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 emerges. 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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Conditioned reflexes are reactions of the whole organism or any part of it to external or internal stimuli. They manifest themselves through the disappearance, weakening or strengthening of certain activities.
Conditioned reflexes are the body’s assistants, allowing it to quickly respond to any changes and adapt to them.
Story
The idea of a conditioned reflex was first put forward by the French philosopher and scientist R. Descartes. Somewhat later, the Russian physiologist I. Sechenov created and experimentally proved a new theory regarding the reactions of the body. For the first time in the history of physiology, it was concluded that conditioned reflexes are a mechanism that is activated not only; the entire nervous system is involved in its work. This allows the body to maintain a connection with the environment.
Studied by Pavlov. This outstanding Russian scientist was able to explain the mechanism of action of the cerebral cortex and cerebral hemispheres. At the beginning of the 20th century, he created the theory of conditioned reflexes. This scientific work became a real revolution in physiology. Scientists have proven that conditioned reflexes are reactions of the body that are acquired throughout life, based on unconditioned reflexes.
Instincts
Certain reflexes of the unconditional type are characteristic of each type of living organism. They are called instincts. Some of them are quite complex. An example of this would be bees making honeycombs or birds making nests. Thanks to the presence of instincts, the body is able to optimally adapt to environmental conditions.
They are congenital. They are inherited. In addition, they are classified as species, since they are characteristic of all representatives of a certain species. Instincts are permanent and persist throughout life. They manifest themselves in response to adequate stimuli that are applied to a specific single receptive field. Physiologically, unconditioned reflexes are closed in the brainstem and at the level of the spinal cord. They manifest themselves through anatomically expressed
As for monkeys and humans, the implementation of most of the complex unconditioned reflexes is impossible without the participation of the cerebral cortex. When its integrity is violated, pathological changes in unconditioned reflexes occur, and some of them simply disappear.
Classification of instincts
Unconditioned reflexes are very strong. Only under certain conditions, when their manifestation becomes unnecessary, can they disappear. For example, the canary, domesticated about three hundred years ago, currently does not have the instinct to build nests. The following types of unconditioned reflexes are distinguished:
Which is the body's reaction to a variety of physical or chemical stimuli. Such reflexes, in turn, can manifest locally (withdrawal of the hand) or be complex (flight from danger).
- Food instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of sequential actions - from searching for prey to attacking it and further eating it.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.
A comfortable instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- Orienting instinct, when the eyes and head are turned towards the stimulus. This reflex is necessary to preserve life.
- The instinct of freedom, which is especially clearly expressed in the behavior of animals in captivity. They constantly want to break free and often die, refusing water and food.
The emergence of conditioned reflexes
During life, acquired reactions of the body are added to the inherited instincts. They are called conditioned reflexes. They are acquired by the body as a result of individual development. The basis for obtaining conditioned reflexes is life experience. Unlike instincts, these reactions are individual. They may be present in some members of the species and absent in others. In addition, a conditioned reflex is a reaction that may not persist throughout life. Under certain conditions, it is produced, consolidated, and disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.
The mechanism of the conditioned reflex closes at the level. If it is removed, then only instincts will remain.
The formation of conditioned reflexes occurs on the basis of unconditioned ones. To carry out this process, a certain condition must be met. In this case, any change in the external environment must be combined in time with the internal state of the body and perceived by the cerebral cortex with a simultaneously carried out unconditional reaction of the body. Only in this case does a conditioned stimulus or signal appear that contributes to the emergence of a conditioned reflex.
Examples
For the body’s reaction to occur, such as the release of saliva when knives and forks clink, as well as when an animal’s feeding cup is knocked (in humans and dogs, respectively), an indispensable condition is the repeated coincidence of these sounds with the process of providing food.
In the same way, the sound of a bell or the turning on of a light bulb will cause the dog's paw to flex if these phenomena have repeatedly occurred accompanied by electrical stimulation of the animal's leg, as a result of which an unconditioned type of flexion reflex appears.
The conditioned reflex is the child's hands being pulled away from the fire and subsequent crying. However, these phenomena will only occur if the type of fire, even once, coincides with a burn.
Reaction components
The body's reaction to irritation is a change in breathing, secretion, movement, etc. As a rule, unconditioned reflexes are quite complex reactions. That is why they contain several components at once. For example, the defensive reflex is accompanied not only by defensive movements, but also by increased breathing, accelerated activity of the heart muscle, and changes in blood composition. In this case, vocal reactions may also appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.
