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1. SENSOR SYSTEMS

1.1 Understanding sensory systems

Sensory - from the Latin sensus - feeling, feeling.

The sensory system is an integral nervous mechanism that receives and analyzes sensory information. A synonym for the sensory system in Russian 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 of the cortex. 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 multi-level belonging 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).

Tactile sensitivity was singled out as the epicritical, or discriminative, sensitivity of the highest level; 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 information to a person coming from the outside world and is the main reception that connects a 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 the sensation increases evenly (in arithmetic progression), the corresponding increase in signal intensity occurs physically unevenly, 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 recently created mathematical models that describe 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 permanent 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 the conditions for stabilizing the image relative to the retina of the eyes were artificially created 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 (dark adaptation time reaches several tens of minutes), 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 to 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 be attributed to 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 exposure to second-signal stimuli. For example: a change in the electrical conductivity of the eyes and tongue in response to the words "sour lemon", which actually 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, an excitation process occurs, which, on the contrary, causes a concentration process, 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 fact of the occurrence of panic fear when exposed to the sound of ultra-low frequencies. 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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Sensor system (analyzer)- they call the part of the nervous system, consisting of perceiving elements - sensory receptors, nerve pathways that transmit information from receptors to the brain and parts of the brain that process and analyze this information

The sensory system includes 3 parts

1. Receptors - sense organs

2. Conductor section that connects receptors with the brain

3. Department of the cerebral cortex, which perceives and processes information.

Receptors- a peripheral link designed to perceive stimuli of the external or internal environment.

Sensory systems have a common structural plan and sensory systems are characterized by

Layering- the presence of several layers of nerve cells, the first of which is associated with receptors, and the last with neurons in the motor areas of the cerebral cortex. Neurons are specialized for processing different types of sensory information.

Multichannel- the presence of many parallel channels for processing and transmitting information, which provides a detailed signal analysis and greater reliability.

Different number of elements in neighboring layers, which forms the so-called "sensor funnels" (contracting or expanding) They can ensure the elimination of information redundancy or, conversely, a fractional and complex analysis of signal features

Differentiation of the sensory system vertically and horizontally. Vertical differentiation means the formation of parts of the sensory system, consisting of several neuronal layers (olfactory bulbs, cochlear nuclei, geniculate bodies).

Horizontal differentiation represents the presence of different properties of receptors and neurons within the same layer. For example, rods and cones in the retina of the eye process information differently.

The main task of the sensory system is the perception and analysis of the properties of stimuli, on the basis of which sensations, perceptions, and representations arise. This constitutes the forms of sensual, subjective reflection of the external world.

Functions of sensory systems

1. Signal detection. Each sensory system in the process of evolution has adapted to the perception of adequate stimuli inherent in this system. The sensory system, for example the eye, can receive different - adequate and inadequate irritations (light or a blow to the eye). Sensory systems perceive force - the eye perceives 1 light photon (10 V -18 W). Impact on the eye (10 V -4 W). Electric current(10V-11W)
2. Distinguishing signals.
3. Signal transmission or conversion. Any sensory system works like a transducer. It converts one form of energy of the acting stimulus into the energy of nervous irritation. The sensory system must not distort the stimulus signal.

• May be spatial
• Temporal transformations
• limitation of information redundancy (inclusion of inhibitory elements that inhibit neighboring receptors)
• Identification of essential features of a signal

1. Information encoding - in the form of nerve impulses
2. Signal detection, etc. e. highlighting signs of a stimulus that has behavioral significance
3. Provide image recognition
4. Adapt to stimuli
5. Interaction of sensory systems, which form the scheme of the surrounding world and at the same time allow us to correlate ourselves with this scheme, for our adaptation. All living organisms cannot exist without the perception of information from the environment. The more accurately the organism receives such information, the higher will be its chances in the struggle for existence.

Sensory systems are capable of responding to inappropriate stimuli. If you try the battery terminals, it causes a taste sensation - sour, this is the action of an electric current. Such a reaction of the sensory system to adequate and inadequate stimuli raised the question for physiology - how much we can trust our senses.

Johann Müller formulated in 1840 the law of the specific energy of the sense organs.

The quality of sensations does not depend on the nature of the stimulus, but is determined entirely by the specific energy inherent in the sensitive system, which is released under the action of the stimulus.

With this approach, we can only know what is inherent in ourselves, and not what is in the world around us. Subsequent studies have shown that excitations in any sensory system arise on the basis of one energy source - ATP.

Müller's student Helmholtz created symbol theory, according to which he considered sensations as symbols and objects of the surrounding world. The theory of symbols denied the possibility of knowing the surrounding world.

These 2 directions were called physiological idealism. What is sensation? Feeling is a subjective image of the objective world. Feelings are images of the external world. They exist in us and are generated by the action of things on our sense organs. For each of us, this image will be subjective, i.e. it depends on the degree of our development, experience, and each person perceives the surrounding objects and phenomena in his own way. They will be objective, i.e. that means they exist independently of our consciousness. Since there is a subjectivity of perception, how to decide who perceives most correctly? Where will the truth be? The criterion of truth is practical activity. There is gradual knowledge. At each stage, new information is obtained. The child tastes toys, disassembles them into details. It is on the basis of this profound experience that we acquire deeper knowledge about the world.

Classification of receptors.

1. Primary and secondary. primary receptors represent the receptor ending, which is formed by the very first sensitive neuron (Pacini's corpuscle, Meissner's corpuscle, Merkel's disc, Ruffini's corpuscle). This neuron lies in the spinal ganglion. Secondary receptors perceive information. Due to specialized nerve cells, which then transmit excitation to the nerve fiber. Sensitive cells of the organs of taste, hearing, balance.
2. Remote and contact. Some receptors perceive excitation with direct contact - contact, while others can perceive irritation at some distance - distant
3. Exteroreceptors, interoreceptors. Exteroreceptors- perceive irritation from the external environment - vision, taste, etc., and they provide for adaptation to the environment. Interoreceptors- receptors of internal organs. They reflect the state of the internal organs and the internal environment of the body.
4. Somatic - superficial and deep. Superficial - skin, mucous membranes. Deep - receptors of muscles, tendons, joints
5. Visceral
6. CNS receptors
7. Special sense receptors - visual, auditory, vestibular, olfactory, gustatory

By the nature of perception of information

1. Mechanoreceptors (skin, muscles, tendons, joints, internal organs)
2. Thermoreceptors (skin, hypothalamus)
3. Chemoreceptors (aortic arch, carotid sinus, medulla oblongata, tongue, nose, hypothalamus)
4. Photoreceptor (eye)
5. Pain (nociceptive) receptors (skin, internal organs, mucous membranes)

Mechanisms of excitation of receptors

In the case of primary receptors, the action of the stimulus is perceived by the ending of the sensitive neuron. An active stimulus can cause hyperpolarization or depolarization of the surface membrane of receptors, mainly due to changes in sodium permeability. An increase in the permeability to sodium ions leads to membrane depolarization and a receptor potential appears on the receptor membrane. It exists as long as the stimulus acts.

Receptor potential does not obey the law "All or nothing", its amplitude depends on the strength of the stimulus. It has no refractory period. This allows the receptor potentials to be summed up under the action of subsequent stimuli. It spreads meleno, with extinction. When the receptor potential reaches a critical threshold, it triggers an action potential at the nearest node of Ranvier. In the interception of Ranvier, an action potential arises, which obeys the law "All or Nothing". This potential will be propagating.

In the secondary receptor, the action of the stimulus is perceived by the receptor cell. A receptor potential arises in this cell, which will result in the release of a mediator from the cell into the synapse, which acts on the postsynaptic membrane of the sensitive fiber and the interaction of the mediator with receptors leads to the formation of another, local potential, which is called generator. It is identical in its properties to the receptor. Its amplitude is determined by the amount of mediator released. Mediators - acetylcholine, glutamate.

Action potentials occur periodically, tk. they are characterized by a period of refractoriness, when the membrane loses the property of excitability. Action potentials arise discretely and the receptor in the sensory system works as an analog-to-discrete converter. In the receptors, an adaptation is observed - adaptation to the action of stimuli. Some are fast adapting and some are slow adapting. With adaptation, the amplitude of the receptor potential and the number of nerve impulses that go along the sensitive fiber decrease. Receptors encode information. It is possible by the frequency of potentials, by the grouping of impulses into separate volleys and by the intervals between volleys. Coding is possible according to the number of activated receptors in the receptive field.

Threshold of irritation and threshold of entertainment.

Irritation threshold- the minimum strength of the stimulus that causes a sensation.

Threshold entertainment- the minimum force of change in the stimulus, at which a new sensation arises.

Hair cells are excited when the hairs are displaced by 10 to -11 meters - 0.1 amstrem.

In 1934, Weber formulated a law that establishes a relationship between the initial strength of irritation and the intensity of sensation. He showed that the change in the strength of the stimulus is a constant value

∆I / Io = K Io=50 ∆I=52.11 Io=100 ∆I=104.2

Fechner determined that sensation is directly proportional to the logarithm of irritation.

S=a*logR+b S-sensation R- irritation

S \u003d KI in A degree I - the strength of irritation, K and A - constants

For tactile receptors S=9.4*I d 0.52

Sensory systems have receptors for self-regulation of receptor sensitivity.

Influence of the sympathetic system - the sympathetic system increases the sensitivity of receptors to the action of stimuli. This is useful in a situation of danger. Increases the excitability of receptors - the reticular formation. Efferent fibers were found in the composition of sensory nerves, which can change the sensitivity of receptors. There are such nerve fibers in the auditory organ.

Sensory hearing system

For most people living in a modern stop, hearing progressively declines. This happens with age. This is facilitated by pollution by environmental sounds - vehicles, disco, etc. Changes in the hearing aid become irreversible. Human ears contain 2 sensitive organs. Hearing and balance. Sound waves propagate in the form of compressions and rarefaction in elastic media, and the propagation of sounds in dense media is better than in gases. Sound has 3 important properties - pitch or frequency, power or intensity and timbre. The pitch of the sound depends on the frequency of vibrations and the human ear perceives with a frequency of 16 to 20,000 Hz. With maximum sensitivity from 1000 to 4000 Hz.

The main frequency of the sound of the larynx of a man is 100 Hz. Women - 150 Hz. When talking, additional high-frequency sounds appear in the form of hissing, whistling, which disappear when talking on the phone and this makes speech clearer.

The sound power is determined by the amplitude of the vibrations. Sound power is expressed in dB. Power is a logarithmic relationship. Whispered speech - 30 dB, normal speech - 60-70 dB. The sound of transport - 80, the noise of the aircraft engine - 160. The sound power of 120 dB causes discomfort, and 140 leads to pain.

The timbre is determined by secondary vibrations on sound waves. Ordered vibrations - create musical sounds. Random vibrations just cause noise. The same note sounds differently on different instruments due to different additional vibrations.

