(BR) is an innate and relatively constant species-specific, stereotypical, genetically fixed reaction of the body, reflexively arising in response to the specific influence of a stimulus, to the influence of a biologically significant (food) adequate for a given type of activity.
BR are associated with vital biological ones and are carried out within a stable reflex pathway. They form the basis of the mechanism for balancing the influences of the external environment on the body.
BD arises in response to direct sensory signs of an adequate stimulus and, thus, can be caused by a relatively limited number of environmental stimuli.
- This is an innate response of the body to irritation with the obligatory participation of the central nervous system (CNS). In this case, the cerebral cortex does not directly participate, but exercises its highest control over these, which allowed I.P. Pavlov to assert the presence of a “cortical representation” of each unconditioned reflex.
Unconditioned reflexes are the physiological basis :
1. Human species, i.e. congenital, inherited, constant, common to the entire human species;
2. Lower nervous activity (LNA). NND from the point of view unconditioned reflexes- this is an unconditioned reflex activity that provides the body with the unification of its parts into a single functional whole. Another definition of NND. NND is a set of neurophysiological processes that ensure the implementation of unconditioned reflexes and instincts.
Approximate unconditioned reflexes that occur with the direct participation of the cerebral cortex are physiological mechanisms cognitive activity person and involuntary attention. In addition, the extinction of orientation reflexes constitutes the physiological basis of addiction and boredom. Habituation is the extinction of the orienting reflex: if the stimulus is repeated many times and does not have special significance for the body, the body stops reacting to it, addiction develops. So, a person living on a noisy street gradually gets used to the noise and no longer pays attention to it.
Instincts are a form of innate. Their physiological mechanism is a chain of innate unconditioned reflexes, into which, under the influence of individual life conditions, links of acquired conditioned reflexes can be “woven together.”
As noted by P.V. Simonov, the definition of an unconditioned reflex as hereditary, unchangeable, the implementation of which is machine-like is usually exaggerated. Its implementation depends on the available animal and correlates with the dominant need at the moment. It may fade or intensify. Under the influence of early individual innate reflexes undergo significant changes.
The famous experiments of H. Harlow and R. Hind demonstrate how significant changes in the innate reflexes of monkeys are under the influence of early individual experience. If a six-month-old baby remained for several days in a group of monkeys without a mother, although he was surrounded by increased attention from other females, profound changes were found in him (he uttered cries of alarm more often, moved less, spent time in a characteristic hunched position, and experienced fear). When his mother returned, he spent much more time holding on to her than before the separation. The previous orienting-exploratory behavior (independent exploration of the environment) was restored within several weeks. The effects of such separations have been pervasive and lasting. These individuals were distinguished for several years by their great timidity in unfamiliar surroundings (fear).
Unconditioned reflexes and their classification.
There is no single generally accepted classification of unconditioned reflexes. Many attempts have been made to describe and classify unconditioned reflexes, and various criteria were used: 1) according to the nature of the stimuli that cause them; 2) according to their biological role; 3) according to the order in which they occur in a given specific behavioral act.
Pavlov's classification:
- simple
- complex
- the most complex (these are instincts - an innate form of adaptive behavior)
- individual (food activity, passive-defensive, aggressive, freedom reflex, exploratory, play reflex). These reflexes ensure individual self-preservation of the individual.
- species (sexual instinct and parental instinct). These reflexes ensure the preservation of the species.
In accordance with the nature of the current stimulus. Pavlov distinguished such types of unconditioned reflexes as:
- food (swallowing, sucking, etc.);
- sexual (“tournament fights”, erection, ejaculation, etc.);
- protective (coughing, sneezing, blinking, etc.);
- indicative (alertness, listening, turning the head towards the sound source, etc.), etc.
The implementation of all these reflexes is due to the presence of corresponding needs that arise as a result of temporary violations of internal constancy(homeostasis) of the body or as a result of complex interactions with the outside world.
So, for example, an increase in the amount of hormones in the blood (a change in the internal constancy of the body) leads to the manifestation of sexual reflexes, and an unexpected rustle (impact from the outside world) leads to alertness and the manifestation of an orientation reflex.
Therefore, we can believe that the emergence of an internal need is actually a condition for the implementation of an unconditional reflex and, in a certain sense, its beginning.
