The outstanding Russian physiologist I.M. Sechenov was the first to express the idea of a connection between human consciousness and thinking and the reflex activity of his brain. This idea was developed and convincingly confirmed in numerous experiments by I.P. Pavlova. Therefore I.P. Pavlov is considered the creator of the doctrine of higher nervous activity.
Higher nervous activity- these are the functions of the cortex cerebral hemispheres brain and the nearest subcortical formations, where temporary nerve connections (conditioned reflexes) are developed anew, ensuring the most subtle and perfect individual adaptation of the body to changing conditions external environment.
UNCONDITIONED AND CONDITIONED REFLEXES
Higher nervous activity is reflexive in nature. Higher animals and humans have unconditioned and conditioned reflexes. Their specificity is as follows.
Unconditioned reflexes ensuring the maintenance of vital functions in relatively constant environmental conditions, are inherent in a person from birth. These include food (sucking, swallowing, salivation, etc.), defensive (coughing, blinking, withdrawing a hand, etc.), reproduction (feeding and caring for offspring), respiratory, etc.
Conditioned reflexes are developed on the basis of unconditioned ones under the influence of a conditioned stimulus. They provide a more perfect adaptation of the body to changing environmental conditions. They help to find food by smell, avoid danger, navigate, etc.
Meaning of the word. In humans, conditioned reflexes can be formed not only as in animals, on the basis of the first signal system, when the conditioned stimuli are directly objects of the external world, but also on the basis of the second (speech) signal system, when the conditioned stimuli are words expressing concepts about objects and phenomena . Conditioned reflexes are physiological basis technical processes, the basis of thinking. The word is a kind of irritant for many conditioned reflexes. For example, just talking about food or describing it can cause a person to salivate.
| Unconditioned reflexes | Conditioned reflexes (temporary connections) |
| Congenital, hereditary reflex reactions of this type | Acquired in progress individual development based on unconditioned reflexes |
| Reflex centers are located in the subcortical nuclei, brain stem and spinal cord | Reflex centers are located in the cerebral cortex |
| Racks. They persist throughout life. Their number is limited | Changeable. New reflexes arise, and old ones fade away when environmental conditions change. Quantity is unlimited |
| Carry out the relationship between parts of the body, reflex self-regulation and maintaining the constancy of the internal environment | Carry out a reflex reaction of the body to a stimulus (conditioned), signaling the upcoming action of an unconditioned stimulus |
Human consciousness is associated with the activity of the cerebral cortex. This has been convincingly proven by numerous experiments by I.P. Pavlov, as well as by the study of diseases and dysfunctions of the brain.
The teachings of I. P. Pavlov on the higher nervous activity of man convincingly proved the inconsistency and anti-scientific nature of religious ideas about the “soul”.
Inhibition of conditioned reflexes. When environmental conditions change, previously developed conditioned reflexes fade away and new ones are formed. I.P. Pavlov distinguished two types of inhibition of conditioned reflexes.
External braking occurs when the body is exposed to an irritant that is stronger than the previous one. At the same time, a new focus of excitation is formed in the cerebral cortex. For example, in a dog, the conditioned salivary reflex developed in response to light (see “Digestion”) is inhibited under experimental conditions by a stronger stimulus - the sound of a bell. The latter causes strong stimulation in the auditory zone of the cerebral cortex. Initially, it generates inhibition of neighboring areas, and then spreads to the visual area. Therefore, excitation cannot be carried out through the neurons located in it and the arc of the previous conditioned reflex is interrupted.
Internal inhibition occurs in the arc of a conditioned reflex when the conditioned stimulus ceases to receive reinforcement from the unconditioned stimulus and the temporary connections formed in the cortex are gradually inhibited. When conditioned reflexes are repeated in the same sequence, dynamic stereotypes are formed that make up habits and skills.
Hygiene of physical and mental work. The activity of the body depends on the state of the central nervous system. Overwork leads to disruption of the vital functions of the body, reduces perception, attention, memory and performance.
During monotonous physical labor, only one muscle group works and only one part of the central nervous system is excited, which leads to its fatigue.
To avoid overwork, it is useful to perform industrial exercises during breaks, which involve other muscles. This, in turn, leads to the excitation of new areas of the cerebral cortex, inhibition of previously working areas, their rest and restoration of performance.
Mental work also causes fatigue in the central nervous system. The best vacation this involves gymnastics or other physical activity.
The daily routine is of great importance in the formation of conditioned reflexes. When followed, a person develops many important conditioned reflexes that stimulate the better functioning of various organ systems and prevent their overwork.
