Sensory systems: functions, structure and basic processes occurring in sensory systems. Types of sensory systems

General information

Adhering to the cognitive approach to the description of the psyche, we represent a person as a kind of system that processes symbols in solving its problems, then we can imagine the most important feature of a person's personality - the sensory organization of the personality.

Sensory organization of personality

The sensory organization of the personality is the level of development of individual systems of sensitivity and the possibility of their association. The sensory systems of a person are his sense organs, as if receivers of his sensations, in which sensation is transformed into perception.

Every receiver has a certain sensitivity. If we turn to the animal world, we will see that the predominant level of sensitivity of any species is a generic trait. For example, bats have developed sensitivity to the perception of short ultrasonic pulses, dogs have olfactory sensitivity.

The main feature of the sensory organization of a person is that it develops as a result of his entire life path. The sensitivity of a person is given to him at birth, but its development depends on the circumstances, desire and efforts of the person himself.

What do we know about the world and about ourselves? Where do we get this knowledge from? How? The answers to these questions come from the depths of centuries from the cradle of all living things.

Feel

Sensation is a manifestation of the general biological property of living matter - sensitivity. Through sensation there is a psychic connection with the external and inner world. Thanks to sensations, information about all the phenomena of the external world is delivered to the brain. In the same way, a loop closes through sensations to receive feedback about the current physical and, to some extent, mental state of the organism.

Through sensations, we learn about taste, smell, color, sound, movement, the state of our internal organs, etc. From these sensations, holistic perceptions of objects and the whole world are formed.

It is obvious that the primary cognitive process takes place in human sensory systems, and already on its basis, cognitive processes that are more complex in their structure arise: perceptions, representations, memory, thinking.

No matter how simple the primary cognitive process may be, but it is precisely this that is the basis of mental activity, only through the “entrances” of sensory systems does the world around us penetrate into our consciousness.

Sensation Processing

After the information is received by the brain, the result of its processing is the development of a response or strategy aimed, for example, at improving physical tone, focusing more on current activities, or setting up for accelerated inclusion in mental activity.

Generally speaking, the response or strategy worked out at any given time is the best choice of the options available to the person at the time of the decision. However, it is clear that the number of options available and the quality of choice vary from person to person and depend on, for example:

mental properties of personality,

strategies for interacting with others

some of the physical condition,

experience, the availability of the necessary information in memory and the possibility of retrieving it.

the degree of development and organization of higher nervous processes, etc.

For example, the baby went out naked in the cold, his skin feels cold, perhaps chills appear, he becomes uncomfortable, a signal about this enters the brain and a deafening roar is heard. The reaction to cold (stimulus) in an adult may be different, he will either rush to get dressed, or jump into a warm room, or try to warm himself in another way, for example, by running or jumping.

Improving the higher mental functions of the brain

Over time, children improve their reactions, multiplying the effectiveness of the result achieved. But after growing up, the opportunities for improvement do not disappear, despite the fact that the adult's susceptibility to them decreases. It is in this that "Effekton" sees part of its mission: increasing the efficiency of intellectual activity by training the higher mental functions of the brain.

Effekton's software products make it possible to measure various indicators of the human sensorimotor system (in particular, the Jaguar package contains tests of the time of a simple audio and visual-motor reaction, a complex visual-motor reaction, and the accuracy of perception of time intervals). Other packages of the "Effekton" complex evaluate the properties of cognitive processes of higher levels.

Therefore, it is necessary to develop the perception of the child, and the use of the package "Jaguar" can help you with this.

Physiology of sensations

Analyzers

The physiological mechanism of sensations is the activity of the nervous apparatus - analyzers, consisting of 3 parts:

receptor - the perceiving part of the analyzer (carries out the conversion of external energy into a nervous process)

central part of the analyzer - afferent or sensory nerves

cortical sections of the analyzer, in which the processing of nerve impulses takes place.

Certain receptors correspond to their sections of cortical cells.

The specialization of each sense organ is based not only on the structural features of the receptor analyzers, but also on the specialization of the neurons that make up the central nervous apparatus, which receive signals perceived by the peripheral senses. The analyzer is not a passive receiver of energy; it is reflexively rebuilt under the influence of stimuli.

The movement of stimulus from the outer to the inner world

According to the cognitive approach, the movement of a stimulus during its transition from the external world to the internal one occurs as follows:

the stimulus causes certain changes in energy in the receptor,

energy is converted into nerve impulses

information about nerve impulses is transmitted to the corresponding structures of the cerebral cortex.

Sensations depend not only on the capabilities of the brain and sensory systems of a person, but also on the characteristics of the person himself, his development and condition. With illness or fatigue, a person changes sensitivity to certain influences.

There are also cases of pathologies when a person is deprived, for example, of hearing or sight. If this trouble is congenital, then there is a violation of the flow of information, which can lead to mental retardation. If these children were taught special techniques to compensate for their shortcomings, then some redistribution within the sensory systems is possible, thanks to which they will be able to develop normally.

Properties of sensations

Each type of sensation is characterized not only by specificity, but also has general properties with other types:

quality,

intensity,

duration,

spatial localization.

But not every irritation causes a sensation. The minimum value of the stimulus at which a sensation appears is the absolute threshold of sensation. The value of this threshold characterizes the absolute sensitivity, which is numerically equal to the value inversely proportional to the absolute threshold of sensations. And sensitivity to a change in the stimulus is called relative or difference sensitivity. The minimum difference between two stimuli, which causes a slightly noticeable difference in sensations, is called the difference threshold.

Based on this, we can conclude that it is possible to measure sensations. And once again you come to admiration from amazing delicately working devices - human sense organs or human sensory systems.

Effekton's software products allow you to measure various indicators of the human sensory system (for example, the Jaguar package contains tests of the speeds of a simple audio and visual-motor reaction, a complex visual-motor reaction, the accuracy of time perception, the accuracy of space perception, and many others). Other packages of the "Effekton" complex also evaluate the properties of cognitive processes of higher levels.

Classification of sensations

Five basic types of sensations: sight, hearing, touch, smell and taste - were already known to the ancient Greeks. At present, ideas about the types of human sensations have been expanded, about two dozen different analyzer systems can be distinguished, reflecting the impact of the external and internal environment on receptors.

Sensations are classified according to several principles. The main and most significant group of sensations brings information from the outside world to a person and connects him with the external environment. These are exteroceptive - contact and distant sensations, they arise in the presence or absence of direct contact of the receptor with the stimulus. Sight, hearing, smell are distant sensations. These types of sensations provide orientation in the nearest environment. Taste, pain, tactile sensations - contact.

According to the location of receptors on the surface of the body, in muscles and tendons, or inside the body, they are distinguished, respectively:

exteroception - visual, auditory, tactile and others;

proprioception - sensations from muscles, tendons;

interoception - feelings of hunger, thirst.

In the course of the evolution of all living things, sensitivity has undergone changes from the most ancient to the modern. So, distant sensations can be considered more modern than contact ones, but in the structure of the contact analyzers themselves, one can also reveal more ancient and completely new functions. So, for example, pain sensitivity is more ancient than tactile.

Such classification principles help to group all kinds of sensations into systems and see their interaction and connections.

Types of sensations

Vision, hearing

Let us consider various types of sensations, bearing in mind that vision and hearing are the most well studied.

The eye is a completely unusual device that "mother nature" could only invent for our vision, a sensory organ with a very complex anatomical structure. Light waves, reflected from objects, are refracted, pass through the lens of the eye, which provides focusing of light, and appear on the retina in the form of an image.

Clear, sharp vision of equidistant objects is provided by a change in the curvature of the lens, called accommodation. This is the most important regulator of the function of vision. Various disorders can affect accommodation, which affects visual acuity, the level of discrimination small parts.

The retina of the eye is the front edge of the brain, the part of the visual analyzer farthest from the brain, which first perceives light, processes and converts light energy into irritation - a signal in which all information about what the eye sees is encoded. The study of this nerve formation helps to reveal the secrets of the visual mechanism created by nature. Yes, of course, "mother nature" did a great job creating such a perfect instrument of our vision.

The eye itself is a distant receptor, because it makes it possible to recognize objects remote from the sense organs and phenomena occurring around us. Our vision helps to determine the distance to objects and their volume. This is possible due to the pairing of the visual analyzer, on the retina, when moving away or approaching an object, the image size changes, and movement, i.e. convergence and dilution of the axes of the eyes.

Optic nerve fibers make up the retina of the eye, which consists of several tens of thousands of endings that are excited under the influence of a light wave. The endings of the optic nerve are different in form and function.

Receptors located in the center of the retina, similar in shape to cones, reflect color and are the apparatus of daytime vision. Rod-shaped nerve endings reflect light. Located around the cones, closer to the edge of the retina, they are the twilight vision apparatus. Cone and rod vision are independent of each other, so if one is impaired, the other remains unchanged.

Two groups of visual sensations can be distinguished:

achromatic, reflecting the transition from white to black, with all shades gray color and

chromatic, reflecting the color gamut with a large number of shades and tones of color.

Without the reflection of color, the human world would become much poorer, and the emotional background is also expressed in color sensations, for example, they often talk about warm and cold color tones. The emotional impact of color is widely used in painting, and in any kind of art craft.

