The physiological basis of the sensation process. Feeling. Physiological basis of sensations. Classification of sensations. The analyzer consists of three sections
The physiological basis of sensations is the activity of complex complexes of anatomical structures, named by I.P. Pavlov analyzers . Each analyzer consists of three parts:
1) the peripheral section, called the receptor (the receptor is the perceiving part of the analyzer, its main function is the transformation of external energy into a nervous process);
2) conducting nerve pathways;
3) cortical sections of the analyzer (they are also called the central sections of the analyzers), in which the processing of nerve impulses coming from the peripheral sections takes place.
The cortical part of each analyzer includes an area that is a projection of the periphery (i.e., a projection of the sense organ) in the cerebral cortex, since certain areas of the cortex correspond to certain receptors. For the sensation to arise, it is necessary to use all the components of the analyzer. If any part of the analyzer is destroyed, the occurrence of the corresponding sensations becomes impossible. So, visual sensations stop when the eyes are damaged, and when the integrity of the optic nerves is violated, and when the occipital lobes of both hemispheres are destroyed.
Analyzer - this is an active organ that reflexively rebuilds under the influence of stimuli, so sensation is not a passive process, it always includes motor components. So, the American psychologist D. Neff, observing a skin area with a microscope, made sure that when it is irritated with a needle, the moment of sensation is accompanied by reflex motor reactions of this skin area. Subsequently, numerous studies found that sensation is closely related to movement, which sometimes manifests itself in the form of a vegetative reaction (vasoconstriction, galvanic skin reflex), sometimes in the form of muscle reactions (eye rotation, neck muscle tension, motor reactions of the hand, etc.). d.). Thus, sensations are not passive processes at all - they are active, or reflex, in nature.
3. Classification of types of sensations.
There are various approaches to the classification of sensations. It has long been customary to distinguish five (according to the number of sensory organs) basic types of sensations: smell, taste, touch, sight and hearing. This classification of sensation according to the main modalities is correct, although not exhaustive. B. G. Ananiev spoke about eleven types of sensations. A. R. Luria believes that the classification of sensations can be carried out according to at least two basic principles - systematic and genetic (in other words, according to the principle of modality, on the one sides, andon principle difficulties or the level of their construction - on the other).
Consider systematic classification sensations (Fig. 1). This classification was proposed by the English physiologist C. Sherrington. Considering the largest and most significant groups of sensations, he divided them into three main types: interoceptive, proprioceptive and exteroceptive Feel. The former combine signals that reach us from the internal environment of the body; the latter transmit information about the position of the body in space and the position of the musculoskeletal system, provide regulation of our movements; finally, others provide signals from the outside world and provide the basis for our conscious behavior. Consider the main types of sensations separately.
Interoceptive sensations that signal the state of the internal processes of the body arise due to receptors located on the walls of the stomach and intestines, the heart and circulatory system and other internal organs. This is the oldest and most elementary group of sensations. Receptors that receive information about the state of internal organs, muscles, etc., are called internal receptors. Interoceptive sensations are among the least conscious and most diffuse forms of sensation and always retain their proximity to emotional states. It should also be noted that interoceptive sensations are often referred to as organic.
proprioceptive sensations transmit signals about the position of the body in space and form the afferent basis of human movements, playing a decisive role in their regulation. The described group of sensations includes a sense of balance, or a static sensation, as well as a motor, or kinesthetic, sensation.
Peripheral receptors for proprioceptive sensitivity are found in muscles and joints (tendons, ligaments) and are called Paccini bodies.
In modern physiology and psychophysiology, the role of proprioception as an afferent basis of movements in animals was studied in detail by A.A. Orbeli, P.K. Anokhin, and in humans - by N.A. Bernshtein.
Peripheral balance receptors are located in the semicircular canals of the inner ear.
The third and largest group of sensations are exteroceptive Feel. They bring information from the outside world to a person and are the main group of sensations that connects a person with the external environment. The whole group of exteroceptive sensations is conventionally divided into two subgroups: contact and distant sensations.
Rice. one. Systematic classification of the main types of sensations
contact sensations caused by the direct impact of the object on the senses. Taste and touch are examples of contact sensation. distant Feel reflect the qualities of objects located at some distance from the senses. Such sensations include hearing and sight. It should be noted that the sense of smell, according to many authors, occupies an intermediate position between contact and distant sensations, since formally olfactory sensations occur at a distance from the object, but at the same time, the molecules that characterize the smell of the object, with which the olfactory receptor contacts, undoubtedly belong to this subject. This is the duality of the position occupied by the sense of smell in the classification of sensations.
Since a sensation arises as a result of the action of a certain physical stimulus on the corresponding receptor, the primary classification of sensations that we have considered naturally proceeds from the type of receptor that gives the sensation of a given quality, or “modality”. However, there are sensations that cannot be associated with any particular modality. Such sensations are called intermodal. These include, for example, vibration sensitivity, which connects the tactile-motor sphere with the auditory one.
Vibration sensation is the sensitivity to vibrations caused by a moving body. According to most researchers, the vibrational sense is an intermediate, transitional form between tactile and auditory sensitivity. In particular, the school of L. E. Komendantov believes that tactile-vibrational sensitivity is one of the forms of sound perception. With normal hearing, it does not particularly protrude, but with damage to the auditory organ, this function of it is clearly manifested. The main position of the "auditory" theory is that the tactile perception of sound vibration is understood as diffuse sound sensitivity.
Vibration sensitivity acquires special practical significance in case of visual and hearing impairments. It plays an important role in the lives of deaf and deaf-blind people. The deaf-blind, due to the high development of vibration sensitivity, learned about the approach of a truck and other modes of transport at a great distance. In the same way, deaf-blind-mute people know by vibrational sense when someone enters their room. Consequently, sensations, being the simplest kind of mental processes, are in fact very complex and not fully understood.
It should be noted that there are other approaches to the classification of sensations. For example, the genetic approach proposed by the English neurologist H. Head. Genetic classification allows us to distinguish two types of sensitivity: 1) protopathic (more primitive, affective, less differentiated and localized), which includes organic feelings (hunger, thirst, etc.); 2) epicritical (more subtly differentiating, objectified and rational), which includes the main types of human sensations. Epicritical sensitivity is genetically younger and controls protopathic sensitivity.
The well-known Russian psychologist B.M. Teplov, considering the types of sensations, divided all receptors into two large groups: exteroceptors (external receptors) located on the surface of the body or close to it and accessible to external stimuli, and interoceptors (internal receptors) located deep in tissues, such as muscles, or on the surfaces of internal organs. B.M. Teplov considered the group of sensations that we called “proprioceptive sensations” as internal sensations.
All sensations can be characterized in terms of their properties. Moreover, properties can be not only specific, but also common to all types of sensation. The main properties of sensations include: quality, intensity, duration, spatial localization, absolute and relative thresholds of sensations.
