A reflex is the body's response to internal or external stimulation, carried out and controlled by the central nervous system. The first scientists who developed ideas about what was previously a mystery were our compatriots I.P. Pavlov and I.M. Sechenov.
What are unconditioned reflexes?
An unconditioned reflex is an innate, stereotypical reaction of the body to the influence of the internal or environmental environment, inherited by the offspring from the parents. It remains in a person throughout his life. Reflex arcs pass through the brain and the cerebral cortex does not take part in their formation. The significance of the unconditioned reflex is that it ensures the adaptation of the human body directly to those environmental changes that often accompanied many generations of his ancestors.
What reflexes are unconditioned?
An unconditioned reflex is the main form of activity of the nervous system, an automatic reaction to a stimulus. And since a person is influenced by various factors, the reflexes are different: food, defensive, orientation, sexual... Food include salivation, swallowing and sucking. Defensive actions include coughing, blinking, sneezing, and jerking limbs away from hot objects. Approximate reactions include turning the head and squinting the eyes. Sexual instincts include those associated with reproduction, as well as caring for offspring. The significance of the unconditioned reflex is that it ensures the preservation of the integrity of the body and maintains the constancy of the internal environment. Thanks to him, reproduction occurs. Even in newborn children, one can observe an elementary unconditioned reflex - this is sucking. By the way, it is the most important. The irritant in this case is touching the lips of any object (pacifier, mother's breast, toy or finger). Another important unconditioned reflex is blinking, which occurs when a foreign body approaches the eye or touches the cornea. This reaction belongs to the protective or defensive group. Also observed in children, for example, when exposed to strong light. However, the signs of unconditioned reflexes are most clearly manifested in various animals.
What are conditioned reflexes?
Conditioned reflexes are those acquired by the body during life. They are formed on the basis of inherited ones, subject to exposure to an external stimulus (time, knocking, light, and so on). A striking example is the experiments conducted on dogs by academician I.P. Pavlov. He studied the formation of this type of reflexes in animals and was the developer of a unique method for obtaining them. So, to develop such reactions, the presence of a regular stimulus - a signal - is necessary. It triggers the mechanism, and repeated repetition of the stimulus allows it to develop. In this case, a so-called temporary connection arises between the arcs of the unconditioned reflex and the centers of the analyzers. Now the basic instinct awakens under the influence of fundamentally new external signals. These stimuli from the surrounding world, to which the body was previously indifferent, begin to acquire exceptional, vital importance. Each living creature can develop many different conditioned reflexes during its life, which form the basis of its experience. However, this applies only to this particular individual; this life experience will not be inherited.
An independent category of conditioned reflexes
It is customary to classify into a separate category conditioned reflexes of a motor nature developed throughout life, that is, skills or automated actions. Their meaning is to master new skills, as well as develop new motor forms. For example, over the entire period of his life a person masters many special motor skills that are associated with his profession. They are the basis of our behavior. Thinking, attention, and consciousness are freed up when performing operations that have reached automaticity and become a reality of everyday life. The most successful way to master skills is to systematically perform the exercise, timely correction of noticed errors, and knowledge of the ultimate goal of any task. If the conditioned stimulus is not reinforced by the unconditioned stimulus for some time, it is inhibited. However, it does not disappear completely. If you repeat the action after some time, the reflex will be restored fairly quickly. Inhibition can also occur when a stimulus of even greater strength appears.
Compare unconditioned and conditioned reflexes
As mentioned above, these reactions differ in the nature of their occurrence and have different formation mechanisms. In order to understand what the difference is, just compare unconditioned and conditioned reflexes. Thus, the first ones are present in a living creature from birth; throughout life they do not change or disappear. In addition, unconditioned reflexes are the same in all organisms of a particular species. Their significance lies in preparing a living being for constant conditions. The reflex arc of this reaction passes through the brain stem or spinal cord. As an example, here are some (congenital): active secretion of saliva when a lemon enters the mouth; sucking movement of the newborn; coughing, sneezing, withdrawing hands from a hot object. Now let's look at the characteristics of conditioned reactions. They are acquired throughout life, can change or disappear, and, no less important, each organism has its own individual (its own). Their main function is to adapt a living creature to changing conditions. Their temporary connection (reflex centers) is created in the cerebral cortex. An example of a conditioned reflex is the reaction of an animal to a nickname or the reaction of a six-month-old child to a bottle of milk.
Unconditioned reflex diagram
According to the research of academician I.P. Pavlova, the general scheme of unconditioned reflexes is as follows. Certain receptor nerve devices are affected by certain stimuli from the internal or external world of the body. As a result, the resulting irritation transforms the entire process into the so-called phenomenon of nervous excitation. It is transmitted along nerve fibers (as if through wires) to the central nervous system, and from there it goes to a specific working organ, already turning into a specific process at the cellular level of a given part of the body. It turns out that certain stimuli are naturally connected with this or that activity in the same way as cause and effect.
Features of unconditioned reflexes
The characteristics of unconditioned reflexes presented below systematize the material presented above; it will help to finally understand the phenomenon we are considering. So, what are the features of inherited reactions?
