Stimuli are factors in the external or internal environment that cause agitation, increased sensitivity and other mental or physical reactions. We react to many different stimuli. They influence our behavior, sensations and well-being. Some environmental factors can have a direct impact on metabolism, the functioning of the body's defense system and overall well-being. Many external stimuli are simply necessary to maintain the vital functions of the body. For example, under the influence of sunlight, the skin acquires a brown tint - this is a protective reaction of the skin that protects the body from the harmful effects of ultraviolet rays. High temperature is also an irritant. It causes sweating, which is the body's main means of thermoregulation.

The occurrence of many undesirable reactions is due to air pollution and other environmental factors. Chemicals are created every day that irritate the body.

The influence of external stimuli on humans

According to doctors, over the past few decades the number of people suffering from allergic diseases has increased. Of course, not in every case it is possible to accurately determine the causes of an allergic disease, but it is assumed that most often allergies occur under the influence of harmful environmental factors. According to doctors, it is very rare that a person is allergic to only one substance. It is very dangerous when the human immune system exhibits increased sensitivity to many substances. In this case, it is subjected to enormous load, because must constantly adapt to new, unknown stimuli. The immune system seems to be in a state of constant readiness and sometimes reacts too violently to completely harmless substances, which manifests itself in the form of allergies.

Reaction to external stimuli

It is impossible to avoid exposure to harmful environmental factors. Over time, the human body gets used to a particular stimulus and ceases to be sensitive to it. For example, housewives who spend a lot of time in the kitchen can tolerate heat more easily than other people. The reaction to stimuli can change - increase or decrease. For example, patients with chronic pain become accustomed to it over time.

Hyposensitization

This is a treatment method, the use of which allows you to reduce the body’s sensitivity to the allergen, and often cope with allergies. The patient is given small doses of the allergen in order to cause addiction. Doses are gradually increased, which leads to a decrease in the body's sensitivity. The procedures are repeated until the allergy goes away. The allergen should not be administered to pregnant women, as well as to women during menstruation, a few days before and after them. If the allergen is not identified, then nonspecific hyposensitization is carried out, which consists of the use of physiotherapeutic agents, climatotherapy, and acupuncture. One of the most effective methods of mitigating the effects of excess stimuli is autogenic training. This method allows you to cure mild forms of allergic diseases. By the way, positive results are achieved by using many other relaxation methods.

Hyposensitization is not carried out in all cases (it requires a lot of patience from the patient, since the treatment lasts a very long time). This method can only be used by an experienced doctor (allergist).

Useful stimuli

There are many irritants that have a positive effect on the body. For example, climatotherapy, massage, heat or cold treatment and many other similar methods contribute to recovery and health maintenance. Many medications and vaccines have an irritating effect on the body and immune system (they help the body cope with diseases). In homeopathy, substances that cause disease are used as medicines. They are diluted many times and given to the patient. Homeopathic remedies promote spontaneous recovery.

I. E. Wolpert’s technique, developed in our laboratory, is devoid of the disadvantages of Lenz’s technique, since the content of the dream is not suggested. It is physiologically more accurate than the Klein technique, since a strict dosage of external stimulus is carried out in terms of strength and duration. In addition, our studies are accompanied by objective recording of the process of hypnotic sleep using the above electrophysiological techniques. Our main advantage over American work is that we experiment on the basis of . This is a significant theoretical advantage.

I. E. Volpert used the method of fractional analysis of suggested dreams in hypnosis. During hypnotic sleep, the hypnotist tells the subject “you are dreaming” and at the same time produces some kind of irritation. After 2 min. the doctor wakes up the subject and asks about the dream. The subject reports a dream she just had. It continues again. After some time, sleep is again suggested with the application of irritation. After 2 min. the subject is woken up, and she tells the dream that she saw during the second period of sleep. The same thing is done a third time. Some previously trained individuals are given some kind of irritation, but the suggestion “you are dreaming” is not given. After the end of the hypnotic session, the subject is questioned regarding all her experiences during hypnotic sleep.