The human ear has 3 parts - outer, middle and inner ear. The outer ear is represented by the auricle, which acts as a sound-catching funnel. The human ear picks up sounds less perfectly than that of a rabbit, a horse that can control its ears. At the base of the auricle is cartilage, with the exception of the earlobe. Cartilage gives elasticity and shape to the ear. If the cartilage is damaged, then it is restored by growing. The external auditory canal is S-shaped - inward, forward and downward, length 2.5 cm. The auditory meatus is covered with skin with low sensitivity of the outer part and high sensitivity of the inner part. There are hairs on the outside of the ear canal that prevent particles from entering the ear canal. The ear canal glands produce a yellow lubricant that also protects the ear canal. At the end of the passage is the tympanic membrane, which consists of fibrous fibers covered on the outside with skin and inside with mucous. The eardrum separates the middle ear from the outer ear. It fluctuates with the frequency of the perceived sound.

The middle ear is represented by the tympanic cavity, the volume of which is approximately 5-6 drops of water and the tympanic cavity is filled with air, lined with a mucous membrane and contains 3 auditory ossicles: the hammer, anvil and stirrup. The middle ear communicates with the nasopharynx using the Eustachian tube. At rest, the lumen of the Eustachian tube is closed, which equalizes the pressure. Inflammatory processes leading to inflammation of this tube cause a feeling of congestion. The middle ear is separated from the inner ear by an oval and round opening. The vibrations of the tympanic membrane are transmitted through the system of levers by the stirrup to the oval window, and the outer ear transmits sounds by air.

There is a difference in the area of ​​the tympanic membrane and the oval window (the area of ​​the tympanic membrane is 70 mm square, and that of the oval window is 3.2 mm square). When vibrations are transmitted from the membrane to the oval window, the amplitude decreases and the strength of the vibrations increases by 20-22 times. At frequencies up to 3000 Hz, 60% of E is transmitted to the inner ear. In the middle ear there are 2 muscles that change vibrations: the tensor tympanic membrane muscle (attached to the central part of the tympanic membrane and to the handle of the malleus) - with an increase in contraction force, the amplitude decreases; stirrup muscle - its contractions limit the movement of the stirrup. These muscles prevent injury to the eardrum. In addition to air transmission of sounds, there is also bone transmission, but this sound power is not able to cause vibrations of the bones of the skull.

inside ear

the inner ear is a maze of interconnected tubes and extensions. The organ of balance is located in the inner ear. The labyrinth has a bone base, and inside there is a membranous labyrinth and there is an endolymph. The cochlea belongs to the auditory part, it forms 2.5 turns around the central axis and is divided into 3 ladders: vestibular, tympanic and membranous. The vestibular canal begins with the membrane of the oval window and ends with a round window. At the apex of the cochlea, these 2 canals communicate with a helicocream. And both of these canals are filled with perilymph. The organ of Corti is located in the middle membranous canal. The main membrane is built from elastic fibers that start at the base (0.04mm) and reach the top (0.5mm). To the top, the density of the fibers decreases by 500 times. The organ of Corti is located on the main membrane. It is built from 20-25 thousand special hair cells located on supporting cells. Hair cells lie in 3-4 rows (outer row) and in one row (inner). At the top of the hair cells are stereociles or kinocilies, the largest stereociles. Sensory fibers of the 8th pair of cranial nerves from the spiral ganglion approach the hair cells. At the same time, 90% of the isolated sensitive fibers end up on the inner hair cells. Up to 10 fibers converge per inner hair cell. And in the composition of nerve fibers there are also efferent ones (olive-cochlear bundle). They form inhibitory synapses on sensory fibers from the spiral ganglion and innervates the outer hair cells. Irritation of the organ of Corti is associated with the transmission of vibrations of the bones to the oval window. Low-frequency oscillations propagate from the oval window to the top of the cochlea (the entire main membrane is involved). At low frequencies, excitation of the hair cells lying on the top of the cochlea is observed. Bekashi studied the propagation of waves in a cochlea. He found that as the frequency increased, a smaller column of liquid was drawn in. High-frequency sounds cannot involve the entire fluid column, so the higher the frequency, the less the perilymph fluctuates. Oscillations of the main membrane can occur during the transmission of sounds through the membranous canal. When the main membrane oscillates, the hair cells move upward, which causes depolarization, and if downward, the hairs deviate inward, which leads to hyperpolarization of the cells. When the hair cells depolarize, Ca channels open and Ca promotes an action potential that carries information about the sound. The external auditory cells have efferent innervation and the transmission of excitation occurs with the help of Ash on the external hair cells. These cells can change their length: they shorten during hyperpolarization and elongate during polarization. Changing the length of the outer hair cells affects the oscillatory process, which improves the perception of sound by the inner hair cells. The change in the potential of hair cells is associated with the ionic composition of the endo- and perilymph. Perilymph resembles CSF, and endolymph has a high concentration of K (150 mmol). Therefore, the endolymph acquires a positive charge to the perilymph (+80mV). Hair cells contain a lot of K; they have a membrane potential and are negatively charged inside and positive outside (MP = -70mV), and the potential difference makes it possible for K to penetrate from the endolymph into the hair cells. Changing the position of one hair opens 200-300 K-channels and depolarization occurs. Closure is accompanied by hyperpolarization. In the organ of Corti, frequency coding occurs due to the excitation of different parts of the main membrane. At the same time, it was shown that low-frequency sounds can be encoded by the same number of nerve impulses as the sound. Such coding is possible with the perception of sound up to 500 Hz. Encoding of sound information is achieved by increasing the number of fiber volleys for a more intense sound and due to the number of activated nerve fibers. The sensory fibers of the spiral ganglion terminate in the dorsal and ventral nuclei of the cochlea of ​​the medulla oblongata. From these nuclei, the signal enters the olive nuclei of both its own and the opposite side. From its neurons there are ascending paths as part of the lateral loop that approach the inferior colliculus of the quadrigemina and the medial geniculate body of the thalamus opticus. From the latter, the signal goes to the superior temporal gyrus (Geshl gyrus). This corresponds to fields 41 and 42 (primary zone) and field 22 (secondary zone). In the CNS, there is a topotonic organization of neurons, that is, sounds are perceived with different frequencies and different intensities. The cortical center is important for perception, sound sequence and spatial localization. With the defeat of the 22nd field, the definition of words is violated (receptive opposition).

The nuclei of the superior olive are divided into medial and lateral parts. And the lateral nuclei determine the unequal intensity of sounds coming to both ears. The medial nucleus of the superior olive picks up temporal differences in the arrival of sound signals. It was found that signals from both ears enter different dendritic systems of the same perceiving neuron. Hearing impairment can be manifested by ringing in the ears when the inner ear or auditory nerve is irritated, and two types of deafness: conductive and nervous. The first is associated with lesions of the outer and middle ear (wax plug). The second is associated with defects in the inner ear and lesions of the auditory nerve. Elderly people lose the ability to perceive high-pitched voices. Due to the two ears, it is possible to determine the spatial localization of sound. This is possible if the sound deviates from the middle position by 3 degrees. When perceiving sounds, it is possible to develop adaptation due to the reticular formation and efferent fibers (by acting on the outer hair cells.

visual system.

Vision is a multi-link process that begins with the projection of an image onto the retina of the eye, then there is excitation of photoreceptors, transmission and transformation in the neural layers of the visual system, and ends with the decision of the higher cortical sections about the visual image.

The structure and functions of the optical apparatus of the eye. The eye has a spherical shape, which is important for turning the eye. Light passes through several transparent media - the cornea, lens and vitreous body, which have certain refractive powers, expressed in diopters. The diopter is equal to the refractive power of a lens with a focal length of 100 cm. The refractive power of the eye when viewing distant objects is 59D, close ones is 70.5D. An inverted image is formed on the retina.

Accommodation- adaptation of the eye to a clear vision of objects at different distances. The lens plays a major role in accommodation. When considering close objects, the ciliary muscles contract, the ligament of zinn relaxes, the lens becomes more convex due to its elasticity. When considering distant ones, the muscles are relaxed, the ligaments are stretched and stretch the lens, making it more flattened. The ciliary muscles are innervated by parasympathetic fibers of the oculomotor nerve. Normally, the farthest point of clear vision is at infinity, the nearest one is 10 cm from the eye. The lens loses elasticity with age, so the nearest point of clear vision moves away and senile farsightedness develops.

Refractive anomalies of the eye.

Nearsightedness (myopia). If the longitudinal axis of the eye is too long or the refractive power of the lens increases, then the image is focused in front of the retina. The person can't see well. Spectacles with concave lenses are prescribed.

Farsightedness (hypermetropia). It develops with a decrease in the refractive media of the eye or with a shortening of the longitudinal axis of the eye. As a result, the image is focused behind the retina and the person has trouble seeing nearby objects. Spectacles with convex lenses are prescribed.

Astigmatism is the uneven refraction of rays in different directions, due to the non-strictly spherical surface of the cornea. They are compensated by glasses with a surface approaching a cylindrical one.

Pupil and pupillary reflex. The pupil is the hole in the center of the iris through which light rays pass into the eye. The pupil improves the clarity of the image on the retina by increasing the depth of field of the eye and by eliminating spherical aberration. If you cover your eye from the light, and then open it, the pupil quickly narrows - the pupillary reflex. In bright light, the size is 1.8 mm, with an average - 2.4, in the dark - 7.5. Zooming in results in poorer image quality, but increases sensitivity. The reflex has an adaptive value. The sympathetic pupil dilates, the parasympathetic pupil narrows. In healthy people, the size of both pupils is the same.

Structure and functions of the retina. The retina is the inner light-sensitive membrane of the eye. Layers:

Pigmentary - a row of process epithelial cells of black color. Functions: shielding (prevents scattering and reflection of light, increasing clarity), regeneration of visual pigment, phagocytosis of fragments of rods and cones, nutrition of photoreceptors. The contact between the receptors and the pigment layer is weak, so it is here that retinal detachment occurs.

Photoreceptors. Flasks are responsible for color vision, there are 6-7 million of them. Sticks for twilight, there are 110-123 million of them. They are unevenly located. In the central fovea - only flasks, here - the greatest visual acuity. Sticks are more sensitive than flasks.

The structure of the photoreceptor. It consists of an outer receptive part - the outer segment, with a visual pigment; connecting leg; nuclear part with a presynaptic ending. The outer part consists of disks - a two-membrane structure. The outdoor segments are constantly updated. The presynaptic terminal contains glutamate.

visual pigments. In sticks - rhodopsin with absorption in the region of 500 nm. In flasks - iodopsin with absorptions of 420 nm (blue), 531 nm (green), 558 (red). The molecule consists of the protein opsin and the chromophore part - retinal. Only the cis-isomer perceives light.