Quality - this is a property that characterizes the basic information displayed by a given sensation, distinguishing it from other types of sensations and varying within this type of sensation. For example, taste sensations provide information about certain chemical characteristics of an object: sweet or sour, bitter or salty. The sense of smell also provides us with information about the chemical characteristics of the object, but of a different kind: the smell of flowers, the smell of almonds, the smell of hydrogen sulfide, etc.
It should be borne in mind that very often, when talking about the quality of sensations, they mean the modality of sensations, since it is the modality that reflects the main quality of the corresponding sensation.
Intensity sensation is its quantitative characteristic and depends on the strength of the acting stimulus and the functional state of the receptor, which determines the degree of readiness of the receptor to perform its functions. For example, if you have a runny nose, the intensity of perceived odors may be distorted.
Duration Feel - This is a temporal characteristic of the sensation that has arisen. It is also determined by the functional state of the sense organ, but mainly by the time of action of the stimulus and its intensity. It should be noted that sensations have a so-called latent (hidden) period. When a stimulus is applied to the sense organ, the sensation does not occur immediately, but after some time. The latent period of different types of sensations is not the same. For example, for tactile sensations, it is 130 ms, for pain - 370 ms, and for taste - only 50 ms.
The sensation does not arise simultaneously with the beginning of the action of the stimulus and does not disappear simultaneously with the termination of its action. This inertia of sensations is manifested in the so-called aftereffect. A visual sensation, for example, has a certain inertia and does not disappear immediately after the cessation of the action of the stimulus that caused it. The trace from the stimulus remains in the form of a consistent image. Distinguish between positive and negative sequential images. positive serial image corresponds to the initial irritation, consists in maintaining a trace of irritation of the same quality as the current stimulus.
Negative serial image consists in the appearance of a quality of sensation that is opposite to the quality of the irritant. For example, light-darkness, heaviness-lightness, heat-cold, etc. The appearance of negative sequential images is explained by a decrease in the sensitivity of this receptor to a certain effect.
And finally, sensations are characterized spatial localization irritant. The analysis carried out by the receptors gives us information about the localization of the stimulus in space, that is, we can tell where the light comes from, the heat comes from, or which part of the body is affected by the stimulus.
All of the above properties to some extent reflect the qualitative characteristics of sensations. However, the quantitative parameters of the main characteristics of sensations are no less important, in other words, the degree sensitivity .
4. Patterns of sensations.
So far, we have been talking about the qualitative difference between the types of sensations. However, quantitative research, in other words, their measurement, is equally important.
Sensitivity and its measurement. Various sense organs that give us information about the state of the external world around us can be more or less sensitive to the phenomena they display, i.e. can display these phenomena with greater or lesser accuracy. Sensitivity sense organ is determined by the minimum stimulus, which under given conditions is capable of causing a sensation. The minimum strength of the stimulus that causes a barely noticeable sensation is called lower absolute sensitivity threshold .
Irritants of lesser strength, the so-called subthreshold ones, do not cause sensations, and signals about them are not transmitted to the cerebral cortex. The cortex at every single moment from an infinite number of impulses perceives only the vital ones, delaying all the rest, including impulses from the internal organs. This position is biologically reasonable. It is impossible to imagine the life of an organism in which the cerebral cortex would equally perceive all impulses and provide reactions to them. This would lead the body to inevitable death. It is the cerebral cortex that stands guard over the vital interests of the body and, by raising the threshold of its excitability, turns irrelevant impulses into subthreshold ones, thereby relieving the body of unnecessary reactions.
However, subthreshold impulses are not indifferent to the organism. This is confirmed by numerous facts obtained in the clinic of nervous diseases, when it is precisely weak, subcortical stimuli from the external environment that are created in the cortex. hemispheres dominant focus and contribute to the occurrence of hallucinations and "deception of the senses." Subthreshold sounds can be perceived by the patient as a host of intrusive voices with simultaneous complete indifference to real human speech; a weak, barely noticeable beam of light can cause hallucinatory visual sensations of various contents; barely noticeable tactile sensations - from skin contact with clothing - a series of perverse sharp skin sensations.
The lower threshold of sensations determines the level of absolute sensitivity of this analyzer. There is an inverse relationship between absolute sensitivity and the threshold value: the lower the threshold value, the higher the sensitivity of this analyzer. This relationship can be expressed by the formula:
where E is sensitivity, and P is the threshold value of the stimulus.
Our analyzers have different sensitivities. The threshold of one human olfactory cell for the corresponding odorous substances does not exceed 8 molecules. It takes at least 25,000 times more molecules to produce a taste sensation than it does to create an olfactory sensation.
The sensitivity of the visual and auditory analyzer is very high. The human eye, as the experiments of S.I. Vavilov (1891-1951) showed, is able to see light when only 2-8 quanta of radiant energy hit the retina. This means that we would be able to see a burning candle in complete darkness at a distance of up to 27 kilometers. At the same time, in order for us to feel touch, we need 100-10,000,000 times more energy than with visual or auditory sensations.
The absolute sensitivity of the analyzer is not limited to the lower, but also upper threshold of sensation . The upper absolute threshold of sensitivity is the maximum strength of the stimulus at which a sensation adequate to the acting stimulus still arises. A further increase in the strength of stimuli acting on our receptors causes only a painful sensation in them (for example, an ultra-loud sound, blinding brightness).
The value of absolute thresholds, both lower and upper, varies depending on various conditions: the nature of the activity and the age of the person, the functional state of the receptor, the strength and duration of stimulation, etc.
With the help of the sense organs, we can not only ascertain the presence or absence of a particular stimulus, but also distinguish stimuli by their strength and quality. The smallest difference between two stimuli that causes a barely perceptible difference in sensations is called discrimination threshold or difference threshold . The German physiologist E. Weber (1795-1878), testing a person's ability to determine the heavier of the two objects in the right and left hand, found that the difference sensitivity is relative, not absolute. This means that the ratio of the additional stimulus to the main stimulus must be a constant value. So, if there is a load of 100 grams on the arm, then for a barely noticeable sensation of an increase in weight, you need to add about 3.4 grams. If the weight of the load is 1000 grams, then for a sensation of a barely noticeable difference, you need to add about 33.3 grams. Thus, the greater the value of the initial stimulus, the greater should be the increase to it.
The discrimination threshold is characterized by a relative value that is constant for a given analyzer. For the visual analyzer, this ratio is approximately 1/100, for the auditory - 1/10, for the tactile - 1/30. Experimental verification of this provision showed that it is valid only for stimuli of medium strength.
Based on the experimental data of Weber, the German physicist G. Fechner (1801-1887) expressed the dependence of the intensity of sensations on the strength of the stimulus by the following formula:
where S is the intensity of sensations, J is the strength of the stimulus, K and C are constants. According to this provision, which is called the basic psychophysical law, the intensity of sensation is proportional to the logarithm of the strength of the stimulus. In other words, with an increase in the strength of the stimulus exponentially, the intensity of sensation increases in an arithmetic progression (Weber-Fechner law).
