What receptors work when feeling. Medical Encyclopedia - Touch

04.10.2020

Human has five basic feelings: touch, vision, rumor, smelling and taste. Feeling authorities associated with each other send information to the brain to help us understand and. People also have other feelings in addition to the main five. That's how they work.

People have many feelings. But traditionally five senses of man are recognized as vision, rumor, taste, smell and touch. There is also the ability to detect other stimuli in addition to those governed by these most widely recognized feelings, and these sensory modalities include a temperature (thermal waste), a kinesthetic meaning (proprioceptation), pain (nociception), equilibrium, vibration (mehanorez fee) and various internal incentives (for example , different chemoreceptors to determine the concentration of salt and carbon dioxide In the blood, the feeling of hunger and the feeling of thirst).

By making these comments, let's see the main five senses of man:

Touch

The touch is considered the first sense that the person develops, according to the Stanford Encyclopedia. The touch consists of several different sensations transmitted by the brain through specialized neurons in the skin. Pressure, temperature, easy touch, vibration, pain and other sensations are part of the touch and all of them are attributed to various receptors on the skin.

Touch is not just the meaning used to interact with the world; It is also very important for the well-being of a person. For example, touch as a compassion of one person to another.

This feeling, thanks to which we distinguish various quality bodies: -Tell as warmly and cold, hardness and softness, roughness and smoothness.

Vision

Vision or perception of eyes is a complex process. First, the light is reflected from the object to the eye. The transparent outer layer of the eye, called the cornea, bends light passing through the pupil hole. Pupil (which is a color part of the eye) works like a camera shutter, narrows to skip less light or opens wider to let the more light.

The cornea focuses most of the world, and then the light passes through the lens that continues to focus the light.

Then the lens eye flexs the light and focus it on the retina, which is full of nerve cells. These cells have the shape of rods and cones and are named according to their forms. Cones translate light in colors, central vision and details. Wands also give people a vision when there is a limited light, for example, at night. The information translated from the light is sent in the form of electrical pulses to the brain through the visual nerve.

Hearing

The rumor works through a complex labyrinth, which is human ear. The sound is sent through the external ear and is supplied to the outer hearing pass. Then the sound waves reach the eardrum. This is a thin sheet of connective tissue, which vibrates when the sound waves reach it.

Vibrations move to the middle ear. There are vibrating hearing bones - three tiny bones, called Malleus (hammer), incus (anvil) and Stapes (stirrup).

People retain their feeling of equilibrium, because the Eustachius tube, or a pharyngotimic tube, in the middle ear lines the air pressure with atmospheric. The vestibular complex in the inner ear is also important for the balance, since it contains receptors that regulate the feeling of equilibrium. The inner ear is connected with the vestibular cooler nerve, which transmits sound and equilibrium information to the brain.

Smean

The smell by which we distinguish the smells, the various kinds of which transmit different impressions of the mind. Organs of animal and vegetable origin, as well as most other bodies, exposed to air, constantly send odors, as well as the state of life and growth, as in the state of fermentation and rotting. These Effluia, drawn in the nostrils along with air, are a means that allocate all the bodies.

According to researchers, people can feel more than 1 trillion fragrances. They make it with an olfactory slit, which is located in the upper part of the nasal cavity, next to the olfactory bulb and the hole. The endings in the olfactory cracks transmit smells into the brain.

In fact, poor sense of smell in people can be a symptom of health or aging. For example, a distorted or reduced sense of smell is a symptom of schizophrenia and depression. Old age can also reduce this ability. According to data published in 2006 by the National Institute of Health, more than 75 percent of people over 80 may have serious olfactory violations.

Taste

The taste is usually divided into perception of four different flavors: salted, sweet, sour and bitter. There may be many other tastes that have not yet been discovered. Also spicy, the taste is not.

The feeling of taste helps people check the food they eat. Bitter or sour taste indicates that the plant can be poisonous or rot. Something salty or sweet, however, often means that food is rich in nutrients.

The taste is felt in taste receptors. Adults have from 2000 to 4000 taste receptors. Most of them are in language, but they also pull the back of the throat, the nastestrian, the cavity of the nose and the esophagus.

This is a myth that language has special zones for each fragrance. Five tastes can be felt in all parts of the language, although the parties are more sensitive than the middle. About half of the sensory cells of taste receptors react to several of the five main tastes.

