Sensitivity is one of the phylogenetically ancient functions nervous system. In the process of evolution, it arose as a means of adequate contact of the organism with the environment, as the basis of the feedback mechanism. The sense organs provide the perception of stimuli, the conduction and processing of information that comes from the environment, all organs and tissues of the body. Signal processing is carried out with the help of various nerve formations. Part of the information that is perceived by our senses is transformed into a sensation, an awareness of the really existing external world. Another part of the nerve impulses that for the most part come from normally functioning internal organs, although they are perceived by the brain, but by a certain time they are not recognized by a person. All perceptions of the influence of the environment and the internal environment in physiology are commonly referred to as "reception".
Sensitivity is part of the broad concept of reception; sensitivity includes only that part of the reception that is perceived by the receptors and is realized by the cortex.
All nervous elements that provide the perception, conduction and processing of information belong to sensory systems (from Latin sensus - sensation) or to the system of analyzers according to I.P. Pavlov. They perceive and process stimuli of different modality.
The analyzer is a functional system, which includes receptors, afferent pathways and the corresponding area of the cerebral cortex.
The cortical end of the analyzer is the primary projection zones of the cortex, for which the characteristic somatotopic principle of structure is characteristic. The analyzer provides perception, conduction and processing of the same type of nerve impulses.
Analyzers are divided into two subgroups: external, or exteroceptive, and internal, or interoceptive.
External analyzers analyze information about the state and changes that occur in the environment. These include visual, auditory, olfactory, gustatory and analyzer of superficial types of sensitivity. Internal analyzers process information about changes in the internal environment of the body, for example, the state of the cardiovascular system, alimentary canal and other organs. The internal analyzers include a motor analyzer, thanks to which the brain constantly receives signals about the state of the muscular-articular apparatus. It plays an important role in the mechanisms of regulation of movements.
Receptors are specialized peripheral sensory formations that can perceive any changes inside the body, as well as on the outer surface of the body, and transmit these irritations in the form of nerve impulses. In other words, receptors are capable of converting one form of energy into another without twisting the information content. Irritants of the environment or internal environment, transforming into a nervous process, enter the brain in the form of nerve impulses.
According to the location, as well as depending on the functional characteristics, the receptors are divided into extero-, proprio- and interoreceptors.
Exteroreceptors are divided into contact receptors, which perceive irritations during direct contact with it (pain, temperature, tactile, etc.), and distant receptors, which perceive irritations from distant sources (sound, light).
Proprioreceptors perceive irritation that occurs in deep tissues (muscles, periosteum, tendons, ligaments, articular surfaces) and carry information about muscle tone, the position of the body and its parts in space, and the volume of voluntary movements. This determined the name "muscle-articular feeling", or "sense of position and movement (kinesthetic sensation)". Proprioreceptors also include labyrinth receptors, which provide the body with information regarding the position and movements of the head.
Interoreceptors perceive a variety of irritations from internal organs and blood vessels. Their main role is to ensure that information about changes in the internal state of the body enters the central nervous system. Most interoreceptors are polymodal. They respond to chemical (chemoreceptors) and mechanical stimuli (baroreceptors), temperature changes (thermoreceptors), pain (nocireceptors) and are related to the autonomic (vegetative) nervous system.
Each type of receptor reacts only to its specific type of stimulation. Due to this specialization of receptors, a primary analysis of external stimuli is carried out at the level of peripheral endings of afferent nerve fibers.
The greatest number of receptors is localized in the skin. There are mechanoreceptors (react to touch, pressure), thermoreceptors (perceive cold, heat) and nocireceptors (perceive pain).
Skin receptors include free nerve endings of sensory nerves and encapsulated terminal formations. The simplest in structure are the free nerve endings of the dendrites of sensory neurons. They are located between the epidermal cells and perceive pain stimuli. The tactile bodies of Merkel and Meissner respond to touch. Pressure and vibration are perceived by Vater-Pacini lamellar bodies. Krause's flasks are cold receptors, and Ruffini's bodies are heat receptors.
Receptors are also located in deeper tissues: muscles, tendons, joints. The most important of the muscle receptors are the neuromuscular spindles. They respond to passive stretching of the muscles and are responsible for the implementation of the stretch reflex, or myotatic reflex. There are Golgi receptors in the tendons, which also respond to stretch, but their sensitivity threshold is higher. Special receptors in the body that perceive pleasure are benereceptors.
The receptors of the visual and auditory analyzers, which are concentrated in the retina and in the inner ear, have the most complex structure. The complex morphological structure of these receptors affects their function: for example, retinal ganglion cells respond to electromagnetic radiation of a certain frequency spectrum, auditory - to mechanical vibrations of the air. However, this specificity is relative. The sensation of light occurs not only when a quantum of electromagnetic radiation enters the eye, but also in the case of mechanical irritation of the eye.