Physiology of photoreception. Upon absorption of a quantum of light, cis-retinal turns into trans-retinal. This causes spatial changes in the protein part of the pigment. The pigment becomes colorless and transforms into metarhodopsin II, which is able to interact with the membrane-bound protein transducin. Transducin is activated and binds to GTP, activating phosphodiesterase. PDE destroys cGMP. As a result, the concentration of cGMP falls, which leads to the closure of ion channels, while the concentration of sodium decreases, leading to hyperpolarization and the appearance of a receptor potential that spreads throughout the cell to the presynaptic terminal and causes a decrease in glutamate release.

Restoration of the initial dark state of the receptor. When metarhodopsin loses its ability to interact with tranducine, guanylate cyclase, which synthesizes cGMP, is activated. Guanylate cyclase is activated by a drop in the concentration of calcium ejected from the cell by the exchange protein. As a result, the concentration of cGMP rises and it again binds to the ion channel, opening it. When opening, sodium and calcium enter the cell, depolarizing the receptor membrane, turning it into a dark state, which again accelerates the release of the mediator.

retinal neurons.

Photoreceptors are synaptically connected to bipolar neurons. Under the action of light on the neurotransmitter, the release of the mediator decreases, which leads to hyperpolarization of the bipolar neuron. From the bipolar signal is transmitted to the ganglion. Impulses from many photoreceptors converge to a single ganglion neuron. The interaction of neighboring retinal neurons is provided by horizontal and amacrine cells, the signals of which change the synaptic transmission between receptors and bipolar (horizontal) and between bipolar and ganglionic (amacrine). Amacrine cells carry out lateral inhibition between adjacent ganglion cells. The system also contains efferent fibers that act on synapses between bipolar and ganglion cells, regulating the excitation between them.

Nerve pathways.

1st neuron is bipolar.

2nd - ganglionic. Their processes go as part of the optic nerve, make a partial decussation (necessary to provide each hemisphere with information from each eye) and go to the brain as part of the optic tract, entering the lateral geniculate body of the thalamus (3rd neuron). From the thalamus - to the projection zone of the cortex, the 17th field. Here is the 4th neuron.

visual functions.

Absolute sensitivity. For the appearance of a visual sensation, it is necessary that the light stimulus has a minimum (threshold) energy. The stick can be excited by one quantum of light. Sticks and flasks differ little in excitability, but the number of receptors that send signals to one ganglion cell is different in the center and on the periphery.

Visual adaptation.

Adaptation of the visual sensory system to conditions of bright illumination - light adaptation. The reverse phenomenon is dark adaptation. The increase in sensitivity in the dark is gradual, due to the dark restoration of visual pigments. First, iodopsin flasks are reconstituted. It has little effect on sensitivity. Then the rhodopsin of the sticks is restored, which greatly increases the sensitivity. For adaptation, the processes of changing connections between retinal elements are also important: weakening of horizontal inhibition, leading to an increase in the number of cells, sending signals to the ganglion neuron. The influence of the CNS also plays a role. When illuminating one eye, it lowers the sensitivity of the other.

Differential visual sensitivity. According to Weber's law, a person will distinguish a difference in lighting if it is stronger by 1-1.5%.

Brightness Contrast occurs due to mutual lateral inhibition of optic neurons. A gray stripe on a light background appears darker than a gray one on a dark one, since the cells excited by the light background inhibit the cells excited by the gray stripe.

Blinding brightness of light. Light that is too bright causes an unpleasant sensation of blinding. The upper limit of blinding brightness depends on the adaptation of the eye. The longer the dark adaptation was, the less brightness causes glare.

Vision inertia. Visual sensation appears and disappears immediately. From irritation to perception, 0.03-0.1 s passes. The stimuli quickly following one another merge into one sensation. The minimum frequency of repetition of light stimuli, at which the fusion of individual sensations occurs, is called the critical frequency of flicker fusion. This is what cinema is based on. Sensations that continue after the cessation of irritation are sequential images (the image of a lamp in the dark after it is turned off).

Color vision.

The entire visible spectrum from violet (400nm) to red (700nm).

Theories. Three-component theory of Helmholtz. Color sensation provided by three types of bulbs sensitive to one part of the spectrum (red, green or blue).

Goering's theory. The flasks contain substances sensitive to white-black, red-green and yellow-blue radiation.

Consistent color images. If you look at a painted object and then at a white background, the background will acquire an additional color. The reason is color adaptation.

Color blindness. Color blindness is a disorder in which it is impossible to distinguish colors. With protanopia, red color is not distinguished. With deuteranopia - green. With tritanopia - blue. Diagnosed by polychromatic tables.

A complete loss of color perception is achromasia, in which everything is seen in shades of gray.

Perception of space.

Visual acuity- the maximum ability of the eye to distinguish individual details of objects. The normal eye distinguishes between two points seen at an angle of 1 minute. Maximum sharpness in the region of the macula. Determined by special tables.

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• Introduction
• Conclusion
• Applications
• Introduction
• One of the physiological functions of the body is the perception of the surrounding reality. Obtaining and processing information about the surrounding world is a necessary condition for maintaining the homeostatic constants of the organism and the formation of behavior. Among the stimuli acting on the body, only those for the perception of which there are specialized formations are caught and perceived. Such stimuli are called sensory stimuli, and complex structures designed to process them are called sensory systems (sense organs).
• The human sensory system consists of the following subsystems: visual system, auditory system, somatosensory system, gustatory system, olfactory system.

The sensory information that we receive with the help of the sense organs (analyzers) is important not only for organizing the activity of internal organs and behavior in accordance with the requirements of the environment, but also for the full development of a person.

The sense organs are the "windows" through which the outside world enters our consciousness. Without this information, the optimal organization of both the most primitive, “animal” functions of our body and the higher cognitive mental processes of a person would be impossible.

However, a person does not perceive all changes in the environment, he is not able, for example, to feel the effect of ultrasound, X-rays or radio waves. The range of human sensory perception is limited by the sensory systems available to him, each of which processes information about stimuli of a certain physical nature.

• The purpose and objectives of this work are to consider the concept of "sensory systems", analyze human sensory systems and determine the significance of each of them in the development and life of a person.
• 1. Psychophysiology of sensory systems: concept, functions, principles, general properties
• sensory analyzer brain man
• Human sensory systems are part of his nervous system, capable of perceiving information external to the brain, transmitting it to the brain and analyzing it. Obtaining information from the environment and one's own body is a prerequisite for human existence.
• The sensory system (lat. sensus - feeling) is a set of peripheral and central structures of the nervous system, which consists of a group of cells (receptors) responsible for the perception of signals of various modalities from the environment or internal environment, transmitting it to the brain and analyzing it. Smirnov V.M. Physiology of sensory systems and higher nervous activity: Proc. allowance / V.M. Smirnov, S.M. Budylin. - M.: Academy, 2009. - 304 p. - S. 178-196.
• The term "sensory systems" replaced the name "sense organs", which was retained only to refer to the anatomically isolated peripheral parts of some sensory systems (such as the eye or ear). In domestic literature, the concept of "analyzer" proposed by I.P. is used as a synonym for the sensory system. Pavlov and indicating the function of the sensory system.

The human sensory system consists of the following subsystems: visual system, auditory system, somatosensory system, gustatory system, olfactory system. Types of analyzers are shown in Appendix 1.

• According to I.P. Pavlov, any analyzer has three main sections (Table 1):
• 1. The peripheral section of the analyzer is represented by receptors. Its purpose is the perception and primary analysis of changes in the external and internal environments of the body. The perception of stimuli in the receptors occurs through the transformation of the energy of the stimulus into a nerve impulse (this part is the sense organs - the eye, ear, etc.).
• 2. The conductive section of the analyzer includes afferent (peripheral) and intermediate neurons of the stem and subcortical structures of the central nervous system (CNS). It provides the conduction of excitation from receptors to the cerebral cortex. In the conductor department, partial processing of information occurs at the stages of switching (for example, in the thalamus).

3. The central or cortical section of the analyzer consists of two parts: the central part - the "nucleus", - represented by specific neurons that process afferent information from receptors, and the peripheral part - "scattered elements" - neurons dispersed throughout the cerebral cortex. The cortical ends of the analyzers are also called "sensory zones", which are not strictly limited areas, they overlap each other. These features of the structure of the central department provide the process of compensating for impaired functions. At the level of the cortical department, the highest analysis and synthesis of afferent excitations is carried out, which provide a complete picture of the environment.

• Table 1 - Comparative characteristics of the departments of the sensory system
• Comparative characteristics of the peripheral section of the analyzers, and a comparative characteristic of the conductive and central sections of the analyzers are presented in Appendix 2.
• Sensory systems are organized hierarchically, i.e. include several levels of sequential processing of information. The lowest level of such processing is provided by primary sensory neurons, which are located in specialized sensory organs or in sensitive ganglia and are designed to conduct excitation from peripheral receptors to the central nervous system.
• Peripheral receptors are sensitive, highly specialized formations capable of perceiving, transforming and transmitting the energy of an external stimulus to primary sensory neurons. The central processes of primary sensory neurons terminate in the brain or spinal cord on second-order neurons, whose bodies are located in the switching nucleus. It contains not only excitatory, but also inhibitory neurons involved in the processing of transmitted information.
• Representing a higher hierarchical level, the neurons of the switching nucleus can regulate the transmission of information by amplifying some and inhibiting or suppressing other signals. Axons of neurons of the second order form pathways to the next switching nucleus, the total number of which is determined by the specific features of different sensory systems. The final processing of information about the current stimulus occurs in the sensory areas of the cortex.

Each sensory system forms connections with various structures of the motor and integrative systems of the brain. Sensory systems are a necessary link for the formation of responses to environmental influences. The sensory system is characterized by the presence of feedbacks addressed to the receptor or the first central section. Activating them makes it possible to regulate the process of perception of information and its conduction along the ascending pathways in the brain.

• Each individual sensory system responds only to certain physical stimuli (for example, the visual system responds to light stimuli, the auditory system to sound stimuli, etc.). The specificity of such a reaction led to the concept of "modality". A stimulus of this modality, adequate for a particular sensory system, is considered to be such a stimulus that causes a reaction at a minimum physical intensity. By modality, stimuli are divided into mechanical, chemical, thermal, light, etc.
• All sensory systems, regardless of the nature of the acting stimulus, perform the same functions and have common principles of their structural organization. At the same time, the most important principles are as follows: Batuev A.S. Physiology of higher nervous activity and sensory systems. General principles for the design of sensor systems / A.S. Batuev. - St. Petersburg: Peter, 2010. - S. 46-51. - 317 p.

1. The principle of multi-channel (duplication in order to increase the reliability of the system).

2. The principle of multi-level transmission of information.

3. The principle of convergence (terminal branches of one neuron are in contact with several neurons of the previous level; Sherrington's funnel).