Alternation of physical and mental labor, rationalization of work, adherence to the daily routine, leisure are of paramount importance for protecting the central nervous system from fatigue.
Sleep gives the most complete rest to the central nervous system. Alternation of sleep and wakefulness - necessary condition human existence. I.P. Pavlov experimentally proved that sleep is an inhibition that involves the cerebral cortex and other parts of the brain. During sleep, metabolism, hearing, smell, and the intensity of activity of a number of organ systems decrease, muscle tone decreases, and thinking turns off. Sleep is a protective device against overwork of the nervous system. Infants sleep 20-22 hours, schoolchildren - 9-11 hours, adults - 7-8 hours. With lack of sleep, a person loses his ability to work. In order for the body to receive the most complete rest during sleep, it is necessary to go to bed at the same time, eliminate bright light, noise, ventilate the room, etc.
Reflexes- this is the body’s response to irritation of sensitive nerve formations - receptors, carried out with the participation of the nervous system.
Types of reflexes: conditioned and unconditioned
|
Reflexes |
Unconditioned reflexes |
Conditioned reflexes |
|
Characteristic |
1. These are congenital , hereditarily transmitted reactions of the body. 2. Are species-specificthose. formed in the process of evolution and characteristic of all representatives of a given species. 3. They are relative permanent and persist throughout the life of the organism. 4. Occur on a specific (adequate) stimulus for each reflex. 5. Reflex centers are at the level spinal cord and brain stem. |
1. These are purchased in the process of life, reactions of the body that are not inherited by the offspring. 2. Are individual,those. arising from " life experience" of each organism. 3. They are fickle, and depending depending on certain conditionscan be produced zach repent or fade away. 4. May form on any perceived by the body stimulus. 5. Reflex centers prey are materially incerebral cortex. |
|
Examples |
Nutritional, sexual, defensive, orientation, maintaining homeostasis. |
Salivation for smell, precise movements when writing and playing the piano. |
|
Meaning |
They help survival, this is “putting the experience of ancestors into practice”. |
P help adjustedadapt to changing conditions external environment. |
Reflex arc
With the help of a reflex, excitation spreads along reflex arcs and the process of inhibition occurs.
Reflex arc- this is the path along which nerve impulses are carried out during a reflex.
Reflex arc diagram
5 reflex arc links:
1. Receptor - perceives irritation and converts it into a nerve impulse.
2. Sensitive (centripetal) neuron - transmits excitation to the center.
3. Nerve center - excitation switches from sensory neurons to motor ones (there is an interneuron in the three-neuron arch).
4. Motor (centrifugal) neuron - carries excitation from the central nervous system to the working organ.
5. Working body - reacts to the received irritation.
Information from the receptors of the working organ enters the nerve center to confirm the effectiveness of the reaction and, if necessary, coordinate it.
Diagram of a knee reflex reflex arc (a simple arc of two neurons)
Diagram of the reflex arc of the flexion reflex (complex arc of several neurons)
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A source of information:
Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.
Rezanova E.A. Human biology. In tables and diagrams./ M.: 2008.
Differences between conditioned reflexes and unconditioned ones. Unconditioned reflexes are innate reactions of the body; they were formed and consolidated in the process of evolution and are inherited. Conditioned reflexes arise, become consolidated, and fade away throughout life and are individual. Unconditioned reflexes are specific, i.e. they are found in all individuals of a given species. Conditioned reflexes may be developed in some individuals of a given species, but absent in others; they are individual. Unconditioned reflexes do not require special conditions for their occurrence; they necessarily arise if adequate stimuli act on certain receptors. Conditioned reflexes require special conditions for their formation; they can be formed in response to any stimuli (of optimal strength and duration) from any receptive field. Unconditioned reflexes are relatively constant, persistent, unchanging and persist throughout life. Conditioned reflexes are changeable and more mobile.
Unconditioned reflexes can occur at the level of the spinal cord and brain stem. Conditioned reflexes can be formed in response to any signals perceived by the body and are primarily a function of the cerebral cortex, realized with the participation of subcortical structures.
Unconditioned reflexes can ensure the existence of an organism only at the very early stage of life. The body's adaptation to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life. Conditioned reflexes are changeable. In the process of life, some conditioned reflexes, losing their meaning, fade away, while others are developed.