This method of dream research represents a further experimental improvement of the method of suggested dreams in hypnosis. As an example, we give the described study.

In this example, one can see how the irritation produced by the researcher (in this case, cutaneous-proprioceptive) enters into the content of the dream, which consists of a combination of elements of irritation and elements of past life experience. There is nothing incomprehensible from the point of view of causal analysis in these dreams.

Thus, in hypnotic sleep and in natural sleep, there is an interaction between existing irritations and neural traces of former irritations during the development of dreams. In this case, individual characteristics and the type of nervous system are of great importance (which will be discussed further in Section XII). In this regard, Pavlov’s doctrine of analyzers is of great importance for the physiological understanding of dreams. The role of individual cortical analyzers varies from person to person. Thus, artists have a more developed visual analyzer, while musicians have a more developed auditory one. This physiological difference is reflected in their dreams. Some neurotics (especially hysterics) often have olfactory dreams. Thus, patient G. had a heightened sense of smell and often experienced olfactory dreams. She said about herself that she “lived in the realm of sounds and smells all her life.”

What is presented in this section leads us to the following conclusions. External and internal stimuli acting during sleep play the role of the first impulse in the deployment of the chain of disinhibition of nerve traces. In this case, a mechanism of summation of long-acting irritation leading to disinhibition of traces is possible.

The effect of external and internal irritations during sleep comes down to the following options:

1) to a general disinhibition of sleep and the appearance of shallow phases of sleep, which is associated with the development of dreams due to the reproduction of nerve traces; in this case, existing irritations cause disinhibition of sleep, but do not directly cause dreams;
2) to disinhibition and the emergence of a dream with the participation of this analyzer; in this case, existing stimuli cause disinhibition, cause a dream and enter into its content;
3) to disinhibition and the emergence of a dream due to another analyzer or other analyzers; in this case, existing irritations cause disinhibition, cause a dream, but are not part of its content;
4) in dreams, a distortion of the strength of external stimuli may occur based on the pattern of the paradoxical hypnotic phase.*
All of the above illuminates only one side of the physiology of dreams. The other side is the disinhibition of nerve traces without the participation of existing stimuli.

* We will talk about the nervous mechanism of dreams based on Pavlovian hypnotic phases further, in section VIII.

Structural and functional state of the human body

1.1 External and internal stimuli of the human body

A person is constantly exposed to a continuous stream of external stimuli, as well as a variety of information about the processes that occur in the middle of the body and outside it. External irritants that lead to deterioration of health are classified as accidents. These are injuries, acute occupational diseases, poisoning, etc. Acute occupational diseases and poisonings include those that arose after exposure to harmful substances and hazardous factors. They can arise as a result of:

Chemical factors - acute bronchitis, tracheitis, conjunctivitis, anemia, dermatitis, etc.;

Ionizing radiation - acute radiation sickness, acute radiation injuries;

Laser irradiation - skin burns, damage to the cornea of ​​the eye;

Diseases also occur at high levels of human exposure that cause undesirable biological effects.

Any physiological, physical, chemical or emotional influences, be it air temperature, excessive atmospheric pressure or excitement, joy, sadness, can cause the body to go out of balance. At low levels of exposure to the stimulus, a person simply perceives information coming from outside. He sees the world around him, hears its sounds, inhales various smells, etc. In cases of extreme exposure to the body, the nervous system forms protective-adaptive reactions and determines the ratio of the influencing and protective effects.

1.2 Human perception of the state of the external environment and characteristics of analyzers

A person constantly needs information about the state and changes in the external environment, processing this information and drawing up life support programs. The ability to obtain information about the environment, the ability to navigate in space and evaluate the properties of the environment are provided by analyzers (sensory systems). They are systems for entering information into the brain for analyzing this data Getia I.G., Getia S.I., Komissarova T.A. and others. Life safety. Practical lessons. Textbook manual for average professional education / Under. ed. I.G. Getia. - M.: Kolos, IPR SPO, 2008. .