With the help of a visual analyzer, you can distinguish the brightness of the color and highlight the object from the general background. Black on white or white on black is especially visible. Thanks to the law of contrast, it becomes possible to distinguish all planar black and white images. If the object is far away and at the same time poorly lit, then for its unmistakable definition, the contrast should be high enough.

Perhaps, in the life of any person, visual sensations play the greatest role, without them human activity is very limited, and some types of activity are generally impossible, because. the main source of information is vision. The eyes, during long work, for example, on a computer, get tired, they need rest, the exercises of the "Comfort" package will come to their aid.

Hearing

Auditory sensations are also distant sensations. The sensory endings of the auditory nerve are located in the inner ear, the cochlea with the auditory membrane and sensory hairs. The auricle, the so-called outer ear, collects sound vibrations, and the mechanism of the middle ear transmits them to the cochlea. The sensory endings of the cochlea are excited as a result of resonance, i.e. the endings of the auditory nerve, different in length and thickness, set in motion at a certain number of oscillations per second, and the received signals are transmitted to the brain. These oscillations occur in elastic bodies and are transmitted by the air medium. We know from physics that sound has a wave nature and is characterized by frequency and amplitude.

The frequency of sound is determined by the number of wave periods per unit of time. So, for example, the auditory range of an adult is in the range of 15 - 20,000 Hz, decreasing with age. Sounds differ not only in frequency, but also in timbre, giving uniqueness and peculiar coloring to the voice and sound of various musical instruments. The loudness of a sound depends on its amplitude and is measured in decibels (logarithmic scale). Normal conversation occurs at 50 - 60 dB, and rock music up to 130 dB, i.e. reaches the pain threshold.

There are three types of auditory sensations: speech, music and noise. In these types of sensations, the sound analyzer distinguishes four qualities of sound:

force (loud - weak),

height (high - low),

sound duration and tempo-rhythmic pattern of perceived sounds.

Phonemic hearing is called hearing, using which you can distinguish the sounds of speech. It is formed during life and depends on the speech environment. Good knowledge of a foreign language involves the development of a new system of phonemic hearing. The ability to learn foreign languages is determined by phonemic hearing, which also affects the literacy of written speech.

The musical ear of a person is brought up and formed, as well as speech. The ability to enjoy music is a centuries-old result of the development of the musical culture of mankind.

Noises and rustles are less significant for a person, unless they interfere with his life. Noises can cause a pleasant emotional mood, for example, the sound of rain, the roar of the surf, and, one of my acquaintances, a computer network administrator, said that he cannot fall asleep when he does not hear the noise of working fans from three or four computers. Noises can also serve as a danger signal - the hiss of gas, the clatter of feet behind your back, the howl of a siren.

Smell, touch, vibratory and proprioceptive sensations

A person has the most developed vision and hearing, respectively, they are the most studied, although there are other senses that are also important for a person in his daily life.

vibration sensations

Vibrational sensitivity can be associated with auditory sensations, because. they have a common nature of reflected physical phenomena. Vibration sensations reflect vibrations of an elastic medium. This kind of sensitivity can be called "contact hearing". No specific vibration receptors have been found in humans. It is believed that the vibrational sense is one of the most ancient types of sensitivity, and all tissues of the body can reflect the vibrations of the external and internal environment.

In human life, vibrational sensitivity is subordinated to auditory and visual. The cognitive value of vibration sensitivity increases in those activities where vibrations become a signal of malfunctions in the operation of the machine. In the life of the deaf and deaf-blind, vibrational sensitivity compensates for hearing loss. The body of a healthy person is energized by short vibrations, long and intense vibrations tire and cause painful phenomena.

Smell

The olfactory sensation receptor is the end of the olfactory nerve in the nasal cavity, it belongs to the distant ones. Microscopic particles of substances that enter the nasal cavity with air, being irritants, cause olfactory sensations.

In animals, the sense of smell is the main distant receptor, guided by smell, the animal finds food or avoids danger. The sexual behavior of animals depends on the production of special substances - pheromones. There is a theory that in humans, pheromones play an important role in matters of sex.

Man in modern world there is no need to follow the olfactory sensations, orienting in the environment. The function of smell in humans is suppressed by sight and hearing. The absence in the language of special words for designating olfactory sensations indicates their insufficient development and instability. Usually they say: "the smell of the sea", "the smell of roses", "the smell of the stables".

Olfactory sensitivity is closely related to taste, helps to recognize the quality of food. The sense of smell warns of a dangerous air environment for the body, allows you to distinguish in some cases chemical composition substances.

Taste sensations are contact, arising from the contact of the sense organ (tongue) with the object itself. The sense of taste detects molecules dissolved in saliva.

There are four main qualities of taste stimuli: sour, sweet, bitter, salty. From the combinations of these four sensations, to which tongue movements are added, a complex of taste sensations arises.

Initially, the sensory process occurs in the taste buds, and each of the papillae has from 50 to 150 receptor cells, which are quickly worn out from contact with food and then renewed. Sensory signals then travel along nerves to the hindbrain, thalamus, and gustatory cortex, which processes taste sensations.

Taste sensations, like olfactory ones, increase a person's appetite. By analyzing the quality of food, taste sensations also have a protective function and are important for survival. When fasting, taste sensitivity increases, when saturated or satiety - decreases.

In the skin there are several independent analyzer systems:

tactile (sensation of touch),

temperature,

All types of skin sensitivity are referred to as contact sensitivity. The largest accumulation of tactile cells is in the palm, on the fingertips and on the lips. Skin receptors transmit information to spinal cord, making contact with motor neurons, which makes possible reflex actions such as, for example, pulling the hand away from the fire. The sense of touch is the tactile sensations of the hand along with the musculo-articular sensitivity.

Temperature sensitivity regulates heat transfer between the body and the environment. The distribution of heat and cold receptors over the skin is uneven. The back is most sensitive to cold, the least - the chest.

Strong pressure on the surface of the body causes pain. The receptor endings of pain sensitivity are located under the skin, deeper than the tactile receptors. Where there are more tactile receptors, there are fewer pain receptors. Tactile sensitivity gives knowledge about the qualities of the object, and pain sensitivity gives a signal about the harm caused by the stimulus.

proprioceptive sensitivity

Kinesthesia

Kinesthetic sensations are sensations of movement and position of individual parts of the body. Kinesthetic sensation receptors are located in muscles and tendons. Irritation in these receptors occurs under the influence of muscle stretching and contraction.

A large number of motor receptors are located in the fingers, tongue and lips, since these organs need to carry out precise and subtle working and speech movements. The activity of the motor analyzer allows a person to coordinate and control his movements. Hand exercises of the "Comfort" package improve blood circulation, reduce tension and fatigue, promote better coordination of movements and increase mental performance.

It is clear that the development of kinesthetic sensations is one of the most important tasks of education.

Speech kinesthesias are formed in the infantile and preschool periods of human development. Education foreign language requires the development of such speech kinesthesias that are not typical for the native language.

vestibular sense

Static, or gravitational, sensitivity reflects the position of our body in space. Its receptors are located in the vestibular apparatus of the inner ear: semicircular canals and vestibular sacs convert signals about relative motion and gravity and transmit them to the cerebellum and the cortex of the temporal region. Sudden and frequent changes in the position of the body relative to the plane of the earth, such as swinging on a swing or sea rolling, lead to dizziness - "seasickness".

Do humans have enough sense organs?

Sensations provide the body with adequate orientation in the environment. Could a person get to know the world around him more deeply if he had more sense organs?

Philosophers-idealists made a conclusion about the limited cognitive capabilities of a person, linking this with the limitedness of the sense organs and the variety of phenomena in the surrounding world.

Materialists believed that the existing sense organs are sufficient for a complete knowledge of the world. Cognition goes deeper, the cognitive power of a person lies in the fact that the activity of his sense organs is added to the activity of thinking, which pushes the limits of cognitive possibilities.

Lecture

The value of sensory systems for the human body.

Visual and auditory sensory systems:

Structure, function and hygiene.

Plan

1. The value of sensory systems for the human body.

2. Visual sensory system: structure, functions. Visual disturbances.

3. Prevention of visual impairment in children and adolescents.

4. Embryology of the eye. Age features visual reflex responses.

5. Auditory sensory system: structure, functions.

6. Ear diseases and hearing hygiene. Prevention of the negative impact of "school" noise on the student's body.

7. Age features of the auditory analyzer.

Basic concepts: sense organs, analyzer, sensory systems, visual analyzer, auditory analyzer, receptors, adaptation, eyeball, auxiliary apparatus of the eye, photoreceptors, blind spot, yellow spot, accommodation, hyperopia, myopia, refraction, refraction, hypermetropia, emmetropia, myopia, astigmatism, ophthalmic training, natural and artificial lighting, light factor, outer ear, middle ear, inner ear, Phonoreceptors, organ of Corti.

Literature

1. Datsenko I.I. Hygiene and human ecology. Tutorial Lvov: Afisha, 2000. S. 238-242.

2. Podolyak-Shumilo N.G., Poznansky S.S. School hygiene. Proc. allowance for ped. in-tiv. - K .: Higher School, 1981. - S. 48-53.

3. Popov S.V. Valeology at school and at home (On the physical well-being of schoolchildren) .- St. Petersburg: SOYUZ, 1997.-S. 80-92.