Cells are characterized by the sensitivity level. Each of them has a certain palette of flavors with fixed ranking, so some cells can be more sensitive to sweet, followed by bitter, acidic and salty. The full picture of taste is made only after all information from different parts of the language is combined.

In this picture, Pietro Poolini, each individual is one of the five senses of man.

Sixth sense of man

In addition to the traditional big five, there is another sixth sense of a person - a sense of space that concerns how the brain understands where your body is in space. This meaning is called proprice.

Propriocecia includes a sense of movement and position of our limbs and muscles. For example, proprioceptor allows a person to touch the tip of the nose, even closing his eyes. This allows a person to climb along the steps, without looking at each. People with poor proprice can be clumsy.

Researchers out National Institute Health (NIH) found that people who are particularly bad proprice, such as feeling when someone presses on your skin, (may have a mutated gene, which is transmitted from generation to generation) may not work, so their neurons cannot detect Movement of touches or limbs.

Feelings of people: List

Here is a list of other feelings of people relatively basic five feelings:

Pressure
Temperature
Thirst
Hunger
Direction
Time
Muscular tension
Propriocecia (ability to recognize your body in detail relative to other parts of the body)
The sense of balance (ability to keep the balance and sensation of the body movement in terms of acceleration and changes in the direction)
Tensile receptors (they are in places such as light, bladder, stomach, blood vessels, and gastrointestinal tract.)
Hemoreceptors (this is the trigger of the oblong brain in the brain, which is involved in blood detection. It also participates in reflex vote.)

Thin senses of man

There are thinner senses of a person who most people never perceive. For example, there are neurons sensors that perceive movement to control the balance and head slope. Specific kinesthetic receptors exist to detect stretching in muscles and tendons, helping people follow their limbs. Other receptors detect oxygen levels in certain blood flow arteries.

Sometimes people do not even perceive feelings equally. For example, people with synesthesia can see sounds like colors or associate certain views with odors.

Question 1. What are the receptors in the skin?

Tactile receptors are in the thicker of the skin.

Question 2. Touch is a complex feeling. List which receptors are working when feeling, for example, the surface of the table.

With the help of the skin, we feel cold and heat, pain, touch, pressure. Touching gives an idea of \u200b\u200bthe surface of the subject, its form, sizes, mass. When we touch the subject, keep it or feel, in the nervous endings of the skin, as well as muscle receptors and tendons arise arises. The excitation of nerves is transmitted to the brain - into the zone of the skin-muscular sensitivity of the parietal fraction of the cortex of large hemispheres of the brain. There are sensations of the mass of the subject, the state of its surface.

Question 3. Track the path of excitement from the evaluating receptors to the nearest zone of the large hemispheam bark.

In the walls of the upper shell of the nasal cavity is the sense of smell. It contains many olfactory cells and microwaves. When inhalation of air (smell) through the nose (nasal cavity), there is an excitation of nerve endings. On these nerves, the excitement goes to the bark of the brain. After that, there is a feeling of smell.

Question 4. Why is it dangerous to inhale chemicals?

Inhalation of unknown substances is dangerous. Some of them can cause a dangerous disease - toxicizing. Puffy substances are easily absorbed in the nasal cavity in the blood and poison the body. It is dangerous smells of drugs used in dry cleaning, in medicine (ether), and many other odorous substances. A sharp inhalation of ammonia alcohol can lead to a stopping of breathing and fainting.

Question 5. What safety techniques need to be applied by determining the smell of this or that substance?

It is necessary to correctly handle the odorous substances. It is impossible to bring vessels with them to the nose. It is necessary to wash your hand near the vessel, sending the jet of the air to the nose. This is enough to feel the smell.

Question 6. How do taste organ function?

The taste of food is a person perceives with special groups of taste cells with microvills, which are in the walls of the oral cavity. Especially many of them on the surface of the language; They are in special formations - taste nipples. The tip of the language perceives the sweet, the root is bitter, the sides - sour, edges and tip - salty. Mixed taste sensations arise with simultaneous irritation of various nerve endings. On nerves and nervous paths, the first impulses reach the taste area of \u200b\u200bthe cortex, where the analysis and recognition of flavoring substances occurs. Nervous endings irritate only substances dissolved in water. Dry food seems tasteless.