4. The principle of divergence (multiplication; contact with several neurons of a higher level).

5. The principle of feedback (all levels of the system have both an ascending and a descending path; feedbacks have inhibitory significance as part of the signal processing process).

6. The principle of corticalization (all sensory systems are represented in the neocortex; therefore, the cortex is functionally polysemantic, and there is no absolute localization).

7. The principle of bilateral symmetry (exists in a relative degree).

8. The principle of structural-functional correlations (corticalization of different sensory systems has a different degree).

The main functions of sensory systems: Bezrukikh M.M. Psychophysiology. Dictionary / M.M. Bezrukikh, D.A. Faber - M.: PER SE, 2006. - signal detection; signal discrimination; transfer and transformation; feature coding and detection; image recognition. This sequence is observed in all sensory systems, reflecting the hierarchical principle of their organization. At the same time, the detection and primary discrimination of signals is provided by receptors, and the detection and recognition of signals - by neurons of the cerebral cortex. Transmission, transformation and encoding of signals is carried out by neurons of all layers of sensory systems.

1. Detection of signals begins in the receptor - a specialized cell, evolutionarily adapted to the perception of a stimulus of a certain modality from the external or internal environment and its transformation from a physical or chemical form into a form of nervous excitation.

2. An important characteristic of the sensory system is the ability to notice differences in the properties of simultaneously or sequentially acting stimuli. Discrimination begins in the receptors, but the neurons of the entire sensory system are involved in this process. It characterizes the minimum difference between stimuli that the sensory system can notice (differential, or difference, threshold).

3. The processes of transformation and transmission of signals in the sensory system convey to the higher centers of the brain the most important (essential) information about the stimulus in a form convenient for its reliable and fast analysis. Signal transformations can be conditionally divided into spatial and temporal. Among the spatial transformations, changes in the ratio of different parts of the signal are distinguished.

4. Coding of information is called the transformation of information into a conditional form - a code, performed according to certain rules. In a sensory system, signals are encoded by a binary code, that is, by the presence or absence of an electrical impulse at one time or another. Information about the stimulation and its parameters is transmitted in the form of individual impulses, as well as groups or "packages" of impulses ("volleys" of impulses). The amplitude, duration, and shape of each pulse are the same, but the number of pulses in a burst, their frequency, the duration of bursts and intervals between them, as well as the temporal “pattern” of a burst, are different and depend on the characteristics of the stimulus. Sensory information is also encoded by the number of simultaneously excited neurons, as well as by the place of excitation in the neuronal layer.

5. Signal detection is the selective selection by a sensory neuron of one or another sign of a stimulus that has behavioral significance. Such an analysis is carried out by detector neurons that selectively respond only to certain parameters of the stimulus. Thus, a typical neuron in the visual area of ​​the cortex responds with a discharge to only one specific orientation of a dark or light strip located in a certain part of the visual field. At other slopes of the same strip, other neurons will respond. In the higher parts of the sensory system, detectors of complex features and whole images are concentrated.

6. Pattern recognition is the final and most complex operation of the sensory system. It consists in assigning the image to one or another class of objects that the organism encountered earlier, i.e., in the classification of images. Synthesizing signals from neurons-detectors, the higher part of the sensory system forms the "image" of the stimulus and compares it with the many images stored in memory. Recognition ends with a decision about which object or situation the organism encountered. As a result of this, perception occurs, that is, we are aware of whose face we see in front of us, whom we hear, what smell we smell. Recognition often occurs regardless of signal variability. So, we reliably identify objects in their different illumination, color, size, angle, orientation and position in the field of view. This means that the sensory system forms an (invariant) sensory image independent of changes in a number of signal features.

Thus, the sensory system (analyzer) is a functional system consisting of a receptor, an afferent pathway, and a zone of the cerebral cortex where this type of sensitivity is projected.

Cortical analyzers of the human cerebrum, and their functional connection with various organs, are clearly shown in the figure in Appendix 3.

Human sensory systems provide:

1) the formation of sensations and the perception of existing stimuli;

2) control of voluntary movements;

3) control of the activities of internal organs;

4) the level of brain activity necessary for a person to wake up.

The process of transmission of sensory signals (they are often called sensory messages) is accompanied by their multiple transformations and recoding at all levels of the sensory system and ends with the recognition of the sensory image. Sensory information entering the brain is used to organize simple and complex reflex acts, as well as to form mental activity. The entry of sensory information into the brain may be accompanied by awareness of the presence of a stimulus (sensation of the stimulus). A sensation is a subjective sensory response to an actual sensory stimulus (eg, a sensation of light, warmth or cold, touch, etc.). as mentioned earlier, the totality of sensations provided by any one analyzer is denoted by the term "modality", which may include various qualitative types of sensations. Independent modalities are touch, sight, hearing, smell, taste, feeling of cold or heat, pain, vibration, sensation of the position of the limbs and muscle load. Within the modalities there are different qualities or submodalities; for example, taste modality distinguishes between sweet, salty, sour, and bitter tastes.

On the basis of the totality of sensations, sensory perception is formed, i.e., comprehension of sensations and readiness to describe them. Perception is not a simple reflection of the current stimulus, it depends on the distribution of attention at the moment of its action, memory of past sensory experience and subjective attitude to what is happening, expressed in emotional experiences.

Thus, the sensory system enters information into the brain and analyzes it. The work of any sensory system begins with the perception by receptors of physical or chemical energy external to the brain, its transformation into nerve signals and their transmission to the brain through chains of neurons. The process of transmission of sensory signals is accompanied by their multiple transformation and recoding and ends with higher analysis and synthesis (image recognition), after which the body's response is formed.

2. Characteristics of the main sensory systems

In physiology, it is customary to divide analyzers into external and internal. External analyzers of a person react to those stimuli that come from the external environment. The internal analyzers of a person are those structures that respond to changes within the body. For example, in muscle tissue there are specific receptors that respond to pressure and other indicators that change inside the body.

External analyzers are divided into contact (in direct contact with the stimulus) and distant, which respond to remote stimuli:

1) contact: taste and touch;

2) distant: sight, hearing and smell.

The activity of each of the sense organs is an elementary mental process - sensation. Sensory information from external stimuli enters the central nervous system in 2 ways:

1) Characteristic sensory pathways:

a) vision - through the retina, lateral geniculate body and superior tubercles of the quadrigemina into the primary and secondary visual cortex;

b) hearing - through the nuclei of the cochlea and quadrigemina, the medial geniculate body into the primary auditory cortex;

c) taste - through the medulla oblongata and thalamus to the somatosensory cortex;

d) sense of smell - through the olfactory bulb and piriform cortex to the hypothalamus and limbic system;

e) touch - passes through the spinal cord, brain stem and thalamus to the somatosensory cortex.

2) Non-specific sensory pathways: pain and temperature sensations located in the nuclei of the thalamus and brain stem.

The visual sensory system provides the brain with more than 90% of sensory information. Vision is a multi-link process that begins with the projection of an image onto the retina. Then there is excitation of photoreceptors, transmission and transformation of visual information in the neural layers of the visual system, and visual perception ends with the adoption of a decision about the visual image by the higher cortical sections of this system.

The adaptation of the eye to a clear vision of objects at different distances is called accommodation, the main role here is played by the lens, which changes its curvature and, consequently, its refractive power.

The peripheral part of the visual sensory system is the eye (Fig. 1). It consists of the eyeball and auxiliary structures: the lacrimal glands, the ciliary muscle, blood vessels and nerves. Characteristics of the membranes of the eyeball in Appendix 4.

The conductor department of the visual sensory system is the optic nerve, the nuclei of the superior colliculus of the quadrigemina of the midbrain, the nuclei of the external geniculate body of the diencephalon.

The central part of the visual analyzer is located in the occipital lobe.

The eyeball has a spherical shape, which makes it easier to turn to aim at the object in question. The amount of light that enters the retina is regulated by the pupil, which is able to expand and contract. The pupil is the hole in the center of the iris through which light rays pass into the eye. The pupil sharpens the image on the retina, increasing the depth of field of the eye.

The light beam breaks on the cornea, lens and vitreous body. Thus, the image falls on the retina, which contains many nerve receptors - rods and cones. Thanks to chemical reactions, an electrical impulse is formed here, which follows the optic nerve and is projected in the occipital lobes of the cerebral cortex.

Figure 1 - Organ of vision:

1 - protein shell; 2 - cornea; 3 - lens; 4 - ciliary body; 5 - iris; 6 - choroid; 7 - retina; 8 - blind spot; 9 - vitreous body; 10 - posterior chamber of the eye; 11 - anterior chamber of the eye; 12 - optic nerve

The retina is the inner light-sensitive membrane of the eye. There are two types of photoreceptors here (rod and cone: cones function in high light conditions, they provide day and color vision; much more light-sensitive rods are responsible for twilight vision) and several types of nerve cells. All of these retinal neurons with their processes form the nervous apparatus of the eye, which not only transmits information to the visual centers of the brain, but also participates in its analysis and processing. Therefore, the retina is called the part of the brain that is placed on the periphery. From the retina, visual information travels along the optic nerve fibers to the brain.

The auditory sensory system is one of the most important remote sensory systems in humans. The receptor here is the ear. Like any other analyzer, the auditory one also consists of three parts: the auditory receptor, the auditory nerve with its pathways, and the auditory zone of the cerebral cortex, where sound stimuli are analyzed and evaluated (Fig. 2).

The peripheral auditory sensory system consists of three parts: the outer, middle, and inner ear.

Conductor department. Hair cells are covered by nerve fibers of the cochlear branch of the auditory nerve, which carries a nerve impulse to the medulla oblongata, then, crossing with the second neuron of the auditory pathway, it goes to the posterior tubercles of the quadrigemina and the nuclei of the internal geniculate bodies of the diencephalon, and from them to the temporal region of the cortex, where is the central part of the auditory analyzer located.

Figure 2 - Organ of hearing:

A - general view: 1 - external auditory meatus; 2 - eardrum; 3 - middle ear;

4 - hammer; 5 - anvil; 6 - stirrup; 7 - auditory nerve; 8 - snail; 9 - auditory (Eustachian) tube; B - a section of a snail; B - cross section of the cochlear canal: 10 - bone labyrinth; 11 - membranous labyrinth; 12 - spiral (Korti) organ; 13 - main (basal) plate

The central part of the auditory analyzer is located in the temporal lobe. The primary auditory cortex occupies the upper edge of the superior temporal gyrus and is surrounded by the secondary cortex. The meaning of what is heard is interpreted in associative zones. In humans, in the central nucleus of the auditory analyzer, Wernicke's area, located in the posterior part of the superior temporal gyrus, is of particular importance. This zone is responsible for understanding the meaning of words, it is the center of sensory speech. With prolonged action of strong sounds, the excitability of the sound analyzer decreases, and with a long stay in silence, it increases. This adaptation is observed in the zone of higher sounds.