In the cerebral cortex - the highest link of the central system (CNS) - information coming from the external environment is analyzed and a response program is selected or developed, i.e. information is generated about changes in the organization of life processes in such a way that this change does not lead to damage or death of the organism.

The sensors of the systems are specific structural nerve formations called receptors. They are the endings of sensitive nerve fibers that can be excited by a stimulus. Some of them perceive changes in the environment, and some - in the internal environment of the body. There is a group of receptors located in skeletal muscles, tendons and signaling muscle tone. According to the nature of sensations, visual, auditory, olfactory, tactile receptors, pain receptors, and body position receptors in space are distinguished.

Receptors are a cell equipped with movable hairs or cilia (movable antennas) that provide sensitivity to the receptors. So, to excite photoreceptors (perceiving light stimuli), 5...10 quanta of light are enough, and for olfactory receptors - one molecule of the substance.

The information received by the receptors, encoded in nerve impulses, is transmitted along the nerve pathways to the central sections of the corresponding analyzers and is used for control by the nervous system, which coordinates the work of the executive organs. The functional diagram of the analyzer is shown in Figure 1.

Figure 1. Functional diagram of the analyzer

The concepts of “sensory organ” and “receptor” should not be confused; for example, the eye is an organ of vision, and the retina is a photoreceptor, one of the components of the organ of vision. In addition to the retina, the organ of vision includes refractive media, various membranes, and the muscular system. The concept of “sense organ” is largely arbitrary, because by itself it cannot provide sensation. To do this, it is necessary that the excitation that arises in the receptors enters the central nervous system - special parts of the cerebral cortex, because It is with the activity of the higher parts of the brain that the emergence of subjective relationships is associated. Through vision, a person knows the shape, size, color of an object, direction and distance at which it is located. The visual analyzer is the eyes, optic nerves and visual center located in the occipital lobe of the cerebral cortex.

To see the shape of an object, you need to clearly distinguish its boundaries and outlines. This ability of the eye is characterized by visual acuity. Visual acuity is measured by the minimum angle (from 0.5 to 10°) at which two points at a distance of 5 m are still perceived separately. The eye is sensitive to the visible range of the electromagnetic spectrum (380 - 770 nm).

Hearing is the body’s ability to perceive and distinguish sound vibrations. This ability is carried out by the auditory analyzer. The human ear is accessible to the range of sounds (mechanical vibrations) with a frequency of 16...20,000 Hz Dronov A.A. Creatively formative training in life safety for university students: Methodological. manual for secondary vocational education / A.A. Dronov. - Voronezh Mechanical College, 2005. .

The mechanism for protecting the auditory analyzer from damage when exposed to intense sounds is provided by the anatomical structure of the middle ear, the system of auditory ossicles and muscle fibers, which are the mechanical transmission link responsible for the appearance of the acoustic sound blocking reflex in response to an intense sound stimulus. The occurrence of an acoustic reflex protects the sensitive structures of the cochlea of ​​the inner ear from destruction.

The organ of hearing - the ear - is the perceiving part of the sound analyzer. It has 3 sections: the outer, middle and inner ear. They serve to transmit sound vibrations to the brain, where the corresponding auditory representation is synthesized.

The organ of hearing does not perceive all the numerous sounds of the environment. Frequencies close to the upper and lower limits of audibility produce an auditory sensation only at high intensity and for this reason are usually inaudible. Very intense sounds in the audible range can cause ear pain and even damage your hearing 3 . With age, hearing sensitivity is lost. Thus, the organ of hearing performs two tasks: it supplies the body with information and ensures self-preservation, resisting the damaging effects of the acoustic signal.