TOUCH (tACTUS.) - the process of perceiving actions of physical environmental factors using the skin receptors, musculoskeletal system (muscles, tendons, joints, fascia, etc.), as well as mucous membranes of some organs (lips, language, genital organs, etc.) . At the heart of O. lies the ability of various receptors to respond to touch, pressure, stretching, vibration (see Mechanoresceptors), heat or cold (see thermoreceptors), as well as pain irritants (see pain) with the subsequent transformation of incoming information in various departments c. n. with.

The feeling of O. arises as a result of the complex perception of various qualities of an irritant acting on this or that group of receptors. The perception of any environmental objects with O. allows you to evaluate their shape, dimensions, surface properties, consistency, temperature, dryness, or humidity, position and movement in space. The receptors involved in O. processes are distributed in the body unevenly. The person has them especially much on the skin surface of the fingers, palms, soles of legs, lips, genitals, which ensures these areas a high sensitivity to adequate irritation. The most common type of receptors associated with O. are free nervous endings (see). They are abundantly branched in the tissues, due to which one nervous fiber can innervate a large area (eg, in the tissues of the cornea, such an area reaches 0.5 cm 2). Innervation areas (receptive fields) of individual nerve fibers are usually significantly overlapped with each other. In the hair part of the skin, K-paradium is approx. 90% of the skin surface, the nerve endings are especially numerous around the root vagina of the hair (see the skin), as well as around special tactile hair - Vibribiss (they are absent in humans, but widespread among mammals, including primates).

The organs of O. include various types of more complex receptors, such as lamellar calves (Taurus Pacini), tactile calves (Taurus Maissener), Bulb-shaped Taurus (Taurus Golgji - Mats-Tsoni), End flasks (flabs Krause), etc. (rice . one).

Information from O. receptors comes by afferent conductors in C. n. p., Through the medial loop (lemnskaya path) and an extractive path to Talamus, and then in the somatosensory bark of large hemispheres. The combination of all structures c. n. with. and peripheral sensory elements associated with leather and mucous membranes, received the name of the skin analyzer.

Process O. may be passive and active. Passive O. arises under the influence of various stimuli acting on the surface of the body in the absence of active actions on the part of the body aimed at perceiving the properties of the existing object. The main perceiving function in such processes O. is performed by receptors located in the skin and mucous membranes. With an active O., a large role is played by various kinds of movement, aimed at the best perception of certain characteristics of the subject, for example, feeling the objects of the subjects. In the processes of active O., along with the information coming in C. n. with. From receptor devices of the skin analyzer, the signaling from the receptor of the support apparatus is of great importance - kinesthetic alarm system (see proprioceptors).

There are four main types of tactile sensations: tactile, thermal, cold and pain. At the same time, they believe that skin sensations are discrete, that is, they occur only in certain places. The sensitivity of these sections to the active irritant depends on the number of sensitive points and the density of their distribution in different parts of the body surface. With simultaneously irritation of two closely arranged skin sites, sensations can merge and the impression of only one tactile incentive arises. The smallest distance (in millimeters) between two adjacent skin points, with simultaneous irritation of the to-ry, there is a sense of action of two separate stimuli, the name of the space threshold. This indicator of tactile sensitivity is determined using a Weber Circle (a conventional circuit with movable bone legs) or an Esteziometer Zive-King (a variant of the cigl with thin, slightly blued legs, on a scale of the to-it is easy to determine the distance between the sections of the irritable skin surface). The thresholds of the space (Fig. 2) are minimal on the top of the tongue and the tips of the fingers (within 1 - 2 mm), and the maximum on the middle of the thigh and the back (s. 65 mm). Skin sites, within the limits of recent two simultaneous contacts are perceived as one, received the name of tactile wheels; This title is not exactly accurate, because Krugs Weber rarely have right shape: On the limbs, they are usually oval, stretched along the longitudinal axis, on other parts of the body of the outline may be far from the circle. Tactile sensitivity is also investigated by determining the absolute threshold, K-ry is characterized by the minimum power of the pressure causing the threshold feeling. The definition of the absolute threshold of sensitivity is most often done using Frey hairsset (having a different diameter having a different diameter). The larger the diameter of hairs, the greater the effort is necessary for its bend.