Acoustic (sound) signals are air vibrations with different frequencies and strengths. They excite auditory receptors located in the cochlea of ​​the inner ear. The receptors activate the first auditory neurons, after which sensory information is transmitted to the auditory area of ​​the cerebral cortex through a series of successive sections:

Outer ear - the ear canal conducts sound vibrations to the eardrum. The tympanic membrane, which separates the outer ear from the tympanic cavity, or middle ear, is a thin (0.1 mm) septum shaped like an inward funnel. The membrane vibrates under the action of sound vibrations that come to it through the external auditory canal.

In the middle ear, filled with air, there are three bones: the hammer, anvil and stirrup, which successively transmit the vibrations of the tympanic membrane to the inner ear. The hammer is woven with a handle into the eardrum, its other side is connected to the anvil, which transmits vibrations to the stirrup. Due to the peculiarities of the geometry of the auditory ossicles, vibrations of the tympanic membrane of reduced amplitude, but increased strength, are transmitted to the stirrup.

There are two muscles in the middle ear: the tensor tympanic membrane and the stirrup. The first of them, contracting, increases the tension of the tympanic membrane and thereby limits the amplitude of its oscillations during strong sounds, and the second fixes the stirrup and thereby limits its movement. By this, the inner ear is automatically protected from overload;

The cochlea contains the auditory receptors in the inner ear. The cochlea is a bony spiral canal, forming 2.5 turns. Inside the middle canal of the cochlea, on the main membrane, there is a sound-perceiving apparatus - a spiral organ containing receptor hair cells. These cells transform mechanical vibrations into electrical potentials.

Comparative characteristics of the parts of the hearing organ in Appendix 5.

The mechanisms of auditory reception are as follows. Sound, which is air vibrations, in the form of air waves, enters the external auditory canal through the auricle and acts on the eardrum. The vibrations of the tympanic membrane are transmitted to the auditory ossicles, the movements of which cause the vibration of the membrane of the oval window. These vibrations are 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 synthesis and synthesis of sound signals takes place.

The gustatory sensory system is a cluster of sensitive chemical receptors that respond to certain chemicals. Taste, like smell, is based on chemoreception. Chemoreceptors - taste cells - are located at the bottom of the taste bud. They are covered with microvilli that come into contact with substances dissolved in water.

Taste buds carry information about the nature and concentration of substances entering the mouth. Their excitation triggers a complex chain of reactions in different parts of the brain, leading to different work of the digestive organs or to the removal of substances harmful to the body that have entered the mouth with food.

The peripheral part of this system is represented by taste buds - taste receptors - located in the epithelium of the grooved, foliate and mushroom papillae of the tongue and in the mucous membrane of the palate, pharynx and epiglottis. Most of them are on the tip, edges and back of the tongue. Each of the approximately 10,000 human taste buds consists of several (2-6) receptor cells and, in addition, of supporting cells. The taste bud is flask-shaped; in humans, its length and width are about 70 microns. The taste bud does not reach the surface of the mucous membrane of the tongue and is connected to the oral cavity through the taste pore.

The conductor section of this analyzer is represented by the trigeminal nerve, the tympanic string, the glossopharyngeal nerve, the nuclei of the medulla oblongata, and the nuclei of the thalamus.

The central section (cortical end) of the taste analyzer is located in the evolutionarily ancient formations of the cerebral hemispheres, located on their medial (middle) and lower surfaces. This is the cortex of the hippocampus (Ammon's horn), parahippocampus and hook, as well as the lateral part of the postcentral gyrus (Fig. 5.3).

Rice. 5.3. Fornix and hippocampus:

1 - hook; 9 - dentate gyrus; 2 - parahippocampal gyrus; 3 - leg of the hippocampus; 4 - hippocampus; 5 - corpus callosum; 6 - central furrow; 7 - occipital lobe; 8 - parietal lobe; 9 - temporal lobe

The conductors of all types of taste sensitivity are the string tympani and the glossopharyngeal nerve, the nuclei of which in the medulla oblongata contain the first neurons of the taste system. Many of the fibers coming from the taste buds are distinguished by a certain specificity, since they respond with an increase in impulse discharges only to the action of salt, acid and quinine. Other fibers react to sugar. The most convincing is the hypothesis according to which information about the 4 main taste sensations: bitter, sweet, sour and salty is encoded not by impulses in single fibers, but by a different distribution of the frequency of discharges in a large group of fibers differently excited by the taste substance.

Taste afferent signals enter the nucleus of a single bundle of the brainstem. From the nucleus of a single bundle, the axons of the second neurons ascend as part of the medial loop to the arcuate nucleus of the thalamus, where the third neurons are located, the axons of which are directed to the cortical center of taste. The research results do not yet allow us to assess the nature of the transformations of gustatory afferent signals at all levels of the gustatory system.

Olfactory analyzer. The peripheral part of the olfactory sensory system is located in the upper-posterior nasal cavity, it is the olfactory epithelium, in which there are olfactory cells that interact with molecules of odorous substances.

The conductor section is represented by the olfactory nerve, olfactory bulb, olfactory tract, nuclei of the amygdala complex.

The central, cortical section is the hook, the hippocampal gyrus, the transparent septum and the olfactory gyrus.

The nuclei of the gustatory and olfactory analyzers are closely related to each other, as well as to the brain structures responsible for the formation of emotions and long-term memory. From this it is clear how important the normal functional state of the gustatory and olfactory analyzer is.

The olfactory receptor cell is a bipolar cell, on the apical pole of which there are cilia, and an unmyelinated axon departs from its basal part. The axons of the receptors form the olfactory nerve, which penetrates the base of the skull and enters the olfactory bulb.

Molecules of odorous substances enter the mucus produced by the olfactory glands with a constant flow of air or from the oral cavity during meals. Sniffing accelerates the flow of odorous substances to the mucus.

Each olfactory cell has only one type of membrane receptor protein. This protein itself is able to bind many odorous molecules of various spatial configurations. The rule "one olfactory cell - one olfactory receptor protein" greatly simplifies the transmission and processing of information about odors in the olfactory bulb - the first nerve center for switching and processing chemosensory information in the brain.

A feature of the olfactory system is, in particular, that its afferent fibers do not switch in the thalamus and do not pass to the opposite side of the cerebrum. The olfactory tract leaving the bulb consists of several bundles that go to different parts of the forebrain: the anterior olfactory nucleus, the olfactory tubercle, the prepiriform cortex, the periamygdala cortex, and part of the nuclei of the amygdala complex. The connection of the olfactory bulb with the hippocampus, piriform cortex and other parts of the olfactory brain is carried out through several switches. It has been shown that the presence of a significant number of centers of the olfactory brain is not necessary for the recognition of odors, therefore, most of the nerve centers into which the olfactory tract is projected can be considered as associative centers that ensure the connection of the olfactory sensory system with other sensory systems and the organization on this basis of a number of complex forms. behavior - food, defensive, sexual, etc.

The sensitivity of the human olfactory system is extremely high: one olfactory receptor can be excited by one molecule of an odorous substance, and the excitation of a small number of receptors leads to a sensation. Adaptation in the olfactory system occurs relatively slowly (tens of seconds or minutes) and depends on the air flow velocity over the olfactory epithelium and on the concentration of the odorous substance.

The somatosensory system (musculoskeletal sensory system) includes the skin sensitivity system and the sensitive system of the musculoskeletal system, which are the corresponding receptors located in different layers of the skin. The receptor surface of the skin is huge (1.4-2.1 m2). Many receptors are concentrated in the skin. They are localized at different depths of the skin and distributed unevenly over its surface.

The peripheral part of this most important sensory system is represented by a variety of receptors, which are divided into skin receptors, proprioceptors (receptors of muscles, tendons and joints) and visceral receptors (receptors of internal organs) according to their location. According to the nature of the perceived stimulus, mechanoreceptors, thermoreceptors, chemoreceptors and pain receptors - nociceptors are distinguished.

The role of the sense organ here, in fact, is the entire surface of the human body, its muscles, joints, and, to a certain extent, internal organs.

The conductor section is represented by numerous afferent fibers, centers of the posterior horns of the spinal cord, nuclei of the medulla oblongata, and nuclei of the thalamus.

The central section is located in the parietal lobe: the primary cortex is in the posterior central gyrus, the secondary is in the upper parietal lobule.

There are several analyzer systems in the skin: tactile (sensations of touch), temperature (sensations of cold and heat), and pain. The system of tactile sensitivity is unevenly distributed throughout the body. But most of all, the accumulation of tactile cells is observed on the palm, on the fingertips and on the lips. The tactile sensations of the hand, combined with the muscular-articular sensitivity, form the sense of touch - a specifically human system of cognitive activity of the hand developed in labor.

If you touch the surface of the body, then press on it, the pressure can cause pain. Thus, tactile sensitivity provides knowledge about the qualities of an object, and pain sensations signal the body about the need to move away from the stimulus and have a pronounced emotional tone.

The third type of skin sensitivity - temperature sensations - is associated with the regulation of heat transfer between the body and the environment. The distribution of heat and cold receptors on the skin is uneven. The back is most sensitive to cold, the least - the chest.

Static sensations signal the position of the body in space. Static sensitivity receptors are located in the vestibular apparatus of the inner ear. Sudden and frequent changes in body position relative to the ground plane can lead to dizziness.

Mechanisms of excitation of skin receptors: the stimulus leads to deformation of the receptor membrane, as a result of which the electrical resistance of the membrane decreases. An ion current begins to flow through the receptor membrane, leading to the generation of the receptor potential. When the receptor potential increases to a critical level in the receptor, impulses are generated that propagate along the fiber in the CNS.

Conclusion

Thus, information about the surrounding world is perceived by a person through the sense organs, called sensory systems (analyzers) in physiology.

The activity of the analyzers is associated with the emergence of five senses - sight, hearing, taste, smell and touch, with the help of which the body is connected with the external environment.

Sense organs are complex sensory systems (analyzers), including perceptive elements (receptors), nerve pathways and corresponding sections in the brain, where the signal is converted into sensation. The main characteristic of the analyzer is sensitivity, which is characterized by the value of the sensation threshold.

The main functions of the sensory system are: detection and discrimination of signals; transmission and conversion of signals; information encoding; signal detection and pattern recognition.

Each sensory system includes three sections: 1) peripheral or receptor, 2) conductive, 3) cortical.

Sensory systems receive signals from the outside world and carry to the brain the information necessary for the body to navigate in the external environment and to assess the state of the body itself. These signals arise in the perceiving elements - sensory receptors that receive stimuli from the external or internal environment, nerve pathways, and are transmitted from the receptors to the brain and those parts of the brain that process this information - through the chains of neurons and the nerve fibers of the sensory system that connect them.