Biological significance of conditioned reflexes. The body is born with a certain fund of unconditioned reflexes. They provide him with the maintenance of vital functions in relatively constant conditions of existence. These include unconditioned reflexes: food (chewing, sucking, swallowing, secretion of saliva, gastric juice, etc.), defensive (pulling a hand away from a hot object, coughing, sneezing, blinking when a stream of air enters the eye, etc.), sexual reflexes (reflexes associated with sexual intercourse, feeding and caring for offspring), thermoregulatory, respiratory, cardiac, vascular reflexes, maintaining the constancy of the internal environment of the body (homeostasis), etc.
Conditioned reflexes provide a more perfect adaptation of the body to changing living conditions. They help to find food by smell, timely escape from danger, and orientation in time and space. Conditioned reflex separation of saliva, gastric, pancreatic juices in appearance, smell, meal time creates Better conditions to digest food before it enters the body. Enhancing gas exchange and increasing pulmonary ventilation before starting work, only when seeing the environment in which the work is being done, contributes to greater endurance and better performance of the body during muscular activity.
When a conditioned signal is applied, the cerebral cortex provides the body with preliminary preparation for responding to those environmental stimuli that will subsequently have an impact. Therefore, the activity of the cerebral cortex is signaling.
Conditions for the formation of a conditioned reflex. Conditioned reflexes are developed on the basis of unconditioned ones. Conditioned reflex so named by I.P. Pavlov because certain conditions are needed for its formation. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or a specific change internal state body. In the laboratory of I.P. Pavlov, the flashing of an electric light bulb, the bell, the gurgling of water, skin irritation, gustatory, olfactory stimuli, the clinking of dishes, the sight of a burning candle, etc. were used as conditioned stimuli. Conditioned reflexes are temporarily developed in a person by observing a work schedule, eating at the same time, consistent with bedtime.
A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex. In this way, conditioned reflexes of the second order are formed, then the indifferent stimulus must be reinforced with a conditioned stimulus of the first order. It was possible to form conditioned reflexes of the third and fourth orders in the experiment. These reflexes are usually unstable. Children managed to develop sixth-order reflexes.
The possibility of developing conditioned reflexes is hampered or completely eliminated by strong extraneous stimuli, illness, etc.
In order to develop a conditioned reflex, the conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that evokes an unconditioned reflex. The clinking of knives in the dining room will cause salivation in a person only if this clinking is supported by food one or more times. The ringing of knives and forks in our case is a conditioned stimulus, and the unconditioned stimulus that causes the salivary unconditioned reflex is food. The sight of a burning candle can become a signal for a child to withdraw his hand only if at least once the sight of a candle coincides with pain from a burn. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).
The mechanism of formation of a conditioned reflex. According to the ideas of I.P. Pavlov, the formation of a conditioned reflex is associated with the establishment of a temporary connection between two groups of cortical cells: between those who perceive conditioned and those who perceive unconditional stimulation. This connection becomes stronger the more often both areas of the cortex are simultaneously excited. After several combinations, the connection turns out to be so strong that under the influence of only one conditioned stimulus, excitation also occurs in the second focus (Fig. 15).
Initially, an indifferent stimulus, if it is new and unexpected, causes a general generalized reaction of the body - an orienting reflex, which I. P. Pavlov called the exploratory or “what is it?” reflex. Any stimulus, if used for the first time, causes a motor reaction (general shudder, turning the eyes and ears towards the stimulus), increased breathing, heartbeat, generalized changes in the electrical activity of the brain - the alpha rhythm is replaced by rapid oscillations (beta rhythm). These reactions reflect generalized generalized arousal. When a stimulus is repeated, if it does not become a signal for a specific activity, the orienting reflex fades away. For example, if a dog hears a bell for the first time, it will give a general approximate reaction to it, but will not produce saliva. Now let's back up the sound of the bell with food. In this case, two foci of excitation will appear in the cerebral cortex - one in the auditory zone, and the other in the food center (these are areas of the cortex that are excited under the influence of the smell and taste of food). After several reinforcements of the bell with food, a temporary connection will arise (close) in the cerebral cortex between the two foci of excitation.
In the course of further research, facts were obtained indicating that the closure of the temporary connection occurs not only along horizontal fibers (bark - bark). Gray matter was separated by incisions in dogs different areas cortex, however, this did not prevent the formation of temporary connections between the cells of these areas. This gave reason to believe that the cortex-subcortex-cortex pathways also play an important role in establishing temporary connections. In this case, centripetal impulses from the conditioned stimulus through the thalamus and nonspecific system (hippocampus, reticular formation) enter the corresponding zone of the cortex. Here they are processed and along descending pathways reach the subcortical formations, from where the impulses come again to the cortex, but already in the zone of representation of the unconditioned reflex.