Other methods are used to evaluate tactile sensitivity, including more modern and more accurate electronically measuring devices (see Esthesiometry). The thresholds of the absolute tactile sensitivity of the person are minimal in the field of lips, nose, tongue, finger tips and maximal in the area of \u200b\u200bthe back, abdomen, soles of the foot. Thresholds of tactile sensitivity can be estimated and using dynamic irritation methods. In this case, the feeling occurs due to the excitation of more sensitive phase, fast-adaptable mechanoreceptors. Such characteristics can be expressed both in amplitudes and in the shifting speeds of the skin surface under the action of an irritant. Of particular interest is the vibration sensitivity (see), i.e., sensitivity to rhythmic dynamic effects. The greatest sensitivity to the action of such irritation in a person was found on the fingers of the hands, and the smallest - on the skin of the abdominal and butorous regions. The dependence of the thresholds from the area of \u200b\u200bvibration exposure is revealed. Mechanoreceptors located in more superficial layers of skin and mucous membranes ensure the perception of low-frequency stimuli (about 0.5-50 Hz) y and deeply located allow the body to perceive high-frequency incentives (up to 1000-1200 Hz). The minimum thresholds of perception of vibration stimuli lie in the range from 200 to 450 Hz (Fig. 3). For finger tips, threshold shifts at these frequencies can reach 10 -4 -10 -5 mm, which is well consistent with the experiments on single-dimensional lamellar calves isolated from the body, which are the most sensitive mechanoreceptors of the skin. An important criterion for evaluating O. is the differential threshold of Mechanorezpp. Another 19 century The presence of a quantitative relationship between the change in the impact value and its feeling was established (see): an increase in the irritation force in geometric progression causes an increase in the degree of sensation in arithmetic progression (Weber's law - fechner). Despite a number of clarifications, this law is generally preserved its value. The thresholds of tactile sensitivity of the skin do not remain constant, they vary depending on the stretching of the skin, peripheral influences from the excited mechanoreceptors of the surrounding sites in the type of axon reflexes and humorally, as well as from the effects of sympathetic nervous system. Recipers of the musculoskeletal system involved in O. are under constant centrifugal control by gamma-effecting fibers governing the sensitivity of muscle receptors.

Memo-sensitive points on the surface of the body are unevenly located. Their most on the face, especially on the lips and centuries. The heat points are significantly less than cold, and in a number of areas, for example, on the periphery of the cornea and the conjunctiva of the eyes, they are completely absent. The study of the response time to temperature effects, as well as the thermal conductivity of the skin showed that the thermal points are locked at the depth of approx. 0.3 mm, and cold - more superficially, at a depth of approx. 0.15 mm. What kind of receptors are perceived temperature incentives, it is not completely installed. Some researchers believe that there are specific thermal and cold receptors, others involve the presence of single thermistors causing, depending on the irritation conditions, the feeling of the cold, the feeling of heat. The concept is actively developing, according to the swarm of specific thermistors at all, and there are only different types of mechanoreceptors in the skin, which are excited during deformations under the action of the temperatures of their environmental structures (for example, the collagen of the skin or contract elements). With the help of psychophysical experiments, it was found that the ability to feel the temperature depends on the absolute intradermal temperature, the speed of its change, as well as the place of irritation. At the same time, the threshold of the feeling of the cold is higher than the thermoreceptor excitation threshold, i.e., part of the afferent impulsation from thermistors is a porch for nerve centers. It is believed that an absolute temperature of the temperature is believed to be an adequate stimulus for thermistors, and not a temporary or spatial temperature gradient.

The question of the mechanisms of perception of pain (nociceptive) stimuli is the least designed. According to one of the two main hypotheses about the mechanism of pain perception, the nociceptive impact activates specific pain receptors, which include free nervous endings with a high instance threshold. The followers of another hypothesis denied the existence of specific pain receptors and believe that the pain is the result of the summation in C. n. with. Excitation streams arising from intensive irritation of ordinary skin receptors (see leather).