Difference sensitivity, or discrimination sensitivity, is also inversely related to the difference threshold value: the higher the discrimination threshold, the lower the difference sensitivity.
The concept of differential sensitivity is used not only to characterize the discrimination of stimuli by intensity, but also in relation to other features of certain types of sensitivity. For example, they talk about sensitivity to distinguishing shapes, sizes and colors of visually perceived objects or to sound-altitude sensitivity.
Adaptation . The sensitivity of analyzers, determined by the magnitude of absolute thresholds, is not constant and changes under the influence of a number of physiological and psychological conditions, among which the phenomenon of adaptation occupies a special place.
Adaptation, or adaptation, is a change in the sensitivity of the sense organs under the influence of the action of a stimulus.
Three varieties of this phenomenon can be distinguished.
1. Adaptation as the complete disappearance of sensation in the process of prolonged action of the stimulus. We mentioned this phenomenon at the beginning of this chapter, speaking about the peculiar disposition of analyzers to change stimuli. In the case of constant stimuli, the sensation tends to fade. For example, a light load resting on the skin soon ceases to be felt. The distinct disappearance of olfactory sensations shortly after we enter an atmosphere with an unpleasant odor is also a common fact. The intensity of the taste sensation weakens if the corresponding substance is kept in the mouth for some time and, finally, the sensation may die out altogether.
Full adaptation of the visual analyzer under the action of a constant and immobile stimulus does not occur. This is due to compensation for the immobility of the stimulus due to the movements of the receptor apparatus itself. Constant voluntary and involuntary eye movements ensure the continuity of the visual sensation. Experiments in which the conditions for stabilizing the image relative to the retina were artificially created showed that in this case, the visual sensation disappears 2–3 seconds after its occurrence, i.e. complete adaptation.
2. Adaptation is also called another phenomenon, close to the one described, which is expressed in the dulling of sensation under the influence of a strong stimulus. For example, when a hand is immersed in cold water, the intensity of the sensation caused by a cold stimulus decreases. When we move from a semi-dark room into a brightly lit space, we are at first blinded and unable to distinguish any details around. After some time, the sensitivity of the visual analyzer decreases sharply, and we begin to see normally. This decrease in the sensitivity of the eye to intense light stimulation is called light adaptation.
The described two types of adaptation can be combined with the term negative adaptation, since as a result of them the sensitivity of the analyzers decreases.
3. Finally, adaptation is called an increase in sensitivity under the influence of a weak stimulus. This kind of adaptation, which is characteristic of certain types of sensations, can be defined as positive adaptation.
In the visual analyzer, this is dark adaptation, when the sensitivity of the eye increases under the influence of being in the dark. A similar form of auditory adaptation is silence adaptation. In temperature sensations, positive adaptation is found when a pre-cooled hand feels warm, and a pre-heated hand feels cold when immersed in water of the same temperature. The question of the existence of negative pain adaptation has long been controversial. It is known that repeated use of a painful stimulus does not reveal negative adaptation, but, on the contrary, acts more and more strongly over time. However, new facts indicate the presence of a complete negative adaptation to needle pricks and intense hot irradiation.
Studies have shown that some analyzers detect fast adaptation, others slow. For example, touch receptors adapt very quickly. On their sensory nerve, when any prolonged stimulus is applied, only a small burst of impulses runs through at the beginning of the action of the stimulus. The visual receptor adapts relatively slowly (the time of dark adaptation reaches several tens of minutes), the olfactory and gustatory receptors.
Adaptive regulation of the level of sensitivity, depending on which stimuli (weak or strong) affect the receptors, is of great biological importance. Adaptation helps to catch weak stimuli through the sense organs and protects the sense organs from excessive irritation in case of unusually strong influences.
The phenomenon of adaptation can be explained by those peripheral changes that occur in the functioning of the receptor during prolonged exposure to a stimulus. So, it is known that under the influence of light, visual purple, located in the rods of the retina, decomposes (fades). In the dark, on the contrary, visual purple is restored, which leads to an increase in sensitivity. With regard to other sense organs, it has not yet been proven that their receptor apparatuses contain any substances that chemically decompose when exposed to a stimulus and are restored in the absence of such exposure. The phenomenon of adaptation is also explained by the processes taking place in the central sections of the analyzers. With prolonged stimulation, the cerebral cortex responds with internal protective inhibition, which reduces sensitivity. The development of inhibition causes increased excitation of other foci, which contributes to an increase in sensitivity in new conditions (the phenomenon of successive mutual induction).
Interaction of sensations . The intensity of sensations depends not only on the strength of the stimulus and the level of adaptation of the receptor, but also on the stimuli currently affecting other sense organs. A change in the sensitivity of the analyzer under the influence of irritation of other sense organs is called the interaction of sensations.
The literature describes numerous facts of sensitivity changes caused by the interaction of sensations. Thus, the sensitivity of the visual analyzer changes under the influence of auditory stimulation. SV Kravkov (1893-1951) showed that this change depends on the loudness of auditory stimuli. Weak sound stimuli increase the color sensitivity of the visual analyzer. At the same time, a sharp deterioration in the distinctive sensitivity of the eye is observed when, for example, the loud noise of an aircraft engine is used as an auditory stimulus.
Visual sensitivity also increases under the influence of certain olfactory stimuli. However, with a pronounced negative emotional coloring of the smell, a decrease in visual sensitivity is observed. Similarly, with weak light stimuli, auditory sensations are enhanced, and exposure to intense light stimuli worsens auditory sensitivity. There are known facts of increasing visual, auditory, tactile and olfactory sensitivity under the influence of weak pain stimuli.
A change in the sensitivity of any analyzer is also observed with subthreshold stimulation of other analyzers. So, P.I. Lazarev (1878-1942) obtained evidence of a decrease in visual sensitivity under the influence of skin irradiation with ultraviolet rays.
Thus, all our analyzer systems are capable of influencing each other to a greater or lesser extent. At the same time, the interaction of sensations, like adaptation, manifests itself in two opposite processes: an increase and a decrease in sensitivity. The general pattern here is that weak stimuli increase and strong ones decrease the sensitivity of the analyzers during their interaction.
Sensitization . An increase in sensitivity as a result of the interaction of analyzers and exercise is called sensitization.
The physiological mechanism for the interaction of sensations is the processes of irradiation and concentration of excitation in the cerebral cortex, where the central sections of the analyzers are represented. According to I.P. Pavlov, a weak stimulus causes an excitation process in the cerebral cortex, which easily irradiates (spreads). As a result of the irradiation of the excitation process, the sensitivity of another analyzer increases. Under the action of a strong stimulus, a process of excitation occurs, which, on the contrary, has a tendency to concentration. According to the law of mutual induction, this leads to inhibition in the central sections of other analyzers and a decrease in the sensitivity of the latter.
Changes in the sensitivity of the analyzers can be caused by exposure to secondary signal stimuli. Thus, the facts of changes in the electrical sensitivity of the eyes and tongue in response to the presentation of the words "sour as a lemon" to the subjects were obtained. These changes were similar to those observed when the tongue was actually irritated with lemon juice.