What happens in the neurons involved in the formation of a temporary connection? There are different points of view on this matter. One of them assigns the main role to morphological changes in the endings of nerve processes.
Another point of view about the mechanism of the conditioned reflex is based on the principle of dominance by A. A. Ukhtomsky. In the nervous system at each moment of time there are dominant foci of excitation - dominant foci. The dominant focus has the property of attracting to itself the excitation entering other nerve centers, and thereby intensifying. For example, during hunger, a persistent focus with increased excitability appears in the corresponding parts of the central nervous system - a food dominant. If you let a hungry puppy lap milk and at the same time begin to irritate the paw with an electric current, then the puppy does not withdraw its paw, but begins to lap with even greater intensity. In a well-fed puppy, irritation of the paw with an electric current causes a reaction of its withdrawal.
It is believed that during the formation of a conditioned reflex, the focus of persistent excitation that arose in the center of the unconditioned reflex “attracts” to itself the excitation that arose in the center of the conditioned stimulus. As these two excitations combine, a temporary connection is formed.
Many researchers believe that the leading role in fixing the temporary connection belongs to changes in protein synthesis; Specific protein substances associated with imprinting a temporary connection have been described. The formation of a temporary connection is associated with the mechanisms of storing traces of excitation. However, memory mechanisms cannot be reduced to “belt connection” mechanisms.
There is evidence of the possibility of storing traces at the level of single neurons. Cases of imprinting from a single action of an external stimulus are well known. This gives grounds to believe that the closure of a temporary connection is one of the mechanisms of memory.
Inhibition of conditioned reflexes. Conditioned reflexes are plastic. They can persist for a long time, or they can be inhibited. Two types of inhibition of conditioned reflexes have been described - internal and external.
Unconditional, or external, inhibition. This type of inhibition occurs in cases where in the cerebral cortex, during the implementation of a conditioned reflex, a new, sufficiently strong focus of excitation appears, not associated with this conditioned reflex. If a dog has developed a conditioned salivary reflex to the sound of a bell, then turning on a bright light at the sound of a bell in this dog inhibits the previously developed salivation reflex. This inhibition is based on the phenomenon of negative induction: a new strong focus of excitation in the cortex from extraneous stimulation causes a decrease in excitability in the areas of the cerebral cortex associated with the implementation of the conditioned reflex, and, as a consequence of this phenomenon, inhibition of the conditioned reflex occurs. Sometimes this inhibition of conditioned reflexes is called inductive inhibition.
Inductive inhibition does not require development (that is why it is classified as unconditioned inhibition) and develops immediately as soon as an external stimulus, foreign to the given conditioned reflex, acts.
External braking also includes transcendental braking. It manifests itself when the strength or time of action of the conditioned stimulus increases excessively. In this case, the conditioned reflex weakens or completely disappears. This inhibition has a protective value, as it protects nerve cells from stimuli of too great strength or duration that could disrupt their activity.
Conditioned, or internal, inhibition. Internal inhibition, in contrast to external inhibition, develops within the arc of the conditioned reflex, i.e., in those nervous structures that are involved in the implementation of this reflex.
If external inhibition occurs immediately as soon as the inhibitory agent has acted, then internal inhibition must be developed; it occurs under certain conditions, and this sometimes takes a long time.
One type of internal inhibition is extinction. It develops if the conditioned reflex is not reinforced by an unconditioned stimulus many times.
Some time after extinction, the conditioned reflex can be restored. This will happen if we again reinforce the action of the conditioned stimulus with the unconditioned one.
Fragile conditioned reflexes are restored with difficulty. Extinction can explain the temporary loss of labor skills and the ability to play musical instruments.
In children, decline occurs much more slowly than in adults. This is why it is difficult to wean children from bad habits. Extinction is the basis of forgetting.
The extinction of conditioned reflexes has important biological significance. Thanks to it, the body stops responding to signals that have lost their meaning. How many unnecessary, superfluous movements would a person make during writing, labor operations, and sports exercises without extinctive inhibition!
