of an unpleasant picture causes nausea, nausea may occur - these are examples of conditioned reflexes in humans. Note that these reactions can be individual for each living organism; temporary connections are formed in the cerebral cortex and send a signal when an external stimulus occurs.

Throughout life, conditioned reactions can arise and also disappear. It all depends on For example, in childhood a child reacts to the sight of a bottle of milk, realizing that it is food. But when the baby grows up, this object will not form an image of food for him; he will react to a spoon and a plate.

Heredity

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

Animal reactions

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

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

Resume

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

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

Unconditioned reflexes	Conditioned reflexes
1. Congenital, genetically programmed reactions of the body, characteristic of all animals and humans. 2. Reflex arcs of these reflexes are formed in the process prenatal development, sometimes in postnatal period. Ex: sexual congenital reflexes are finally formed in a person only at the time of puberty in adolescence. They have little changing reflex arcs passing through the subcortical sections of the central nervous system. The participation of the cortex in the course of many unconditioned reflexes is optional. 3. Are species-specific, i.e. formed in the process of evolution and are characteristic of all representatives of this species. 4. Regarding permanent and persist throughout the life of the organism. 5. Occur on specific(adequate) stimulus for each reflex. 6. Reflex centers are at the level spinal cord and in brain stem	1. Purchased reactions of higher animals and humans developed as a result of learning (experience). 2. Reflex arcs are formed during the process postnatal development. They are characterized by high mobility and the ability to change under the influence of environmental factors. Reflex arcs of conditioned reflexes pass through the highest part of the brain - the cerebral cortex. 3. Are individual, i.e. arise on the basis of life experience. 4. Fickle and, depending on certain conditions, they can be developed, consolidated or fade away. 5. Can form on any stimulus perceived by the body 6. Reflex centers are located in cerebral cortex
Example: food, sexual, defensive, indicative.	Example: salivation to the smell of food, precise movements when writing, playing musical instruments.
Meaning: help survival, this is “putting the experience of ancestors into practice”	Meaning: help adapt to changing environmental conditions.

Classification of unconditioned reflexes.

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

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

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

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

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

5.Sexual reflexes.

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

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

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

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

Physiological mechanisms of formation of conditioned reflexes

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

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

The excitation that occurs in the visual receptors at the sight of a lemon travels along centripetal fibers to the visual cortex of the cerebral hemispheres (occipital region) and causes excitation cortical neurons- arises source of excitation.

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

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

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

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

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

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

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

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

4. Repetition.

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

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

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

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

Classifications of conditioned reflexes

Due to their large number, it is difficult.

According to the location of the receptor:

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

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

3. proprioceptive, arising from irritation of muscle receptors.

By the nature of the receptor:

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

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

By action sign:

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

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

By the nature of the response:

1. motor;

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

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

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

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

Higher nervous activity is a system that allows the human and animal body to adapt to variable environmental conditions. Evolutionarily, vertebrates have developed a number of innate reflexes, but their existence is not enough for successful development.

In the process of individual development, new adaptive reactions are formed - these are conditioned reflexes. Outstanding domestic scientist I.P. Pavlov is the founder of the doctrine of unconditioned and conditioned reflexes. He formed the conditioned reflex theory, which states that the acquisition of a conditioned reflex is possible through the action of a physiologically indifferent irritation on the body. As a result, a more complex system of reflex activity is formed.

I.P. Pavlov - the founder of the doctrine of unconditioned and conditioned reflexes

An example of this is Pavlov's study of dogs that salivated in response to a sound stimulus. Pavlov also showed that innate reflexes are formed at the level of subcortical structures, and new connections are formed in the cerebral cortex throughout the life of an individual under the influence of constant stimulation.

Conditioned reflexes

Conditioned reflexes are formed on the basis of unconditional ones, in the process of individual development of the organism, against the background of a changing external environment.