Knowing the patterns of changes in the sensitivity of the sense organs, it is possible, by using specially selected side stimuli, to sensitize one or another receptor, i.e. increase its sensitivity.
Sensitivity and exercise . Sensitization of the sense organs is possible not only through the use of side stimuli, but also through exercise. The possibilities for training the sense organs and their improvement are very great. There are two areas that determine the increase in the sensitivity of the senses:
1) sensitization, which spontaneously leads to the need to compensate for sensory defects (blindness, deafness);
2) sensitization caused by activity, specific requirements of the subject's profession.
Loss of sight or hearing is compensated to a certain extent by the development of other types of sensitivity.
There are cases when people deprived of sight are engaged in sculpture, their sense of touch is highly developed. The development of vibrational sensations in the deaf belongs to the same group of phenomena. Some deaf people develop vibration sensitivity to such an extent that they can even listen to music. To do this, they put their hand on the instrument or turn their backs to the orchestra. The deaf-blind O. Skorokhodova, holding her hand to the throat of the speaking interlocutor, can thus recognize him by his voice and understand what he is talking about. The deaf-blind-mute Helen Keller has such a highly developed olfactory sensitivity that she can associate many friends and visitors with their smells, and her memories of acquaintances are as well associated with the sense of smell as most people are associated with the voice.
Of particular interest is the emergence in humans of sensitivity to stimuli for which there is no adequate receptor. Such, for example, is the remote sensitivity to obstacles in the blind.
The phenomena of sensitization of the sense organs are observed in persons who have been engaged in certain special professions for a long time.
The extraordinary visual acuity of grinders is known. They see gaps from 0.0005 millimeters, while untrained people only up to 0.1 millimeters. Fabric dyeers distinguish between 40 and 60 shades of black. To the untrained eye, they appear exactly the same. Experienced steelmakers are able to quite accurately determine its temperature and the amount of impurities in it from the faint color shades of molten steel.
A high degree of perfection is achieved by olfactory and gustatory sensations in tasters of tea, cheese, wine, and tobacco. Tasters can accurately indicate not only what grape variety the wine is made from, but also the place where this grape was grown.
Painting makes special demands on the perception of shapes, proportions and color relationships when depicting objects. Experiments show that the artist's eye is extremely sensitive to the assessment of proportions. He distinguishes between changes equal to 1/60-1/150 of the size of the subject. The subtlety of color sensations can be judged by the mosaic workshop in Rome - it contains more than 20,000 shades of primary colors created by man.
Opportunities for the development of auditory sensitivity are also quite large. Thus, playing the violin requires a special development of pitch hearing, and violinists have it more developed than pianists. Experienced pilots can easily determine the number of engine revolutions by ear. They freely distinguish between 1300 and 1340 rpm. Untrained people catch the difference only between 1300 and 1400 rpm.
All this is proof that our sensations develop under the influence of the conditions of life and the requirements of practical labor activity.
Despite the large number of such facts, the problem of exercising the sense organs has not yet been studied enough. What underlies the exercise of the sense organs? It is not yet possible to give an exhaustive answer to this question. An attempt has been made to explain the increased tactile sensitivity in the blind. It was possible to isolate tactile receptors - special little bodies present in the skin of the fingers of blind people. For comparison, the same study was conducted on the skin of sighted people of various professions. It turned out that the number of tactile receptors is increased in the blind. So, if in the skin of the nail phalanx of the first finger in the sighted, the number of bodies on average reached 186, then in the blind born it was 270.
Thus, the structure of receptors is not constant, it is plastic, mobile, constantly changing, adapting to the best performance of a given receptor function. Together with the receptors and inseparably from them, the structure of the analyzer as a whole is rebuilt in accordance with the new conditions and requirements of practical activity.
Synesthesia . The interaction of sensations is manifested in another kind of phenomena called synesthesia. Synesthesia is the occurrence under the influence of irritation of one analyzer of sensations, characteristic of another analyzer. Synesthesia is seen in a wide variety of sensations. The most common visual-auditory synesthesia, when, under the influence of sound stimuli, the subject has visual images. Different people do not have overlap in these synesthesias, however they are quite constant for each individual. It is known that some composers (N.A. Rimsky-Korsakov, A.M. Skryabin and others) possessed the ability of color hearing. We find a vivid manifestation of this kind of synesthesia in the work of the Lithuanian artist M.K. Churlionis - in his symphonies of colors.
The phenomenon of synesthesia is the basis for the creation in recent years of color-music devices that turn sound images into light, and an intensive study of color music. Less common are cases of auditory sensations when exposed to visual stimuli, taste sensations in response to auditory stimuli, etc. Not all people have synesthesia, although it is quite widespread. No one doubts the possibility of using such expressions as “pungent taste”, “screaming color”, “sweet sounds”, etc. The phenomena of synesthesia are another evidence of the constant interconnection of the analyzer systems of the human body, the integrity of the sensory reflection of the objective world.
Thus, the structure of receptors is not constant, it is plastic, mobile, constantly changing, adapting to the best performance of a given receptor function. Together with the receptors and inseparably from them, the structure of analysis as a whole is also being reconstructed in accordance with the new conditions and requirements of practical activity.
The physiological basis of sensations is the activity of complex complexes of anatomical structures, called by I. P. Pavlov analyzers. The analyzer is an anatomical and physiological apparatus for receiving influences from the external and internal environment and processing them into sensations. Each analyzer consists of three parts:
1) the peripheral section, called the receptor (the receptor is the perceiving part of the analyzer, a specialized nerve ending, its main function is the transformation of external energy into a nervous process);
2) conducting nerve pathways (afferent section - transmits excitation to the central section; efferent section - a response is transmitted through it from the center to the periphery);
3) the core of the analyzer - the cortical sections of the analyzer (they are also called the central sections of the analyzers in another way), in which the processing of nerve impulses coming from the peripheral sections takes place. The cortical part of each analyzer includes an area that is a projection of the periphery (i.e., a projection of the sense organ) in the cerebral cortex, since certain areas of the cortex correspond to certain receptors.
Thus, the organ of sensation is the central section of the analyzer.