The delay of conditioned reflexes also refers to internal inhibition. It develops if the reinforcement of a conditioned stimulus by an unconditioned stimulus is delayed. Usually, when developing a conditioned reflex, a conditioned stimulus-signal (for example, a bell) is turned on, and after 1-5 s food is given (unconditioned reinforcement). When the reflex is developed, immediately after the bell is turned on, without giving food, saliva begins to flow. Now let’s do this: turn on the bell, and gradually delay the food reinforcement until 2-3 minutes after the bell starts sounding. After several (sometimes very multiple) combinations of a sounding bell with delayed reinforcement with food, a delay develops: the bell turns on, and saliva will no longer flow immediately, but 2-3 minutes after the bell is turned on. Due to the non-reinforcement of the conditioned stimulus (bell) for 2-3 minutes by the unconditioned stimulus (food), the conditioned stimulus acquires an inhibitory value during the period of non-reinforcement.
The delay creates conditions for better orientation of the animal in the surrounding world. The wolf does not immediately rush at the hare when it sees it at a considerable distance. He waits for the hare to approach. From the moment the wolf saw the hare until the time the hare approached the wolf, a process of internal inhibition took place in the wolf’s cerebral cortex: motor and food conditioned reflexes were inhibited. If this did not happen, the wolf would often be left without prey, breaking into pursuit as soon as he sees the hare. The resulting delay provides the wolf with prey.
Delay in children is developed with great difficulty under the influence of upbringing and training. Remember how a first-grader impatiently reaches out his hand, waving it, getting up from his desk so that the teacher notices him. And only by high school age (and even then not always) do we notice endurance, the ability to restrain our desires, and willpower.
Similar sound, olfactory and other stimuli can signal completely different events. Only an accurate analysis of these similar stimuli ensures biologically appropriate reactions of the animal. Analysis of stimuli consists of distinguishing, separating different signals, differentiating similar interactions on the body. In the laboratory of I.P. Pavlov, for example, it was possible to develop the following differentiation: 100 metronome beats per minute were reinforced with food, and 96 beats were not reinforced. After several repetitions, the dog distinguished 100 metronome beats from 96: at 100 beats she salivated, at 96 beats the saliva did not separate. Discrimination, or differentiation, of similar conditioned stimuli is developed by reinforcing some and non-reinforcing other stimuli. The inhibition that develops suppresses the reflex reaction to non-reinforced stimuli. Differentiation is one of the types of conditioned (internal) inhibition.
Thanks to differential inhibition, it is possible to identify signal-significant signs of a stimulus from many sounds, objects, faces, etc. around us. Differentiation is developed in children from the first months of life.
Dynamic stereotype. The external world acts on the body not with single stimuli, but usually with a system of simultaneous and sequential stimuli. If this system is often repeated in this order, then this leads to the formation of a dynamic stereotype.
A dynamic stereotype is a sequential chain of conditioned reflex acts, carried out in a strictly defined, time-fixed order and resulting from a complex systemic reaction of the body to a complex of conditioned stimuli. Thanks to the formation of chain conditioned reflexes, each previous activity of the body becomes a conditioned stimulus - a signal for the next one. Thus, by previous activity the body is prepared for the subsequent one. A manifestation of a dynamic stereotype is a conditioned reflex for time, which contributes to the optimal functioning of the body with the correct daily routine. For example, eating at certain hours ensures good appetite and normal digestion; Consistency in keeping a bedtime helps children and adolescents fall asleep quickly and thus sleep longer; Carrying out educational work and work activities always at the same hours leads to faster processing of the body and better assimilation of knowledge, skills, and abilities.
A stereotype is difficult to develop, but if it is developed, then maintaining it does not require significant strain on cortical activity, and many actions become automatic. ;d A dynamic stereotype is the basis for the formation of habits in a person, the formation of a certain sequence in labor operations, and the acquisition of skills.
Walking, running, jumping, skiing, playing the piano, using a spoon, fork, knife when eating, writing - all these are skills that are based on the formation of dynamic stereotypes in the cerebral cortex.
The formation of a dynamic stereotype underlies the daily routine of every person. Stereotypes persist for many years and form the basis of human behavior. Stereotypes that arise in early childhood are very difficult to change. Let us remember how difficult it is to “retrain” a child if he has learned to hold a pen incorrectly when writing, sit incorrectly at the table, etc. The difficulty of remaking stereotypes forces Special attention on the correct methods of raising and teaching children from the first years of life.
A dynamic stereotype is one of the manifestations of the systemic organization of higher cortical functions aimed at ensuring stable reactions of the body.
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 the one that suits you best 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 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
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 coordinated activities of various functional systems organism, aimed at maintaining its homeostasis and interaction with 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 are the basis innate behavior 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 - conditional and unconditional.
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, causing 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 lowest 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 natural conditions are a property of an unconditioned stimulus, they 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.
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
According to 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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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, that is, characteristic of all representatives of a given 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.