Reflex arc The conditioned reflex consists of three components: afferent, intermediate (intercalary) and efferent. These links carry out the perception of irritation, the transmission of impulses to cortical structures and the formation of a response.

The reflex arc of the somatic reflex performs motor functions (for example, flexion movement) and has the following reflex arc:

The sensitive receptor perceives the stimulus, then the impulse goes to the dorsal horns of the spinal cord, where the interneuron is located. Through it, the impulse is transmitted to the motor fibers and the process ends with the formation of movement - flexion.

A necessary condition for the development of conditioned reflexes is:

The presence of a signal that precedes the unconditional;
the stimulus that will cause the catch reflex must be inferior in strength to the biologically significant effect;
normal functioning of the cerebral cortex and the absence of distractions are mandatory.

Conditioned reflexes are not formed instantly. They are formed over a long period of time under constant observance of the above conditions. In the process of formation, the reaction either fades away or resumes again until stable reflex activity occurs.

An example of developing a conditioned reflex

Classification of conditioned reflexes:

A conditioned reflex formed on the basis of the interaction of unconditioned and conditioned stimuli is called first order reflex.
Based on the classical acquired reflex of the first order, it is developed second order reflex.

Thus, a third-order defensive reflex was formed in dogs, the fourth could not be developed, and the digestive reflex reached the second. In children, conditioned reflexes of the sixth order are formed, in an adult up to the twentieth.

The variability of the external environment leads to the constant formation of many new behaviors necessary for survival. Depending on the structure of the receptor that perceives the stimulus, conditioned reflexes are divided into:

Exteroceptive– irritation is perceived by body receptors and predominates among reflex reactions (taste, tactile);
intraceptive– caused by action on internal organs (changes in homeostasis, blood acidity, temperature);
proprioceptive– are formed by stimulating the striated muscles of humans and animals, providing motor activity.

There are artificial and natural acquired reflexes:

Artificial occur under the influence of stimulation that has no connection with the unconditioned stimulus (sound signals, light stimulation).

Natural are formed in the presence of a stimulus similar to the unconditioned one (the smell and taste of food).

Unconditioned reflexes

These are innate mechanisms that ensure the preservation of the integrity of the body, the homeostasis of the internal environment and, most importantly, reproduction. Congenital reflex activity is formed in the spinal cord and cerebellum and is controlled by the cerebral cortex. Typically, they last a lifetime.

Reflex arcs hereditary reactions are laid down before a person is born. Some reactions are characteristic of a certain age and then disappear (for example, in small children - sucking, grasping, searching). Others do not manifest themselves at first, but appear (sexually) after a certain period of time.

Unconditioned reflexes are characterized by the following features:

Occur regardless of the consciousness and will of a person;
specific - manifested in all representatives (for example, coughing, salivation at the smell or sight of food);
endowed with specificity - they appear when exposed to a receptor (the reaction of the pupil occurs when a beam of light is directed to photosensitive areas). This also includes salivation, secretion of mucous secretions and enzymes of the digestive system when food enters the mouth;
flexibility - for example, different foods lead to the secretion of a certain amount and varied chemical composition of saliva;
On the basis of unconditioned reflexes, conditioned ones are formed.

Unconditioned reflexes are needed to fulfill the needs of the body; they are constant, but as a result of illness or bad habits they can disappear. So, when the iris of the eye is diseased, when scars form on it, the reaction of the pupil to light exposure disappears.

Classification of unconditioned reflexes

Congenital reactions are classified into:

Simple(quickly remove your hand from the hot object);
complex(maintaining homeostasis in situations of increased CO 2 concentration in the blood by increasing the frequency of respiratory movements);
the most complex(instinctive behavior).

Classification of unconditioned reflexes according to Pavlov

Pavlov divided innate reactions into food, sexual, protective, orientation, statokinetic, homeostatic.

TO food This includes the secretion of saliva at the sight of food and its entry into the digestive tract, the secretion of hydrochloric acid, gastrointestinal motility, sucking, swallowing, chewing.