Unconditioned instinct and reflex of animals
The exceptional constancy of the nervous connection underlying unconditional instinct is explained by the fact that all animals are born with a nervous system. She is already able to respond appropriately to specific environmental stimuli. For example, a creature may flinch at a sharp sound; he will secrete digestive juice and saliva when food enters his mouth or stomach; it will blink when visually stimulated, and so on. Innate in animals and humans are not only individual unconditioned reflexes, but also much more complex forms of reactions. They are called instincts.
An unconditioned reflex, in fact, is not a completely monotonous, template, transfer reaction of an animal to an external stimulus. It is characterized, although elementary, primitive, but still by variability, variability, depending on external conditions (strength, peculiarities of the situation, position of the stimulus). In addition, it is influenced by the internal states of the animal (decreased or increased activity, posture, etc.). So, also I.M. Sechenov, in his experiments with decapitated (spinal) frogs, showed that when the toes of the hind legs of this amphibian are exposed, the opposite motor reaction occurs. From this we can conclude that the unconditioned reflex still has adaptive variability, but within insignificant limits. As a result, we find that the balancing of the organism and the external environment achieved with the help of these reactions can be relatively perfect only in relation to slightly changing factors of the surrounding world. The unconditioned reflex is not able to ensure the animal’s adaptation to new or sharply changing conditions.
As for instincts, sometimes they are expressed in the form of simple actions. For example, the rider, thanks to his sense of smell, finds the larvae of another insect under the bark. It pierces the bark and lays its egg in the found victim. This ends all of its actions that ensure continuation of the family. There are also complex unconditioned reflexes. Instincts of this kind consist of a chain of actions, the totality of which ensures procreation. Examples include birds, ants, bees and other animals.
Species specificity
Unconditioned reflexes (specific) are present in both humans and animals. It should be understood that such reactions will be the same in all representatives of the same species. An example is a turtle. All species of these amphibians retract their heads and limbs into their shell when danger arises. And all the hedgehogs jump and make a hissing sound. In addition, you should know that not all unconditioned reflexes occur at the same time. These reactions vary with age and season. For example, the breeding season or the motor and sucking actions that appear in an 18-week fetus. Thus, unconditioned reactions are a kind of development for conditioned reflexes in humans and animals. For example, as cubs grow older, they transition into the category of synthetic complexes. They increase the body's adaptability to external environmental conditions.
Unconditional inhibition
In the process of life, each organism is regularly exposed - both from the outside and from the inside - to various stimuli. Each of them is capable of causing a corresponding reaction - a reflex. If all of them could be realized, then the life activity of such an organism would become chaotic. However, this does not happen. On the contrary, reactionary activity is characterized by consistency and orderliness. This is explained by the fact that unconditioned reflexes are inhibited in the body. This means that the most important reflex at a particular moment in time delays the secondary ones. Typically, external inhibition can occur at the moment of starting another activity. The new pathogen, being stronger, leads to the attenuation of the old one. And as a result, the previous activity will automatically stop. For example, a dog is eating, and at that moment the doorbell rings. The animal immediately stops eating and runs to meet the newcomer. There is a sharp change in activity, and the dog’s salivation stops at this moment. 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 from all possible options the most adequate one, capable of protecting against excessive activity. This process also contributes to the exercise of so-called biological precautions.
Reflex- This is the body’s response to irritation of receptors, carried out by the nervous system. The path along which a nerve impulse travels during a reflex is called a reflex arc.
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 cerebral cortex |
| 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.
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.
MORE INFORMATION: Reflex, reflex arc, conditioned and unconditioned reflexes, Development and inhibition of conditioned reflexes
TASKS PART 2: Reflexes
Tests and assignments
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
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
Choose three options. The peculiarity of unconditioned reflexes is that they
5) are congenital
6) are not inherited
Choose three correct answers out of six and write down the numbers under which they are indicated. Unconditioned reflexes that ensure the vital functions of the 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
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
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
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
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
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
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
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
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
3. Establish a correspondence between the characteristics and types of reflexes: 1) conditional, 2) unconditional. Write numbers 1 and 2 in the order corresponding to the letters.
A) acquired in the course of life
B) are characteristic of all representatives of this species
C) unstable, capable of fading
D) provide adaptation to changing environmental conditions
D) permanent, lasting throughout life
E) are passed on to offspring over generations
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
Choose one, the most correct option. The basis of nervous activity in humans and animals is
1) thinking
2) instinct
3) excitement
4) reflex
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
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
© D.V. Pozdnyakov, 2009-2018
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Unconditioned reflexes- These are innate, hereditarily transmitted reactions of the body. Conditioned reflexes- these are reactions acquired by the body in the process of individual development on the basis of “life experience”.
Unconditioned reflexes are specific, i.e.
Unconditioned and conditioned reflexes
characteristic of all representatives of this species. Conditioned reflexes are individual: some representatives of the same species may have them, while others may not.
Unconditioned reflexes are relatively constant; conditioned reflexes are not constant and, depending on certain conditions, they can be developed, consolidated or disappear; This is their property and is reflected in their very name.
Unconditioned reflexes are carried out in response to adequate stimulation applied to one specific receptive field.
Conditioned reflexes can be formed to a wide variety of stimuli applied to various receptive fields.