The transmission of signals is accompanied by multiple transformations and recoding at all levels of the sensory system and ends with the recognition of the sensory image.

Bibliography

1. Atlas of human anatomy: textbook. allowance for medical textbook institutions / ed. T.S. Artemiev, A.A. Vlasova, N.T. Shindin. - M.: RIPOL CLASSIC, 2007. - 528 p.

2. Fundamentals of psychophysiology: Textbook / Ed. ed. Yu.I. Alexandrov. - St. Petersburg: Peter, 2003. - 496 p.

3. Ostrovsky M.A. Human physiology. Textbook. In 2 vols. T. 2 / M.A. Ostrovsky, I.A. Shevelev; Ed. V.M. Pokrovsky, G.F. Briefly. - M. - 368 p. - S. 201-259.

4. Rebrova N.P. Physiology of sensory systems: Educational and methodological manual / N.P. Rebrova. - St. Petersburg: NP "Future Strategy", 2007. - 106 p.

5. Serebryakova T.A. Physiological foundations of mental activity: Textbook. - N.-Novgorod: VGIPU, 2008. - 196 p.

6. Smirnov V.M. Physiology of sensory systems and higher nervous activity: Proc. allowance / V.M. Smirnov, S.M. Budylin. - M.: Academy, 2009. - 336 p. - S. 178-196.

7. Titov V.A. Psychophysiology. Lecture notes / V.A. Titov. - M.: Prior-izdat, 2003. - 176 p.

8. Physiology of sensory systems and higher nervous activity: textbook. In 2 vols. T. 1. / Ed. Ya.A. Altman, G.A. Kulikov. - M. Academy, 2009. - 288 p.

9. Human Physiology / Ed. V.M. Smirnova - M.: Academy, 2010. - pp. 364-370, 372-375,377-378, 370-371,381-386.

Appendix 1

Types of analyzers

Analyzer	Functions (what stimuli it perceives)	Peripheral department	conductor department	Central department
Visual	light	Retinal photoreceptors	optic nerve	Visual zone in the occipital lobe of the cerebral cortex
Auditory	Sound	Auditory receptors in the organ of Corti	Auditory nerve	The auditory zone in the temporal lobe of the CBP
Vestibular (gravitational)	Mechanical	Receptors of the semicircular canals and ottolith apparatus	Vestibular then auditory nerve	Vestibular zone in the temporal lobe of the CBP
Sensorimotor sensitive (somatosensory)	Mechanical, thermal, pain.	touch receptors in the skin	Spinothalamic pathway: nerves of skin sensation	Somatosensory zone in the posterior central gyrus of the CBP
Sensorimotor motor (motor)	Mechanical	Proprioreceptors in muscles and joints	Sensory nerves of the musculoskeletal system	Somatosensory zone and motor zone in the anterior central gyrus of the CBP
Olfactory	Gaseous chemicals	Olfactory receptors in the nasal cavity	Olfactory nerve	Olfactory nuclei and olfactory centers of the temporal lobe of the CBP
Taste	Chemical solutes	Taste buds in the mouth	Facial glossopharyngeal nerve	Taste zone in the parietal lobe of the CBP
Visceral (internal environment)	Mechanical	Interoreceptors of internal organs	Vagus, celiac and pelvic nerves	Limbic system and sensorimotor area

Appendix 2

Comparative characteristics of the peripheral section of the analyzers

Analyzers	sensitive organ	Quality	Receptors
visual analyzer	Retina	Brightness, Contrast, Motion, Size, Color	Rods and cones
auditory analyzer		Height, timbre of sound	hair cells
Vestibular analyzer	vestibular organ	Force of gravity	vestibular cells
Vestibular analyzer	vestibular organ	Rotation	vestibular cells
Skin analyzer		Touch	Touch, cold and heat receptors
Taste Analyzer		Sweet and sour taste	Taste buds at the tip of the tongue
Taste Analyzer		Bitter and salty taste	Taste buds at the base of the tongue
Olfactory analyzer	Olfactory nerves		Olfactory receptors

Comparative characteristics of the conductive and central sections of the analyzers

Analyzers	Switch levels: primary	Switch levels secondary	Switch levels: tertiary	Central department
visual analyzer	Retina		Primary and secondary visual cortex	Occipital lobes of the brain
auditory analyzer	snail kernels		primary auditory cortex	temporal lobe of the brain
Vestibular analyzer	Vestibular nuclei		Somatosensory cortex	Parietal and temporal lobes of the brain
Skin analyzer	Spinal cord		Somatosensory cortex	Superior portion of the posterior central gyrus of the brain
Olfactory analyzer	Olfactory bulb	piriform bark	limbic system, hypothalamus	Temporal lobe (cortex of the seahorse gyrus) of the brain
Taste Analyzer	Medulla		Somatosensory cortex	Inferior portion of the posterior central gyrus of the brain

Annex 3

Cortical analyzers of the human brain, and their functional relationship with various organs

1 - peripheral link; 2 - conductive; 3 - central, or cortical; 4 - interoreceptive; 5 - motor; 6 - gustatory and olfactory; 7 - skin, 8 - auditory, 9 - visual)

Appendix 4

Comparative characteristics of the membranes of the eyeball

Shells		Structural features
	Sclera (protein coat)		Support, protective
Fibrous sheath (outer sheath)	Cornea	Transparent, connective tissue, has a convex shape	Transmits and refracts light rays
	The choroid proper	Contains many blood vessels	Uninterrupted eye supply
Vascular membrane (middle layer)	ciliary body	Contains ciliary muscle	Change in the curvature of the lens
Vascular membrane (middle layer)		Contains pupil, muscle and melanin pigment	Transmits light rays and detects eye color
	Retina (inner shell)	Two layers: outer pigmented (contains the pigment fuscin) and inner light-sensitive (contains rods, cones)	Converts light stimulation into a nerve impulse, primary processing of the visual signal
Shells		Structural features
Fibrous sheath (outer sheath)	Sclera (protein coat)	Opaque, connective tissue	Support, protective

Annex 5

Comparative characteristics of the parts of the organ of hearing

	Structural features
outer ear	auricle, external auditory meatus	Protective (hairs, earwax), conductive, resonator
Middle ear	Tympanic cavity, tympanic membrane, auditory ossicles (hammer, anvil, stirrup), auditory (Eustachian) tube	Conductor, increase in the power of vibrations, protective (from strong sound vibrations)
inner ear	The cochlea of ​​the membranous labyrinth, which contains the spiral (corti) organ	Conductive, sound-perceiving (spiral organ)

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Properties of the conductor section of the analyzers

This department of analyzers is represented by afferent pathways and subcortical centers. The main functions of the conductor department are: analysis and transmission of information, implementation of reflexes and inter-analyzer interaction. These functions are provided by the properties of the conductive section of the analyzers, which are expressed in the following.

1. From each specialized formation (receptor), there is a strictly localized specific sensory path. These pathways usually transmit signals from receptors of the same type.

2. Collaterals depart from each specific sensory pathway to the reticular formation, as a result of which it is a structure of convergence of various specific pathways and the formation of multimodal or non-specific pathways, in addition, the reticular formation is a place of interanalyzer interaction.

3. There is a multi-channel conduction of excitation from receptors to the cortex (specific and non-specific pathways), which ensures the reliability of information transmission.

4. During the transfer of excitation, there is a multiple switching of excitation at different levels of the central nervous system. There are three main switching levels:

• spinal or stem (medulla oblongata);
• visual tubercle;
• the corresponding projection area of ​​the cerebral cortex.

At the same time, within the sensory pathways, there are afferent channels for the urgent transmission of information (without switching) to higher brain centers. It is believed that through these channels, the pre-adjustment of higher brain centers to the perception of subsequent information is carried out. The presence of such pathways is a sign of improving the design of the brain and increasing the reliability of sensory systems.

5. In addition to specific and non-specific pathways, there are so-called associative thalamo-cortical pathways associated with associative areas of the cerebral cortex. It has been shown that the activity of thalamo-cortical associative systems is associated with intersensory assessment of the biological significance of the stimulus, etc. Thus, the sensory function is carried out on the basis of the interconnected activity of specific, non-specific and associative formations of the brain, which ensure the formation of an adequate adaptive behavior of the body.

Central, or cortical, part of the sensory system , according to I.P. Pavlov, it consists of two parts: central part, i.e. "nucleus", represented by specific neurons that process afferent impulses from receptors, and peripheral part, i.e. "scattered elements" - neurons dispersed throughout the cerebral cortex. The cortical ends of the analyzers are also called "sensory zones", which are not strictly limited areas, they overlap each other. Currently, in accordance with cytoarchitectonic and neurophysiological data, projection (primary and secondary) and associative tertiary cortical zones are distinguished. Excitation from the corresponding receptors to the primary zones is directed along fast-conducting specific pathways, while the activation of secondary and tertiary (associative) zones occurs along polysynaptic non-specific pathways. In addition, the cortical zones are interconnected by numerous associative fibers.

CLASSIFICATION OF RECEPTORS

The classification of receptors is based primarily on on the nature of feelings that arise in a person when they are irritated. Distinguish visual, auditory, olfactory, gustatory, tactile receptors thermoreceptors, proprio and vestibuloreceptors (receptors of the position of the body and its parts in space). The question of the existence of special pain receptors .

Receptors by location divided into external , or exteroreceptors, and internal , or interoreceptors. Exteroreceptors include auditory, visual, olfactory, taste and tactile receptors. Interoreceptors include vestibuloreceptors and proprioreceptors (receptors of the musculoskeletal system), as well as interoreceptors that signal the state of internal organs.

By the nature of contact with the external environment receptors are divided into distant receiving information at a distance from the source of irritation (visual, auditory and olfactory), and contact - excited by direct contact with the stimulus (gustatory and tactile).

Depending on the nature of the type of perceived stimulus , to which they are optimally tuned, there are five types of receptors.

· Mechanoreceptors excited by their mechanical deformation; located in the skin, blood vessels, internal organs, musculoskeletal system, auditory and vestibular systems.

· 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 (changes in O 2 and CO 2 voltage, osmolarity and pH, glucose levels and other substances). Such receptors are found in the mucous membrane of the tongue and nose, the carotid and aortic bodies, the hypothalamus, and the medulla oblongata.

· thermoreceptors react to temperature changes. They are divided into heat and cold receptors and are found in the skin, mucous membranes, blood vessels, internal organs, hypothalamus, middle, medulla and spinal cord.

· Photoreceptors in the retina, the eyes perceive light (electromagnetic) energy.