Simonov classification:
Simonov believed that the biological significance of unconditioned reflexes is not limited to individual and species self-preservation. Considering the progress of the historical self-movement of living nature P.V. Simonov develops the idea that the progressive development of unconditioned reflexes constitutes the phylogenetic basis for improving the needs (need-motivational sphere) of animals and humans.
Needs reflect the selective dependence of organisms on environmental factors essential for self-preservation and self-development, and serve as a source of activity of living beings, the motivation and purpose of their behavior in the environment. This means that the evolutionary progress of the need-motivational sphere reflects the tendency of the evolutionary genesis of self-development mechanisms. From an evolutionary point of view, each creature occupies a certain spatiotemporal place in the geosphere, biosphere and sociosphere, and for humans, in the noosphere (intellectual development of the world), although the phylogenetic prerequisites for the latter are found only in higher animals. According to P.V. Simonov, the development of each sphere of the environment corresponds to three different classes of reflexes:
1. Vital unconditioned reflexes provide individual and species preservation of the organism. These include food, drinking, regulation, defensive and orientation reflex (reflex of “biological caution”), reflex of saving strength and many others. The criteria for reflexes of the vital group are the following: 1) failure to satisfy the corresponding need leads to the physical death of the individual and 2) the implementation of the unconditioned reflex does not require the participation of another individual of the same species.
2. Role-playing (zoosocial) unconditioned reflexes can only be realized through interaction with other individuals of their own species. These reflexes underlie sexual, parental, territorial behavior, the phenomenon of emotional resonance (“empathy”) and the formation of a group hierarchy, where an individual invariably acts
3. Unconditioned reflexes of self-development focused on mastering new spatio-temporal environments, facing the future. These include exploratory behavior, the unconditioned reflex of resistance (freedom), imitation (imitative) and play, or, as P.V. calls them. Simonov, reflexes of preventive “arming”.
A feature of the group of unconditioned reflexes of self-development is their independence; it cannot be derived from other needs of the body and cannot be reduced to others. Thus, the reaction to overcome an obstacle (or the freedom reflex, in the terminology of I.P. Pavlov) is carried out regardless of what need primarily initiated the behavior and what the goal is, on the way to which an obstacle arose. It is the nature of the obstacle (stimulus-obstacle situation), and not the primary motive, that determines the composition of actions in behavior that can lead to the goal.
Reflex- This is the body’s response to irritation of receptors, carried out by the nervous system. The path along which the nerve impulse passes during the implementation of the reflex is called.
The concept of “reflex” was introduced by Sechenov, he believed that “reflexes form the basis of the nervous activity of humans and animals.” Pavlov divided reflexes into conditioned and unconditioned.
Comparison of conditioned and unconditioned reflexes
| unconditional | conditional |
| present from birth | acquired during life |
| do not change or disappear during life | may change or disappear during life |
| identical in all organisms of the same species | Each organism has its own, individual |
| adapt the body to constant conditions | adapt the body to changing conditions |
| reflex arc passes through the spinal cord or brain stem | temporary connection is formed in the cortex cerebral hemispheres |
| Examples | |
| salivation when lemon enters mouth | salivation at the sight of lemon |
| newborn sucking reflex | 6 month old baby's reaction to a bottle of milk |
| sneezing, coughing, pulling your hand away from the hot kettle | reaction of a cat/dog to a name |
Development of a conditioned reflex
Conditional (indifferent) the stimulus must precede unconditional(causing an unconditioned reflex). For example: a lamp is lit, after 10 seconds the dog is given meat.
Inhibition of conditioned reflexes
Conditional (non-reinforcement): the lamp lights up, but the dog is not given meat. Gradually, salivation when the lamp is turned on stops (the conditioned reflex fades).
Unconditional: During the action of a conditioned stimulus, a powerful unconditioned stimulus arises. For example, when the lamp is turned on, the bell rings loudly. No saliva is produced.