In animals with a developed cerebral cortex, conditioned reflexes are a function of the cerebral cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain. This indicates that in the implementation of unconditioned reflexes, in contrast to conditioned ones, the leading role belongs to the lower parts of the central nervous system - the subcortical nuclei, brain stem and spinal cord. It should be noted, however, that in humans and monkeys, who have a high degree of corticalization of functions, many complex unconditioned reflexes are carried out with the obligatory participation of the cerebral cortex. This is proven by the fact that its lesions in primates lead to pathological disorders of unconditioned reflexes and the disappearance of some of them.
It should also be emphasized that not all unconditioned reflexes appear immediately at the time of birth. Many unconditioned reflexes, for example, those associated with locomotion and sexual intercourse, arise in humans and animals a long time after birth, but they necessarily appear under the condition of normal development of the nervous system. Unconditioned reflexes are part of the fund of reflex reactions strengthened in the process of phylogenesis and hereditarily transmitted.
Conditioned reflexes are developed on the basis of unconditioned reflexes. For the formation of a conditioned reflex, it is necessary to combine in time some kind of change in the external environment or the internal state of the body, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition does a change in the external environment or internal state of the body become a stimulus to a conditioned reflex - a conditioned stimulus, or signal. The irritation that causes an unconditioned reflex - unconditioned irritation - must, during the formation of a conditioned reflex, accompany the conditioned irritation and reinforce it.
In order for the clinking of knives and forks in the dining room or the knocking of a cup from which a dog is fed to cause salivation in the first case in a person, in the second case in a dog, it is necessary to re-coincidence of these sounds with food - reinforcement of stimuli that are initially indifferent to salivary secretion by feeding , i.e., unconditional irritation of the salivary glands. Likewise, the flashing of an electric light bulb in front of a dog’s eyes or the sound of a bell will only cause conditioned reflex flexion of the paw if they are repeatedly accompanied by electrical irritation of the skin of the leg, causing an unconditioned flexion reflex whenever it is used.
Similarly, a child’s crying and his hands pulling away from a burning candle will be observed only if the sight of the candle first coincided at least once with the feeling of a burn. In all the above examples, external agents that are initially relatively indifferent - the clinking of dishes, the sight of a burning candle, the flashing of an electric light bulb, the sound of a bell - become conditioned stimuli if they are reinforced by unconditioned stimuli. Only under this condition do the initially indifferent signals of the external world become stimuli for a certain type of activity.
For the formation of conditioned reflexes, it is necessary to create a temporary connection, a closure between the cortical cells that perceive conditioned stimulation and the cortical neurons that are part of the unconditioned reflex arc.
When conditioned and unconditioned stimulation coincide and combine, a connection is established between different neurons in the cerebral cortex, and a process of closure occurs between them.
Main article: Higher nervous activity
Reflex- This is the body’s response to external and internal irritations through the nervous system. The reflex is a basic and specific function of the central nervous system. All activities of the human body are carried out through reflexes. For example, feeling pain, moving limbs, breathing, blinking and other actions are essentially reflexes.
Reflex arc
Each reflex has its own reflex arc, which consists of the following five parts:
- a receptor located in tissues and organs and perceiving irritations from the external and internal environment;
- sensitive nerve fiber, which transmits impulses generated when the receptor is excited to the nerve center;
- nerve center, which consists of sensitive, intercalary, motor nerve cells located in the brain;
- motor nerve fiber, which transmits the excitation of the nerve center to the working organ;
- working organ - muscles, glands, blood vessels, internal organs and others.
Types of reflexes
Depending on which part of the central nervous system is involved in the manifestation of the body's response to stimuli, two types of reflexes are distinguished: unconditioned and conditioned.
Unconditioned reflexes
see Normal reflexes
The lower parts of the central nervous system—the nerve centers of the spinal cord, medulla oblongata, midbrain, and diencephalon—are involved in the formation of unconditioned reflexes. Unconditioned reflexes are innate, since their nerve pathways already exist in a newborn child. These reflexes serve to ensure important life processes in the human body. For example, chewing food (baby suckling), swallowing, digestion, excretion of feces and urine, breathing, blood circulation and others. Unconditioned reflexes are permanent, that is, they do not change (do not disappear) during a person’s life. Their number and type are almost the same in all people. These reflexes are inherited.
Conditioned reflexes
The centers of conditioned reflexes are located in the cortex of the large hemispheres of the brain. At the birth of a child, these reflexes are absent; they are formed during a person’s life. The neural pathways of conditioned reflexes are also absent at birth; they are formed subsequently as a result of upbringing, training and life experience.