Physiology of attention
| Experiments with a dissected hemisphere of the brain cover that attention processes are closely related to the work of the corpus callosum, while the left hemisphere provides selective attention, and the right hemisphere provides support. general level alertness. According to I.P. Pavlov, attention reflects the presence of a focus of excitation in the cerebral cortex, which, in turn, is a manifestation of an unconditioned orienting reflex. Such a focus of excitation, due to the process of negative induction, inhibits neighboring areas of the cerebral cortex, and at the same time all the mental activity of the organism is focused on one object. According to Ukhtomsky, attention is determined by the dominant - the dominant, stable focus of excitation in the cortex. The dominant not only inhibits other foci of excitation, but is also able to increase at their expense, switching over to itself the processes of excitation that occur in other nerve centers. The intensity of attention is especially pronounced when the goal is due to biologically significant motivation (hunger, thirst, sexual instinct). In this case, there is a kind of "pumping" of nervous energy from the part of the brain associated with the satisfaction of the need to the part of the cortex associated with a certain object of the external world. According to modern scientific data, in the process of activating attention, other brain structures play an important role in addition to the cerebral cortex. For example, the thalamus serves as a kind of filter that filters out part of the information, and only new and important signals pass to the cortex. The reticular formation activates the brain and is an important energy component of the attention process. PHYSIOLOGY OF CONSCIOUSNESS There is a wide variety of opinions about what constitutes consciousness. One can define consciousness as a subjectively experienced sequence of events opposed to unconscious processes. Often consciousness is associated with a person's awareness of what is happening to him or what he perceives. Philosophy considers consciousness as a set of some cognitive operations associated with the subjective experience of one's thoughts, feelings, impressions and the ability to convey them to others through speech, actions or creative products. This is shared by P.V. Simonov, who considers consciousness as joint knowledge. The physiological prerequisite for consciousness is wakefulness. During wakefulness, the activity of higher centers increases and their threshold of excitation decreases. This state is promoted by the activating action of the reticular formation of the brain stem. According to Pavlov's conditioned reflex theory, signals are perceived when they acquire the character of elements of the second signal system, that is, they are expressed in words. External stimuli are not only perceived, but the subject is aware of the fact of this perception. The problem of the conscious and the unconscious came into focus only through the work of Freud. Freud's concept, although much of it has now been rejected, still has a significant influence on modern scientific thinking and should be viewed in its proper perspective. Unconscious information processing processes, the influence of which the subject is not aware of, are usually classified as unconscious. There are three groups of manifestations of the unconscious. The first group is the unconscious. It covers our biological needs, expressed in unconditioned reflexes and congenital forms behavior (instincts), as well as in the genetically predetermined properties of temperament. The second group of the unconscious is the subconscious. It includes everything that was previously realized and can again become realized under certain conditions. These are various automated skills, stereotypes of automated behavior. They also include unconscious stimuli of activity (motives, semantic attitudes), norms of behavior deeply assimilated by a person, motivational conflicts forced out of the sphere of consciousness. In the process of evolution, the subconscious mind arose as a means of protecting consciousness from unnecessary work and intolerable loads. It protects a person from excessive energy expenditure, protects against stress. The third group of unconscious phenomena is superconsciousness, or intuition associated with creative processes that are not controlled by consciousness. Superconsciousness is a source of new information, hypotheses, discoveries. Superconsciousness refers to the highest stage creative process. Its neurophysiological basis is the transformation of memory traces and the birth of new combinations from them, the creation of new temporary connections, the generation of analogies. We are aware of the existence of our own mental processes. This overlapping phenomenon is the basis of self-awareness. In connection with our sensations, actions and experiences, we are aware of the existence and unity of our personality. The question arises: how did this human ability to become aware of mental processes related to the environment develop? As already noted, awareness involves the simultaneous reflection of events in the form of speech or thought ("inner speech"). The development of speech function simultaneously meant the emergence of consciousness. The language of primitive people was extremely specific: each natural phenomenon was called by its name. So, for example, there were different words for rainy weather, clear weather and sunny weather, and the abstract concept of "weather" did not exist. In the process of more and more differentiated labor activity and social development, our conscious, articulate, abstract and rational speech developed from this unconscious, monosyllabic, concrete, emotional speech. The physiological basis for the generalization of secondary signals must be sought in the processes of irradiation and generalization of excitation in the cerebral cortex. When we express the general qualities of surrounding objects, the processes of abstraction lead to the fact that words become concepts. Concepts arise as a result of separating essential properties and relations from non-essential ones. In the brain, this occurs in the form of a concentration of excitation. Thus, the physiological basis of abstraction is the irradiation and concentration in the brain neurons of newly formed signals expressed in verbal form. A person's thoughts can be considered as "inner speech". Excitation related to the second signal system, in this case, occurs, but it does not cause motor reactions, i.e. movements necessary to pronounce words. Consciousness is thus connected with the second signaling system. G.P. Grabovoi considers human consciousness as an element of the world in which all elements are interconnected, then a change in human consciousness (or the form of the object’s reaction) entails a change in all other elements of the world, allows you to gain knowledge about the external environment and optimize the processes taking place in it. The advantage of consciousness is that the process can be tracked literally continuously. The consciousness of the cell, which is the primary element of life, is inextricably linked with the material components, which ensures the harmonization of life at all levels of existence of the living: the morphological integrity of the structures of the body is determined by the speed and fullness of cell self-renewal; the stability of the functioning of tissues is ensured by the optimal exchange of information between cells; the full-fledged function of the organs depends on the final result of the work, taking into account the informational influences of other organs; homeostasis of the whole organism is determined by the adequacy of the external signal and the state of the structures that perceive it. These levels are interconnected by step-by-step information interactions, the degree of orderliness and generalization of which determines the selectivity of functioning. |
Physiological basis perception.
The physiological basis of perception is the processes taking place in the sense organs, nerve fibers and the central nervous system. So, under the influence of stimuli in the endings of the nerves present in the sense organs, nervous excitation arises, which is transmitted along the conductive pathways to the nerve centers and, ultimately, to the cerebral cortex. Here it enters the projection (sensory) zones of the cortex, which are, as it were, the central projection of the nerve endings present in the sense organs. Depending on which organ the projection zone is associated with, certain sensory information is formed.
The mechanism described above is the mechanism for the emergence of sensations. Therefore, sensations can be considered as a structural element of the process of perception. Own physiological mechanisms of perception are included in the process of forming a holistic image at subsequent stages, when the excitation from the projection zones is transmitted to the integrative zones of the cerebral cortex, where the formation of images of real world phenomena is completed. Therefore, the integrative zones of the cerebral cortex, which complete the process of perception, are often called perceptual zones. Their function differs significantly from the function of the projection zones.
The physiological basis of perception is even more complicated by the fact that it is closely connected with motor activity, with emotional experiences, and various thought processes. Consequently, having begun in the sense organs, nervous excitations caused by external stimuli pass to the nerve centers, where they cover various zones of the cortex and interact with other nervous excitations. This entire network of excitations, interacting with each other and widely covering different areas of the cortex, constitutes the physiological basis of perception.
From a practical point of view, the main function of perception is to provide recognition of objects, i.e. assigning them to one category or another. In fact, by recognizing objects, we draw conclusions about the many hidden properties of the object. Any object has a certain shape, size, color, etc. All these properties are important for its recognition.
Currently, it is customary to single out several stages in the process of object recognition, some of which are preliminary, others are final. In the preliminary stages, the perceptual system uses information from the retina and describes the object in terms of elementary components such as lines, edges, and corners. At the final stages, the system compares this description with descriptions of the forms of various kinds of objects stored in visual memory and selects the best match for it. Moreover, during recognition, most of the information processing, both at the preliminary and final stages of recognition, is inaccessible to consciousness.