Conditioned reactions usually reproduce the structure of unconditioned ones. This occurs due to the stimulation of the same nerve centers by stimuli.
Classification of conditioned reflexes
The responses acquired by the body to various stimuli are divided into types. Some of the existing classifications are of great importance in solving not only theoretical, but also practical problems. One of the areas of application of this knowledge is sports activity.
Natural and artificial reactions of the body
There are conditioned reflexes that arise under the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the sight and smell of food. Such conditioned reflexes are natural. They are characterized by rapid production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The importance of the conditioned reflex is especially great in the very first stages of an organism’s life, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature changes, light, etc. Under natural conditions, they are not irritants. It is precisely such reactions that are called artificial. They are developed slowly and, in the absence of reinforcement, quickly disappear. For example, artificial conditioned human reflexes are reactions to the sound of a bell, touching the skin, weakening or increasing lighting, etc.
First and highest order
There are types of conditioned reflexes that are formed on the basis of unconditioned ones. These are first order reactions. There are also higher categories. Thus, reactions that are developed on the basis of already existing conditioned reflexes are classified as higher-order reactions. How do they arise? When developing such conditioned reflexes, the indifferent signal is reinforced with well-learned conditioned stimuli.
For example, irritation in the form of a bell is constantly reinforced by food. In this case, a first-order conditioned reflex is developed. On its basis, a reaction to another stimulus, for example, to light, can be fixed. This will become a second-order conditioned reflex.
Positive and negative reactions
Conditioned reflexes can influence the activity of the body. Such reactions are considered positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the body, then the reactions are classified as negative. For the process of adaptation to constantly changing environmental conditions, both one and the second species are of great importance.
At the same time, there is a close relationship between them, since when one type of activity is manifested, the other is certainly suppressed. For example, when the command “Attention!” is heard, the muscles are in a certain position. At the same time, motor reactions (running, walking, etc.) are inhibited.
Education mechanism
Conditioned reflexes occur with the simultaneous action of a conditioned stimulus and an unconditioned reflex. In this case, certain conditions must be met:
The unconditioned reflex is biologically stronger;
- the manifestation of a conditioned stimulus is somewhat ahead of the action of instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditional;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli producing a distracting effect is met.
The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (closure) with each other. In this case, the irritation is perceived by cortical neurons, which are part of the unconditioned reflex arc.
Inhibition of conditioned reactions
In order to ensure adequate behavior of the organism and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. An action in the opposite direction will be required. This is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not necessary. According to the theory developed by Pavlov, certain types of cortical inhibition are distinguished. The first of these is unconditional. It appears as a response to the action of some extraneous stimulus. There is also internal inhibition. It is called conditional.
External braking
This reaction received this name due to the fact that its development is facilitated by processes taking place in those areas of the cortex that do not participate in reflex activity. For example, an extraneous smell, sound, or change in lighting before the onset of the food reflex can reduce it or contribute to its complete disappearance. A new stimulus acts as an inhibitor for a conditioned response.
Eating reflexes can also be eliminated by painful stimuli. Inhibition of the body's reaction is facilitated by bladder overflow, vomiting, internal inflammatory processes, etc. All of them inhibit food reflexes.
Internal inhibition
It occurs when the received signal is not reinforced by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, an animal is periodically turned on an electric light bulb in front of its eyes during the day without bringing food. It has been experimentally proven that saliva production will decrease each time. As a result, the reaction will fade away completely. However, the reflex will not disappear without a trace. He will simply slow down. This has also been proven experimentally.
Conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the body’s reaction to this stimulus will subsequently disappear forever.
Types of internal braking
Several types of elimination of the body's reaction to stimuli are classified. Thus, the basis for the disappearance of conditioned reflexes, which are simply not needed under given specific conditions, is extinctive inhibition. There is another type of this phenomenon. This is discriminative or differentiated inhibition. Thus, an animal can distinguish the number of metronome beats at which food will be brought to it. This happens when this conditioned reflex is previously developed. The animal distinguishes between stimuli. The basis of this reaction is internal inhibition.