Formation of conditioned reflexes
Conditioned reflexes are formed on the basis of unconditioned ones. For the formation of a conditioned reflex, it is necessary that the unconditioned stimulus act first, and then the conditioned stimulus. So, for example, to develop a conditioned salivary reflex in a dog, first turn on an electric light bulb or a bell as a conditioned one, then give it food as an unconditioned stimulus. When this experience is repeated several times, a temporary connection is formed between the centers of nutrition and vision or hearing in the brain. As a result, just turning on an electric light bulb or a bell will cause the dog to salivate (even in the absence of food), that is, a salivary conditioned reflex will appear in response to a flash of light or a bell (Fig. 70). In this case, the flash of an electric light bulb excites the visual center in the ordinal part of the brain. This excitation, through a temporary connection, causes excitation of the subcortical food center. This, in turn, causes stimulation of the food center located in the medulla oblongata, and as a result of increased activity of the salivary glands through nerve fibers, salivation begins. The figure shows, first, under the influence of light, the excitation of the subcortical visual center, its spread through a temporary connection to the subcortical food center, and from it to the subcortical center in the medulla oblongata, and finally, its entry into the salivary glands, causing salivation. Material from the site http://wiki-med.com
Inhibition of conditioned reflexes
It is known that during the implementation of the formed conditioned reflex, if some strong external stimulus suddenly affects a dog (or a person), then strong excitement occurs in the nerve center of the brain. This excitation by induction inhibits the center of the conditioned reflex and the reflex temporarily stops. Thus, in the figure you can see how, under the influence of the light of an electric lamp, a conditioned reflex of salivation appears in a dog; As a result of an additional strong stimulus - a bell - the auditory center is excited, the centers of conditioned reflexes are inhibited and salivation stops.
Pathological reflexes
§1. Conditioned and unconditioned reflexes
Pathological reflexes
Reflex Research
see Reflex Research
In clinical practice, normal segmental as well as pathological reflexes are examined. The course of segmental processes is influenced by suprasegmental structures, therefore segmental reflexes are often disrupted with certain suprasegmental lesions, and in the implementation of a number of pathological reflexes suprasegmental disorders are of decisive importance.
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Material from the site http://Wiki-Med.com
Classification of reflexes. What types of reflexes are there?
The functioning of the nervous system is based on the inextricable unity of congenital and acquired forms of adaptation, i.e. unconditioned and conditioned reflexes.
Unconditioned reflexes are innate, relatively constant species-specific reactions of the body, carried out through the nervous system in response to the action of certain stimuli. They ensure the coordinated activity of various functional systems of the body, aimed at maintaining its homeostasis and interaction with the environment. Examples of simple unconditioned reflexes include knee, blink, swallow and others.
There is a large group of complex unconditioned reflexes: self-preservation, food, sexual, parental (caring for offspring), migration, aggressive, locomotor (walking, running, flying, swimming), etc. Such reflexes are called instincts. They underlie the innate behavior of animals and represent complexes of stereotypical species-specific motor acts and complex forms of behavior.
A conditioned reflex is a reaction of the body acquired during an individual’s life, carried out due to the formation in the higher parts of the central nervous system of temporary variable reflex pathways in response to the action of any signal stimulus, for the perception of which there is a responsible receptor apparatus. An example is the classical conditioned reflex of I.P. Pavlov - the release of saliva by a dog to the sound of a bell, which had previously been connected several times with feeding animals. A conditioned reflex is formed as a result of a combination of the action of two stimuli - conditioned and unconditioned.
An unconditioned stimulus is a stimulus that causes an unconditioned reflex to occur. For example, turning on a bright light causes the pupil to constrict; the action of an electric current causes the dog to withdraw its paw.
A conditioned stimulus is any neutral stimulus that, after repeated combination with an unconditioned stimulus, acquires a signal value. Yes, the sound of the bell, which is repeated, leaves the animal indifferent to it. However, when the sound of the bell is combined with feeding the animal (an unconditioned stimulus), then after several repetitions of both stimuli the bell becomes a conditioned stimulus, alerting the animal to the presentation of food and causing it to salivate.
Conditioned reflexes can be classified according to receptor characteristics, the nature of the conditioned stimulus, the time of action of the conditioned and unconditioned stimuli, and the effector characteristic.
Based on receptor characteristics, conditioned reflexes are divided into external and interoceptive.
- Exteroceptive reflexes are produced in response to visual, auditory, olfactory, gustatory, skin-mechanical stimuli, etc. They play a major role in the interaction of the organism with the environment, and therefore are formed and specialized relatively easily.
- Interoceptive conditioned reflexes are formed by combining stimulation of the receptors of internal organs with any unconditioned reflex. They form much more slowly and are diffuse in nature.
According to the nature of the conditioned stimulus, conditional reflexes are divided into natural and artificial. Natural reflexes are formed under the influence of natural unconditioned stimuli, for example, salivation to the smell or sight of food. Conditioned reflexes are called artificial. Artificial reflexes are often used in scientific experiments, since their parameters (strength, duration, etc.) can be arbitrarily adjusted.
Based on the time of action of conditioned and unconditioned stimuli, they are distinguished existing and trace conditioned reflexes. Existing conditioned reflexes are formed when reinforcement is given within the duration of the conditioned stimulus. Trace reflexes are conditioned reflexes that are formed in the event of the action of a reinforcing stimulus after the end of the conditioned signal. A special type of trace conditioned reflexes are timed reflexes, which are formed under the condition of regular repetition of an unconditioned stimulus at certain intervals.
According to the effector sign, conditional reflexes are divided into vegetative and somatomovement. Autonomic ones include food, cardiovascular, excretory, sexual and similar conditioned reflexes.