Smell - the ability to perceive odors, is carried out through the olfactory analyzer, the receptor of which is nerve cells located in the mucous membrane of the upper and, partly, middle nasal passages. A person has varying sensitivity to odorous substances, and to some substances it is especially sensitive. For example, ethyl mercaptan is felt at a content of 0.00019 mg in 1 liter of air.

A decreased sense of smell often occurs due to inflammatory processes in the nasal mucosa. In some cases, impaired sense of smell is one of the significant symptoms of central nervous system damage.

Taste is a sensation that occurs when irritants act on specific receptors located on different parts of the tongue. The sense of taste consists of the perception of sour, salty, sweet and bitter.

Variations in taste result from a combination of the basic sensations listed. Different parts of the tongue have unequal sensitivity to taste substances: the tip of the tongue is more sensitive to sweet, the edges of the tongue to sour, the tip and edges to salty and the root of the tongue is most sensitive to bitter.

The mechanism of perception of taste substances is associated with chemical reactions at the “substance - taste receptor” boundary. It is assumed that each receptor contains highly sensitive protein substances that disintegrate when exposed to certain flavoring substances. Excitation from taste buds is transmitted to the central nervous system along specific pathways Frolov M.P. and others. Fundamentals of life safety. Textbook for students. - M.: Education, 2006. .

Touch is a complex sensation that occurs when receptors in the skin, mucous membranes and muscle-articular apparatus are irritated. The main role in the formation of the sense of touch belongs to the skin analyzer, which perceives external mechanical, temperature, chemical and other stimuli. The sense of touch consists of tactile, temperature, pain and motor sensations. The main role in sensation belongs to tactile reception - touch and pressure.

The skin, the outer covering of the body, is an organ with a very complex structure that performs a number of important vital functions.

One of the main functions of the skin is protective; the skin is a protective organ. Thus, sprains, pressure, and bruises are neutralized by the elastic fat layer and elasticity of the skin. The normal stratum corneum protects the deep layers of the skin from drying out and is very resistant to various chemicals.

The secretory function is provided by the sebaceous and sweat glands. Some medicinal substances (iodine, bromine), intermediate metabolic products, microbial toxins and poisons can be released with sebum. The function of the sebaceous and sweat glands is regulated by the autonomic nervous system.

The metabolic function of the skin is to participate in the processes of regulation of general metabolism in the body, especially water, mineral and carbohydrate. The skin is the “peripheral brain”, a tireless watchman who is always on the alert, constantly notifying the central brain of every aggression and danger.

With the help of analyzers, a person receives extensive information about the world around him. The amount of information is usually measured in binary characters - bits. For example, the flow of information through the human visual receptor is 10 8 - 10 9 bits/s, the nerve pathways transmit 2 * 10 6 bits/s, only 1 bit/s is firmly retained in memory, therefore, not everything is analyzed and evaluated in the cerebral cortex incoming information, and the most important. Information received from the external and internal environment determines the functioning of the functional systems of the body and human behavior.

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Stimulus is a factor external or internal in relation to the excitable structure of the environment, which, when acting or changing the action, is capable of causing excitation.

Naturally, we are talking about defining the concept of stimulus in the context of the physiology of excitable tissues.

Let me remind you that the structure can respond to the action of an irritant (stimulus) with irritation (a nonspecific reaction) and excitation (a specific electrical reaction). Excitation occurs when the corresponding laws of irritation are fulfilled. For an irritation reaction in the same excitable structures, the fulfillment of the laws we are considering today is not at all necessary.

Only excitable tissues, their components and organs consisting of them can respond to irritation with excitation. For example, muscle fiber, muscle tissue, muscle (organ). Let me remind you that excitable tissues include nervous, muscle and glandular tissues.

Increasingly, instead of the term “irritant” the term “stimulus” is used. These are synonyms. And in the future we will use the term stimulus very often. But remember! In the physiology of excitable tissues there is the concept of excitation, but there is no concept of pathogen. Excitation occurs in response to the action of an irritant (stimulus).