There is also a single theory explaining the processes of O. to explain the skin sensitivity several hypotheses are proposed. At the heart of one of them is the representation of I. Muller on the specific energy and the existence of specific receptors that perceive some one, a certain type of irritation. In this case, all skin receptors are divided into four main types (tactile, thermal, cold and pain), differing in structure and bonds with relevant central neurons. It has been established that a series of receptors O. has a lot of specificity; For example, lamellar and tactile calves, tactile menisci (Merkel discs) are highly specialized mechanoreceptors. At the same time, it is obvious that other receptors (eg, free nervous endings) can perceive the most different stimuli. So, R. L. Gavrilov et al. It is shown that irritation of the same temperature point of the skin is strictly focused ultrasound beam can cause a feeling of cold in some cases, and in others - the feeling of heat. There are other facts that contradict the hypothesis of specificity. At the same time, although in its original form, this hypothesis cannot be recognized as satisfactory, in various modifications in a number of researchers, it continues to be popular.

The hypothesis of the dual perception of the city of Ging is less common, there are two types of skin sensitivity, due to the existence on the periphery of two different sensory systems: general, generalized (protopa-ticked), and specialized (egacritical). In the process of regeneration of the convertible sensitive nerve, protopathic sensitivity is first restored (pain, coarse temperature), and then epicritical (tactile, thin temperature). Later it was found that there are at least two independent afferent pathways from the skin to the Talamus: one associated with lateral spinctalamic structures and (possibly) by reticular formation, and the other with the structures included in the rear pilots of the white substance and medial loops. The prescription fields of the first system (it provides the prototect-tichetic sensitivity) is very large and sometimes covered by the whole body and are often non-specific. Recipe fields of neurons of the second system (Eichritic) are small and have significant specificity in relation to the stimulus.

The third hypothesis that received the name of the theory of images is based on the assumption that the differential skin sensitivity is due to differences in the action of incentives of different modality on the same afferent structures, that is, that the spatial and temporal distribution of nerve impulses lie in the population Afferent fibers associated with nervous endings (they can be individually similar). The known differences in the structure of receptor structures and the various velocities of nerve pulses according to afferent nerve fibers only contribute to the dispersion of pulse activity on its path in C. n. With. where there is a decoding of the entered pulse flow: in the end, this or that feeling appears. It should be borne in mind that with all the value this hypothesis that deny any specificity of peripheral devices (O. receptors) is unlikely to be recognized as satisfactory.

With the help of O. The body can a certain extent to compensate for the absence of other senses (vision, hearing) in case of damage or underdevelopment. In the early stages of the lives of malicious animals O. plays a leading role in the processes of their interaction with the surrounding world. O. serves as an important additional channel of obtaining information in various kinds of complex situations (eg, at the pilots at the moments of overloads of visual and auditory sensory systems). O. O. is extremely important and especially depleting (see Peproklukhonemot). After appropriate learning and training, using O., blind can read books written by a special convex font, write, perform various thin hand work. O. Allows it to navigate in space: Using simple tools, such as ordinary stick, and more complex devices (various types of vibration equipment, etc.), they are based on O. can be a fairly accurate idea of \u200b\u200bthe position of the surrounding items and move among them. At the blind people, O. can achieve emergency acute - they increase the sensitivity of the hands, especially the fingertips. Morphologically, this is reflected in the increase in the number of receptors, in particular the encapsulated - type of plate taurus, determining the thresholds of tactile perception. People deprived of sight and hearing, O. is the main source of environmental information. With sufficient training, such people can even take music and speech. In this case, the perception is carried out primarily with the help of high-adult mechanoreceptors, very sensitive to the action of vibratory stimuli.