Reflex (biology)
An example of an autonomic conditioned reflex is the classic salivary reflex. Somatomotive include protective, food-producing conditioned reflexes, as well as complex behavioral reactions.
In real life, conditioned reflexes are usually formed not to one, but to several stimuli, so they can be divided into simple and complex(complex). Complex conditioned reflexes can be simultaneous or sequential, depending on the combination and sequence of action of a set of stimuli.
Unconditioned reflexes constitute the lower nervous activity, ensuring the implementation of various motor acts of life support, as well as the regulation of the functions of internal organs.
The elements of higher nervous and mental activity in the human animal are instincts and conditioned reflexes (learning reactions), which manifest themselves in the form of behavioral reactions.
Topic: “Development of a conditioned blink reflex”
Goal of the work: Master the technique of developing a conditioned blink reflex.
Equipment: arc-shaped stand, tripod, rubber tube with bulb, whistle.
Mechanical irritation of the cornea and sclera causes an unconditioned blink reflex. On the basis of this unconditioned stimulus, a conditioned blink reflex can be developed - a bell is used as a conditioned stimulus, and an intermittent stream of air is used as an unconditioned stimulus.
Progress:
1. Development of an unconditioned blink reflex. The subject's chin is placed on an arched stand mounted on a tripod. The end of the tube conducting air from the cylinder is placed at eye level at a distance of 5-10 cm.
Conditioned and unconditioned reflexes
Select the strength of the air stream that causes an unconditioned protective reflex of blinking. If the reflex is not evoked, repeat the experiment, changing the position of the metal tube.
Development of a conditioned blink reflex. The experimenter with a whistle stands behind the subject - his task is to use the whistle to produce a conditioned stimulus (whistle). The second experimenter continues to squeeze the bulb and apply a stream of air (unconditioned stimulus). When giving a sound signal, you must immediately press the pear. After 1-2 minutes, repeat this combination of stimuli, while maintaining the same delivery interval between them. After 8-9 combinations, give a sound signal without reinforcing it with an unconditioned stimulus (a stream of air) - a conditioned blink reflex will appear.
3. Draw conclusions based on the results of the experiment. Draw a diagram of the unconditioned and conditioned blink reflex. An example of a conditioned blink reflex is this diagram:
Rice. 1. Scheme of the conditioned blink reflex: 1- receptors of the organ of hearing, 2- afferent pathway (auditory nerve), 3- nerve center, 4- efferent pathway (oculomotor nerve), 5- ciliary muscle of the eye.
Control questions:
1. What is a reflex?
2. What types of reflexes do you know?
3. What are unconditioned reflexes?
4. What are conditioned reflexes?
5. What conditions must be observed when developing conditioned reflexes? In what order should conditioned and unconditioned stimuli be applied?
6. What is the essence of the mechanism for the development of conditioned reflexes?
7. How many links does the reflex arc include? Reflex ring?
8. What types of receptors do you know by location?
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Conditioned reflex, definition, classification of conditioned reflexes.
A conditioned reflex is a complex multicomponent reaction that is developed on the basis of unconditioned reflexes using a previous indifferent stimulus. It has a signaling character, and the body meets the impact of an unconditioned stimulus prepared. For example, in the pre-race period an athlete undergoes a redistribution of blood, increased breathing and blood circulation, and when the muscle load begins, the body is already prepared for it.
Classification of conditioned reflexes
Conditioned reflexes, as well as unconditioned ones, can be classified according to biological modality - food, drink, defensive;
Depending on the nature of the relationship between signal, conditioned and unconditioned stimuli, conditioned reflexes are divided into natural and artificial. Natural conditioned reflexes are developed to agents that, under natural conditions, are a property of the unconditioned stimulus and act together with the stimulus that causes the unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes are artificial, i.e. are produced in response to agents that are not normally associated with the action of an unconditioned stimulus, for example, the food salivary reflex to a bell.
Based on their effector characteristics, conditioned reflexes are divided into secretory, motor, cardiac, vascular, etc.
Based on their role in the implementation of goal-directed behavior, conditioned reflexes are divided into preparatory and executive.
5. If you develop a strong conditioned food reflex, for example, to light, then such a reflex is a conditioned reflex of the first order. On its basis, a second-order conditioned reflex can be developed; for this, a new, previous signal, for example a sound, is additionally used, reinforcing it with a first-order conditioned stimulus (light).
As a result of several combinations of sound and light, the sound stimulus also begins to cause salivation. Thus, a new, more complex indirect time connection arises. It should be emphasized that the reinforcement for a conditioned reflex of the second order is precisely the conditioned stimulus of the first order, and not the unconditioned stimulus (food), since if both light and sound are reinforced with food, then two separate conditioned reflexes of the first order will arise. With a sufficiently strong conditioned reflex of the second order, a conditioned reflex of the third order can be developed. To do this, a new stimulus is used, for example, touching the skin. In this case, the touch is reinforced only by a second-order conditioned stimulus (sound), the sound excites the visual center, and the latter excites the food center. An even more complex temporal relationship arises. Higher order reflexes (4, 5, 6, etc.) are developed only in primates and humans.