So, according to the definition, a stimulus can be a factor that has not previously acted on the excitable structure. For example, a neighbor touched your hand. If you felt this, excitement arose in certain excitable structures.

Another example. In the receptors that control the gas composition of the blood, excitation occurs when the concentration of oxygen or carbon dioxide in the blood changes.

Can arousal occur without an external stimulus? Yes, as a result of spontaneous depolarization of the cell. These processes are characteristic of pacemaker cells of the heart muscle and gastrointestinal tract.

Types of stimuli

Signs by which irritants differ:

1. Nature (modality, valency): physical, chemical, etc.

2. Biological significance (adequate, inadequate)

3. The ratio of the force of influence to the excitation threshold (subthreshold, threshold, superthreshold).

4. Single or serial

By nature, stimuli are divided into chemical, mechanical, radiant, temperature, electrical, etc. In this case, they talk about the modality of the stimulus.

Stimuli of the same modality differ in valence. For example, chemical (modality) stimuli can be salty, sweet, bitter, sour (valency). The term modality is more often used in the field of sensory physiology regarding receptors and analyzers in general. And when they talk about the modality of a stimulus, they mean the nature of the sensations caused by the stimulus. But let’s not forget that receptors, and analyzers in general, are excitable structures.

Within each modality, the valence of the stimulus can be distinguished. For example, a chemical irritant can be an acid, an alkali, or a salt.

According to their biological significance, regardless of modality, stimuli are divided into adequate and inadequate.

Adequate stimuli are capable of causing an excitation reaction when exposed to certain excitable structures.

In other words, a stimulus, acting on different biological structures, can cause excitation only in some of them. For these structures this stimulus will be adequate. For example, the action of light only causes stimulation in certain structures of the retina. It is adequate for them.

It is not necessary, when speaking about adequate stimuli, to confine oneself within the framework of “natural conditions” and to identify the concepts of “natural stimulus” and “adequate stimulus.” For example, the effect of food chemicals on the taste buds causes arousal. Food chemicals, of course, in this case are both natural and adequate irritants. But if we apply electric current to these same receptors in laboratory conditions, excitation may also occur. In this case, the stimulus will not be natural, but will be adequate for the receptors in question.

Let us quote another definition of adequate stimuli. “Adequate stimuli are those that act under natural conditions on strictly defined receptors and excite them [++484+ p238].” You should understand why the definition given is, to say the least, imprecise.

Inappropriate stimuli When exposed to certain excitable structures, they are capable of causing an excitation reaction, but this requires significantly greater energy expenditure than when excitation of the same structures from an adequate stimulus.

For example, visible light for the receptors of the retina or sound in the range of its perception for the receptors of the auditory analyzer is an adequate stimulus. However, the sensation of a flash of light (phosphene, “sparks from the eyes”) or an audible sound (ringing in the ears) can occur when exposed to mechanical (a blow to the head) and other stimuli of sufficient force. In this case, excitation also occurs in the visual or auditory analyzers, respectively, but under the influence of inadequate stimuli that are not typical for them.

The adequacy of the stimulus is manifested in the fact that its threshold strength is significantly lower compared to the threshold strength of an inadequate stimulus. For example, the sensation of light occurs in a person when the minimum intensity of the light stimulus is only 10 -17 - 10 -18 W, and more than the mechanical one. 10 -4 W, i.e. the difference between light and mechanical threshold stimuli for human eye receptors reaches 13-14 orders of magnitude.

Let me emphasize once again that inadequate stimuli can also cause excitement. When we talk about inadequate stimuli for any excitable structure, we mean that there are adequate stimuli for the same structure.

Can stimuli of the same modality, but of different valence, differ in their adequacy to the excitable structure? Yes they can. For example, such chemical (modality) stimuli as sugar, salt (valency) are adequate for different taste receptors of the tongue.