Thus, at the level of the receptor, the primary processing of information is carried out, which consists in recognizing the modality of the stimulus. This processing ends with the formation of nerve impulses, which, with a certain frequency, enter the higher parts of the central nervous system.
The impulses that arise in the receptor apparatus are carried to the nerve centers by sensitive fibers at different speeds. The German anatomist Gasser (J. Gasseri, 18th century) divided sensory fibers into three groups depending on structural and functional features: covered with a thick layer of myelin, thin and non-myelinated. The speed of nerve impulse conduction by these three groups of fibers is not the same. Fibers with a thick myelin sheath, or group A fibers, conduct an impulse at a speed of 40-60 m per 1 s; fibers with a thin myelin sheath, or group B fibers, at a speed of 10-15 m per 1 s; unmyelinated, or C-fibers, - at a speed of 0.5-1.5 m per 1 s.
Group A fibers with a high speed of impulse conduction are conductors of tactile and deep sensitivity.
Group B fibers average speed impulse conduction are conductors of localized pain and tactile sensitivity.
Group C fibers, which slowly conduct impulses, are conductors of pain sensitivity, predominantly diffuse, non-localized.
sensitivity classification. There are general (simple) and complex sensitivity. General sensitivity, taking into account the localization of receptors, is divided into exteroceptive, or superficial (skin and mucous membranes), proprioceptive, or deep (muscles, connections, joints), and interoceptive (internal organs).
To exteroceptive, or superficial, sensitivity include pain, temperature (heat and cold) and tactile. Proprioceptive sensitivity includes the sensation of passive and active movements (muscle-articular sensation), vibrational sensation, pressure and mass sensation, kinesthetic sensation - determining the direction of movement of the skin fold. General, or simple, sensitivity is directly related to the function of individual receptors, analyzers.
Complex types of sensitivity are due to the combined activity of different types of receptors and cortical sections of analyzers: a sense of localization of the injection, with the help of which the location of the applied irritation is determined; stereognosis - the ability to recognize objects by touching them; two-dimensional-spatial sensation - the patient recognizes, with his eyes closed, which figure, number or letter is written on the skin; discrimination - the ability to perceive separately two simultaneously applied irritations at close range. Complex types of sensitivity do not have separate analyzers, they are carried out by general types of sensitivity.
Interoceptive is called sensitivity, which occurs in case of irritation of the internal organs, the walls of blood vessels. As already noted, under normal conditions, impulses from the internal organs are practically not realized. During the irrigation of the interoreceptors, pain of varying intensity and a feeling of discomfort occur.
Sensory systems in the process of evolution experience an improvement that predetermines the emergence of a special sensation: sight, hearing, smell, taste, touch.
In the clinic, another classification has become widespread, which is based on biogenetic data. In accordance with these ideas and, distinguish between protopathic and epicritical sensitivity.
Protopathic sensitivity is phylogenetically older. It serves to perceive and conduct strong nociceptive stimuli that can cause tissue destruction or threaten the life of the organism. These irritations are mostly non-localized and cause a general generalized reaction. The center of protopathic sensitivity is the thalamus. Therefore, this system also has the name of vital, nociceptive, thalamic, unmitigated feeling.
Epicritical sensitivity is a phylogenetically new kind of sensitivity. It provides a fine quantitative and qualitative differentiation of irritations, their localization, which allows the body to accurately navigate in the environment, to adequately respond to irritation. Epicritical sensitivity is caused by sensations that arise in the cerebral cortex. It is in it that subjective sensations of pain are formed. Therefore, this system of sensitivity is called epicritical, cortical, gnostic, it is able to soften the sensation of pain.
Depending on the source of stimuli acting on the receptors, sensations are divided into three groups. Each of these groups, in turn, consists of various specific sensations (Fig. 5.7).
Rice. 5.7.
- Exteroceptive sensationsreflect the properties of objects and phenomena of the external environment (“five senses”). These include visual, auditory, taste, temperature and tactile sensations. In fact, there are more than five receptors that provide these sensations, and the so-called "sixth sense" has nothing to do with it.
For example, visual sensations arise when excited sticks (“twilight, black and white vision”) and cones ("daylight, color vision").