· Nociceptors , the excitation of which is accompanied by pain sensations (pain receptors). The irritants of these receptors are mechanical, thermal and chemical (histamine, bradykinin, K +, H +, etc.) factors. Painful stimuli are perceived by free nerve endings that are found in the skin, muscles, internal organs, dentin, and blood vessels. From a psychophysiological point of view, receptors are divided into visual, auditory, gustatory, olfactory and tactile.

Depending on the structure of the receptors they are subdivided into primary , or primary sensory, which are specialized endings of a sensitive neuron, and secondary , or secondary-sensing, which are cells of epithelial origin, capable of generating a receptor potential in response to the action of an adequate stimulus.

Primary sensory receptors can themselves generate action potentials in response to stimulation by an adequate stimulus, if the value of their receptor potential reaches a threshold value. These include olfactory receptors, most skin mechanoreceptors, thermoreceptors, pain receptors or nociceptors, proprioceptors, and most internal organ interoreceptors. The body of the neuron is located in the spinal ganglion or in the ganglion of the cranial nerves. In the primary receptor, the stimulus acts directly on the endings of the sensory neuron. Primary receptors are phylogenetically more ancient structures, they include olfactory, tactile, temperature, pain receptors and proprioceptors.

Secondary sensory receptors respond to the action of the stimulus only by the appearance of a receptor potential, the magnitude of which determines the amount of mediator secreted by these cells. With its help, secondary receptors act on the nerve endings of sensory neurons that generate action potentials depending on the amount of mediator released from the secondary sensory receptors. In secondary receptors there is a special cell synaptically connected to the end of the dendrite of the sensory neuron. This is a cell, such as a photoreceptor, of epithelial nature or neuroectodermal origin. Secondary receptors are represented by taste, auditory and vestibular receptors, as well as chemosensitive cells of the carotid glomerulus. Retinal photoreceptors, which have a common origin with nerve cells, are more often referred to as primary receptors, but their lack of the ability to generate action potentials indicates their similarity to secondary receptors.

According to the speed of adaptation Receptors are divided into three groups: adaptable (phase), slowly adapting (tonic) and mixed (phasnotonic), adapting at an average speed. Examples of rapidly adapting receptors are the receptors for vibration (Pacini corpuscles) and touch (Meissner corpuscles) on the skin. Slowly adapting receptors include proprioceptors, lung stretch receptors, and pain receptors. Retinal photoreceptors and skin thermoreceptors adapt at an average speed.

Most receptors are excited in response to the action of stimuli of only one physical nature and therefore belong to monomodal . They can also be excited by some inadequate stimuli, for example, photoreceptors - by strong pressure on the eyeball, and taste buds - by touching the tongue to the contacts of a galvanic battery, but it is impossible to obtain qualitatively distinguishable sensations in such cases.

Along with monomodal, there are polymodal receptors, adequate stimuli of which can serve as stimuli of a different nature. To this type of receptors belong some pain receptors, or nociceptors (lat. nocens - harmful), which can be excited by mechanical, thermal and chemical stimuli. Polymodality is present in thermoreceptors that respond to an increase in the concentration of potassium in the extracellular space in the same way as to an increase in temperature.

Visual perception begins with the projection of an image onto the retina and excitation of photoreceptors, then the information is sequentially processed in the subcortical and cortical visual centers, resulting in a visual image that, due to the interaction of the visual analyzer with other analyzers, quite correctly reflects objective reality. Visual sensory system - a sensory system that provides: - coding of visual stimuli; and hand-eye coordination. Through the visual sensory system, animals perceive objects and objects of the outside world, the degree of illumination and the length of daylight hours.

The visual sensory system, like any other, consists of three departments:

1. Peripheral department - the eyeball, in particular - the retina of the eye (perceives light irritation)

2. Conductor department - axons of ganglion cells - optic nerve - optic chiasm - optic tract - diencephalon (geniculate bodies) - midbrain (quadrigemina) - thalamus

3. The central section - the occipital lobe: the region of the spur groove and adjacent convolutions.

optic tract make up several neurons. Three of them - photoreceptors (rods and cones), bipolar cells and ganglion cells - are located in the retina.

After decussation, the optic fibers form optic tracts, which, at the base of the brain, go around the gray tubercle, pass along the lower surface of the legs of the brain and end in the lateral geniculate body, the cushion of the optic tubercle (thalamus opticus) and the anterior quadrigemina. Of these, only the first is a continuation of the visual path and the primary visual center.

At the ganglion cells of the external geniculate body, the fibers of the optic tract end and the fibers of the central neuron begin, which pass through the posterior knee of the internal capsule and then, as part of the Graziole bundle, go to the cortex of the occipital lobe, cortical visual centers, in the region of the spur groove.

So, the nerve path of the visual analyzer begins in the layer of retinal ganglion cells and ends in the cortex of the occipital lobe of the brain and has peripheral and central neurons. The first consists of the optic nerve, chiasm and visual pathways with the primary visual center in the lateral geniculate body. Here begins the central neuron, which ends in the cortex of the occipital lobe of the brain.

The physiological significance of the visual pathway is determined by its function, which conducts visual perception. The anatomical relationships of the central nervous system and the visual pathway determine its frequent involvement in the pathological process with early ophthalmological symptoms, which are of great importance in the diagnosis of diseases of the central nervous system and in the dynamics of monitoring the patient.

For a clear vision of an object, it is necessary that the rays of each of its points be focused on the retina. If you look into the distance, then close objects are not clearly visible, blurry, since the rays from near points are focused behind the retina. It is impossible to see objects equally clearly at different distances from the eye at the same time.

Refraction(ray refraction) reflects the ability of the optical system of the eye to focus the image of an object on the retina. The peculiarities of the refractive properties of any eye include the phenomenon spherical aberration . It lies in the fact that the rays passing through the peripheral parts of the lens are refracted more strongly than the rays passing through its central parts (Fig. 65). Therefore, the central and peripheral rays do not converge at one point. However, this feature of refraction does not interfere with a clear vision of the object, since the iris does not transmit rays and thereby eliminates those that pass through the periphery of the lens. The unequal refraction of rays of different wavelengths is called chromatic aberration .

The refractive power of the optical system (refraction), that is, the ability of the eye to refract, is measured in conventional units - diopters. The diopter is the refractive power of a lens, in which parallel rays, after refraction, are collected at a focus at a distance of 1 m.

We see the world around us clearly when all departments of the visual analyzer "work" harmoniously and without interference. In order for the image to be sharp, the retina must obviously be in the back focus of the optical system of the eye. Various violations of the refraction of light rays in the optical system of the eye, leading to defocusing of the image on the retina, are called refractive errors (ametropia). These include myopia, hyperopia, age-related farsightedness and astigmatism (Fig. 5).

Fig.5. The course of rays in various types of clinical refraction of the eye

a - emetropia (normal);

b - myopia (myopia);

c - hypermetropia (farsightedness);

D - astigmatism.

With normal vision, which is called emmetropic, visual acuity, i.e. the maximum ability of the eye to distinguish individual details of objects usually reaches one conventional unit. This means that a person is able to see two separate points, visible at an angle of 1 minute.

With an anomaly of refraction, visual acuity is always below 1. There are three main types of refractive error - astigmatism, myopia (myopia) and farsightedness (hypermetropia).

Refractive errors cause nearsightedness or farsightedness. The refraction of the eye changes with age: it is less than normal in newborns, in old age it can decrease again (the so-called senile farsightedness or presbyopia).

Astigmatism due to the fact that, due to congenital features, the optical system of the eye (cornea and lens) refracts rays differently in different directions (along the horizontal or vertical meridian). In other words, the phenomenon of spherical aberration in these people is much more pronounced than usual (and it is not compensated by pupil constriction). So, if the curvature of the surface of the cornea in a vertical section is greater than in a horizontal one, the image on the retina will not be clear, regardless of the distance to the object.

The cornea will have, as it were, two main focuses: one for the vertical section, the other for the horizontal. Therefore, the rays of light passing through the astigmatic eye will be focused in different planes: if the horizontal lines of the object are focused on the retina, then the vertical lines are in front of it. Wearing cylindrical lenses, matched to the real defect in the optical system, to a certain extent compensates for this refractive error.

Nearsightedness and farsightedness due to changes in the length of the eyeball. With normal refraction, the distance between the cornea and the central fovea (yellow spot) is 24.4 mm. With myopia (nearsightedness), the longitudinal axis of the eye is more than 24.4 mm, so the rays from a distant object are focused not on the retina, but in front of it, in the vitreous body. To see clearly into the distance, it is necessary to place concave lenses in front of myopic eyes, which will push the focused image onto the retina. In a far-sighted eye, the longitudinal axis of the eye is shortened; less than 24.4 mm. Therefore, rays from a distant object are focused not on the retina, but behind it. This lack of refraction can be compensated by an accommodative effort, i.e. an increase in the convexity of the lens. Therefore, a far-sighted person strains the accommodative muscle, considering not only close, but also distant objects. When viewing close objects, the accommodative efforts of far-sighted people are insufficient. Therefore, for reading, farsighted people should wear glasses with biconvex lenses that enhance the refraction of light.

Refractive errors, in particular myopia and hyperopia, are also common among animals, for example, in horses; myopia is very often observed in sheep, especially cultivated breeds.

Skin receptors

• pain receptors.
• Pacinian corpuscles are encapsulated pressure receptors in a round multilayered capsule. They are located in the subcutaneous fat. They are fast-adapting (they react only at the moment of the beginning of the impact), that is, they register the force of pressure. They have large receptive fields, that is, they represent rough sensitivity.
• Meissner bodies are pressure receptors located in the dermis. They are a layered structure with a nerve ending passing between the layers. They are fast adapting. They have small receptive fields, that is, they represent a subtle sensitivity.
• Merkel discs are non-encapsulated pressure receptors. They are slowly adapting (they respond to the entire duration of exposure), that is, they record the duration of pressure. They have small receptive fields.
• Hair follicle receptors - respond to hair deflection.
• Ruffini's endings are stretch receptors. They are slowly adapting, have large receptive fields.

Basic functions of the skin: The protective function of the skin is the protection of the skin from mechanical external influences: pressure, bruises, tears, stretching, radiation exposure, chemical irritants; immune function of the skin. T-lymphocytes present in the skin recognize exogenous and endogenous antigens; Largenhans cells deliver antigens to the lymph nodes, where they are neutralized; Receptor function of the skin - the ability of the skin to perceive pain, tactile and temperature irritation; The thermoregulatory function of the skin lies in its ability to absorb and release heat; The metabolic function of the skin combines a group of private functions: secretory, excretory, resorption and respiratory activity. Resorption function - the ability of the skin to absorb various substances, including drugs; The secretory function is carried out by the sebaceous and sweat glands of the skin, which secrete lard and sweat, which, when mixed, form a thin film of water-fat emulsion on the surface of the skin; Respiratory function - the ability of the skin to absorb oxygen and release carbon dioxide, which increases with an increase in ambient temperature, during physical work, during digestion, and the development of inflammatory processes in the skin.