4. Soviets S.E. etc. School hygiene. Proc. allowance for students ped. in-tiv.- K .: Higher School, 1971.- S. 70-75.

5. Starushenko L.1. Clinical anatomy and human physiology: Textbook M.: USMP, 2001. S. 231-237.

6. Prisyazhnyuk M.S. Man and his health: Samples, textbook. allowance.-M.: Phoenix, 1998.-S. 59-71.

7. Khripkova A.G. Age Physiology and School Hygiene. Allowance for ped. in-tov / A.G. Khripkova, M.V. Antropova, D.A. Farber.- M.: Enlightenment, 1990.- P. 79-96.

8. Khripkova A.G., Kolesov D.V. Hygiene and health of the student.- M.: Education, 1988.- S. 141-148.

The value of sensory systems for the human body

The system that provides the perception, transmission and processing of information about environmental phenomena is called analyzer, or sensor system. The doctrine of analyzers was developed by I.P. Pavlov. The analyzer, according to the teachings of I.P. Pavlova, consists of three inextricably linked departments:

1) receptor - peripheral perceiving apparatus, which perceives irritation and turns it into a nervous process of excitation;

2) excitation conductor- centripetal nerve fiber, which transmits excitation to the brain;

3) nerve center- a section of the cerebral cortex in which a subtle analysis of excitation takes place and sensations arise.

Thus, each analyzer consists of peripheral, conductive and central sections. The receptor apparatus belongs to the peripheral section, afferent neurons and pathways belong to the wire section, and sections of the cortex of the cerebral hemispheres belong to the central section. The peripheral section of the analyzer represents the sense organs with receptors embedded in them, with the help of which a person cognizes the world around him, receives information about it. They are called the sense organs, or exteroreceptors.

Exteroreceptors- sensitive formations that carry out the perception of irritations from the environment. These include the perceiving cells of the retina of the eye, ears, skin receptors (touch and pressure), organs of smell, taste.

Interoreceptors- sensitive formations that perceive changes in the internal environment of the body.

Interoreceptors are located in the tissues of various internal organs (heart, liver, kidneys, blood vessels, etc.) and perceive changes in the internal environment of the body and the state of internal organs. As a result of the receipt of impulses from the receptors of the internal organs, self-regulation of respiration, blood pressure, and heart activity occurs.

Proprioreceptors- sensitive formations that signal the position and movement of the body are contained in the muscles, joints and perceive the contraction and stretching of the muscles.

Thus, a person has sense organs: vision, hearing, sense of body position in space, taste, smell, skin sensitivity, musculo-articular feeling.

According to the nature of interaction with the stimulus, receptors are divided into contact and remote; according to the type of energy, it is transformed into receptors - mechanoreceptors, chemoreceptors, photoreceptors and others.

Contact receptors can receive information about the properties of an object, phenomenon, get irritation only upon contact, direct contact with an environmental agent. These are chemoreceptors of the tongue, tactile receptors of the skin.

Thanks to remote receptors can receive information at a distance: the agent of the environment distributes wave energy - light, sound. It is she who is caught by remote sense organs, for example, the eye, the ear.

Mechanoreceptors transform mechanical energy into energy of nervous excitation (for example, tactile receptors), chemoreceptors - mimic (olfactory, taste receptors), photoreceptors - light (receptors of the organ of vision), thermoreceptors - heat (cold and heat receptors of the skin).

The receptors are distinguished by a very high excitability in terms of the adequacy of stimuli. The stimuli specific for a certain receptor, to which it is specially adapted in the process of phylo- and ontogenesis, are called adequate. Under the action of adequate stimuli, sensations arise that are characteristic of a particular sense organ (the eye perceives only light waves, but does not perceive smells, sound).

In addition to adequate, there are inadequate stimuli that cause only primitive sensations inherent in a particular analyzer. For example, a blow to the ear causes ringing in the ears.

The excitability of receptors depends both on the state of the entire analyzer and on the general state of the organism. The smallest difference in the strength of two stimuli of the same kind that can be perceived by the senses is called threshold of discrimination. However, most of the impulses from the receptors of the internal organs, reaching the cerebral cortex, do not cause mental phenomena. Such impulses are called subsensory: they are below the threshold of sensations and therefore do not cause sensations.

Receptors are able to get used to the strength of the stimulus. This property is called adaptation, in which the sensitivity of receptors decreases or increases. The maximum rate of adaptation for receptors that perceive touch on the skin, the lowest - for muscle receptors. The receptors of blood vessels and lungs adapt more slowly, providing constant self-regulation of blood pressure and respiration. Adaptation is due, first of all, to changes in the cortical sections of the analyzers, as well as to the processes that take place in the receptors themselves.

conductor department sensory systems consists of precentral (afferent) nerve fibers as part of sensory nerves and some subcortical formations (nuclei of the hypothalamus, thalamus and reticular formation). In this section, the impulse from the receptors is not only carried out, but also encoded and converted.

In the central department analyzer, nerve impulses acquire new qualities and are reflected in consciousness in the form of sensations. On the basis of sensation, complex subjective images arise: perceptions, ideas.

In children, the sense organs are still imperfect and are in the process of development. The organs of taste and smell develop first, and then the organs of touch. For the improvement of various sense organs in children, it is of great importance that the masses are properly trained in the process of development.

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1. SENSOR SYSTEMS

1.1 Understanding sensory systems

Sensory - from the Latin sensus - feeling, sensation.

The sensory system is an integral nervous mechanism that receives and analyzes sensory information. Synonymous with the sensory system in domestic psychology is the term "analyzer", which was first introduced by the outstanding Russian physiologist I.P. Pavlov.

The analyzer consists of three parts:

1) the peripheral section - a receptor that receives and transforms external energy into a nervous process, and an effector - an organ or system of organs that reacts to the actions of external or internal stimuli, acting as the executive link of a reflex act; sensory visual sensitivity sensitization

2) pathways - afferent (ascending) and efferent (descending), connecting the peripheral section of the analyzer with the central one;

3) the central section - represented by the subcortical and cortical nuclei and the projection sections of the cerebral cortex, where the processing of nerve impulses coming from the peripheral sections takes place.

Each analyzer has a core, i.e. the central part, where the main mass of receptor cells is concentrated, and the periphery, consisting of scattered cellular elements, which are located in one quantity or another in various areas bark. The nuclear part of the analyzer consists of a large mass of cells that are located in the area of the cerebral cortex where the centripetal nerves from the receptor enter. Scattered (peripheral) elements of this analyzer enter the regions adjacent to the nuclei of other analyzers. This ensures participation in a separate sensory act of a large part of the entire cerebral cortex. The analyzer core performs the function of fine analysis and synthesis, for example, it differentiates sounds by pitch. Scattered elements are associated with the function of rough analysis, for example, distinguishing between musical sounds and noises.

Certain cells of the peripheral parts of the analyzer correspond to certain parts of the cortical cells. So, spatially different points in the cortex are, for example, different points of the retina; spatially different arrangement of cells is presented in the cortex and the organ of hearing. The same applies to other sense organs.

Numerous experiments carried out by methods of artificial stimulation make it possible at the present time to quite definitely establish the localization in the cortex of one or another type of sensitivity. Thus, the representation of visual sensitivity is concentrated mainly in the occipital lobes of the cerebral cortex. Auditory sensitivity is localized in the middle part of the superior temporal gyrus. Tactile-motor sensitivity is represented in the posterior central gyrus, etc.

For the emergence of a sensory process, the work of the entire analyzer as a whole is necessary. The impact of the stimulus on the receptor causes the appearance of irritation. The beginning of this irritation lies in the transformation of external energy into a nervous process, which is produced by the receptor. From the receptor, this process reaches the nuclear part of the analyzer along ascending pathways. When excitation reaches the cortical cells of the analyzer, the body responds to irritation. We sense light, sound, taste, or other qualities of stimuli.

Thus, the analyzer constitutes the initial and most important part of the entire path of nervous processes, or the reflex arc. The reflex arc consists of a receptor, pathways, a central part, and an effector. The relationship of the elements of the reflex arc provides the basis for the orientation of a complex organism in the surrounding world, the activity of the organism, depending on the conditions of its existence.

1.2 Types of sensory systems

For a long time, visual, auditory, tactile, olfactory and gustatory sensitivity seemed to be the basis on which, with the help of associations, the entire mental life of a person is built. In the 19th century, this list began to expand rapidly. Sensitivity to the position and movement of the body in space was added to it, vestibular sensitivity, tactile sensitivity, etc. were discovered and studied.

The first classification was put forward by Aristotle, who lived in 384-322. BC, who identified 5 types of "external senses": visual, auditory, olfactory, tactile, gustatory.

The German physiologist and psychophysicist Ernst Weber (1795-1878) expanded the Aristotelian classification by proposing to divide the sense of touch into: the sense of touch, the sense of weight, the sense of temperature.

In addition, he singled out a special group of feelings: a sense of pain, a sense of balance, a sense of movement, a sense of internal organs.

The classification of the German physicist, physiologist, psychologist Hermann Helmholtz (1821-1894) is based on the categories of modality, in fact this classification is also an extension of Aristotle's classification. Since modalities are distinguished according to the corresponding sense organs, for example, sensory processes associated with the eye belong to the visual modality; sensory processes associated with hearing - to the auditory modality, etc. In the modern modification of this classification, an additional concept of submodality is used, for example, in such a modality as skin feeling, submodalities are distinguished: mechanical, temperature and pain. Similarly, within the visual modality, achromatic and chromatic submodalities are distinguished.