The value of eliminating reactions
Conditioned inhibition plays a significant role in the life of the body. Thanks to it, the process of adaptation to the environment occurs much better. The ability to navigate in a variety of complex situations is provided by a combination of excitation and inhibition, which are two forms of a single nervous process.
Conclusion
There are an infinite number of conditioned reflexes. They are the factor that determines the behavior of a living organism. With the help of conditioned reflexes, animals and humans adapt to their environment.
There are many indirect signs of body reactions that have signaling value. For example, an animal, knowing in advance that danger is approaching, organizes its behavior in a certain way.
The process of developing conditioned reflexes, which belong to a higher order, is a synthesis of temporary connections.
The basic principles and patterns manifested in the formation of not only complex but also elementary reactions are the same for all living organisms. From this follows an important conclusion for philosophy and the natural sciences that something cannot but obey the general laws of biology. In this regard, it can be studied objectively. However, it is worth keeping in mind that the activity of the human brain is qualitatively specific and fundamentally different from the activity of the animal brain.
“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.
Reflex- this is the body’s response to irritation from the external or internal environment, carried out with the help of the central nervous system. There are unconditioned and conditioned reflexes.
Unconditioned reflexes- these are congenital, permanent, hereditarily transmitted reactions characteristic of representatives of a given type of organism. For example, pupillary, knee, Achilles and other reflexes. Unconditioned reflexes ensure the interaction of the organism with the external environment, its adaptation to environmental conditions and create conditions for the integrity of the organism. Unconditioned reflexes arise immediately after the action of a stimulus, since they are carried out along ready-made, inherited reflex arcs, which are always constant. Complex unconditioned reflexes are called instincts.
Unconditioned reflexes include sucking and motor reflexes, which are already characteristic of an 18-week fetus. Unconditioned reflexes are the basis for the development of conditioned reflexes in animals and humans. In children, with age, they turn into synthetic complexes of reflexes, which increases the body’s adaptability to the external environment.
Conditioned reflexes- reactions are adaptive, temporary and strictly individual. They are inherent only in one or several representatives of the species, subjected to training (training) or exposure to the natural environment. Conditioned reflexes are developed gradually, in the presence of a certain environment, and are a function of the normal, mature cortex of the cerebral hemispheres and lower parts of the brain. In this regard, conditioned reflexes are related to unconditioned ones, since they are a response of the same material substrate - nervous tissue.
If the conditions for the development of reflexes are constant from generation to generation, then the reflexes can become hereditary, that is, they can turn into unconditioned. An example of such a reflex is the opening of the beak of blind and fledgling chicks in response to the shaking of the nest by a bird flying in to feed them. Since shaking the nest is followed by feeding, which was repeated in all generations, the conditioned reflex becomes unconditioned. However, all conditioned reflexes are adaptive reactions to a new external environment. They disappear when the cerebral cortex is removed. Higher mammals and humans with damage to the cortex become deeply disabled and die in the absence of the necessary care.
Numerous experiments conducted by I.P. Pavlov showed that the basis for the development of conditioned reflexes is formed by impulses arriving along afferent fibers from extero- or interoreceptors. For their formation, the following conditions are necessary: 1) the action of an indifferent (future conditioned) stimulus must precede the action of an unconditioned stimulus. With a different sequence, the reflex is not developed or is very weak and quickly fades away; 2) for a certain time, the action of the conditioned stimulus must be combined with the action of the unconditioned stimulus, that is, the conditioned stimulus is reinforced by the unconditioned. This combination of stimuli should be repeated several times. In addition, a prerequisite for the development of a conditioned reflex is the normal function of the cerebral cortex, the absence of painful processes in the body and extraneous stimuli.
Otherwise, in addition to the reinforced reflex being developed, an indicative or reflex of the internal organs (intestines, bladder, etc.) will also occur.
An active conditioned stimulus always causes a weak focus of excitation in the corresponding area of the cerebral cortex. The unconditioned stimulus that is connected (after 1-5 s) creates a second, stronger focus of excitation in the corresponding subcortical nuclei and the area of the cerebral cortex, which distracts the impulses of the first (conditioned) weaker stimulus. As a result, a temporary connection is established between both foci of excitation of the cerebral cortex. With each repetition (i.e. reinforcement), this connection becomes stronger. The conditioned stimulus turns into a conditioned reflex signal. To develop a conditioned reflex, a conditioned stimulus of sufficient strength and high excitability of the cells of the cerebral cortex are required, which must be free from external stimuli. Compliance with the above conditions accelerates the development of a conditioned reflex.