Skin structure

Causes of pain. Pain occurs when, firstly, the integrity of the protective integumentary membranes of the body (skin, mucous membranes) and internal cavities of the body (meninges, pleura, peritoneum, etc.) is violated, and, secondly, the oxygen regime of organs and tissues to a level that causes structural and functional damage.

Pain classification. There are two types of pain:

1. Somatic, arising from damage to the skin and the musculoskeletal system. Somatic pain is divided into superficial and deep. Superficial pain is called pain of skin origin, and if its source is localized in the muscles, bones and joints, it is called deep pain. Superficial pain is manifested in tingling, tingling. Deep pain, as a rule, is dull, poorly localized, has a tendency to radiate to surrounding structures, is accompanied by discomfort, nausea, severe sweating, and a drop in blood pressure.

2. Visceral, arising from damage to internal organs and having a similar picture with deep pain.

Projection and reflected pain. There are special types of pain - projection and reflected.

As an example projection pain you can cause a sharp blow to the ulnar nerve. Such a blow causes an unpleasant, hard to describe sensation that spreads to those parts of the hand that are innervated by this nerve. Their occurrence is based on the law of pain projection: no matter what part of the afferent pathway is irritated, pain is felt in the region of the receptors of this sensory pathway. One of the most common causes of projection pain is compression of the spinal nerves at their entry into the spinal cord as a result of damage to the intervertebral cartilage discs. Afferent impulses in nociceptive fibers in such a pathology cause pain sensations that are projected into the area associated with the injured spinal nerve. Projection (phantom) pain also includes pain that patients feel in the area of ​​the remote part of the limb.

Reflected pains pain sensations are called not in the internal organs, from which pain signals are received, but in certain parts of the skin surface (Zakharyin-Ged zones). So, with angina pectoris, in addition to pain in the region of the heart, pain is felt in the left arm and shoulder blade. Reflected pain differs from projection pain in that it is not caused by direct stimulation of nerve fibers, but by irritation of some receptive endings. The occurrence of these pains is due to the fact that the neurons that conduct pain impulses from the receptors of the affected organ and the receptors of the corresponding skin area converge on the same neuron of the spinothalamic pathway. Irritation of this neuron from the receptors of the affected organ, in accordance with the law of pain projection, leads to the fact that pain is also felt in the area of ​​skin receptors.

Anti-pain (antinociceptive) system. In the second half of the twentieth century, data were obtained on the existence of a physiological system that limits the conduction and perception of pain sensitivity. Its important component is the “gate control” of the spinal cord. It is carried out in the posterior columns by inhibitory neurons, which, through presynaptic inhibition, limit the transmission of pain impulses along the spinothalamic pathway.

A number of brain structures exert a downward activating effect on the inhibitory neurons of the spinal cord. These include the central gray matter, the raphe nuclei, the locus coeruleus, the lateral reticular nucleus, the paraventricular and preoptic nuclei of the hypothalamus. The somatosensory area of ​​the cortex integrates and controls the activity of the structures of the analgesic system. Violation of this function can cause unbearable pain.

The most important role in the mechanisms of the analgesic function of the CNS is played by the endogenous opiate system (opiate receptors and endogenous stimulants).

Endogenous stimulants of opiate receptors are enkephalins and endorphins. Some hormones, such as corticoliberin, can stimulate their formation. Endorphins act mainly through morphine receptors, which are especially abundant in the brain: in the central gray matter, raphe nuclei, and the middle thalamus. Enkephalins act through receptors located predominantly in the spinal cord.

Theories of pain. There are three theories of pain:

1.intensity theory . According to this theory, pain is not a specific feeling and does not have its own special receptors, but arises under the action of superstrong stimuli on the receptors of the five sense organs. Convergence and summation of impulses in the spinal cord and brain are involved in the formation of pain.

2.Specificity theory . According to this theory, pain is a specific (sixth) sense that has its own receptor apparatus, afferent pathways and brain structures that process pain information.

3.Modern theory pain is based primarily on the theory of specificity. The existence of specific pain receptors has been proven.

At the same time, in the modern theory of pain, the position on the role of central summation and convergence in the mechanisms of pain is used. The most important achievement in the development of modern pain theory is the study of the mechanisms of the central perception of pain and the analgesic system of the body.

Functions of proprioreceptors

Proprioreceptors include muscle spindles, tendon organs (or Golgi organs), and articular receptors (receptors for the articular capsule and articular ligaments). All these receptors are mechanoreceptors, the specific stimulus of which is their stretching.

muscle spindles human, are elongated formations several millimeters long, tenths of a millimeter wide, which are located in the thickness of the muscle. In different skeletal muscles, the number of spindles per 1 g of tissue varies from a few to hundreds.

Thus, muscle spindles, as sensors of the state of muscle strength and the rate of its stretching, respond to two influences: peripheral - a change in muscle length, and central - a change in the level of activation of gamma motor neurons. Therefore, the reactions of the spindles in the conditions of natural muscle activity are quite complex. When a passive muscle is stretched, activation of spindle receptors is observed; it causes the myotatic reflex, or stretch reflex. With active muscle contraction, a decrease in its length has a deactivating effect on the spindle receptors, and excitation of gamma motor neurons, accompanying excitation of alpha motor neurons, leads to reactivation of the receptors. As a result, the impulse from the spindle receptors during movement depends on the length of the muscle, the speed of its shortening and the force of contraction.

Tendon organs (Golgi receptors) of a person are located in the area of ​​\u200b\u200bconnection of muscle fibers with a tendon, sequentially with respect to muscle fibers.

The tendon organs are an elongated spindle-shaped or cylindrical structure, the length of which in humans can reach 1 mm. This primary sensory receptor. At rest, i.e. when the muscle is not contracted, background impulses come from the tendon organ. Under conditions of muscle contraction, the impulse frequency increases in direct proportion to the magnitude of muscle contraction, which makes it possible to consider the tendon organ as a source of information about the force developed by the muscle. At the same time, the tendon organ reacts poorly to muscle stretching.

As a result of the sequential attachment of the tendon organs to the muscle fibers (and in some cases to the muscle spindles), the tendon mechanoreceptors are stretched when the muscles are tense. Thus, unlike muscle spindles, tendon receptors inform the nerve centers about the degree of tension in the mouse, and the rate of its development.

Articular receptors they react to the position of the joint and to changes in the articular angle, thus participating in the feedback system from the motor apparatus and in controlling it. Articular receptors inform about the position of individual parts of the body in space and relative to each other. These receptors are free nerve endings or endings enclosed in a special capsule. Some articular receptors send information about the magnitude of the articular angle, i.e., about the position of the joint. Their impulsation continues throughout the entire period of conservation of a given angle. It is the greater the frequency, the greater the angle shift. Other articular receptors are excited only at the moment of movement in the joint, that is, they send information about the speed of movement. The frequency of their impulsation increases with an increase in the rate of change in the articular angle.

Conductor and cortical departments proprioceptive analyzer of mammals and humans. Information from muscle, tendon and joint receptors enters the spinal cord through the axons of the first afferent neurons located in the spinal ganglia, where it partially switches to alpha motor neurons or interneurons (for example, to Renshaw cells), and partially goes along ascending pathways to higher parts of the brain. In particular, along the Flexig and Gowers pathways, proprioceptive impulses are delivered to the cerebellum, and along the Gaulle and Burdach bundles, passing in the dorsal cords of the spinal cord, it reaches the neurons of the nuclei of the same name located in the medulla oblongata.

Axons of thalamic neurons (neurons of the third order) terminate in the cerebral cortex, mainly in the somatosensory cortex (postcentral gyrus) and in the region of the Sylvian sulcus (regions S-1 and S-2, respectively), and also partially in the motor ( prefrontal) area of ​​the cortex. This information is used by the motor systems of the brain quite widely, including for making a decision about the idea of ​​movement, as well as for its implementation. In addition, on the basis of proprioceptive information, a person forms ideas about the state of muscles and joints, as well as, in general, about the position of the body in space.

Signals coming from the receptors of muscle spindles, tendon organs, articular bags and tactile skin receptors are called kinesthetic, that is, informing about the movement of the body. Their participation in voluntary regulation of movements is different. Signals from articular receptors cause a noticeable reaction in the cerebral cortex and are well understood. Thanks to them, a person perceives differences in joint movements better than differences in the degree of muscle tension in static positions or weight maintenance. Signals from other proprioceptors, coming mainly to the cerebellum, provide unconscious regulation, subconscious control of movements and postures.

Thus, proprioceptive sensations enable a person to perceive changes in the position of individual parts of the body at rest and during movements. Information coming from proprioceptors allows him to constantly control the posture and accuracy of voluntary movements, dose the force of muscle contractions when counteracting external resistance, for example, when lifting or moving a load.

Sensory systems, their meaning and classification. Interaction of sensory systems.

To ensure the normal functioning of an organism*, the constancy of its internal environment, connection with the constantly changing external environment and adaptation to it are necessary. The body receives information about the state of the external and internal environments with the help of sensory systems that analyze (distinguish) this information, provide the formation of sensations and ideas, as well as specific forms of adaptive behavior.

The concept of sensory systems was formulated by I. P. Pavlov in the study of analyzers in 1909 during his study of higher nervous activity. Analyzer- a set of central and peripheral formations that perceive and analyze changes in the external and internal environments of the body. The concept of "sensory system", which appeared later, replaced the concept of "analyzer", including the mechanisms of regulation of its various departments with the help of direct and feedback connections. Along with this, there is still the concept of "sense organ" as a peripheral entity that perceives and partially analyzes environmental factors. The main part of the sense organ is receptors, equipped with auxiliary structures that provide optimal perception.

With the direct impact of various environmental factors with the participation of sensory systems in the body, there are Feel, which are reflections of the properties of objects of the objective world. The peculiarity of sensations is their modality, those. the totality of sensations provided by any one sensory system. Within each modality, according to the type (quality) of the sensory impression, different qualities can be distinguished, or valency. Modalities are, for example, sight, hearing, taste. Qualitative types of modality (valency) for vision are various colors, for taste - the sensation of sour, sweet, salty, bitter.

The activity of sensory systems is usually associated with the emergence of five senses - sight, hearing, taste, smell and touch, with the help of which the organism is connected with the external environment. However, in reality there are much more of them.

The classification of sensory systems can be based on various features: the nature of the acting stimulus, the nature of the sensations that arise, the level of sensitivity of receptors, the rate of adaptation, and much more.

The most significant is the classification of sensory systems, which is based on their purpose (role). In this regard, there are several types of sensory systems.

External sensor systems perceive and analyze changes in the external environment. This should include visual, auditory, olfactory, gustatory, tactile and temperature sensory systems, the excitation of which is perceived subjectively in the form of sensations.

Internal (visc