Choose one, the most correct option. The centers of conditioned reflexes, in contrast to unconditioned ones, are located in humans in
1) cerebral cortex
2) medulla oblongata
3) cerebellum
4) midbrain
Answer
Choose one, the most correct option. Salivation in a person at the sight of a lemon is a reflex
1) conditional
2) unconditional
3) protective
4) approximate
Answer
Choose three options. The peculiarity of unconditioned reflexes is that they
5) are congenital
6) are not inherited
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. Unconditioned reflexes that ensure life activity human body,
1) are developed in the process of individual development
2) formed in the process of historical development
3) are present in all individuals of the species
4) strictly individual
5) formed under relatively constant environmental conditions
6) are not congenital
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. The peculiarity of unconditioned reflexes is that they
1) arise as a result of repeated repetition
2) are a characteristic characteristic of an individual individual of the species
3) are genetically programmed
4) are characteristic of all individuals of the species
5) are congenital
6) build skills
Answer
Choose one, the most correct option. What are the features of spinal reflexes in humans and mammals?
1) acquired during life
2) are inherited
3) are different in different individuals
4) allow the organism to survive in changing environmental conditions
Answer
Choose one, the most correct option. The extinction of a conditioned reflex when it is not reinforced by an unconditioned stimulus is
1) unconditional inhibition
2) conditioned inhibition
3) rational action
4) conscious action
Answer
Choose one, the most correct option. Conditioned reflexes of humans and animals provide
1) adaptation of the body to constant environmental conditions
2) adaptation of the body to the changing external world
3) development of new motor skills by organisms
4) discrimination by animals of the trainer’s commands
Answer
Choose one, the most correct option. A baby's reaction to a bottle of milk is a reflex that
1) inherited
2) is formed without the participation of the cerebral cortex
3) acquired during life
4) persists throughout life
Answer
Choose one, the most correct option. When developing a conditioned reflex, the conditioned stimulus must
1) act 2 hours after unconditional
2) come immediately after the unconditional
3) precede the unconditional
4) gradually weaken
Answer
1. Establish a correspondence between the meaning of the reflex and its type: 1) unconditional, 2) conditional. Write numbers 1 and 2 in the correct order.
A) provides instinctive behavior
B) ensures the adaptation of the organism to the environmental conditions in which many generations of this species lived
C) allows you to gain new experience
D) determines the behavior of the organism in changed conditions
Answer
2. Establish a correspondence between the types of reflexes and their characteristics: 1) conditional, 2) unconditional. Write numbers 1 and 2 in the order corresponding to the letters.
A) are congenital
B) adaptation to new emerging factors
C) reflex arcs are formed in the process of life
D) are the same in all representatives of the same species
D) are the basis of learning
E) are constant, practically do not fade during life
Answer
Choose one, the most correct option. Conditioned (internal) inhibition
1) depends on the type of higher nervous activity
2) appears when a stronger stimulus occurs
3) causes the formation of unconditioned reflexes
4) occurs when the conditioned reflex fades
Answer
Choose one, the most correct option. The basis of nervous activity in humans and animals is
1) thinking
2) instinct
3) excitement
4) reflex
Answer
1. Establish a correspondence between the examples and types of reflexes: 1) unconditional, 2) conditional. Write numbers 1 and 2 in the correct order.
A) withdrawing a hand from the fire of a burning match
B) a child crying at the sight of a man in a white coat
C) a five-year-old child reaching out to the sweets he saw
D) swallowing pieces of cake after chewing them
D) salivation at the sight of a beautifully set table
E) downhill skiing
Answer
2. Establish a correspondence between the examples and the types of reflexes that they illustrate: 1) unconditional, 2) conditioned. Write numbers 1 and 2 in the order corresponding to the letters.
A) sucking movements of the child in response to touching his lips
B) constriction of the pupil illuminated by the bright sun
C) performing hygiene procedures before bed
D) sneezing when dust enters the nasal cavity
D) secretion of saliva to the clink of dishes when setting the table
E) roller skating
Answer
© D.V. Pozdnyakov, 2009-2019
Such habitual actions as breathing, swallowing, sneezing, blinking occur without conscious control, are innate mechanisms, help a person or animal to survive and ensure the preservation of the species - all these are unconditioned reflexes.
What is an unconditioned reflex?