Temperature sensations in a person occur with separate excitationcold and heat receptors.Tactile sensations reflect the impact on the surface of the body, and they occur when excited or sensitivetouch receptorsin the upper layer of the skin, or with a stronger effect onpressure receptorsin the deep layers of the skin. - Interoreceptivesensations reflect the state of internal organs. These include sensations of pain, hunger, thirst, nausea, suffocation, etc. Painful sensations signal damage and irritation of human organs, are a kind of manifestation of the protective functions of the body. Intensity pain It can be different, reaching in some cases great strength, which can even lead to the onset of a state of shock.
- proprioceptive sensations(musculoskeletal). These are sensations that reflect the position and movement of our body. With the help of muscle-motor sensations, a person receives information about the position of the body in space, about the relative positionof all its parts, about the movement of the body and its parts, about the contraction, stretching and relaxation of muscles, the state of joints and ligaments, etc. Musculoskeletal sensations are complex. Simultaneous stimulation of receptors of different quality gives sensations of a peculiar quality:
- irritation of receptor endings in the muscles creates a feeling of muscle tone when performing a movement;
- sensations of muscle tension and effort are associated with irritation of the nerve endings of the tendons;
- irritation of the receptors of the articular surfaces gives a sense of direction, shape and speed of movement.
- To the same group of sensations, many authors include the sensations of balance and acceleration, which arise as a result of excitation of the receptors of the vestibular analyzer.
There are two kinds of nerve endings in the muscles: centrifugal, or motor, through which nerve impulses descend from the brain into the muscles, and centripetal, or sensitive, which send signals to the brain about the movement made by the muscles. These sensitive nerve endings in the muscles and are receptors for muscle sensations. It is believed that from 1/3 to 1/2 of all fibers in the nerve connecting the spinal cord to the muscle are sensitive, or centripetal. Considering the huge number of all human muscles, one can imagine a huge number of muscle receptors. These receptors are found not only in muscle tissue, but also in tendons, in capsules of muscles and tendons, etc. Therefore, the receptors of the entire motor apparatus are called muscular-articular. These receptors are diverse in their structure. In muscle tissue there are so-called Ruffini endings, in tendons - Golgi apparatuses, in muscle capsules and tendons - Golgi bodies - Mazzoni, etc.
Muscle-articular receptors are divided into groups of fusiform and tendon, as well as connective. Fusiform endings are found among the striated muscles. Each such "spindle" has its own shell, its own blood and lymphatic vessels. Several nerve fibers branch within this "spindle", forming complex spirals, rings and flower-like branches. Human muscles are predominantly characterized by these flower-like branches.
The size of the spindle-shaped endings is different in different muscles
8 Ibid., pp. 433-434.
20 B. G. Ananiev
muscles (from 0.05 to 13.0 mm). These endings are most numerous in the limbs, especially their extreme parts (fingers, hands and feet). In the muscles there are muscle receptors of a different structure (naked nerve endings scattered between muscle and tendon fibers, pain receptors in connective tissue formations). -x there are special receptors - spindle-shaped formations (up to 1.5 mm in length), most often located at the junction of muscles and tendons. Muscular-articular receptors arise during excitation and muscle contractions. Their "irritant is therefore the movement of one or another part of the body. .
When moving any part of the body, there is movement in the joint: moving the articular surfaces one relative to the other, changing the tension of the ligaments, tendons, passive tension of the muscles. During movements, the general tone, or muscle tension, changes, which is a state of incomplete contraction or muscle tension, not accompanied by fatigue. Therefore, a change in the tone of certain muscles and associated tendons is a specific stimulus for muscle-articular sensations. changes are transmitted along the sensory (or afferent) pathways to the spinal cord, and the final station for receiving these tonic impulses is the cerebral cortex.
Muscular-articular receptors are irritated by tonic changes mainly in a mechanical way. Their work is closest to the work of skin-mechanical receptors, with the difference that the latter are irritated by the mechanical properties of muscles and joints (especially the elastic properties of muscle tissue).
With certain tonic changes, a change in the skin occurs. Consequently, the general state of the tone of the muscular apparatus of a given part of the body is also reflected in the general state of the skin-mechanical receptors.
Both this fact and the close proximity of the paths of the tactile and musculo-articular sensory nerves testify to the commonality of tactile and musculo-articular receptors in terms of their sources and nature.