THOUGHT ACTIVITY
Thinking activity is an executive
apparatus of functional systems of the mental level. Through mental
activities, the operation of information
processes in the brain, a kind of "behavior" at the informational level.
Nodal mechanisms of mental activity. From the point of view of the general
theory of functional systems, the process of thinking includes universal
system nodes:
The result as a leading system-forming factor of mental
human activity;
Evaluation of the result of mental activity using the feedback
afferentations;
The system-organizing role of the initial biological and social
needs and the dominant ones formed on their basis
motivations in the construction of mental activity;
Programming of mental activity with the help of the device
acceptor of the result of an action based on the mechanisms of afferent
synthesis and decision making;
Effector expression of thought processes through behavior,
somatovegetative components and through specially
organized speech apparatus.
Information equivalents of mental activity.
The operational architectonics of mental activity is built on the basis of
emotional and verbal equivalents of reality. It's in
in a certain sense, consonant with the teachings of I.P. Pavlova about the first and second signal
reality systems. However, if the representations of I.P. Pavlova
were based on information evaluation of signals (conditioned stimuli
physical and verbal character), then from the standpoint of the systemic organization of mental activity, the information content
functional systems of the mental level determine the corresponding adaptive
for human activity results. In case the results
activities have only physical parameters, then the corresponding
the functional systems of mental activity organized by them are built
on informational equivalents physical properties these
results. If the results of the activity have speech, verbal
parameters corresponding to the functional systems of mental
activities are built on an informational verbal basis.
Only in humans is the informational equivalent of functional
systems of mental activity associated with speech function. In animals these
processes are limited to physical and emotional levels.
Emotional basis of mental activity. Thinking Process
continuously accompanied by subjective emotional
experiences by a person of his needs and subjective attitude to
influence of environmental factors in order to meet these
needs. With the help of emotions, traces of memory are also realized. Emotions
a person evaluates his needs, the effect of environmental factors,
relation to objects and other individuals, and, finally, satisfaction
needs. Mental needs as well as biological needs
usually accompanied by emotional feelings of negative
character, and the satisfaction of needs - a variety of
positive emotions. Based on repeated satisfactions of the same type
mental needs formed anticipation of positive
emotions of satisfying a need due to its inclusion in the acceptor apparatus
action result. In a certain situation, it is expected
negative emotions, which ultimately creates probabilistic forecasting
emotional states. System organization of thinking on
emotional basis is genetically determined. It already appears in
newborns, in deaf-blind-mute, as well as in people who are in a circle
people who speak a language foreign to them. Emotional basis
thinking, as experiments with self-irritation show, is also characteristic
for animals.
Pathological processes are built on strong emotional sensations.
attraction to alcohol and drugs. emotional states
under certain circumstances, they can independently build
functional systems.
The verbal basis of mental activity. Word quantization
thinking is unique to man. Human assessment of needs and their
satisfaction, as well as a variety of external influences on the body
along with emotional sensations is carried out with the help of
language symbols, phrases, verbal concepts of oral and written
character. This level of thinking requires special training, first
language turn. With the help of linguistic symbols, thoughts are realized in
discrete phrases that can constitute inner speech, as well as
be transformed into external speech and actions.
The mental activity that is formed in a person on verbal
basis, in comparison with emotional activity acquires
qualitatively new information properties, although its general architectonics
retains all the typical features of a functional system.
A kind of verbal quantization of mental activity
is the process of singing. A person on an emotional basis can
learn a certain melody and fill this melody with the appropriate
words that add up to system quanta - bars and couplets.
Asymmetry of the brain in the processes of mental activity.
The emotional and verbal basis of thinking, as shown by modern
research is built by the functions of different hemispheres of the brain. Right
hemisphere determines predominantly sensual, emotional
component of mental activity. The left hemisphere determines the functions
language and speech. Increasingly, ideas about
activity of the cerebral hemispheres on the basis of their mutual complementarity. This
point of view is in good agreement with the theory of functional systems. FROM
positions of the theory of functional systems in the implementation of effective
mental activity both hemispheres on emotional and speech
basis should dynamically contribute to the achievement by the subject
adaptive results.
Structural bases of mental activity. Processes
mental activity and speech of a person are associated with the activities of various
brain structures. Reveal the participation of brain structures in these processes
allow clinical observations of patients with lesions of various sites
Agnosia. With damage to the occipital cortex, a person sees
objects, walks around them without bumping into them, but does not recognize them. it
recognition disorder was called agnosia (from the Greek. gnosis - knowledge). At
violation of the temporal parts of the cerebral cortex observed auditory agnosia.
A person hears sounds, but does not associate them with a specific sounder.
subject. Such patients lose the ability to perceive the meaning of speech.
interlocutor. When the upper parietal cortex is damaged, patients manifest
tactile agnosia - subjects lose the ability to recognize objects when
their palpation, although they feel the touch.
From a systemic standpoint in subjects with impaired visual, temporal
and parietal areas of the cortex, the mechanism of the previously developed assessment
action results.
Apraksin. Damage to the motor cortex in humans
there is a violation of purposeful action, although he understands that
need to do. This violation is called "apraxia" (from the Greek.
praxis - action). The patient cannot, for example, light a match, cut
apple, fasten the buttons, although his hands are not paralyzed. In this case
one can think of a violation of the systemic processes of efferent synthesis and
actions.
Aphasia - impaired speech; motor aphasia develops in
violation of the functions of the lower frontal gyrus of the left hemisphere (frontal aphasia
Brock). The patient understands the speech of the interlocutor, but his own speech
extremely difficult or completely broken. At the same time, it loses
be saved. Patients are able to scream, make separate sounds, but
can't say a single meaningful word. Patients have impaired
efferent processes of speech formation.
Sensory aphasia occurs when the posterior pole of the superior
temporal cortex (sensitive, or temporal, Wernicke's aphasia). Wherein
in patients, the processes of speech perception are disturbed: they stop
understand both spoken and written language. The ability to pronounce
speech phrases in such patients is not lost, they are even excessively
talkative, but the speech is distorted and completely incomprehensible. Such people
music (amusia). It can be assumed that such patients have impaired mechanisms
acceptor of the result of the action and the ability to evaluate the achieved
result of mental activity.
Other disorders are observed with damage to the parietal cortex:
patients forget individual words, more often nouns, cannot
remember the right words and replace them with a long description. Wherein
there is also an account disorder (acalculia). Patients have impaired
memory mechanism.
With bilateral damage to the base of the temporal and occipital
lobes of the cortex, unusual agnosia is observed: patients stop recognizing
people by their faces (prosoagnosia), but nevertheless recognize them by
the visual parameter of evaluation of familiar personalities suffers selectively.
In case of damage to the angular gyrus without a lesion nearby
located Wernicke's area and Broca's area in patients in the absence of a violation
perception of auditory information and speech, difficulties are manifested in
understanding writing and pictures (anomic aphasia). In this case
the transmission of visual information to Wernicke's area is disrupted.