Depending on the method of development, conditioned reflexes are divided into secretory, motor, vascular, reflexes of changes in internal organs, etc.
A reflex developed by reinforcing a conditioned stimulus with an unconditioned one is called a first-order conditioned reflex. Based on it, you can develop a new reflex. For example, by combining a light signal with feeding, a dog has developed a strong conditioned salivation reflex. If you give a bell (sound stimulus) before the light signal, then after several repetitions of this combination the dog begins to salivate in response to the sound signal. This will be a second-order reflex, or secondary, reinforced not by an unconditioned stimulus, but by a first-order conditioned reflex. When developing conditioned reflexes of higher orders, it is necessary that a new indifferent stimulus is turned on 10-15 s before the onset of the conditioned stimulus of a previously developed reflex. If the stimulus acts at intervals that are closer or combined, then a new reflex will not appear, and the previously developed one will fade away, as inhibition will develop in the cerebral cortex. Repeated repetition of jointly acting stimuli or a significant overlap of the time of action of one stimulus on another causes the appearance of a reflex to a complex stimulus.
A certain period of time can also become a conditioned stimulus for developing a reflex. People have a temporary reflex to feel hungry during the hours when they usually eat. Intervals can be quite short. In school-age children, a reflex for time is a weakening of attention before the end of the lesson (1-1.5 minutes before the bell). This is the result not only of fatigue, but also of the rhythmic functioning of the brain during training sessions. The reaction to time in the body is the rhythm of many periodically changing processes, for example, breathing, cardiac activity, awakening from sleep or hibernation, molting of animals, etc. Its occurrence is based on the rhythmic sending of impulses from the corresponding organs to the brain and back to the effector organs devices.
Higher nervous activity of a person is a complex set of nervous processes that underlie human behavior and ensure adaptation to changing conditions of existence.
The material substrate of higher nervous activity is the brain. By receiving information through sensory systems, the brain ensures the interaction of the body with the environment and maintains the constancy of the body's internal environment. The higher functions of the brain are perception of the environment, purposeful movements, emotions, memory and learning, wakefulness and sleep, thinking and speech, unconditioned and conditioned reflexes.
The brain operates on a reflex principle, continuously responding to external and internal stimuli. A reflex is usually understood as the most adequate, stereotypical reaction to sensory stimuli. The body's response to a stimulus is almost always expressed by movement. Any sensation is consciously or unconsciously accompanied by a motor response. Movements can be involuntary, which are mainly part of the system of providing unconditioned reflexes, and voluntary, which, together with involuntary ones, provide conditioned reflexes.
The foundations of the modern doctrine of higher nervous activity were laid by I.P. Pavlov, who developed the theory of conditioned reflexes. All reflexes characteristic of the body, I.P. Pavlov divided into two classes: unconditional and conditional (1903).
Unconditioned reflexes include: coughing when foreign bodies enter the respiratory tract, salivation when seeing food, withdrawing a hand when burned, etc.
For the formation of a conditioned reflex, it is necessary to combine two stimuli in time: a conditioned one (indifferent, signal, indifferent to the reaction being developed) and an unconditioned one, causing a certain unconditioned reflex. The conditioned signal (flash of light, sound of a bell, etc.) should be somewhat ahead of the unconditional reinforcement in time. Typically, a conditioned reflex is developed after several combinations of conditioned and unconditioned stimuli, but in some cases, one presentation of a conditioned and unconditioned stimulus is enough for a conditioned reflex to form.
For example, if you turn on the bell several times before giving the dog food, then, starting at some point, the dog will approach the feeder and salivate every time the bell is turned on, even before the food is presented to it. In this case, the sound becomes a conditioned stimulus, a signal that the body should prepare for an unconditioned reflex food reaction. A temporary functional connection is formed between the stimulus (bell) and the food reaction. A conditioned reflex is developed during the learning process, and the connection between the sensory (in our example, auditory) system that perceives the conditioned stimulus, and the executive (effector) organs that ensure the implementation of the reflex, is formed on the basis of the coincidence of the conditioned stimulus and unconditional reinforcement with food.