I.P. Pavlov, a scientist-physiologist, devoted his life to the study of higher nervous activity. In order to understand what human unconditioned reflexes are, it is important to consider the meaning of the reflex as a whole. Any organism that has a nervous system carries out reflex activity. Reflex is a complex reaction of the body to internal and external stimuli, carried out in the form of a reflex response.
Unconditioned reflexes are innate stereotypical reactions laid down at the genetic level in response to changes in internal homeostasis or environmental conditions. For the emergence of unconditioned reflexes special conditions– these are automatic reactions that can fail only in severe illnesses. Examples of unconditioned reflexes:
- withdrawing a limb from contact with hot water;
- knee reflex;
- sucking, grasping in newborns;
- swallowing;
- salivation;
- sneezing;
- blinking.
What is the role of unconditioned reflexes in human life?
Human evolution over the centuries has been accompanied by changes in the genetic apparatus, selection of traits that are necessary for survival in surrounding nature. became highly organized matter. What is the significance of unconditioned reflexes - answers can be found in the works of physiologists Sechenov, I.P. Pavlova, P.V. Simonova. Scientists have identified several important functions:
- maintaining homeostasis (self-regulation of the internal environment) in optimal balance;
- adaptation and adaptation of the body (mechanisms of thermoregulation, respiration, digestion);
- preservation of species characteristics;
- reproduction.
Signs of unconditioned reflexes
The main feature of unconditioned reflexes is innateness. Nature made sure that all functions important for life in this world were reliably recorded on the DNA nucleotide chain. Other characteristic features:
- preliminary training and control of consciousness are not required;
- are specific;
- strictly specific - occur upon contact with a specific stimulus;
- constant reflex arcs in the lower parts of the central nervous system;
- most unconditioned reflexes persist throughout life;
- a set of unconditioned reflexes helps the body adapt to the environment in the early stages of development;
- are the basic basis for the emergence of conditioned reflexes.
Types of unconditioned reflexes
Unconditioned reflexes have different types classification, I.P. Pavlov was the first to classify them into: simple, complex and most complex. In the distribution of unconditioned reflexes according to the factor of certain space-time regions occupied by each creature, P.V. Simonov divided the types of unconditioned reflexes into 3 classes:
- Role unconditioned reflexes– manifest themselves in interaction with other intraspecific representatives. These are reflexes: sexual, territorial behavior, parental (maternal, paternal), phenomenon.
- Unconditioned vital reflexes– all the basic needs of the body, the deprivation or dissatisfaction of which leads to death. Provide individual safety: drinking, food, sleep and wakefulness, orientation, defensive.
- Unconditioned reflexes of self-development- are included when mastering something new, previously unfamiliar (knowledge, space):
- reflex of overcoming or resistance (freedom);
- game;
- imitative.
Types of inhibition of unconditioned reflexes
Excitation and inhibition are important innate functions of higher nervous activity, which ensure the coordinated activity of the body and without which this activity would be chaotic. Inhibitory unconditioned reflexes in the process of evolution turned into a complex response of the nervous system - inhibition. I.P. Pavlov identified 3 types of inhibition:
- Unconditional inhibition (external)– reaction “What is it?” allows you to assess whether the situation is dangerous or not. In the future, with frequent manifestations of an external stimulus that does not pose a danger, inhibition does not occur.
- Conditioned (internal) inhibition– the functions of conditioned inhibition ensure the extinction of reflexes that have lost their value, help distinguish useful signals with reinforcement from useless ones, and form a delayed reaction to a stimulus.
- Transcendental (protective) inhibition- an unconditional safety mechanism provided by nature, which is triggered by excessive fatigue, excitement, severe injuries (fainting, coma).
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 inner life body. This last property of the unconditioned reflex was especially emphasized by I. P. Pavlov. great importance. 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 in the central nervous system Through the innate pathways of this reflex, 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 exact accordance with the physical and chemical properties 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 receptors of the tongue in a state of increased excitability. This is how children develop their desire to do 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, then 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 on enzyme activity. 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 “tuning” of the receptors of the tongue is prepared by the embryonic development of animals, which ensures successful choice nutrients and the systematic 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, 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 the conditioned signal electric shock leads to a completely clear 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 mechanical properties 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 have a cyclic and behavioral character- 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 is represented in the cerebral cortex. This point of view of I.P. Pavlov was confirmed by research 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, including several various stages animal behavior is also a complex unconditioned reflex. The peculiarities 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 strong damaging (nociceptive) unconditioned excitation (burn hot water) 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 structural and functional formation unconditional reflex. The vital functional systems of a newborn are completely consolidated at the time of birth. Individual links 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. Because maturation functional systems 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.