Conductors (muscular-articular sensory nerves)
To the intervertebral nodes, the paths of the skin and musculo-articular sensory nerves go together without separating. Fibers of the muscle-articular sensory nerves proper
BOBs originate in the cells of the intervertebral nodes. The central cells of these nodes are sent to the spinal cord as part of the posterior roots. At the point of entry into the spinal cord, these fibers divide into short descending and long ascending branches. The latter pass the entire spinal cord to the medulla oblongata, where they form two bundles, from them they go in succession to the pons, to the midbrain, to the thalamus, and then to a certain area of the cerebral cortex. Part of the pathways goes to the cerebellum, which is important for the automatic regulation of motor
The conduction of muscular-articular stimuli along these pathways is characterized by certain currents of action, which can be diverted by special electrophysiological devices. These action currents are biphasic and single-phase oscillations that occur when a muscle is stretched. Between the individual impulses of the action currents, the interval is 0.03 sec. With an increase in the load on the muscle fiber, the frequency of the impulse increases. Long-term constant loading of the fiber leads to a slow decrease in the oscillation frequency. Based on this*, it is believed that muscle-articular receptors adapt less than other receptors due to constant changes in the tone of the muscle or other muscles associated with it.
The action currents, as well as the entire work of receptors and pathways, are affected by the interaction of muscles, especially their mutual inhibition during the work of antagonist muscles (for example, flexors and extensors). Excitation of the flexor centers is accompanied by inhibition of the extensor centers and vice versa, and this form of interaction occurs with the direct participation of impulses from muscle-articular reflexes. Muscle-articular receptors and pathways determine the creation and maintenance of muscle tone, without which no movement is inconceivable. But these sensitive formations are directly involved in the implementation and coordination of all motor acts. This participation is associated with special reflexes to muscle stretch (myotatic reflex), tendon reflexes (for example, knee reflex), rhythmic reflex movements (chain reflex), etc. The degree of complexity and arbitrariness of movements excited by the work of muscle-articular receptors depends on which nerve centers regulate these movements. Voluntary movements, dissected and perfect, are the result of a higher analysis and synthesis of movements performed by the cerebral cortical end of the motor analyzer.
Cortical ends of the human motor analyzer
The problem of cortical conditioning of muscular-articular sensations was first posed and experimentally resolved by Pavlov and his co-workers. Before Pavlov's work, anatomists and physiologists believed that in the cerebral cortex there is a special motor (motor) area in the anterior part of the cerebral hemispheres, which regulates all human movements. At the same time, it was argued that the motor region regulates the movements themselves, but has nothing to do with muscular-articular sensations. So, for example, Brodman divided the cerebral cortex into different fields, in which the localization of movements (in the outer and partly anterior central gyrus) and the localization of muscle-articular sensations (in the posterior central gyrus together with skin sensations) seem to be sharply separated.
As evidence that the region of the anterior central gyrus is the cortical center of movements, they usually referred to the fact that when this area is affected, a person experiences paralysis or paresis (weakening of strength and range of motion).
Pavlov proved the groundlessness of such a view by exact experiments. Forty years ago, Pavlov came to a new understanding of the function of the motor cortex as an area of analysis and synthesis of movements.
Precise experiments by Krasnogorsky in Pavlov's laboratory proved that the areas of the skin-mechanical and motor analyzers did not coincide, and it was established that the area of the motor analyzer is what physiologists considered the motor area of the cerebral cortex.
This is the area of analysis of the body's skeletal-motor energy, just as other areas of it are analyzers. different types external energy acting on the organism.3
Higher analysis and synthesis of movements of body parts is carried out in the process of formation and differentiation of conditioned motor reflexes. Human behavior is made up precisely of conditioned motor reflexes, and not unconditioned motor reflexes, which exist “in their pure form” only in the first months of a child’s life. All human movements, starting from gait and ending with articulatory movements of the speech motor apparatus, are movements, individually
3 The neurological studies of Bekhterev and his collaborators were also of exceptional importance for substantiating the cortical nature of kinesthesia.
acquired, educated and trained. After they have been developed, human movements become automated, but they are not automatic * in the sense of the spinal machinability of innate reflexes. Some conditioned motor reflexes are developed on the basis of others (for example, the skill of writing based on the skill of separate operation of the child's fingers during the game or household operations - holding a spoon, etc.). Only in the very primary basis are these conditioned motor reflexes developed on. the basis of unconditioned motor reflexes (for example, holding an object). The combination of the influence of various external properties of an object with the motor reflex of the child himself forms a complex motor act.
The development of conditioned motor reflexes is carried out by combining any external stimulus (light, sound, etc.) with a motor reflex (orienting, grasping, defensive, etc.). This proposition was proved in detail by Bekhterev and his collaborators. But the very fact of the formation of such complex conditional motor systems does not yet explain the mechanism of the motor analyzer itself. It was important to prove that a conditioned secretory reflex to muscular-articular signals could be developed. This directly proves that the muscular-articular signals come to the cortex, are analyzed by the cerebral cortex and enter into a temporary connection with any other reaction of the body. Then the muscular-articular impulses, like any impulses from the receptors of vision, hearing, etc., become conditioned stimuli. In 1911, Pavlov and Krasnogorsky proved and discovered such a regularity for the first time. They created a stimulus from flexion of the metatarsophalangeal joint, reinforcing it with a food stimulus. Flexion of the other (ankle) joint was not supported by food. In these experiments, an exact answer was obtained to the question posed, since the conditioned salivary reflex was developed to flexion of the metatarsophalangeal joint, and differentiation, i.e., an inhibitory reaction, was obtained to flexion of the ankle joint.