German psychologist, physiologist, philosopher Wilhelm Wundt (1832-1920) is considered the founder of the classification of sensory systems based on the type of energy of an adequate stimulus for the corresponding receptors: physical (vision, hearing); mechanical (touch); chemical (taste, smell).

This idea was not widely developed, although it was used by I.P. Pavlov to develop the principles of physiological classification.

The classification of sensations by the outstanding Russian physiologist Ivan Petrovich Pavlov (1849-1936) is based on the physicochemical characteristics of stimuli. To determine the quality of each of the analyzers, he used the physico-chemical characteristics of the signal. Hence the names of analyzers: light, sound, skin-mechanical, odor, etc., and not visual, auditory, etc., as analyzers were usually classified.

The classifications considered above did not allow reflecting the multi-level nature of different types of receptions, some of which are earlier and lower in terms of development, while others are later and more differentiated. Ideas about the different levels of affiliation of certain sensory systems are associated with the model of human skin receptions developed by G.Head.

The English neurologist and physiologist Henry Head (1861-1940) in 1920 proposed the genetic principle of classification. He distinguished between protopathic sensitivity (lower) and epicritical sensitivity (higher).

As an epicritical or discriminative sensibility top level tactile sensitivity was highlighted; and protopathic sensitivity, archaic, lower level - pain. He proved that protopathic and epicritical components can be both inherent in different modalities and can occur within one modality. The younger and more perfect epicritical sensitivity makes it possible to accurately localize an object in space, it provides objective information about the phenomenon. For example, touch allows you to accurately determine the place of touch, and hearing - to determine the direction in which the sound was heard. Relatively ancient and primitive sensations do not give precise localization either in external space or in the space of the body. For example, organic sensitivity - a feeling of hunger, a feeling of thirst, etc. They are characterized by a constant affective coloration, and they reflect subjective states rather than objective processes. The ratio of protopathic and epicritical components in different types of sensitivity are different.

Aleksey Alekseevich Ukhtomsky (1875-1942), an outstanding Russian physiologist, one of the founders of the physiological school of St. Petersburg University, also applied the genetic principle of classification. According to Ukhtomsky, the highest receptions are hearing, vision, which are in constant interaction with the lower ones, thanks to which they improve and develop. For example, the genesis of visual reception is that first tactile reception passes into tactile-visual, and then into purely visual reception.

The English physiologist Charles Sherrington (1861-1952) in 1906 developed a classification that takes into account the location of the receptor surfaces and the function they perform:

1. Exteroception (external reception): a) contact; b) distant; c) contact-distance;

2. Proprioception (reception in muscles, ligaments, etc.): a) static; b) kinesthetic.

3. Interoception (reception of internal organs).

Ch. Sherrington's system classification divided all sensory systems into three main blocks.

The first block is exteroception, which brings to the person information coming from the outside world and is the main reception that connects the person with the outside world. It includes: sight, hearing, touch, smell, taste. All exteroception is divided into three subgroups: contact, distant and contact-distant.

Contact exteroception is carried out when the stimulus is exposed directly to the surface of the body or the corresponding receptors. A typical example is the sensory acts of touch and pressure, touch, taste.

Distant exteroception is carried out without direct contact of the stimulus with the receptor. In this case, the source of irritation is located at some distance from the receptive surface of the corresponding sensory organ. It includes sight, hearing, smell.

Contact-distant exteroception is carried out both in direct contact with the stimulus, and remotely. It includes temperature, skin and pain. vibrational sensory acts.

The second block is proprioception, which brings to the person information about the position of his body in space and the state of his musculoskeletal system. All proprioception is divided into two subgroups: static and kinesthetic reception.

Static reception signals the position of the body in space and balance. Receptor surfaces that report changes in body position in space are located in the semicircular canals of the inner ear.

Kinesthetic reception signals the state of movement (kinesthesia) of individual parts of the body relative to each other, and the positions of the musculoskeletal system. Receptors for kinesthetic, or deep, sensitivity are found in muscles and articular surfaces (tendons, ligaments). Excitations arising from muscle stretching, changing the position of the joints, cause kinesthetic reception.

The third block includes interoception, signaling the state of the internal organs of a person. These receptors are found in the walls of the stomach, intestines, heart, blood vessels, and other visceral structures. Interoceptive are the feeling of hunger, thirst, sexual sensations, sensations of malaise, etc.

Modern authors use the supplemented classification of Aristotle, distinguishing between reception: touch and pressure, touch, temperature, pain, taste, olfactory, visual, auditory, positions and movements (static and kinesthetic) and organic (hunger, thirst, sexual sensations, pain, sensations of internal organs, etc.), structuring it by C. Sherrington's classification. The levels of organization of sensory systems are based on the genetic principle of G.Head's classification.

1.3 Chusensitivity of sensory systems

Sensitivity - the ability of the sense organs to respond to the appearance of a stimulus or its change, i.e. the ability to mental reflection in the form of a sensory act.

Distinguish between absolute and differential sensitivity. Absolute sensitivity - the ability to perceive stimuli of minimal strength (detection). Differential sensitivity - the ability to perceive a change in a stimulus or distinguish between close stimuli within the same modality.

Sensitivity is measured or determined by the strength of the stimulus, which, under given conditions, is capable of causing a sensation. Feeling is an active mental process partial reflections of objects or phenomena of the surrounding world, as well as the internal states of the body, in the mind of a person with the direct impact of stimuli on the senses.

The minimum strength of the stimulus that can cause a sensation is determined by the lower absolute threshold of sensation. Stimuli of lesser strength are called subthreshold. The lower threshold of sensations determines the level of absolute sensitivity of this analyzer. The lower the threshold value, the higher the sensitivity.

where E is sensitivity, P is the threshold value of the stimulus.

The value of the absolute threshold depends on the age, the nature of the activity, the functional state of the organism, the strength and duration of the acting stimulus.

The upper absolute threshold of sensation is determined by the maximum strength of the stimulus, which also causes a sensation characteristic of this modality. There are suprathreshold stimuli. They cause pain and destruction of the receptors of the analyzers, which are affected by suprathreshold stimulation. The minimum difference between two stimuli that causes different sensations in the same modality determines the difference threshold, or threshold of discrimination. Difference sensitivity is inversely proportional to the discrimination threshold.

The French physicist P. Buger in 1729 came to the conclusion that the difference threshold of visual perception is directly proportional to its initial level. 100 years after P. Buger, the German physiologist Ernst Weber established that this pattern is also characteristic of other modalities. Thus, a very important psychophysical law was found, which was called the Bouguer-Weber law.

Bouguer-Weber law:

where? I - difference threshold, I - initial stimulus.

The ratio of the difference threshold to the value of the initial stimulus is a constant value and is called relative difference or differential threshold.

According to the Bouguer-Weber law, the differential threshold is some constant part of the magnitude of the original stimulus, by which it must be increased or decreased in order to obtain a barely noticeable change in sensation. The value of the differential threshold depends on the modality of sensation. For vision, it is about 1/100, for hearing 1/10, for kinesthesia 1/30, etc.

The reciprocal of the differential threshold is called the differential sensitivity. Subsequent studies have shown that the law is valid only for the middle part of the dynamic range of the sensory system, where the differential sensitivity is maximum. The limits of this zone are different for different sensory systems. Outside this zone, the differential threshold increases, sometimes very significantly, especially when approaching the absolute lower or upper threshold.

The German physicist, psychologist and philosopher Gustav Fechner (1801-1887), the founder of psychophysics as a science of the regular connection of physical and mental phenomena, using a number of psychophysical laws found by that time, including the Bouguer-Weber law, formulated the following law.

Fechner's law:

where S is the intensity of sensation, i is the strength of the stimulus, K is the Bouguer-Weber constant.

The intensity of sensations is proportional to the logarithm of the strength of the acting stimulus, that is, the sensation changes much more slowly than the strength of the irritation grows.

As the intensity of the signal increases, in order for the differences between the units of measurement of sensations (S) to remain equal, an increasingly significant difference between the units of intensity (i) is required. In other words, while sensation increases evenly (in arithmetic progression), the corresponding increase in signal intensity occurs physically non-uniformly, but proportionally (in geometric progression). The relationship between quantities, one of which changes in an arithmetic progression, and the second in a geometric progression, is expressed by a logarithmic function.

Fechner's law has received in psychology the name of the basic psychophysical law.

Stevens' law (power law) is a variant of the basic psychophysical law proposed by the American psychologist Stanley Stevens (1906-1973), and establishes a power-law, rather than a logarithmic relationship between the intensity of sensation and the strength of stimuli:

where S is the intensity of sensation, i is the strength of the stimulus, k is a constant that depends on the unit of measurement, n is the exponent of the function. The exponent n of the power function is different for the sensations of different modalities: the limits of its variation are from 0.3 (for sound volume) to 3.5 (for the strength of an electric shock).