Pathology

The pathology of O. is very diverse, which is determined by the pathology of the pathol, processes affecting the structures involved in the implementation of the feeling of O. In the clinic, various types of skin and muscle sensitivity are usually investigated in parallel and the assessment of their state is an important diagnostic reception. First of all, the ability of perception as such and the ability to determine the intensity of irritation is estimated. There may be a complete disappearance of a particular type of sensation (anesthesia), an increase in thresholds (hy-pixes) or a decrease in their (hyperesthesia). Local changes O. indicate peripheral disorders: with lesions in the area of \u200b\u200brear horns of the spinal cord, segmental disorders are noted, and damage to the spinal cord paths cause changes in the entire body damage to the body. The nature of the lesion is of great importance. Thus, with one-sided damage to the spinal cord, paralysis of brown-seccara arises (see Brown-Secary Syndrome). At the same time, paralysis of the limbs and impaired muscle sensitivity, and the disappearance of tactile sensitivity is observed on the ipsilateral side. This is explained by the fact that the fibers that determine the tactile sensitivity in the spinal cord are crossed out, and fibers that provide deep sensitivity and movement are not crossed. For patol, processes associated with Siringomysel (see), characterized by selective change in different types of O. Initially, the feelings of pain, heat and cold fall out. Tactile sensitivity or persisted, or decreases, but to a lesser extent compared to nociceptive and temperature sensitivity. Sensitivity disorder Sirningomy segmental, although often goes beyond the boundaries of a segment. Sensitivity disorders depending on the localization and the spread of the defeat are both on the one hand and both (in these cases they are usually asymmetrical). With such pathology, as lepring (see), painful sensitivity drops down while maintaining tactile, which is due to the selective lesion of peripheral fibers that ensure the conduct of nociceptive alarm. In Wedge, the practice of space, temporal thresholds and the ability to complex solves, based on the feeling of O.

In the latter case, an incorrect estimate of the size of the subject (macro and microesthesia) and other disorders may occur.

Recovery O. serves as an objective indicator of regeneration processes in nervous trunks and compensatory phenomena in c. n. with. Change O. may be an important diagnostic method for assessing the state of various internal organs. The areas of the skin, the signals from this or that domestic body are "projected", the names of Zakharin zones are obtained (see Zakharin - Ging Zone). The pain arising into such remote areas from the affected pathol, the process of organs, is called reflected. Obtaining various kinds of exposure (massage, pressure, injections, heating, etc.) on the active points of the skin surface and the tissue to be tissue can be affected with heat. The goal of the pathol, phenomena in the internal organs (see reflexology). This is based on acupuncture (see acupuncture). The latter mechanisms are still not clear enough.

Bibliography: Gavrilov R. L. and others. Reception and focused ultrasound, L., 1976; Granite R. Electrophysiolo-Great Research Reception, Per. from English, M., 1957; E with a to about in A.I.I.I. M. Neurophysiological basis of tactile perception, M., 1971; Physiology of sensory systems, ed. A. S. Batuev, L., 1976; Physiology of sensory systems, ed. V.N. Chernigov, part 3, L., 1975; Hensel H. Allgemeine Sinnesphysiologie, Hautsinne, Geschmack, Geruch, B., 1966; Sinclair D. G. Cutaneous Sensation, L., 1967.

O. B. Ilinsky.

What bodies of invertebrate animals perform the functions of touch and smell?

In which zones of the cerebral cortex are processed by signals from the bodies of the taste?

Tangible cells, tentacles, cutting cells, etc.

In temporal

1. What receptors are in the skin?

Tactile receptors are in the thicker of the skin.

2. Touch is a complex feeling. List which receptors are working when feeling, for example, the surface of the table.

3. Make the path of excitement from the evaluating receptors to the nearest zone of the cortex of large hemispheres.

4. Why dangerously inhale chemicals?

5. What safety techniques need to be applied by determining the smell of a substance or another?

6. How do taste organ function?

The touch is a complex sensation that occurs when irritating the skin receptors, the outer surfaces of the mucous membranes and the muscular-articular apparatus. The main place in the formation of the touch belongs to the skin analyzer, which performs the perception of external mechanical, temperature, chemical, and other skin irritations.

The touch, being the most ancient form of sensation, consists of tactile, temperature, pain and motor sensations.

The main role in touch belongs tactile sensations - touch and pressure. (see) Touching the skin is a tree-shaped branched free ending of nerve fibers, the final sprigs of which penetrate between the connecting and epithelial cells, whining the outdoor root vagina of the hair. The oscillation of the long outer part of the hair is transmitted to the root part and causes the excitation of nerve fibers. With an increase in the intensity of touch, a sense of pressure be felt. This means that muscle receptors are affected, and tendons. One nervous fiber, branched, can approach 300 skin receptors. The touch is divided into active and passive. The active touch is manifested in the active actions of the body contributing to the more complete perception of the subject (a person manifests itself in manipulating the subject and feeling it). Passive touch occurs at a simple action of the stimulus on the skin and is not accompanied by specific reactions of the body, usually directed to the refinement of the nature of the irritant itself.