This proved for the first time that, firstly, the cerebral cortex differentiates (performs the highest analysis) muscle-articular signals and, secondly, that the muscle-articular signals analyzed by the cortex can enter into any temporal connection with any external reaction (not only motor, but also secretory). In other words, the cerebral cortex analyzes and synthesizes endless signals from
working muscles and tendons, i.e. from the skeletal motor energy of the body.
As for the motor aggregate as such, it is only an executive device that carries out the "orders" of the cerebral cortex, and different impulses from the cortex can be carried out by the same device (for example, in the act of breathing, eating or eating, coughing, etc.). part of the same muscles, tendons and bones that are part of the human speech motor apparatus, i.e., in acts of speech movements). And, conversely, the same impulses from the cortex can be carried out by different motor devices (for example, a person can write not only with his right hand, but also with his left hand, in case of damage to his hands - with his foot or mouth, etc.), one and the same movements can be performed by different muscle groups, etc.
The brain end of the motor analyzer, like any analyzer, consists of a nucleus and scattered elements that go far beyond the boundaries of the motor area. This explains the extreme plasticity, the substitution of the affected functions by others, developed on the basis of conditioned reflexes. The possibility of restoring the affected complex actions of a person in case of damage to the motor area of the cerebral hemispheres was proven during the Great Patriotic War in our Soviet evacuation hospitals. Especially great work in this respect was done by the physiologist Asratyan and the psychologist Luria. The experience of such recovery proves that motor paralysis is indeed a paralysis of the movement analyzer. The restoration of movement analysis led to one or another restoration of the lost movements themselves. This experience proves, on the other hand, that when the nucleus of the motor analyzer is damaged in the anterior central gyrus of the cerebral cortex, the functions of analysis are taken over by the scattered elements of this analyzer.
The anatomy of the brain and the clinic of brain diseases consider the region of the anterior central gyrus, as well as the zones adjacent to it, as the center of voluntary or conscious movements. In one of the fields of this area are the giant pyramidal cells of Betz (named after the Russian anatomist Betz who discovered them), from which the so-called pyramidal path begins. The fact is that axons depart from Betz cells (axial processes that give rise to a nerve fiber), which reach the spinal cord through the forebrain and brain stem. On the way through the medulla oblongata, they form a decussation, that is, from the right hemisphere they go to the left half
body, from the left hemisphere to the right. The intersection of the pyramidal bundles is the boundary between the medulla oblongata and the spinal cord. But this decussation is not complete, therefore, there are two pyramidal bundles in the spinal cord - direct and decussated. The fibers of the pyramidal pathway, passing along the spinal cord, terminate in the anterior horns of the spinal cord, transmitting impulses to the cells located here, and through them
axons - "- muscles.
This pyramidal path from the anterior central gyrus of the cerebral cortex to the spinal cord, and through it to the muscles, is a motor or centrifugal path. However, the fact that there are from 113 to 112 sensory fibers in the nerve connecting the spinal cord and muscles, as well as the fact that in general the motor area is understood by Pavlov as the area of the motor analyzer, allows us to think that this path is the way of conducting sensory impulses in cerebral cortex. With this, obviously, the extreme dissection of the cortical regulation of the movements of individual parts of the human body is connected. Such dismemberment would be impossible without a fractional analysis of movements from the human cerebral cortex. This must be emphasized because every elementary voluntary movement of a person is individually acquired, conditioned reflex in origin. Therefore, the motor center in the cerebral cortex is formed during life, and the division of functions in this area is entirely the product of analysis and synthesis in the work of the cerebral cortex. This must be emphasized in order to understand the dissected, differentiated nature of the human motor area.
It is characteristic that the general location of the special centers of various movements is exactly the same as in the region of the posterior central gyrus (the core of the skin-mechanical analyzer and the “muscular feeling” itself). "The center of the big toe is located above all, then the center of the foot, lower leg, thigh , abdomen, chest, scapula, shoulder, forearm, hand, little finger, ring, middle, index, thumb, then neck, forehead, upper face, lower face, tongue, masticatory muscles, pharynx,
The most differentiated is the cortical regulation of finger movements. The motor area (motor) is closely connected with the most anterior parts of the frontal lobes (premotor area), which are associated with the regulation of speech-motor functions in general, as well as complex actions of thought processes.