So, for example, the structural design of spinal coordination reflexes turns out to be different in birds, which, after hatching from an egg, immediately become completely independent (chicken), and in birds, which, after hatching from an egg, are for a long time helpless and 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.
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Higher nervous activity (HNA)
Higher nervous activity (HNA) is a complex and interconnected set of nervous processes that underlie human behavior. GND ensures maximum human adaptability to environmental conditions.
GND is based on complex electrical and chemical processes occurring in the cells of the cerebral cortex. By receiving information through the senses, the brain ensures the interaction of the body with the environment and maintains the constancy of the internal environment in the body.
The doctrine of higher nervous activity is based on the works of I.M. Sechenov - “Reflexes of the brain”, I.P. Pavlova (theory of conditioned and unconditioned reflexes), P.K. Anokhin (theory of functional systems) and numerous other works.
Features of human higher nervous activity:
- developed mental activity;
- speech;
- ability for abstract logical thinking.
The creation of the doctrine of higher nervous activity began with the works of the great Russian scientists I.M. Sechenov and I.P. Pavlova.
Ivan Mikhailovich Sechenov in his book “Reflexes of the Brain” proved that a reflex is a universal form of interaction between the body and the environment, that is, not only involuntary, but also voluntary, conscious movements have a reflex character. They begin with irritation of any sensory organs and continue in the brain in the form of certain nervous phenomena that lead to the launch of behavioral reactions.
A reflex is the body's response to stimulation, occurring with the participation of the nervous system.
THEM. Sechenov argued that brain reflexes include three parts:
- The first, initial link is stimulation in the senses caused by external influences.
- The second, central link is the processes of excitation and inhibition occurring in the brain. On their basis arise psychic phenomena(sensations, ideas, feelings, etc.).
- The third, final link is the movements and actions of a person, i.e. his behavior. All these links are interconnected and condition each other.
Sechenov concluded that the brain is an area of continuous change of excitation and inhibition. These two processes constantly interact with each other, which leads to both strengthening and weakening (delay) of reflexes. He also drew attention to the existence of innate reflexes, which people inherit from their ancestors, and acquired ones, which arise throughout life as a result of learning. I.M. Sechenov’s assumptions and conclusions were ahead of their time.
The successor of the ideas of I.M. Sechenov became I.P. Pavlov.
Ivan Petrovich Pavlov divided all reflexes that arise in the body into unconditional and conditional.
Unconditioned reflexes
Unconditioned reflexes are inherited by offspring from their parents, persist throughout the life of the organism and are reproduced from generation to generation ( permanent). They are characteristic of all individuals of a certain species, i.e. group.
In unconditioned reflexes constant reflex arcs, which pass through the brain stem or through the spinal cord (for their implementation participation of the cortex is not necessarycerebral hemispheres).
There are food, defensive, sexual and indicative unconditioned reflexes.
- Food: separation of digestive juices in response to irritation of oral receptors, swallowing, sucking movements in a newborn.
- Defensive: withdrawal of a hand that has touched a hot object or when experiencing painful irritation, coughing, sneezing, blinking, etc.
- Genital: The process of reproduction is associated with sexual reflexes.
- Approximate(I.P. Pavlov called it the “what is this?” reflex) ensures the perception of an unfamiliar stimulus. An indicative reflex appears in response to a new stimulus: a person becomes alert, listens, turns his head, squints his eyes, and thinks.
Thanks to unconditioned reflexes, the integrity of the body is preserved, the constancy of its internal environment is maintained, and reproduction occurs.
A complex chain of unconditioned reflexes is called instinct.
Example:
A mother feeds and protects her child, birds build nests - these are examples of instincts.
Conditioned reflexes
Along with hereditary (unconditioned) reflexes, there are reflexes that are acquired by every person throughout life. Such reflexes individual, and certain conditions are necessary for their formation, which is why they were called conditional.