The touch is a complex sensation arising from irritation of the skin, the outer surface of the mucous membranes and muscles. This sensation is a consequence of the complex work of nervous structures that receive information from skin exteroranceceptors, mucous membranes and kinesthetic muscle receptors and joints.

The main place in the formation of tanging occupies a skin analyzer, which carries out the exterocepture mechanical, thermal, chemical and other irritations falling on the skin. Receptors (see), which perceive the effects on the body of the external environment factors are called exteroceptors (exteroraceptors). The function of the skin analyzer is carried out with the participation of the lemnsk and spinatelastic CNS systems. The first is the nerve fibers carrying tactile information from the skin through the dorsal pillars of the spinal cord to the gentle and wedge-shaped; The cores of the oblong brain. Through the system of media lemnyskov, they reach Ventro-basal nuclei of the Talamus. The spinctalamatic system mainly performs the temperature and painful information through the front-winding poles of the spinal cord into medial crankshafts, i.e., dorsalier than the Ventro-basal complex of Talamus. The spinatelamic system, in contrast to the lemnskaya, modally less specific: 60% of its cells at the level of the thalamus react to tactile, nociceptive and sound irritations. In the crust of large semi-guns, the skin analyzer is represented by two somatosensory zones. The first zone is located in a post-central urinet; Fibers come here from Ventro-basal cores of Talamus. The second somatosensory zone is located in the front ectosylviyeville. An important part of the skin analyzer is the efferent pathways coming from a presenter, post-central convulsion and the posterior dark area of \u200b\u200bthe bark to the wedge-shaped and gentle nuclei; These paths are one of the mechanisms of sensory feedback.

The feeling of touching the feelings of touch and pressure, heat and cold, pain, itching and other mixed sensations are distinguished. The touch of light touch and pressure is a consequence of alarm in the central nervous system with tactile skin receptors that occupy the main place in touching. Specific irritants of tactile receptors serve mechanical effects in a wide range of intensities - from light touch to pressure. The most superficially, in the epidermal layer of the skin, there are mighty-free free nerve endings responsible for the perception of light touch. Located deeper in the skin around the hair bags thick nerve plexuses are tactile receptors that also have a high sensitivity to light touch and flexion of the hairs (deviation of the hairs on the back of the brush in a person only 5 ° leads to the occurrence of a pulse in a single afferent fiber and the corresponding sensation touch). Animals are most sensitive to special tactile hairs - Vibrisians located on a special lump of leather on the upper lip, on the wrist of the front paws. Vibrisians perceive the most minor air fluctuations and allow animals (cats, mice, etc.) to navigate in complete darkness. The skin also contains a large number of specialized tactile receptors (Pacin and Maissener Taurus, Merkel discs, etc.).

According to Dogel (1900), in the human skin there is at least 14 different types of nerve endings.

Initially, the touch was studied by a psychophysical method - by measuring human sensations. Blike (M. BLIX), Frey (M. Frey) and Goldewer (A. Goldscheider) found that the touch is unevenly distributed on the surface of the skin in which highly sensitive points can be isolated, perceive a certain type of irritation. Irritation of such points has always led to the emergence of the same sensation. So, the annoyance of the "cold" point of the skin caused a feeling of cold, regardless of the quality of irritation. Tactile points, heat and cold points and even pain were found, although the existence of the latter is questioned. At different parts of the body contains a different number of sensor points. So, on the smoking of the fingers, their number is so great that is not calculating: 1 cm 2 leather elevations thumb Hands are more than 100; On the wrist - 40, in the middle of the forearm - 15; On the shin - 7-10. The density of the location of the points in this section of the skin underlies the distinctive ability of the touch. The number of points on a specific area of \u200b\u200bthe skin may vary depending on the functional state of the body and under the influence of the external environmental factors (functional mobility, according to P. G. Reminted).