The localization of these dissected motor functions is relative, the substitution of functions in this area is very diverse, which indicates the role of the scattered elements of each of these parts of the human motor analyzer. Like any analyzer, the motor analyzer is two-pronged. The dual unity of the human motor analyzer is especially complex, since the functional inequality of the motor apparatuses on both sides of the human body is exceptionally great.
It is known that right-handedness and left-handedness are a fundamental fact of human motor development. This functional division of the right and left sides is only available to a person, it is associated with upright posture - the vertical position of the body, with the division of functions between both hands (of which one is right - performs the main working operation, the other - left - auxiliary). This i functional inequality was interpreted incorrectly by some scientists, believing that each of the hands is regulated by only one hemisphere (right hand - left, left hand - right), given the cross nature of the paths of the pyramidal | tract. Such a statement seems to be incorrect, since this crossover is partial, incomplete, and the work of each hand is a product of the joint activity of both hemispheres. The recording of bioelectric currents in the motor area of the right and left hemispheres during voluntary movements of the right and left hands (by Idelson from our laboratory) showed that with simple movements of the right hand, active action currents appear in the left hemisphere, / but with the complication of voluntary movements, currents appear actions and in the same (right) hemisphere.
The same fact is evidenced by many cases of restoration of movements of the right hand when the motor area of its centers in the left hemisphere is affected: the substitution of functions is possible because the scattered elements of the motor analyzer of the left hand are also in the left hemisphere, and the right hand - in the right hemisphere.
The same should be said about the motor center of speech (Broca's center) in the posterior third of the frontal gyrus of the left hemisphere. This "center" is the core of the motor analyzer of speech movements, the scattered elements of which are also located in the right hemisphere in right-handed people (in left-handed people this center is in the right hemisphere).
As in other analyzers, each hemisphere works relatively independently, being a special center of the opposite side of the body's motor apparatus. But no less, but more importantly, they work together
locally, coordinated, and the pairing of work depends on the need for such work, dictated by the nature of human activity. That this joint activity of the hands (and, consequently, of both hemispheres) is a general condition for the working capacity of each individual hand, was shown by Sechenov. He established in 1902 that the restoration of the working capacity of the right hand (after the expenditure of great muscular energy) occurred not when the whole body of a person was resting, but when the left hand worked during a break. Sechenov emphasized that this provision applies to the right-hander, for whom the work of the left hand turned out to be a condition for restoring the working capacity of the right hand, since there was a "energy charging of the nerve centers." It is clear that the muscular-articular impulses of the left hand, which arose during her work, “were transmitted to the centers of the right hand, that is, there was an irradiation of excitation in both hemispheres of the brain.
Research by Bychkov, Idelson, Semagin in our laboratory showed that during the muscular work of one of the hands, currents of action take place in both hemispheres. It follows from Semagin's experiments that action currents also arise in the deltoid muscle of the left hand when the right hand is working. All this indicates the spread of excitation in both motor areas of the brain.
But at the same time, it is important to note that the conjugate currents of the action of the hand that is not working at the moment or its cortical center are inhibited (compared to the action currents of the working hand).
As in all other analyzers, the interaction of both hemispheres causes mutual induction of nervous processes. The "leading hand" is the result of negative induction, in which the excitation of the nucleus of the motor analyzer of the left hemisphere causes inhibition of the nucleus of the right part of the motor analyzer, which regulates the work of the left hand. But as in all analyzers, the leading side is not absolute and unchanging, confined to only one of the hemispheres. The right-hander is actually also the left-hander in a number of operations (for example, lifting and holding weights, holding objects, etc.) when the negative induction spreads from the right hemisphere to the left.
Further, it should be noted that it is the inhibition of one of the hemispheres that is the condition for the creation of a focus of excitation in the other (i.e., positive induction). Therefore, the work of one side of the motor analyzer is impossible without interaction with the opposite side of this analyzer. With hemiplegia (unilateral motor lesions)
on the entire given side of the body) there is not only a loss of the motor functions of the affected side, but also a sharp limitation in the volume, speed and complexity of movements of the intact side of the body.
In cases of hemiplegia, there is a disorder in distinguishing the direction of movements, precise coordination of the hand and the object, i.e., spatial relationships. Such patients re-orient themselves in space, and go through a long path of restoring the complex spatial functions of the hand. It can be assumed that the dual unity of the motor analyzer, expressed in the pair work of both hemispheres, the mutual induction of the processes arising in them, is of particular importance in the analysis of the spatial components of the human movements themselves and its orientation in the space of the external world.