CONDITIONED AND UNCONDITIONED REFLEXES
Based on the nature of the relationship of an animal or a person to an unconditioned stimulus, on the basis of which a conditioned reflex is developed, conditioned reflexes are divided into positive and negative. Positive conditioned reflexes bring people closer to the unconditioned stimulus. Negative catch reflexes either move away from him or prevent him from getting closer.
7. Depending on the duration of the period of isolated action of the conditioned signal (PID), conditioned reflexes are divided into coincident (PID = from 0.5 to 3.0 sec.), short-delayed (PID = from 3.0 to 30 sec.), normally delayed ( PID = from 30 to 60 sec.), delayed (PID = more than 60 sec.). The period of isolated action is the period of time from the beginning of the action of the conditioned signal to the moment of action of the unconditioned stimulus.
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1. What reflexes are called conditioned? Give examples of a conditioned reflex.
Conditioned reflexes are acquired by the body in the process of its development, i.e. they are individual. Conditioned reflexes do not have ready-made reflex arcs; they are formed under certain conditions. These reflexes are not constant; they can develop and disappear. The conditioned reflex is formed on the basis of the unconditioned reflex and is carried out due to the activity of the cerebral cortex. For the formation of conditioned reflexes, it is necessary to combine two stimuli in time: an indifferent (conditioned) one for a given type of activity (light, sound, for example, for digestion) and an unconditioned one, causing a certain unconditioned reflex (food, etc.). The conditional signal must precede the unconditional signal. Reinforcement of the conditioned signal by the unconditioned must be repeated in the absence of distracting extraneous stimuli. When a conditioned stimulus (for example, light) acts, a focus of excitation appears in the cortex. The subsequent action of an unconditioned stimulus (for example, food) is accompanied by the appearance of a second focus of excitation in the cortex. A temporary connection arises between them (a Pavlovian closure occurs). After several combinations of conditioned and unconditioned stimuli, the connection becomes stronger. Now only one conditioned stimulus is enough to trigger a reflex. An example of a conditioned reflex: salivation at the sight and smell of food.
Conditioned reflexes are not only developed, but also disappear or weaken when the conditions of existence change as a result of inhibition. I.P. Pavlov distinguished two types of inhibition of conditioned reflexes: unconditioned (external) and conditioned (internal). Unconditioned (external) inhibition occurs as a result of the action of a new stimulus of sufficient strength. In this case, a new focus of excitation appears in the cerebral cortex, which causes inhibition of the existing focus of excitation. In a person, for example, with an acute toothache, a severely wounded finger stops hurting. Conditioned (internal) inhibition develops according to the laws of the conditioned reflex, i.e. if the action of the conditioned stimulus is not reinforced by the action of the unconditioned stimulus. Thanks to inhibition in the cortex, unnecessary temporary connections disappear.
2. What reflexes are called unconditioned? Give examples of an unconditioned reflex.Material from the site
Unconditioned reflexes are innate and inherited. Unconditioned reflexes appear at the first application of the stimulus to the corresponding receptors. These reflexes have permanent inherited ready reflex arcs. They are inherent in all representatives of this species and are carried out in response to adequate stimulation. Unconditioned reflexes are carried out at the level of the spinal cord and brain stem, subcortical nuclei. Examples: salivation, swallowing, breathing, etc.
“If the animal were not... accurately adapted to the outside world, then it would soon or slowly cease to exist... It should react to the outside world in such a way that its existence would be ensured by all its response activity.”
I.P. Pavlov.
The adaptation of animals and humans to changing conditions of existence in the external environment is ensured by the activity of the nervous system and is realized through reflex activity. In the process of evolution, hereditarily fixed reactions (unconditioned reflexes) arose that combine and coordinate the functions of various organs and carry out adaptation of the body. In humans and higher animals, in the process of individual life, qualitatively new reflex reactions arise, which I. P. Pavlov called conditioned reflexes, considering them the most perfect form of adaptation.
While relatively simple forms of nervous activity determine the reflex regulation of homeostasis and autonomic functions of the body, higher nervous activity (HNA) provides complex individual forms of behavior in changing living conditions. GNI is realized due to the dominant influence of the cortex on all underlying structures of the central nervous system. The main processes that dynamically replace each other in the central nervous system are the processes of excitation and inhibition. Depending on their ratio, strength and localization, the control influences of the cortex are built. The functional unit of the GNI is the conditioned reflex.
Higher nervous activity is a set of unconditioned and conditioned reflexes, as well as higher mental functions that ensure adequate behavior in changing natural and social conditions. For the first time, the assumption about the reflex nature of the activity of the higher parts of the brain was made by I.M. Sechenov, which made it possible to extend the reflex principle to human mental activity. The ideas of I.M. Sechenov received experimental confirmation in the works of I.P. Pavlov, who developed a method for objective assessment of the functions of the higher parts of the brain - the method of conditioned reflexes.