To successfully develop a conditioned reflex, three conditions must be met. Firstly, the conditioned stimulus (in our example, the bell) must precede in time the unconditional reinforcement (in our example, food). Secondly, the biological significance of the conditioned stimulus must be less than that of the unconditioned reinforcer. For example, for a female, the cry of her cub is obviously a stronger irritant than food reinforcement. Thirdly, the strength of the conditioned and unconditioned stimuli must have a certain value (the law of strength), since very weak and very strong stimuli do not lead to the development of a stable conditioned reflex.
The classical conditioned reflex, developed to a combination of a conditioned stimulus and unconditional reinforcement, is called a first-order conditioned reflex. A conditioned reflex formed on the basis of another conditioned reflex is called a second-order conditioned reflex, etc.
According to I.P. Pavlov, under the influence of a conditioned stimulus, for example a sound, a focus of excitation is formed in the corresponding zone of the cerebral cortex. Under the influence of an unconditioned stimulus (food, pain, etc.), a second focus of excitation appears in the cortex. A temporary connection arises between these foci (closure, according to I.P. Pavlov). Sometimes such a connection persists for a long time after just one combination of conditioned and unconditioned stimuli, but usually several such combinations are necessary to form a stable conditioned reflex. Now the presentation of one conditioned stimulus is sufficient to evoke a reflex.
If unconditioned reflexes are practically not inhibited, then developed conditioned reflexes can lose their significance when living conditions change. The extinction of conditioned reflexes is called inhibition. There are external and internal inhibition of conditioned reflexes. If, under the influence of a new strong external stimulus, a focus of strong excitation appears in the brain, then the previously developed conditioned reflex connection does not work. For example, the food conditioned reflex is inhibited by strong noise, fear of the dog, exposure to a painful stimulus, etc. This type of inhibition is called external. If the salivation reflex developed in response to a bell is not reinforced by feeding, then gradually the sound ceases to act as a conditioned stimulus and the reflex will begin to fade and slow down. The temporary connection between the two excitation centers in the cortex will be destroyed. This type of inhibition of conditioned reflexes is called internal.
A person makes basic contacts with the outside world while awake. This condition is characterized by a fairly high level of electrical activity in the brain. In ensuring a state of wakefulness, the most important role is played by the reticular formation of the midbrain, from the neurons of which ascending excitatory influences go to the nonspecific nuclei of the thalamus, and from them to all zones of the cerebral cortex. Elimination of these influences leads to decreased attention, deterioration in learning, pathological sleep, loss of consciousness, etc.
Sleep is a specific state of the brain and the entire body as a whole, characterized by muscle relaxation, a weak reaction to external stimuli, etc. The weakening of the body's reactivity depends on a decrease in the sensitivity of the peripheral parts of the analyzers and a decrease in the excitability of the forebrain structures due to the weakening of the reticular excitatory influences on the cortex. One of the main chemical inducers of sleep is serotonin, produced by neurons in the central part of the midbrain. If you destroy this area and reduce the serotonin content in the brain, then the person is deprived of the ability to sleep.
When recording electrical signals from the brain on an electroencephalogram, you can notice that the sleep period is not uniform, but is divided into several cycles, repeating approximately every 90 minutes. During the full cycle, the phase of slow-wave (orthodox) sleep - a period of slow low-voltage waves on the EEG - is replaced by the phase of paradoxical, or fast-wave, sleep. During this phase, rapid eye movements, contractions of facial muscles, and finger movements are observed. During this phase, a person dreams. During the night, 4-6 complete cycles are usually observed.
Thus, sleep is not just a depression of brain activity, but a state when, against the background of a decrease in sensory flow to the brain, certain metabolic processes, processing of previously received information, etc. occur in its structures.
Consciousness is the highest function of the human brain, which consists in reflecting reality and purposefully regulating the relationship of the individual with the environment.
Thinking is a person’s ability to imagine and convey to other people his attitude to what is happening with the help of words and images. Thinking is one of the main functions of the human brain.