The main properties and main forms of human muscular-articular sensations
The muscular-articular sensations of a person are infinitely diverse. This diversity reflects the change in all aspects of human activity in all the various forms of this activity. Nevertheless, it is possible to single out the general and basic properties of these sensations, despite the fact that far from each of these properties is realized by a person separately at every moment of his activity. In contrast to the clearly recognized separation of sensations from stimuli from external sensory organs, these muscular-articular sensations are often perceived by a person together, in the form of the so-called "dark feeling" (Sechenov). However, during exercise, during special types of activity (physical labor, sports, physical education) there is a dissected awareness of these sensations.The general and basic properties of these sensations are, as Kekcheev showed, the following.
1. Reflection of the position of body parts (i.e., the position of one part of the body relative to another). These general sensations of the position of body parts are of the utmost importance for the formation of a body schema, without which a person cannot correctly and voluntarily use its various parts in various actions.
2. Reflection - analysis of passive movements, especially with static muscle tension. These sensations are characterized by certain spatial and temporal moments. Spatial include: a) recognition of distances or the extent of passive movement, b) distance
cognition of the direction of passive movement (up, down, right and left side of movement). Time moments include: a) analysis of the activity of movement and b) analysis of the speed of movement. A common property of all passive movements is also the analysis of the total expenditure of neuromuscular energy, i.e., the state of fatigue.
3. Analysis and synthesis of active movements (during the dynamic work of a person). These sensations are more complex, characterized by a combination of a number of separate reflections of spatio-temporal features of human actions. The spatial moments of these sensations are:
a) distance analysis, b) direction analysis. The time components are: a) duration analysis and b) movement speed analysis.
With the active movement of the hand operating the object and the tool, the most important properties of muscular-articular sensations arise, which include: a) a reflection of the hardness and impenetrability of the external object with which this or that movement is performed human hands,
b) a reflection of the elasticity of this object, c) a reflection of the weight of the object, i.e., a feeling of heaviness. Through the assessment of muscular effort, sensations signal the mechanical properties of external bodies that a person actively operates in his activity. These sensations arise in the process of reflecting the resistance of external bodies to the influence of a person on them. Thus, muscular-articular sensations reflect not only the state of the internal elements of human activity, but also the objective properties of objects and tools of this activity, that is, they are a form of reflection of objective reality.
Due to the spatio-temporal components of muscular-articular sensations, these sensations are, according to Sechenov, a fractional analyzer of the time and space of the external world.
The connection of muscular-articular sensations with all other external sensations provides a sensual basis for a person's reflection of space and time, external, material reality.
These common properties of all muscular-articular sensations appear in a peculiar form and combinations in the following basic forms of human muscular-articular sensitivity:
1. General musculo-articular sensitivity of a person (sensations of the position of body parts one relative to the other).
2. Muscular-articular sensitivity of the human musculoskeletal system.
3. Muscular-articular sensitivity of the human working apparatus (both hands).
4. Musculo-articular sensitivity of the human speech-motor apparatus.
All these forms of sensitivity are interconnected with each other, but at the same time separate and independent. Some of them interact according to the principles of mutual induction, exciting and inhibiting each other, as will be shown below.
Distinctive musculoskeletal sensation
human
The minimum change in muscle tone during a particular movement determines the absolute threshold of muscle-articular sensations. At present, science has not yet developed exact methods for determining this type of absolute sensitivity, has not established values that characterize the absolute thresholds of sensations in various motor apparatuses. The reason for this is not only the extreme difficulty of dosing tonic changes, not especially the separation between the study of the mechanism of the movements themselves and their sensations, which has not yet been overcome in science. Indirect data on shifts in the absolute muscular-articular? sensitivity can be obtained from well-studied data on the difference thresholds of muscular-articular sensations.
Distinctive sensitivity has been most studied in relation to the sensation of heaviness, i.e., the discrimination of the weight of an object (one of the types of sensations of active movements). Usually used for this purpose is a comparison by a person of difference? between loads, the weight of which gradually increased with a constant increase to the initial weight of the load being lifted. It has been established that the minimum sensation of difference? between loads is equal to "/40 of the initial gravity. This value * is constant only within certain limits, since with large loads the increase increases (up to "/ 2o), and the sensitivity decreases due to physical fatigue.
The difference threshold of sensations of heaviness is measured in grams of the weight of the added loads. Difference threshold of sensation? the size of objects and diameters of length, and in connection with this, the direction and extent of felt movements is measured in millimeters (increase in the size of objects relative to the original size). Kekcheev found that the value of the difference threshold for distinguishing the thickness of the sensation
for palpable objects is "/25, for distinguishing the diameter of palpated objects - "/g, -, and for palpating the length of objects -" As. be expressed in degrees.