The complexity of detecting thresholds and fixing changes in the intensity of sensation is the object of research at the present time. Modern researchers studying the detection of signals by various operators have come to the conclusion that the complexity of this sensory action lies not only in the impossibility of perceiving the signal due to its weakness, but in the fact that it is always present against the background of masking interference or "noise". ". The sources of this "noise" are numerous. Among them are extraneous stimuli, spontaneous activity of receptors and neurons in the central nervous system, a change in the orientation of the receptor relative to the stimulus, fluctuations in attention, and other subjective factors. The action of all these factors leads to the fact that the subject often cannot say with complete certainty when the signal was presented and when it was not. As a result, the signal detection process itself acquires a probabilistic character. This feature of the appearance of sensations of near-threshold intensity is taken into account in a number of recent times mathematical models describing this sensory activity.

1.4 Sensitivity variability

The sensitivity of the analyzers, determined by the magnitude of the absolute and difference thresholds, is not constant and can change. This variability of sensitivity depends both on the conditions of the external environment and on a number of internal physiological and psychological conditions. There are two main forms of sensitivity change:

1) sensory adaptation - a change in sensitivity under the influence of the external environment;

2) sensitization - a change in sensitivity under the influence of the internal environment of the body.

Sensory adaptation - adaptation of the organism to the actions of the environment due to a change in sensitivity under the influence of an acting stimulus. There are three types of adaptation:

1. Adaptation as the complete disappearance of sensation in the process of prolonged action of the stimulus. In the case of constant stimuli, the sensation tends to fade. For example, clothes, watches on the hand, soon cease to be felt. The distinct disappearance of olfactory sensations soon after we enter the atmosphere with any persistent odor is also a common fact. The intensity of the taste sensation is weakened if the corresponding substance is kept in the mouth for some time.

And, finally, the sensation may fade away completely, which is associated with a gradual increase in the lower absolute threshold of sensitivity to the level of intensity of a constantly acting stimulus. The phenomenon is characteristic of all modalities, except visual.

Complete adaptation of the visual analyzer under the action of a constant and immobile stimulus does not occur under normal conditions. This is due to the compensation of a constant 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 conditions were artificially created to stabilize the image relative to the retina of the eyes showed that in this case the visual sensation disappears 2–3 seconds after its occurrence.

2. Adaptation as a dulling of sensation under the influence of a strong stimulus. A sharp decrease in sensation with subsequent recovery is a protective adaptation.

So, for example, when we get from a semi-dark room into a brightly lit space, we are first blinded and unable to distinguish any details around. After some time, the sensitivity of the visual analyzer is restored, and we begin to see normally. The same thing happens when we get into the weaving workshop and for the first time, apart from the roar of the machines, we cannot perceive speech and other sounds. After a while, the ability to hear speech and other sounds is restored. This is explained by a sharp increase in the lower absolute threshold and the discrimination threshold, followed by the restoration of these thresholds in accordance with the intensity of the acting stimulus.

Types of adaptation described 1 and 2 can be combined under the general term "negative adaptation", since their result is a general decrease in sensitivity. But "negative adaptation" is not a "bad" adaptation, since it is an adaptation to the intensity of the acting stimuli and helps to prevent the destruction of sensory systems.

3. Adaptation as an increase in sensitivity under the influence of a weak stimulus (decrease in the lower absolute threshold). 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.

Studies have shown that some analyzers detect fast adaptation, others slow. For example, touch receptors adapt very quickly. The visual receptor adapts relatively slowly (the time of dark adaptation reaches several tens of minutes), the olfactory and gustatory receptors.

The phenomenon of adaptation can be explained by those peripheral changes that occur in the functioning of the receptor under the influence of direct and feedback connection with the core of the analyzer.

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.

So, adaptation is one of the most important types of changes in sensitivity, indicating a greater plasticity of the organism in its adaptation to environmental conditions.

Another type of change in sensitivity is sensitization. The process of sensitization differs from the process of adaptation in that in the process of adaptation, the sensitivity changes in both directions - that is, it increases or decreases, and in the process of sensitization - only in one direction, namely, an increase in sensitivity. In addition, the change in sensitivity during adaptation depends on environmental conditions, and during sensitization - mainly on the processes occurring in the body itself, both physiological and mental. Thus, sensitization is an increase in the sensitivity of the sense organs under the influence of internal factors.

There are two main directions of increasing sensitivity according to the type of sensitization. One of them is of a long-term permanent nature and depends mainly on stable changes occurring in the body, the second is of a non-permanent nature and depends on temporary effects on the body.

The first group of factors that change sensitivity include: age, endocrine changes, dependence on the type of nervous system, the general state of the body associated with the compensation of sensory defects.

Studies have shown that the acuteness of the sensitivity of the sense organs increases with age, reaching its maximum by the age of 20-30, in order to gradually decrease in the future.

The essential features of the functioning of the sense organs depend on the type of the human nervous system. It is known that people with a strong nervous system show more endurance and less sensitivity, and people with a weak nervous system with less endurance have more sensitivity.

Of great importance for sensitivity is the endocrine balance in the body. For example, during pregnancy, olfactory sensitivity is sharply aggravated, while visual and auditory sensitivity decreases.

Compensation for sensory defects leads to an increase in sensitivity. Thus, for example, loss of sight or hearing is compensated to a certain extent by an exacerbation of other types of sensitivity. People deprived of sight have a highly developed sense of touch, they are able to read with their hands. This hand-reading process has a special name - haptics. People who are deaf have a strong vibrational sensitivity. For example, the great composer Ludwig van Beethoven, in the last years of his life, when he lost his hearing, used precisely vibrational sensitivity to listen musical works.

The second group of factors that change sensitivity include pharmacological effects, a conditioned reflex increase in sensitivity, the influence of the second signal system and set, the general state of the body associated with fatigue, as well as the interaction of sensations.

There are substances that cause a distinct exacerbation of sensitivity. These include, for example, adrenaline, the use of which causes excitation of the autonomic nervous system. A similar effect, exacerbating the sensitivity of receptors, may have phenamine and a number of other pharmacological agents.

The conditioned reflex increase in sensitivity can include situations in which there were harbingers of a threat to the functioning of the human body, fixed in memory by previous situations. For example, a sharp exacerbation of sensitivity is observed in members of operational groups who participated in hostilities during subsequent combat operations. Taste sensitivity is aggravated when a person enters an environment similar to that in which he previously participated in a plentiful and pleasant feast.

An increase in the sensitivity of the analyzer can also be caused by the influence of second-signal stimuli. For example: change electrical conductivity eyes and tongue in response to the words "sour lemon", which in fact occurs with direct exposure to lemon juice.

An exacerbation of sensitivity is also observed under the influence of the installation. Thus, auditory sensitivity rises sharply when waiting for an important phone call.

Changes in sensitivity occur even in a state of fatigue. Fatigue first causes an exacerbation of sensitivity, that is, a person begins to acutely feel extraneous sounds, smells, etc., not related to the main activity, and then, with the further development of fatigue, a decrease in sensitivity occurs.

A change in sensitivity can also be caused by the interaction of different analyzers.

The general pattern of the interaction of analyzers is that weak sensations cause an increase, and strong sensations cause a decrease in the sensitivity of the analyzers during their interaction. Physiological mechanisms in this case, underlying sensitization. - these are the processes of irradiation and concentration of excitation in the cerebral cortex, where the central sections of the analyzers are represented. According to Pavlov, a weak stimulus causes an excitation process in the cerebral cortex, which easily radiates (spreads). As a result of irradiation, the sensitivity of other analyzers increases. Under the action of a strong stimulus, a process of excitation occurs, which, on the contrary, causes a process of concentration, which leads to inhibition of the sensitivity of other analyzers and a decrease in their sensitivity.

During the interaction of analyzers, intermodal connections may arise. An example of this phenomenon is the occurrence panic fear when exposed to ultra-low frequency sound. The same phenomenon is confirmed when a person feels the effect of radiation or feels a look in the back.

An arbitrary increase in sensitivity can be achieved in the process of targeted training activities. So, for example, an experienced turner is able to "by eye" determine the millimeter dimensions of small parts, tasters of various wines, spirits, etc., even having extraordinary innate abilities, in order to become real masters of their craft, are forced to train the sensitivity of their analyzers for years.

The considered types of sensitivity variability do not exist in isolation precisely because the analyzers are in constant interaction with each other. Related to this is the paradoxical phenomenon of synesthesia.

Synesthesia - the occurrence under the influence of irritation of one analyzer of a sensation characteristic of another (for example: cold light, warm colors). This phenomenon is widely used in art. It is known that some composers had the ability to "color hearing", including Alexander Nikolaevich Skryabin, who owns the first color musical work in history - the symphony "Prometheus", presented in 1910 and including a party of light. The Lithuanian painter and composer Čiurlionis Mykolojus Konstantinas (1875-1911) is known for his symbolic paintings, in which he reflected the visual images of his musical works - “Sonata of the Sun”, “Sonata of Spring”, “Symphony of the Sea”, etc.

The phenomenon of synesthesia characterizes the constant interconnection of the sensory systems of the body and the integrity of the sensory reflection of the world.

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1) Sensor systems

"Sens" - translated as "feeling", "feeling".

Sensory systems are the perceiving systems of the body (visual, auditory, olfactory, tactile, gustatory, pain, tactile, vestibular apparatus, proprioceptive, interoceptive).

It can be said that sensory systems are the “information inputs” of the organism for its perception of the characteristics of the environment, as well as the characteristics of the internal environment of the organism itself. In physiology, it is customary to emphasize the letter "o", while in technology - the letter "e". Therefore, technical perceiving systems are sensory, and physiological systems are sensory.