Morphofunctional bases of visual object identification.
The dynamics of the subject's recognition of a visual image and its reproduction
can be represented as follows. initial recognition and
evaluation of a visual object occurs in the primary visual cortex.
From here, excitation spreads into the angular gyrus and from it to
temporal zone of Wernicke, where the object is evaluated on the basis of previously acquired
verbal concepts and knowledge. From Wernicke's area arousal
extends to Broca's area and to the speech-motor structures of the motor cortex,
which determine the pronunciation of the name of the subject.
Functions of speech in right-handers and left-handers. Speech functions in right-handed people
usually associated with the activity of the left hemisphere, which determines
processes of consistent analytical activity. Right hemisphere at
right-handed determines space-time relationships, for example
recognition of faces, identification of objects by their shape, recognition
musical melodies. Such a strict delimitation of functions is relative.
The diversity of the surrounding world to a certain extent becomes available to us due to the diversity of our sensations.
Sensation is a mental process of reflecting the individual properties of objects and phenomena of the surrounding world, as well as the internal states of the body with the direct influence of stimuli on the corresponding analyzer systems.
Sensation, their nature, the laws of formation and change are studied in a special area of psychology, which is called psychophysics. It arose in the second half of the 19th century, and its name is associated with the main question that is posed and solved in this field of knowledge - with the question of the relationship between sensations and sensations. physical characteristics stimuli affecting the sense organs.
Evolutionary sensations arose on the basis irritations, which are inherent in living matter, which selectively reacts by changing its internal state to biologically significant environmental influences. An elementary response to irritation appears in the simplest unicellular living organisms, which react to the influence of the environment by movement. Irritation, or excitability of the sense organs, is the most important prerequisite for the display of objective properties by the body. environment, which is the essence of the processes of sensibility. According to the hypothesis of O. M. Leont "eva, sensibility "is genetically nothing more than irritation in relation to this kind of environmental influence, which correlates the organism in other influences, i.e. orient the organism in the environment, performing a signal function." Thanks to sensuality, the signs of objects (smells, shape, color), are in themselves indifferent (in the sense that they cannot satisfy organic needs), acquire a signal value.The more developed the senses, the more opportunities to reflect the influence of the external environment.It is necessary to distinguish between stimuli, adequate for a given sense organ and not adequate for it.Specialization of the sense organs to display one or another type of energy, certain properties of objects or phenomena of reality is a product of long evolution, and the sense organs themselves are a product of adaptation to environmental influences.Adequate reflection of reality on the sensory -perceptual level is necessary from an evolutionary-historical point of view, because which is a precondition for survival.
The physiological basis of sensation is a nervous process that occurs when a stimulus is applied to the corresponding analyzer. Speaking of analyzers, two things should be kept in mind. Firstly, this name is not entirely accurate, because the analyzer provides not only analysis, but also the synthesis of stimuli into sensations and images. Secondly, analysis and synthesis can occur outside the conscious control of these processes by a person. Most of the stimuli she feels, processes, but is not aware of.
The feeling is reflex in nature; physiologically it is provided by the analyzer system. The analyzer is a nervous apparatus that performs the function of analyzing and synthesizing stimuli that come from the external and internal environment of the body. The concept of the analyzer And introduced. P. Pavlov. The analyzer consists of three parts:
1) peripheral department - receptor that transforms a certain type of energy into a nervous process;
2) afferent(centripetal) paths that transmit the excitation that arose in the receptor in the higher centers of the nervous system, and efferent (centrifugal), along which impulses from the higher centers are transmitted to lower levels;
3) subcortical and cork projective zones where the processing of nerve impulses from the peripheral regions takes place.
Historically, it so happened that those analyzer systems, the receptor part of which (represented from the anatomical point of view) exists in the form of separate external organs (nose, ear, etc.), are called sense organs. Sight, hearing, smell, touch and taste are distinguished by Aristotle. In reality, there are many more types of sensations. A significant part of physical influences acquires a direct vital significance for living beings, or is simply not perceived by them. For some of the influences that are found on Earth in its pure form and in quantities that threaten human life, it simply does not have the appropriate sense organs. Such an irritant is, for example, radiation. It is also not given to a person to consciously perceive, reflect in the form of sensations ultrasounds, light rays, the wavelength of which goes beyond the allowable range.
The analyzer constitutes the initial and most important part of the entire path of nervous processes, or the reflex arc.
Reflex arc = analyzer + effector. An ephector is a motor organ (a certain muscle) that receives a nerve impulse from the central nervous system (brain). The relationship of the elements of the reflex arc provides the basis for the orientation of a complex organism in the environment, the activity of the organism, depending on the conditions of its existence.
For a feeling to arise, it is not enough that the organism is subjected to the corresponding influence of a material stimulus; some work of the organism itself is also necessary. The process of sensation is optimized through perceptual regulation. The sense organs are closely connected with the organs of movement, which perform not only adaptive, executive functions, but also directly participate in the processes of obtaining information.
In the first case (I), the muscle apparatus acts as an effector. In the second case (II), the organ of sensation itself can be either a receptor or an efector.
Not a single sensory impulse, not a single receptor stimulation by itself can unambiguously determine an adequate image of sensation and perception without muscular correction (since errors are inevitable and require feedback). When receiving a sensory image, this feedback is always present, so there is reason to talk not about a reflex arc, but about a closed reflex ring.
Correction of the sensual image occurs with the help of perceptual actions, in which the image of the object is compared with the real-practical features of this object. The effector components of these actions include hand movements that feel the object, eye movements that track the visible contour, larynx movements that reproduce the heard sound, and others. In all these cases, a copy is created that is comparable to the original, and branching signals, entering the nervous system, can perform a corrective function in relation to the image, and therefore to practical actions. In this way, perceptual action is a self-regulating model what controls the feedback mechanism and adapts to the characteristics of the object under study.
Nature endowed every person with the ability to know the world in which he was born, and, in particular, the ability to feel and perceive the world people, nature, culture, various items and phenomena. The path to the knowledge of the environment and one's own states begins with sensations.
The meaning of feelings:
- sensations allow a person to navigate in the world of sounds, smells, perceive colors, evaluate the weight and size of objects, determine the taste of a product, etc.
- sensations provide material for other more complex mental processes (for example, deaf people will never be able to comprehend the sounds of a human voice, blind people - colors);
- especially developed sensations are a condition for a person's success in a particular profession (for example, a taster, artist, musician, etc.);
- depriving a person of sensations leads to sensory deprivation (sensory hunger - a lack of impressions), which can occur both in natural and laboratory conditions. (according to Lee, sensory deprivation is the main condition for creativity, since 95% of the energy spent on overcoming gravity goes to creativity);
- there is the possibility of influencing the human condition through sensations (the sound of the surf, birdsong, aromatherapy, music).
Feeling (lat. sensus- perception) is a mental cognitive process of reflection individual properties of the real external world and the internal state of a person, which directly affect the sense organs Currently.