Protective accompanied by contraction of muscle fibers in response to an irritating factor. Everyone is familiar with the situation when a hand reflexively withdraws from a hot iron or a sharp knife, sneezing, coughing, watery eyes.

Approximate occur when sudden changes occur in nature or in the body itself. For example, turning the head and body towards sounds, turning the head and eyes towards light stimuli.

Genital are associated with reproduction, preservation of the species, this also includes parental (feeding and caring for offspring).

Statokinetic provide upright posture, balance, and body movement.

Homeostatic– independent regulation of blood pressure, vascular tone, respiratory rate, heart rate.

Classification of unconditioned reflexes according to Simonov

Vital to maintain life (sleep, nutrition, saving energy) depend only on the individual.

Role-playing arise upon contact with other individuals (procreation, parental instinct).

The need for self-development(desire for individual growth, to discover new things).

Innate reflexes are activated when necessary due to a short-term violation of internal constancy or variability in the external environment.

Comparison table of conditioned and unconditioned reflexes

Comparison of the characteristics of conditioned (acquired) and unconditioned (innate) reflexes
Unconditional	Conditional
Congenital	Acquired during life
Present in all representatives of the species	Individual for each organism
Relatively constant	Appear and disappear with changes in the external environment
Formed at the level of the spinal cord and medulla oblongata	Carried out due to the work of the brain
Laid in utero	Produced against the background of innate reflexes
Occurs when a stimulus acts on certain receptor areas	Manifest under the influence of any stimulus that is perceived by the individual

Higher nervous activity operates in the presence of two interrelated phenomena: excitation and inhibition (congenital or acquired).

Braking

External unconditional inhibition(congenital) is carried out by the action of a very strong irritant on the body. The termination of the conditioned reflex occurs due to the activation of nerve centers under the influence of a new stimulus (this is transcendental inhibition).

When the organism under study is exposed to several stimuli at the same time (light, sound, smell), the conditioned reflex fades, but over time the indicative reflex is activated and the inhibition disappears. This type of braking is called temporary.

Conditioned inhibition(acquired) does not arise on its own, it must be developed. There are 4 types of conditioned inhibition:

Extinction (disappearance of a persistent conditioned reflex without constant reinforcement by the unconditioned);
differentiation;
conditional brake;
delayed braking.

Inhibition is a necessary process in our life. In its absence, many unnecessary reactions would occur in the body that would not be beneficial.

Example of external inhibition (dog's reaction to a cat and the SIT command)

The meaning of conditioned and unconditioned reflexes

Unconditioned reflex activity is necessary for the survival and preservation of the species. A good example is the birth of a child. In a new world for him, many dangers await him. Thanks to the presence of innate reactions, the cub can survive in these conditions. Immediately after birth, the respiratory system is activated, the sucking reflex provides nutrients, touching sharp and hot objects is accompanied by an instant withdrawal of the hand (manifestation of defensive reactions).

For further development and existence, one has to adapt to the surrounding conditions; conditioned reflexes help with this. They ensure rapid adaptation of the body and can be formed throughout life.

The presence of conditioned reflexes in animals gives them the ability to quickly respond to the voice of a predator and save their lives. When a person sees food, he or she performs conditioned reflex activity, salivation begins, and gastric juice begins to be produced for rapid digestion of food. The sight and smell of some objects, on the contrary, signals danger: the red cap of the fly agaric, the smell of spoiled food.

The importance of conditioned reflexes in the everyday life of humans and animals is enormous. Reflexes help you navigate the terrain, get food, and escape from danger while saving your life.

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, there are different reflexes: 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 a conditioned stimulus is not reinforced by an 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. Pavlov, 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. Unconditional inhibition of reflexes also includes some innate reactions. 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 the most adequate of all possible options, capable of protecting against excessive activity. This process also contributes to the exercise of so-called biological precautions.