Perception is the translation of the characteristics of an external stimulus into internal neural codes available for processing and analysis by the nervous system (coding), and the construction of a neural model of the stimulus (sensory image).

Perception allows you to build an internal image that reflects the essential characteristics of an external stimulus. The internal sensory image of the stimulus is a neural model consisting of a system of nerve cells. It is important to understand that this neural model cannot fully correspond to the real stimulus and will always differ from it at least in some details.

For example, the cubes in the picture on the right form a model close to reality, but not able to exist in reality...

2) Analyzers and sensor systems

Analyzers are called part of the nervous system, consisting of many specialized perceiving receptors, as well as intermediate and central nerve cells and nerve fibers connecting them.

I.P. Pavlov created the doctrine of analyzers. This is a simplified representation of perception. He divided the analyzer into 3 links.

The structure of the analyzer

The peripheral part (remote) is the receptors that perceive irritation and turn it into nervous excitation.

Conductor department (afferent or sensory nerves) - these are pathways that transmit sensory excitation born in receptors.

The central section is a section of the cerebral cortex that analyzes the sensory excitation that has come to it and builds a sensory image due to the synthesis of excitations.

Thus, for example, the final visual perception occurs in the brain and not in the eye.

The concept of a sensory system is broader than an analyzer. It includes additional devices, adjustment systems and self-regulation systems. The sensory system provides for feedback between the brain's analyzing structures and the perceiving receptive apparatus. Sensory systems are characterized by the process of adaptation to stimulation.

Adaptation is the process of adapting the sensory system and its individual elements to the action of a stimulus.

Differences between the concepts of "sensor system" and "analyzer"

1) The sensory system is active, not passive in excitation transfer.

2) The sensory system includes auxiliary structures that ensure optimal tuning and operation of the receptors.

3) The sensory system includes auxiliary lower nerve centers, which not only transmit sensory excitation further, but change its characteristics and divide it into several streams, sending them in different directions.

4) The sensory system has feedback between subsequent and previous structures that transmit sensory excitation.

5) Processing and processing of sensory excitation occurs not only in the cerebral cortex, but also in the underlying structures.

6) The sensory system actively adjusts to the perception of the stimulus and adapts to it, that is, it adapts.

7) The sensor system is more complex than the analyzer.

Conclusion: Sensory system = analyzer + regulation system.

3) Sensory receptors

Sensory receptors are specific cells that are tuned to perceive various stimuli of the external and internal environment of the body and are highly sensitive to an adequate stimulus. An adequate stimulus is a stimulus that gives the maximum response, with a minimum strength of irritation.

The activity of sensory receptors is necessary condition for the implementation of all functions of the central nervous system. Sensory receptors are the first link in the reflex pathway and the peripheral part of a more complex structure - analyzers. A set of receptors, the stimulation of which leads to a change in the activity of any nerve structures, is called the receptive field.

Receptor classification

The nervous system is distinguished by a wide variety of receptors, the various types of which are shown in the figure:

Rice.

Receptors are classified according to several criteria:

A. The central place is occupied by the division of dependence on the type of perceived stimulus. There are 5 such types of receptors:

III Mechanoreceptors are excited during mechanical deformation. They are located in the skin, blood vessels, internal organs, musculoskeletal system, auditory and vestibular systems.

III Chemoreceptors perceive chemical changes in the external and internal environment of the body. These include taste and olfactory receptors, as well as receptors that respond to changes in the composition of blood, lymph, intercellular and cerebrospinal fluid. Such receptors are found in the mucous membrane of the tongue and nose, the carotid and aortic bodies, the hypothalamus, and the medulla oblongata.

III Thermoreceptors perceive changes in temperature. They are divided into heat and cold receptors and are located in the skin, blood vessels, internal organs, hypothalamus, middle, medulla oblongata and spinal cord.

III Photoreceptors in the retina of the eye perceive light (electromagnetic) energy.

Ш Nociceptors (pain receptors) - their excitation is accompanied by painful sensations. Irritants for them are mechanical, thermal and chemical factors. Painful stimuli are perceived by free nerve endings that are found in the skin, muscles, internal organs, dentin, and blood vessels.

B. From a psychophysiological point of view Receptors are divided according to the sense organs and the sensations formed into visual, auditory, gustatory, olfactory and tactile.

AT. Location in the body Receptors are divided into extero- and interoreceptors. Exteroreceptors include receptors of the skin, visible mucous membranes and sensory organs: visual, auditory, taste, olfactory, tactile, skin, pain and temperature. Interoreceptors include receptors of internal organs (visceroreceptors), blood vessels and the central nervous system, as well as receptors of the musculoskeletal system (proprioreceptors) and vestibular receptors. If the same kind of receptors are localized both in the central nervous system and in other places (vessels), then such vessels are divided into central and peripheral.

G. Depending on the degree of receptor specificity, i.e. from their ability to respond to one or more types of stimuli, monomodal and polymodal receptors are distinguished. In principle, each receptor can respond not only to an adequate, but also to an inadequate stimulus, however, the sensitivity to them is different. If the sensitivity to adequate is much greater than that to inadequate stimuli, then these are monomodal receptors. Monomodality is especially characteristic of extreroreceptors. Polymodal receptors are adapted to the perception of several adequate stimuli, such as mechanical and temperature or mechanical, chemical and pain. These include the irritant receptors of the lungs.

D. By structural and functional organization distinguish between primary and secondary receptors. In the primary receptor, the stimulus acts directly on the end of the sensory neuron: olfactory, tactile, temperature, pain receptors, proprioceptors, receptors of internal organs. In the secondary receptors there is a special cell synaptically connected with the end of the dendrite of the sensory neuron, it transmits a signal through the end of the dendrite to the conduction pathways: auditory, vestibular, taste receptors, retinal photoreceptors.

E. According to the speed of adaptation receptors are divided into 3 groups: phasic (quickly adapting): vibration and skin touch receptors, tonic (slowly adapting): proprioreceptors, lung stretch receptors, part of pain receptors, phasic-tonic (mixed, adapting at an average speed): retinal photoreceptors, thermoreceptors skin.

PROPERTIES OF RECEPTORS

High excitability of receptors. For example, 1 quantum of light is enough to excite the retina, and one molecule of an odorous substance is enough for the olfactory receptor. This property allows you to quickly transfer information to the central nervous system about all changes in the external and internal environment. At the same time, the excitability of different types of receptors is not the same. It is higher in exteroceptors than in intero. Pain receptors have low excitability, they are evolutionarily adapted to respond to the action of extreme stimuli.

Adaptation of receptors - a decrease in their excitability with prolonged exposure to an irritant. An exception is the use of the term "dark adaptation" for photoreceptors, which increase in excitability in the dark. The value of adaptation is that it reduces the perception of stimuli that have properties (long-term effect, low dynamics of force), which reduce their importance for the life of the organism.

Spontaneous activity of receptors. Many types of receptors are capable of generating impulses in a neuron without the action of an irritant on them. This is called background activity and the excitability of such receptors is higher than those without such activity. The background activity of receptors is involved in maintaining the tone of the nerve centers under conditions of physiological rest.

The excitability of receptors is under the neurohumoral control of the whole organism. The nervous system can influence the excitability of receptors in different ways. It has been established that the nerve centers exercise efferent (descending) control over many receptors - vestibular, auditory, olfactory, muscle.

Among efferent inhibitory effects (negative feedback) are better studied. Thus, the effects of strong stimuli are limited. Through efferent pathways, an activating effect on receptors can also be exerted.

Also, the nervous system regulates the activity of receptors through a change in the concentration of hormones (for example, an increase in the sensitivity of visual and auditory receptors under the influence of adrenaline, thyroxine); through the regulation of blood flow in the receptor zone and through pre-receptor influence, i.e. changing the strength of the stimulus to the receptor (for example, changing the flow of light using the pupillary reflex).

The importance for the body of regulation of receptor activity lies in the best coordination of their excitability with the strength of irritation.

4) General principles sensor systems devices

1. The principle of multi-storey

In each sensory system, there are several transmission intermediate instances on the way from receptors to the cerebral cortex. In these intermediate lower nerve centers, a partial processing of excitation (information) occurs. Already at the level of the lower nerve centers, unconditioned reflexes are formed, that is, responses to irritation, they do not require the participation of the cerebral cortex and are carried out very quickly.

For example: The midge flies right into the eye - the eye blinked in response, and the midge did not hit it. For a response in the form of blinking, it is not necessary to create a full-fledged image of a midge, a simple detection that an object is rapidly approaching the eye is sufficient.

One of the pinnacles of the multi-storey sensory system device is the auditory sensory system. It has 6 floors. There are also additional detours to higher cortical structures that bypass several of the lower floors. In this way, the cortex receives a preliminary signal to increase its readiness to the main flow of sensory excitation.

Illustration of the multi-storey principle:

2. The principle of multichannel

Excitation is always transmitted from the receptors to the cortex along several parallel pathways. The excitation flows are partially duplicated and partially separated. They transmit information about the various properties of the stimulus.

An example of parallel paths in the visual system:

1st path: retina - thalamus - visual cortex.

2nd path: retina - quadrigemina (upper hills) of the midbrain (nucleus of the oculomotor nerves).