Skin sites, within which two simultaneous touch are perceived as one, are called tangible Weber circles. The boundary of the tactile circle is the minimum distance on which two touches are felt separately. These borders (they are measured using the Weber Circle) are: at the tip of the language - 1.1 mm, at the ends of the fingers - 2.2, on the cheek - 11.2, on the top of the back - 53, on the thigh and the rear of the neck - 67.5 mm. The definition of the toual sharpness (also a Weber Circle) shows the spatially distinguishable skin ability - the so-called difference threshold of tactile sensitivity. The touch of touch is also characterized by an absolute threshold of tactile sensitivity, i.e., the minimum power of the pressure that causes the feeling. To measure this last magnitude, a set of hairs of different diameters is used (Freya's hairs, a Ryazanov apparatus). Absolute thresholds of tactile sensitivity for a person are closely coincided with difference thresholds and make up (in grams-millimeters) at the tongue tick - 2, on the tips of the fingers - 3, on the palm surface of the forearm - 8, on the caviar of the legs - 15, on the back surface of the forearm - 35 At the lower back - 48, on the sole of the legs - 250. Finally, to determine the skin's ability to distinguish between two consecutive touches to the same point of the skin, the time threshold of tactile sensitivity is served. Its value coincides with the values \u200b\u200bof the above thresholds. The highest sensitivity is marked on the tips of the fingers and the language.

Careful study of tanging with electrophysiological methods showed that the innervation of tactile receptors is carried out, as a rule, thick nerve fibers with a high speed (group A - alpha-, beta and delta fiber) and the fibers of the S. Group, tactile receptors are anatomically interrelated and form a receptive field innervated by separate nervous fiber. Receive fields can overlap. On the distal parts of the body, they have an elongated form in length; The sizes range them from a frog from 2 to 105 mm 2 and in a cat from 3 to 185 mm 2. Each receptive field contains from 2 to 29 individual receptors. The center of the field is usually the most sensitive point; The removal from the center is only 1 mm leads to a drop in the sensitivity. In the process of perception of an adequate stimulus, tactile receptors interact with each other, which contributes to the emphasis of the spatial contrast.

For the excitation of receptors, a certain deformation rate is needed, called the critical steepness displacement of the stimulus. It fluctuates for receptors of different skin areas from 0.8 to 40 mm / s. The perception and differentiation of different forms of touch are associated with the existence of quickly adaptable and slowly adaptable receptors.

Touch of heat and cold is carried out with the participation of specialized thermal and cold receptors. For each of these receptor groups, there are its own sensitimity. For cold sensitivity, it lies in the region of 28 - 38 °. The optimum sensitivity of thermal receptors is shifted towards more high temperatures (35 - 43 °). The innervation of temperature receptors is carried out, as a rule, delta fibers (group A) and the Fibers of the S. Group S. The density of the temperature receptors of non-etinakov on different areas of the skin: the largest on the face, especially on eyelids and lips, the smallest on the soles of the legs. The average depth of occurring in the skin of cold receptors is 0.17 mm, heat - 0.3 mm. Cold receptors in the skin are much larger than thermal.

There is a significant group of tactive-temperature receptors that react to both mechanical and temperature irritation (cold). It is possible that the excitation of these receptors serves as the physiological basis of the so-called Weber illusion: the chilled object seems heavier. The morphophysiological basis of pain and itching is not yet sufficiently clarified.

According to Frey, each type of skin sensitivity corresponds to certain specific receptors in the skin. However, a wide variety of these receptors, which is superior to the number of different forms of touch, makes it difficult to compare these sensations with certain structures of skin receptors. In addition, the existence of double-specific receptors shows that the perception of various irritations can be associated with different types of activity of the same receptor structures (from here, for example, the different frequency of nerve impulses in response to the action of certain irritants).

Based on these and other data, Weddell and Sinclair (G. Weddell, D. Sinclair), the hypothesis of the "discharge sample" was put forward, according to which each type of skin sensitivity corresponds to a certain character of the discharge of pulses in the nervous fiber extending from the skin receptors. However, these performances need further experimental verification, as the pulses transmitted from receptors in the brain can slow down or intensify throughout the touch path, interact with pulses coming from other receptors, etc. Great importance in the formation of sensations with Skin has a reticular formation (see) brain barrel, which is able to regulate the passage of afferent pulses into the highest sections of the central nervous system and facilitate the evoked answers in the cerebral cortex. A significant role in the regulation of the activity of skin receptors is played by a sympathetic nervous system.

Touching is active, accompanied by the actions of the body (feeling, manipulation with the subject), and passive. In the process of labor, the instrumental touch (touch of the subject through a labor instrument is acquired: hammer, forceps, etc.); The main role in this type of touch is played by the recipes of muscles and joints. With loss of vision, the touch becomes the main way to know the world.

Touch disorders - see sensitivity.