Based on the ratio of the strength of the stimulus to the excitation threshold, subthreshold, threshold, and suprathreshold are distinguished. We will talk in more detail about this most important characteristic of the stimulus later, examining the “law of strength” of irritation.

Stimuli can be single or serial.

Single stimuli vary in strength, duration, shape, rate of increase and decrease in strength (gradient) (Fig. 809141947).

Rice. 809141947. Differences in the parameters of single stimuli (stimuli): a - by strength, b - by duration, c - by the rate of increase in strength (gradient), d - by shape (the first is rectangular, the next two are trapezoidal).

Serial irritants vary in frequency, meander (pattern, pattern) (Fig.).

Rice. . The difference in the parameters of serial stimuli (stimuli): A - by frequency, B - by the ratio of the duration of the stimulus to the duration of the pause (duty factor), C - by the nature and order of the pulses (meander).

Please note that all of the above characteristics apply to stimuli of any modality.

Attention! Such incentives, which students often portray, cannot exist.

An irritant a living cell or an organism as a whole can be any change in the external environment or internal state of the organism, if it is large enough, arose quickly enough and lasts long enough.

The infinite variety of possible irritants to cells and tissues can be divided into three groups: physical, physicochemical and chemical.

To the number physical stimuli include temperature, mechanical (impact, injection, pressure, movement in space, acceleration, etc.), electrical, light, sound.

Physico-chemical irritants are changes in osmotic pressure, active reaction of the environment, electrolyte composition of the colloidal state.

To the number chemical irritants refers to many substances with different compositions and properties that change metabolism or cell structure. Chemical irritants that can cause physiological reactions are food substances coming from the external environment, medications, poisons, as well as many chemical compounds formed in the body, such as hormones and metabolic products.

Irritants cells that cause their activity, which have a particularly important significance in life processes, are nerve impulses. Being natural, i.e., occurring in the body itself, electrical and chemical stimuli to cells, nerve impulses, traveling along nerve fibers from nerve endings to the central nervous system or coming from it to peripheral organs - muscles, glands, cause changes in their condition and activity .
According to their physiological significance, all stimuli are divided into adequate and inadequate.

Adequate are those stimuli that act on a given biological structure in natural conditions, to the perception of which it is specially adapted and to which it is extremely sensitive. For the rods and cones of the retina, an adequate stimulus is the rays of the visible part of the solar spectrum, for tactile receptors of the skin - pressure, for the taste buds of the tongue - various chemical substances, for skeletal muscles - nerve impulses flowing to them along the motor nerves.

Those who are called inadequate are those irritants, for the perception of which a given cell or organ is not specially adapted. Thus, a muscle contracts not only under the influence of its adequate stimulus, i.e., impulses coming to it along the motor nerve, but also under the influence of stimuli to which it is not naturally exposed: it contracts when exposed to acid or alkali , electric shock, sudden stretching, mechanical shock, rapid warming, etc.

Cells are much more sensitive to their own adequate stimuli than to inadequate ones. This is an expression of a functional adaptation developed during the process of evolution.

To study the activity of cells, tissues and organs, in particular to study the function of nerve cells and the nervous system as a whole, the use of various stimuli is widely used in physiological experiments. Electrical stimulation is most convenient for these purposes. It is advantageous in that it operates at an electric current strength that does not cause noticeable damage to living tissue. The effect of electric current begins and stops quickly; it can be easily turned on and off; the effect of chemical and temperature stimuli lasts longer. In addition, electrical stimulation is easy to dose according to its strength, duration and rhythm.

In physiological experiments, either direct stimulation is usually applied, applied directly to the tissue under study (muscle or gland), or indirect, applied to the nerve fibers innervating the organ. When nerve fibers are irritated, it is possible to find out how they act on the organ they innervate. To study the reactions of the nervous system, irritation of the perceptive nerve endings - receptors or nerve fibers going to the central nervous system is used.