I.P. Pavlov showed that all reflex reactions can be divided into two groups: unconditional and conditional.
|
Unconditioned reflexes |
Conditioned reflexes |
| 1. Congenital, hereditary reactions, most of them begin to function immediately after birth. | 1. Reactions acquired in the process of individual life. |
| 2. They are specific, i.e. characteristic of all representatives of this species. | 2. Individual. |
| 3. Permanent and maintained throughout life. | 3. Impermanent - they can appear and disappear. |
| 4. Carried out by the lower parts of the central nervous system (subcortical nuclei, brain stem, spinal cord). | 4. They are primarily a function of the cerebral cortex. |
| 5. They arise in response to adequate stimulation acting on a specific receptive field. | 5. Occurs in response to any stimuli acting on different receptive fields. |
Unconditioned reflexes can be simple or complex. Complex innate unconditional reflex reactions are called instincts. Their characteristic feature is the chain nature of the reactions.
Conditioned reflex is a complex multicomponent reaction that is developed on the basis of unconditioned reflexes using a previous indifferent stimulus. It has a signaling character, and the body meets the impact of an unconditioned stimulus prepared. For example, in the pre-launch period, blood is redistributed, breathing and blood circulation are increased, and when the muscle load begins, the body is already prepared for it.
To develop a conditioned reflex it is necessary:
- 1) the presence of two stimuli, one of which is unconditioned (food, painful stimulus, etc.), causing an unconditioned reflex reaction, and the other is conditioned (signal), signaling the upcoming unconditional stimulus (light, sound, type of food, etc. .);
2) multiple combinations of conditioned and unconditioned stimuli (although the formation of a conditioned reflex is possible with their single combination);
3) the conditioned stimulus must precede the action of the unconditional;
4) any stimulus from the external or internal environment can be used as a conditioned stimulus, which should be as indifferent as possible, not cause a defensive reaction, not have excessive force and be able to attract attention;
5) the unconditioned stimulus must be strong enough, otherwise a temporary connection will not be formed;
6) arousal from an unconditioned stimulus should be stronger than from a conditioned one;
7) it is necessary to eliminate extraneous stimuli, as they can cause inhibition of the conditioned reflex;
8) the animal in which the conditioned reflex is developed must be healthy;
9) when developing a conditioned reflex, motivation must be expressed, for example, when developing a food salivary reflex, the animal must be hungry, but in a well-fed animal, this reflex is not developed.
Conditioned reflexes are easier to develop in response to environmentally similar influences for a given animal. In this regard, conditioned reflexes are divided into natural and artificial. Natural conditioned reflexes are developed to agents that, under natural conditions, act together with a stimulus that causes an unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes are artificial, i.e. are produced in response to agents that are not normally associated with the action of an unconditioned stimulus, for example, the food salivary reflex to a bell.
The physiological basis for the emergence of conditioned reflexes is the formation of functional temporary connections in the higher parts of the central nervous system.
Temporary connection is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur during the combined action of conditioned and unconditioned stimuli. I.P. Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - the cortical representations of the conditioned and unconditioned reflexes. Excitation from the center of the conditioned reflex can be transmitted to the center of the unconditioned reflex from neuron to neuron.Consequently, the first way of forming a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical. However, when the cortical representation of the conditioned reflex is destroyed, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection occurs between the subcortical center of the conditioned reflex and the cortical center of the unconditioned reflex. When the cortical representation of the unconditioned reflex is destroyed, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can occur between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex.
Separation of the cortical centers of the conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of the conditioned reflex.
This indicates that a temporary connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex and the cortical center of the unconditioned reflex.There are different opinions on the issue of the mechanisms for the formation of temporary connections. Perhaps the formation of a temporary connection occurs according to the dominant principle. The source of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant, therefore attracts excitation from the focus of conditioned stimulation. If the excitation has passed along some nerve circuits, then next time it will pass along these paths much easier (the phenomenon of “blazing a path”). This is based on: the summation of excitations, a long-term increase in the excitability of synaptic formations, an increase in the amount of mediator in synapses, and an increase in the formation of new synapses. All this creates structural prerequisites for facilitating the movement of excitation along certain neural circuits.
Another idea about the mechanism of formation of a temporary connection is the convergent theory. It is based on the ability of neurons to respond to stimulation of different modalities. According to P.K. Anokhin, conditioned and unconditioned stimuli cause widespread activation of cortical neurons due to the inclusion of the reticular formation. As a result, the ascending signals (conditioned and unconditioned stimuli) overlap, i.e. these excitations meet on the same cortical neurons. As a result of the convergence of excitations, temporary connections arise and stabilize between the cortical representations of the conditioned and unconditioned stimuli.
To pull your hand away from a hot kettle, to close your eyes when there is a flash of light... We perform such actions automatically, without having time to think about what exactly we are doing and why. These are unconditioned human reflexes - innate reactions characteristic of all people without exception.
Discovery history, types, differences
Before examining unconditioned reflexes in detail, we will have to take a short excursion into biology and talk about reflex processes in general.
So what is a reflex? In psychology, this is the name given to the body’s response to changes in the external or internal environment, which is carried out using the central nervous system. Thanks to this ability, the body quickly adapts to changes in the surrounding world or in its internal state. For its implementation, a reflex arc is necessary, that is, the path along which the signal of irritation passes from the receptor to the corresponding organ.
Reflex reactions were first described by Rene Descartes in the 17th century. But the French scientist believed that this was not a psychological phenomenon. He considered reflexes as part of objective natural science knowledge, while psychology at that time was considered not a science, because it dealt only with subjective reality and was not subject to objective experiment.