The basis of consciousness and thinking is the process of constant analysis of a huge amount of information coming both from the external environment through the senses, and from internal receptors that respond to the slightest changes in the internal environment of the body. The set of processes occurring in the central nervous system that ensures the perception and analysis of information, as well as an adequate response of the body, is called the signaling system. Both animals and humans have a first signaling system. It perceives specific material stimuli of the surrounding world and is the basis for the formation of an adequate response to what is happening. In addition, in connection with the appearance of speech, a second signaling system is well developed in humans. It is due to the peculiarity of a person’s higher nervous activity to perceive a spoken or written word, and the signal meaning of a word is determined not by a combination of sounds or letters, but precisely by the semantic meaning that this word carries. With the help of words, a person can very accurately express the most complex abstract concepts, shades of feelings and much more. It should be noted that the rudiments of the second signaling system have been found in many highly developed animals: dogs, cetaceans, ravens, parrots, etc. A dog, for example, is able to learn the meanings of a large number of words, but the specificity of the skull skeleton does not give it the ability to articulate words and phrases.
Choose one correct answer.
1. A stimulus to which there is an innate reaction is called
1) conditional
2) unconditional
3) defensive
4) indifferent
2. Conditioned reflexes
1) are inherited
2) species specific
3) persist throughout life
4) individual
3. Unconditioned reflexes
1) are not inherited
2) during life they form and fade away
3) are congenital
4. Inhibition, which is caused by a strong extraneous stimulus that is not associated with the developed conditioned reflex, is called
2) conditional 4) internal
5. For the first time, inhibition in the central nervous system was discovered
1) L.S. Vygotsky 3) I.M. Sechenov
2) I.P. Pavlov 4) A.A. Ukhtomsky
1) N.I. Pirogov 3) A.A. Ukhtomsky
2) I.P. Pavlov 4) I.M. Sechenov
7. The sleep center is located in
1) spinal cord
2) brain stem
3) cerebellum
4) cerebral cortex
8. Plays a vital role in ensuring a state of wakefulness.
1) substantia nigra of the midbrain
2) reticular formation of the brainstem
3) corpus callosum
4) hippocampus
9. The main chemical inducer of sleep is
1) vasopressin 3) dopamine
2) oxytocin 4) serotonin
10. REM sleep is observed
1) several times during the sleep period
2) at the very beginning of falling asleep
3) once in the middle of the sleep period
4) just before waking up
11. During sleep, the human body experiences
1) processing information received while awake
2) complete muscle relaxation
3) persistent decrease in the intensity of metabolic processes
4) drop in bioelectrical activity of the brain
12. Self-preservation reflexes do not apply
1) food 3) indicative
2) drinking 4) homeostatic
13. Protective reflexes include
1) chewing 3) salivation
2) swallowing 4) sneezing
14. The second signaling system includes conditioned reflexes formed to the following stimuli
1) visual 3) verbal
2) olfactory 4) auditory
15. The second signaling system in humans developed thanks to
1) upright walking
2) the appearance of speech
3) the appearance of stereoscopic vision
4) asymmetrical development of the right and left hemispheres of the brain
Choose three correct answers.
16. Conditioned reflexes
1) are inherited
2) stable, that is, they persist throughout life
3) individual
4) promote survival in changing environmental conditions
5) are not produced when the cerebral cortex is damaged
6) universal
17. Unconditioned reflexes
1) species specific
2) not inherited
3) changeable, that is, constantly forming and fading away
4) remain after removal of the cerebral cortex
5) are congenital
6) individual
18. Paradoxical sleep is characterized by
1) increased heart rate
2) fast-wave electrical activity of the brain
3) drop in heart rate
4) muscle relaxation
5) dreams
6) decreased breathing
19. Slow-wave sleep is characterized by
1) increased breathing
2) active contraction of facial muscles
3) movements of the eyeballs under closed eyelids
4) decrease in heart rate
5) fluctuations in the bioelectrical activity of the brain with a frequency of 1-3 Hz
6) drop in metabolic rate
20. The condition for the development of a conditioned reflex is
1) the presence of two stimuli: conditional and unconditional
2) precedence of the unconditioned stimulus to the conditioned one in time
3) several combinations of conditioned and unconditioned stimuli
4) absence of distracting extraneous stimuli
5) inhibited state of the cerebral cortex
6) the biological significance of the conditioned stimulus must be greater than that of the unconditional reinforcement
21. Establish a correspondence between temperament and the type of higher nervous activity that is characteristic of it.
Keys to tasks
| Question no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| answer | 2 | 4 | 3 | 1 | 3 | 3 | 2 | 2 | 4 | 1 |
| Question no. | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| answer | 1 | 3 | 4 | 3 | 2 | 3,4,5 | 1,4,5 | 1,2,5 | 4,5,6 | 1,3,4 |
Task 21
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