3rd way: retina - thalamus - thalamus cushion - parietal associative cortex.

When different paths are damaged, the results are different.

For example: if you destroy the lateral geniculate body of the thalamus (NKT) in the visual path 1, then complete blindness occurs; if the superior colliculus of the midbrain is destroyed in path 2, then the perception of the movement of objects in the field of view is disturbed; if the thalamic cushion is destroyed in path 3, object recognition and visual memory are lost.

In all sensory systems, there are necessarily three ways (channels) for the transmission of excitation:

1) a specific path: it leads to the primary sensory projection zone of the cortex,

2) non-specific way: it provides the general activity and tone of the cortical section of the analyzer,

3) associative path: it determines the biological significance of the stimulus and controls attention.

Illustration of the multichannel principle:

In the evolutionary process, multi-storey and multi-channel in the structure of sensory pathways is enhanced.

3. Principle of convergence

Convergence is the convergence of neural pathways in the form of a funnel. Due to convergence, an upper-level neuron receives excitation from several lower-level neurons.

For example: there is a large convergence in the retina of the eye. There are several tens of millions of photoreceptors, and no more than one million of ganglion cells. nerve fibers that transmit excitation from the retina are many times smaller than photoreceptors.

4. Principle of divergence

Divergence is a divergence of the excitation flow into several flows from the lowest floor to the highest (resembles a divergent funnel).

5. Feedback principle

Feedback usually means the influence of the managed element on the managing element. For this, there are corresponding paths of excitation from the lower and higher centers back to the receptors.

5) Operation of analyzers and sensor systems

In the work of sensory systems, certain receptors correspond to their own sections of cortical cells.

The specialization of each sense organ is based not only on the structural features of the analyzer receptors, but also on the specialization of the neurons that make up the central nervous apparatus, which receive signals perceived by the peripheral senses. The analyzer is not a passive receiver of energy; it is reflexively rebuilt under the influence of stimuli.

According to the cognitive approach, the movement of a stimulus during its transition from the external world to the internal one occurs as follows:

1) the stimulus causes certain changes in energy in the receptor,

2) energy is converted into nerve impulses,

3) information about nerve impulses is transmitted to the corresponding structures of the cerebral cortex.

Properties of sensations

Each type of sensation is characterized not only by specificity, but also has common properties with other types:

l quality,

b intensity,

b duration,

l spatial localization.

Based on this, we can conclude that it is possible to measure sensations.

General principles of operation of sensor systems:

1. The transformation of the strength of stimulation into a frequency code of impulses is the universal principle of operation of any sensory receptor.

Moreover, in all sensory receptors, the transformation begins with a stimulus-induced change in the properties of the cell membrane. Under the action of a stimulus (stimulus), stimulus-gated ion channels should open in the cell receptor membrane (and, on the contrary, close in photoreceptors). Through them, the flow of ions begins and the state of membrane depolarization develops.

2. Topical correspondence - the flow of excitation (information flow) in all transmission structures corresponds to the significant characteristics of the stimulus. This means that important signs of the stimulus will be encoded in the form of a stream of nerve impulses, and the nervous system will build an internal sensory image similar to the stimulus - the neural model of the stimulus.

3. Detection is the selection of qualitative features. Neurons-detectors respond to certain features of the object and do not respond to everything else. Detector neurons mark contrast transitions. Detectors add meaning and uniqueness to a complex signal. In different signals, they allocate the same parameters. For example, only detection will help you separate the contours of a camouflaged flounder from its surrounding background.

4. Distortion of information about the original object at each level of excitation transfer.

5. Specificity of receptors and sense organs. Their sensitivity is maximum to a certain type of stimulus with a certain intensity.

6. The law of specificity of sensory energies: the sensation is determined not by the stimulus, but by the irritated sensory organ. Even more precisely, one can say this: the sensation is determined not by the stimulus, but by the sensory image that is built in the higher nerve centers in response to the action of the stimulus. For example, the source of pain irritation may be located in one place of the body, and the sensation of pain may be projected to a completely different area. Or: the same stimulus can cause very different sensations depending on the adaptation of the nervous system and / or sensory organ to it.

7. Feedback between subsequent and previous structures. Subsequent structures can change the state of the previous ones and in this way change the characteristics of the excitation flow that comes to them.

The specificity of sensory systems is predetermined by their structure. The structure limits their responses to one stimulus and facilitates the perception of others.

sensory systems- these are specialized parts of the nervous system, including peripheral receptors (sensory organs, or sense organs), nerve fibers extending from them (pathways) and cells of the central nervous system grouped together (sensory centers). Each area of the brain that contains touch center (nucleus) and switching of nerve fibers is carried out, forms level sensory system. In the sensory organs, the energy of an external stimulus is converted into a nerve signal - reception. nerve signal (receptor potential) transforms into impulse activity or action potentials neurons (coding). Action potentials reach the sensory nuclei along the conduction pathways, on the cells of which the switching of nerve fibers and the transformation of the nerve signal take place. (transcoding). At all levels of the sensory system, simultaneously with the coding and analysis of stimuli, decoding signals, i.e. reading the touch code. Decoding is based on the connections of sensory nuclei with the motor and associative parts of the brain. Nerve impulses of axons of sensory neurons in the cells of motor systems cause excitation (or inhibition). The result of these processes is traffic- act or stop movement - inaction. The final manifestation of the activation of associative functions is also movement.

The main functions of sensory systems are:

signal reception;
conversion of the receptor potential into impulse activity of the nerve pathways;
transmission of nervous activity to sensory nuclei;
transformation of nervous activity in sensory nuclei at each level;
signal properties analysis;
identification of signal properties;
signal classification and identification (decision making).

12. Definition, properties and types of receptors.

Receptors are special cells or special nerve endings designed to transform the energy (transformation) of various types of stimuli into a specific activity of the nervous system (into a nerve impulse).

Signals entering the CNS from receptors cause either new reactions or change the course of ongoing activity.

Most receptors are represented by a cell equipped with hairs or cilia, which are such formations that act like amplifiers in relation to stimuli.

Either mechanical or biochemical interaction of the stimulus with receptors occurs. Thresholds for stimulus perception are very low.

According to the action of stimuli, receptors are divided into:

1. Interoreceptors

2. Exteroreceptors

3. Proprioreceptors: muscle spindles and Golgi tendon organs (discovered by I.M. Sechenov the new kind sensitivity - joint-muscular feeling).

There are 3 types of receptors:

1. Phase - these are receptors that are excited in the initial and final period of the stimulus.

2. Tonic - act during the entire period of the stimulus.

3. Phasno-tonic - in which impulses occur all the time, but more at the beginning and at the end.

The quality of perceived energy is called modality.

Receptors can be:

1. Monomodal (perceive 1 type of stimulus).

2. Polymodal (can perceive several stimuli).

The transfer of information from the peripheral organs occurs along sensory pathways, which can be specific and nonspecific.

Specific are monomodal.

Nonspecific are polymodal

Properties

Selectivity - sensitivity to adequate stimuli

Excitability - the minimum amount of energy of an adequate stimulus, which is necessary for the onset of excitation, i.e. arousal threshold.

Low threshold value for adequate stimuli

Adaptation (may be accompanied by both a decrease and an increase in the excitability of receptors. So, when moving from a bright room to a dark one, a gradual increase in the excitability of the photoreceptors of the eye occurs, and a person begins to distinguish dimly lit objects - this is the so-called dark adaptation.)

13. Mechanisms of excitation of primary-sensing and secondary-sensing receptors.

Primary sensory receptors: the stimulus acts on the dendrite of the sensory neuron, the permeability of the cell membrane to ions (mainly to Na +) changes, a local electrical potential (receptor potential) is formed, which electrotonically propagates along the membrane to the axon. An action potential is formed on the axon membrane, which is transmitted further to the CNS.

A sensory neuron with a primary sensory receptor is a bipolar neuron, on one pole of which there is a dendrite with a ciliary, and on the other - an axon that transmits excitation to the CNS. Examples: proprioceptors, thermoreceptors, olfactory cells.

Secondary sensory receptors: in them, the stimulus acts on the receptor cell, excitation occurs in it (receptor potential). On the axon membrane, the receptor potential activates the release of the neurotransmitter into the synapse, as a result of which a generator potential is formed on the postsynaptic membrane of the second neuron (most often bipolar), which leads to the formation of an action potential on neighboring sections of the postsynaptic membrane. This action potential is then transmitted to the CNS. Examples: hair cells in the ear, taste buds, photoreceptors in the eye.

!fourteen. Organs of smell and taste (localization of receptors, first switching, repeated switching, projection zone).

The organs of smell and taste are excited by chemical stimuli. Receptors of the olfactory analyzer are excited by gaseous, and taste - by dissolved chemicals. The development of the olfactory organs also depends on the way of life of animals. The olfactory epithelium is located away from the main respiratory tract and the inhaled air enters there by vortex movements or diffusion. Such vortex motions occur during “sniffing”, i.e. with short breaths through the nose and expansion of the nostrils, which facilitates the penetration of the analyzed air into these areas.

Olfactory cells are represented by bipolar neurons, the axons of which form the olfactory nerve, ending in the olfactory bulb, which is the olfactory center, and then paths go from it to other overlying brain structures. On the surface of the olfactory cells there are a large number of cilia, which significantly increase the olfactory surface.