Sensation does not give a person a complete picture of reflected objects. If, for example, a person is blindfolded and offered to touch an object unfamiliar to him (table, computer, mirror) with his fingertip, then the sensation will give him knowledge of only certain properties of the object (for example, that this object is hard, cold, smooth, etc.). P.).
Sensations are a sensory reflection of objective reality, as they arise due to the influence of various factors (irritants) on the sense organs (vision, hearing, etc.). They are characteristic of all living beings with a nervous system. Moreover, some animals (for example, eagles) have much sharper eyesight than humans, a more subtle sense of smell and hearing (dog). The eyes of ants distinguish ultraviolet rays that are inaccessible to the human eye. Bats and dolphins distinguish between ultrasounds that humans cannot hear. Rattlesnake distinguishes between insignificant temperature fluctuations - 0.001 degrees.
Feelings are both objective and subjective. Objectivity lies in the fact that they reflect a real-life external stimulus. Subjectivity is due to the dependence of sensations on individual features and the current mental state of the person. This is what the well-known proverb says: "There are no comrades for the taste and color."
Associated with the emotional sphere of a person, sensations can give rise to various feelings in him, cause the simplest emotional experiences. For example, the sensation of the sharp sound of car brakes heard somewhere nearby can cause a person passing by to have unpleasant memories of their own driving practice. Negative experiences are generated by sensations of an unloved smell, color and taste.
The structure of the analyzers:
The physiological basis of sensations is laid down in the work of special nervous structures, called analyzers by I. Pavlov. Analyzers- these are the channels through which a person receives all the information about the world (both about the external environment and about his own, internal state).
Analyzer - a nervous formation that carries out the perception, analysis and synthesis of external and internal stimuli acting on the body.
Each type of analyzer is adapted to isolate a certain property: the eye reacts to light stimuli, the ear to sound stimuli, the olfactory organ to smells, etc.
The analyzer consists of 3 blocks:
1. Receptor - the peripheral part of the analyzer, which performs the function of receiving information from stimuli acting on the body. Receptor - a specialized cell designed to perceive a certain stimulus from the external or internal environment and to convert its energy from a physical or chemical form into a form of nervous excitation (impulse).
2. Afferent (conductive) and efferent (exit) paths. Afferent pathways are parts of the nervous system through which the resulting excitation enters the central nervous system. Efferent pathways are sections along which the response impulse (based on information processed in the central nervous system) is transmitted to receptors, determining their motor activity (reaction to a stimulus).
3. Cortical projection zones (central section of the analyzer) - areas of the cerebral cortex in which the processing of nerve impulses received from receptors takes place. Each analyzer in the cerebral cortex has its own “representation” (projection), where the analysis and synthesis of information of a certain sensitivity (sensory modality) takes place.
Sensation, in its essence, is a mental process that occurs during the processing of information received by the brain.
Depending on the type of sensitivity, visual, auditory, olfactory, gustatory, skin, motor and other analyzers are distinguished. Each analyzer from the whole variety of influences allocates incentives of a certain type. For example, the auditory analyzer highlights the waves formed as a result of vibrations of air particles. The taste analyzer generates an impulse as a result of " chemical analysis"molecules dissolved in saliva, and olfactory - in the air. The visual analyzer perceives electromagnetic oscillations, whose characteristics give rise to one or another visual image.
Sensation is a reflection of the properties of objects of the objective world, arising from their direct impact on the sense organs, this is, firstly, the initial moment of the sensorimotor reaction; secondly, the result of conscious activity.
The emergence of sensation is directly related to the work of human receptors. A receptor is an organ specially adapted for the reception of stimuli; it is more easily irritated than other organs or nerve fibers; its sensitivity is especially high. In addition, each receptor is specialized in relation to a particular stimulus.
In the process biological evolution the sense organs themselves were formed in the real relationship of the organism with the environment, under the influence of the outside world. The impact of the outside world forms the receptors themselves. Receptors are, as it were, anatomically fixed in the structure of the nervous system, imprints of the effects of irritation processes.
In sensation, absolute and differential thresholds are distinguished. Not every stimulus causes a sensation, but only one whose intensity has overcome the threshold of sensation. This minimum stimulus intensity at which a sensation occurs is called the lower absolute threshold. Along with the lower, there is also an upper absolute threshold, i.e. the maximum intensity possible to experience a given quality.
The thresholds of sensitivity are significantly shifted depending on the attitude of a person to the task that he solves.
For the sensitivity of an organ, its physiological state is also important. The significance of physiological moments is manifested primarily in the phenomena of adaptation, in the adaptation of an organ to a long-acting stimulus. The phenomenon of contrast is also associated with adaptation, which is associated with a change in sensitivity under the influence of a previous (or accompanying) stimulus.
The differentiation and specialization of receptors does not exclude their interaction, which is expressed in the effect that stimulation of one receptor has on the thresholds of another.
Classification of sensations
organic sensations. Organic sensations include sensations of hunger, thirst, sensations coming from the cardiovascular, respiratory and reproductive systems of the body, and all sensations associated with the state of the human body.
All organic sensations have a number of common features:
They are usually associated with organic needs, which are usually first reflected in consciousness through organic sensations.
All organic sensations are more or less brightly colored.
Organic sensations, reflecting needs, are usually associated with motor impulses and are interconnected in a psychomotor unity.
Static sensations. These are sensations associated with indications of the position of our body in space, its posture, passive and active movements of the body. The central organ that regulates the balance of the body in space is the vestibular apparatus.
kinesthetic sensations. Sensations of movement of various parts of the body are caused by excitations coming from proprioreceptors located in the joints, ligaments and muscles. Through kinesthetic sensations, a person can determine the position and movement of their body parts. Impulses entering the central nervous system from proprioreceptors due to changes that occur during movement in the muscles cause reflex reactions and play a significant role in muscle tone and coordination of movements.
Skin sensitivity. Skin sensitivity is subdivided by the classical physiology of the sense organs into 4 types. These are the receptions of pain, heat, cold and touch (pressure). It is assumed that each of these types of sensitivity has and specific receptors
Touch. Touch includes sensations of touch and pressure in unity with kinesthetic, muscular-articular sensations. The proprioceptive components of touch come from receptors located in muscles, ligaments, and articular bags. When moving, they are irritated by a change in voltage.
Olfactory sensations. Olfactory sensations arise when molecules enter the nasal cavity together with the inhaled air. various substances and are transmitted to the central nervous system via the olfactory receptor.
Taste sensations. Taste sensations, like olfactory sensations, are chemical properties substances. Taste sensations play an important role in adjusting the emotional state of a person, their role is determined by the state of the body's need for food. Arise through the taste receptor, the peripheral part of which is located in the oral cavity.
Auditory sensations. Auditory sensations are a reflection of sound waves affecting the auditory receptor, which are generated by the sounding body and represent a variable condensation and rarefaction of air.
visual sensations. Visual sensations are caused by exposure to the visual analyzer of a light wave, which differ in length and frequency of oscillations.