And if the sense organs do not experience irritation, and sensitivity is lost, mental life freezes. Let us remember the well-known expression: “get tired until you lose your senses.” And indeed, when we are very tired, we, as a rule, do not dream and become almost insensitive to external stimuli: noise, light, even pain.
Sechenov's research was continued by I.P. Pavlov. He came to the conclusion that there are innate reflexes, the occurrence of which does not require any special conditions, and acquired ones, which arise during the body’s adaptation to the external environment.
If the release of saliva when food is served is a typical unconditioned reflex, and it is characteristic of all dogs, then saliva even at the sight of a helper is a typical conditioned reflex developed in individual animals. Hence the main difference between the two types: genetic or occurrence under the influence of the environment. In addition, unconditioned and conditioned reflexes differ in a number of indicators.
- Unconditioned are present in all individuals of the species, regardless of their living conditions; conditional, on the contrary, arise under the influence of the individual living conditions of the organism (this difference is clear from the name of each type).
- Unconditioned reactions are the foundation on which conditioned ones can be formed, but they need constant reinforcement.
- Reflex arcs of unconditioned reflexes are closed in the lower parts of the brain, as well as in the spinal cord. The conditioned arcs are formed in the cerebral cortex.
- Unconditioned reflex processes remain unchanged throughout a person’s life, although they can be somewhat transformed in the case of a serious illness. Conditional - arise and disappear. In other words, in one case the reflex arcs are permanent, in the other they are temporary.
From these differences, a general characteristic of unconditioned reflexes can easily be formed: they are hereditary, unchangeable, inherent in all representatives of the species and support the life of the organism in constant environmental conditions.
Where do they arise?
As already mentioned, both conditioned and unconditioned reflexes are possible thanks to the work of the central nervous system. Its most important components are the brain and spinal cord. As an example of an unconditioned reflex for which the spinal cord is responsible, we can cite the well-known knee reflex.
Unconditioned reflexes of the brain are numerous. In the lower parts of this organ there are various reflex centers. So, if you move up from the spinal cord, the first is the medulla oblongata. Sneezing, coughing, swallowing, salivation - these reflex processes are possible precisely thanks to the work of the medulla oblongata.
Under the control of the midbrain - reactions that occur in response to visual or auditory impulses. This includes constriction or dilation of the pupil depending on the amount of light falling on it, a reflexive turn towards the source of sound or light. The effect of such reflexes extends only to unfamiliar stimuli.
That is, for example, when there are numerous sharp sounds, a person will each time turn to a new place where the noise originates, rather than continue to listen, trying to understand where the first sound came from. The so-called unconditioned reflex of straightening the posture is closed through the intermediate part of the brain. These are the muscle contractions with which our body responds to changes in posture; they allow the body to be held in a new position.
Classification
Classification of unconditioned reflexes is carried out according to different criteria. For example, there is a division that is understandable even to a non-specialist into simple, complex and extremely complex.
The classification is quite simple based on the body’s relationship to the stimulus. If you rely on it, unconditioned reflex reactions are divided into positive (search for food by smell) and negative (desire to escape from the source of noise).
According to their biological significance, the following types of unconditioned reflexes are distinguished:
- Nutritional (swallowing, sucking, salivation).
- Sexual (sexual arousal).
- Defensive or protective (the same withdrawal of hands or the desire to cover the head with hands if a person thinks that a blow is about to follow).
- Indicative (the desire to identify unfamiliar stimuli: turning your head towards a sharp sound or touch). They were already discussed when we talked about the reflex centers of the midbrain.
- Locomotor, that is, serving for movement (support the body in a certain position in space).
Very often in the scientific literature there is a classification proposed by the Russian scientist P. V. Simonov. He divided all unconditioned reflexes into three groups: vital, role and self-development reflexes.
If the corresponding need is not satisfied, the physical existence of the organism ceases; another representative of the species is not needed to implement the reflex - these are the signs that unite all the reactions of this group.
Role-playing can be carried out, on the contrary, only through contact with another individual. These primarily include parental and sexual reflexes. The last group includes such reflexes as play, exploration, and the reflex of imitation of another individual.
Of course, there are other classification options, as well as other views on the methods of division given here. And this is not surprising: there is rarely unanimity among scientists.
Features and meaning
As we have already said, the reflex arcs of unconditioned reflexes are constant, but they themselves can be active at different periods of a person’s life. For example, sexual reflexes appear when the body reaches a certain age. Other reflex processes, on the contrary, fade away after a certain period of time. Suffice it to recall the unconscious grasping of a baby by an adult’s finger when pressing on his palm, which disappears with age.
The importance of unconditioned reflexes is enormous. They help to survive not only an individual organism, but the entire species. They are most significant in the early stages of a person’s life, when knowledge about the world has not yet been accumulated and the child’s activities are guided by reflex processes.
Moreover, according to recent research, certain unconditioned reflexes are carried out even in the womb (for example, sucking). With age, more and more conditioned reflexes are added to the unconditioned ones, which allow a person to better adapt to a changing environment. Author: Evgenia Bessonova