Taste Analyzer serves to determine the nature palatability feed, its suitability for eating. Taste and olfactory analyzers help animals living in water to navigate in the environment, determine the presence of food, females. With the transition to life in the air, the value of the taste analyzer decreases. In herbivorous animals, the taste analyzer is well developed, which can be seen in the pasture and in the feeder, when the animals do not eat grass and hay all in a row.

The peripheral part of the taste analyzer is represented by taste buds located on the tongue, soft palate, back wall pharynx, tonsils and epiglottis. Taste buds are located on the surface of fungiform, foliate and trough papillae.

15. Skin analyzer (localization of receptors, first switching, repeated switching, projection zone).

Various receptor formations are located in the skin. Most simple type sensory receptor are free nerve endings. Morphologically differentiated formations have a more complex organization, such as tactile discs (Merkel discs), tactile bodies (Meissner bodies), lamellar bodies (Pacini bodies) - pressure and vibration receptors, Krause flasks, Ruffini bodies, etc.

Most specialized end structures have a preferential sensitivity to certain types stimulation and only free nerve endings are polymodal receptors.

16. Visual analyzer (localization of receptors, first switching, repeated switching, projection zone).

A person receives the greatest amount of information (up to 90%) about the outside world with the help of the organ of vision. The organ of vision - the eye - consists of the eyeball and an auxiliary apparatus. The auxiliary apparatus includes eyelids, eyelashes, lacrimal glands and muscles of the eyeball. The eyelids are formed by folds of skin lined from the inside with a mucous membrane - the conjunctiva. The lacrimal glands are located in the outer upper corner of the eye. Tears wash the anterior part of the eyeball and enter the nasal cavity through the nasolacrimal canal. The muscles of the eyeball set it in motion and direct it towards the object in question
17. Visual analyzer. The structure of the retina. Formation of color perception. Conductor department. Information processing .

The retina has a very complex structure. It contains light-receiving cells - rods and cones. Rods (130 million) are more sensitive to light. They are called the apparatus of twilight vision. Cones (7 million) are a device for day and color vision. When these cells are stimulated by light rays, excitation occurs, which is carried through the optic nerve to the visual centers located in the occipital zone of the cerebral cortex. The area of the retina from which the optic nerve exits is devoid of rods and cones and therefore is not capable of perceiving light. It's called the blind spot. Almost next to it is a yellow spot formed by a cluster of cones - the place of the best vision.

The structure of the optical, or refractive, system of the eye includes: the cornea, aqueous humor, lens and vitreous body. In people with normal vision, the rays of light passing through each of these media are refracted and then enter the retina, where they form a reduced and inverted image of objects visible to the eye. Of these transparent media, only the lens is able to actively change its curvature, increasing it when looking at close objects and decreasing it when looking at distant objects. This ability of the eye to clearly see objects at different distances is called accommodation. If the rays are refracted too much when passing through transparent media, they are focused in front of the retina, resulting in myopia. In such people, the eyeball is either elongated or the curvature of the lens is increased. The weak refraction of these media leads to focusing of the rays behind the retina, which causes farsightedness. It occurs due to the shortening of the eyeball or flattening of the lens. Properly selected glasses can correct these Conducting paths of the visual analyzer. First, the second and third neurons of the visual analyzer pathway are located in the retina. The fibers of the third (ganglion) neurons in the optic nerve partially cross to form the optic chiasm (chiasm). After the decussation, the right and left visual tracts are formed. The fibers of the optic tract terminate in the diencephalon (the nucleus of the lateral geniculate body and the thalamic cushion), where the fourth neurons of the optic pathway are located. A small number of fibers reach the midbrain in the region of the superior colliculi of the quadrigemina. The axons of the fourth neurons pass through the posterior leg of the internal capsule and are projected onto the cortex of the occipital lobe of the cerebral hemispheres, where the cortical center of the visual analyzer is located.

18. Auditory analyzer (localization of receptors, first switching, repeated switching, projection zone). Conductor department. Information processing. auditory adaptation.

Auditory and vestibular analyzers. The organ of hearing and balance includes three sections: the outer, middle and inner ear. The outer ear consists of the auricle and the external auditory meatus. The auricle is represented by elastic cartilage, covered with skin, and serves to capture sound. The external auditory meatus is a canal 3.5 cm long, which begins with the external auditory opening and ends blindly with the tympanic membrane. It is lined with skin and has glands that secrete earwax.

Behind the tympanic membrane is the middle ear cavity, which consists of the tympanic cavity filled with air, the auditory ossicles and the auditory (Eustachian) tube. The auditory tube connects the tympanic cavity with the nasopharyngeal cavity, which helps to equalize pressure on both sides of the tympanic membrane. The auditory ossicles - the hammer, anvil and stirrup are movably connected to each other. The malleus is fused with the tympanic membrane with a handle, the head of the malleus is adjacent to the anvil, which is connected to the stirrup at the other end. The stirrup with a wide base is connected to the membrane of the oval window leading to the inner ear. The inner ear is located in the thickness of the pyramid of the temporal bone; consists of a bony labyrinth and a membranous labyrinth located in it. The space between them is filled with fluid - perilymph, the cavity of the membranous labyrinth - endolymph. The bony labyrinth contains three sections: the vestibule, the cochlea, and the semicircular canals. The cochlea belongs to the organ of hearing, the rest of its parts - to the organ of balance.

The cochlea is a bony canal, twisted in the form of a spiral. Its cavity is divided by a thin membranous septum - the main membrane. It consists of numerous (about 24 thousand) connective tissue fibers of different lengths. The receptor hair cells of the organ of Corti, the peripheral part of the auditory analyzer, are placed on the main membrane.

Sound waves through the external auditory meatus reach the tympanic membrane and cause its vibrations, which are amplified (almost 50 times) by the auditory ossicles and transmitted to the perilymph and endolymph, then perceived by the fibers of the main membrane. High sounds cause oscillations of short fibers, low sounds - longer, located at the top of the cochlea. These vibrations excite the receptor hair cells of the organ of Corti. Further, the excitation is transmitted along the auditory nerve to the temporal lobe of the cerebral cortex, where the final analysis and synthesis of sound signals take place. The human ear perceives sounds with a frequency of 16 to 20 thousand Hz.

Conducting paths of the auditory analyzer. First neuron of the auditory analyzer pathways - the bipolar cells mentioned above. Their axons form the cochlear nerve, the fibers of which enter the medulla oblongata and terminate in the nuclei, where the cells of the second neuron of the pathways are located. The axons of the cells of the second neuron reach the internal geniculate body, mainly on the opposite side. Here begins the third neuron, through which impulses reach the auditory region of the cerebral cortex.

In addition to the main pathway connecting the peripheral part of the auditory analyzer with its central, cortical part, there are other ways through which reflex reactions to irritation of the hearing organ in the animal can occur even after removal of the cerebral hemispheres. Of particular importance are orienting reactions to sound. They are carried out with the participation of the quadrigemina, to the posterior and partly anterior tubercles of which there are collaterals of fibers heading to the internal geniculate body.

19. Vestibular analyzer (localization of receptors, first switching, repeated switching, projection zone). Conductor department. Information processing .

vestibular apparatus. It is represented by the vestibule and semicircular canals and is an organ of balance. In the vestibule there are two sacs filled with endolymph. At the bottom and in the inner wall of the sacs are receptor hair cells, which are adjacent to the otolith membrane with special crystals - otoliths containing calcium ions. Three semicircular canals are located in three mutually perpendicular planes. The bases of the channels at the points of their connection with the vestibule form extensions - ampoules in which hair cells are located.

Receptors of the otolithic apparatus are excited by accelerating or decelerating rectilinear movements. The receptors of the semicircular canals are irritated by accelerated or slow rotational movements due to the movement of the endolymph. Excitation of the receptors of the vestibular apparatus is accompanied by a number of reflex reactions: a change in muscle tone, contributing to the straightening of the body and maintaining the posture. Impulses from the receptors of the vestibular apparatus through the vestibular nerve enter the central nervous system. The vestibular analyzer is connected to the cerebellum, which regulates its activity.

Conductive pathways of the vestibular apparatus. the path of the statokinetic apparatus carries out the transmission of impulses when the position of the head and body changes, participating together with other analyzers in the orientation reactions of the body relative to the surrounding space. The first neuron of the statokinetic apparatus is located in the vestibular ganglion, which lies at the bottom of the internal auditory canal. The dendrites of the bipolar cells of the vestibular ganglion form the vestibular nerve, formed by 6 branches: superior, inferior, lateral and posterior ampullar, utricular and saccular. They contact with sensitive cells of the auditory spots and scallops located in the ampullae of the semicircular canals, in the sac and uterine vestibule of the membranous labyrinth.

20. Vestibular analyzer. Building a sense of balance. Automatic and conscious control of body balance. Participation of the vestibular apparatus in the regulation of reflexes .

The vestibular apparatus performs the functions of perceiving the position of the body in space, maintaining balance. With any change in the position of the head, the receptors of the vestibular apparatus are irritated. The impulses are transmitted to the brain, from which nerve impulses are sent to the skeletal muscles in order to correct body position and movements. The vestibular apparatus consists of two parts: vestibule and semicircular canals, in which the receptors of the statokinetic analyzer are located.