The difference threshold of sensations of the size of an object expressed in this way is 0.27-0.48 ° for the most sensitive part of the hand in the muscular-articular relation (the articulation between the metacarpal bones and the phalanges of the fingers).
Distinctive muscular-articular sensitivity changes in the process of individual development. In young children, it is still very rough and is limited to the range of habitual household and play movements. A sharp increase in distinctive sensitivity takes place at school age, especially under the influence of drawing and writing skills, and especially physical education. From 8 to 18 years of age, difference sensitivity increases by 1 "/2-2 times. Skilled physical labor and sports activities have a sensitizing effect on muscular-articular sensations. The boundaries of difference sensitivity are constantly expanding in the process of accumulating experience in professional labor and sports movements. Particularly large a role in their development is played by the rationalization of movements by the leaders of labor under the conditions of the socialist organization of labor processes.
Relationship between spatial and temporal moments of muscular-articular sensations
Acceleration or deceleration of movement, i.e., their duration and speed, are reflected in the accuracy of recognition of spatial signs of movement (its length and direction). Slowly performed movements give the greatest number of errors in recognizing not only the duration of movements (overestimation of duration), but also space. Slow movements are more difficult to analyze their extent and direction. However, at all speeds, there are fewer spatial errors than temporal ones.
If we disregard the speed of movements and establish the role of the size of hand movements (its range) in the accuracy of recognition of spatial and temporal moments of movements, then it turns out, according to Kekcheev, that with an increase in the range of movements, the accuracy of recognition of the extent and direction of movements increases, i.e. sensitivity in this in relation to
staggers. On the contrary, with an increase in the range of movements, the accuracy of recognition of the temporal moments of movement (its duration and speed) decreases. Consequently, in muscular-articular sensations we have a fractional and special analysis of spatio-temporal signs of committed objectified movements, i.e., operating with certain things of the external world.
The spatial nature of the movements is especially hidden when a person reproduces active movements. In a sighted person, these movements are performed under the control of vision, in conditions of strong connection, hand-eye coordination. The hand of a sighted person, when acting with closed eyes, is more bound in terms of range of action than that of a blind-born person. At a distance of 15 to 35 cm from the midpoint of the body, the hand of a sighted person gives the most accurate signals about the place, direction and scope of movements. Outside this zone, increasing difficulties begin, greater for distances over 40-50 cm from the body. Particularly difficult to analyze are movements forward and J to the left (for the right hand). These data were confirmed by Kekcheeva in our laboratory Pozdnova, who showed that there are differences between the right and left hands of the same person in this respect.
This fact indicates that there is a dependence of the analysis of movements on the general muscular-articular sensations of the position of body parts. Even greater is the relationship between muscle-and-articular sensations and vision. At the beginning of learning new movements in a person, they are performed under the control of mind-| However, with the formation of motor skills, control over movement is transferred to muscular-articular sensations, the accuracy of which also determines the accuracy of habitual movements. Therefore, the cultivation of muscular-articular sensations is a general and most important condition for increasing the speed and accuracy of any human movements, that is, a condition for increasing the productivity of human movements.
Musculoskeletal sensitivity of the human musculoskeletal system
From observations of the development of a child in the period of 8 months, tsev-1 year 2 months of life, it is known what a complex and difficult process is the formation or formation of walking. This is preceded by transitions in the child from a lying position to a sitting position (with the formation of a constant tone of the muscles of the head, neck, back, arms), to standing with
“supporting an adult or support, crawling, then uncoordinated walking (simultaneously with both legs with a forward tilt, which leads to a fall of the body), etc. For several months, adults specially train the child on the act of jsa^iocTOH-solid walking, forming the necessary for this -act cortical mechanisms. But even after the child has begun to walk independently, his movements are still unstable, weak, uncoordinated for a long time; because of this, the child becomes extremely tired as a result of the large expenditure of muscle energy. Mastering the act of walking is the most complex and lengthy process of formation of an integral system of activity of the human musculoskeletal system. With the formation of this system, the entire behavior of the child changes: only the previously outlined functional inequality of the right and left hands sharply increases, the objective activity of the hands develops rapidly. Visual-motor coordination typical of a person develops, and vision itself expands infinitely over the field of view (fields of vision) and spatial directions.Due to the practical movement in space, the child comes into contact with an infinitely greater range of things and their properties than it was in the motionless, lying position of the baby, etc. Touch and vision receive a sharp impetus in development along with the independent walking of the child. auditory orientation in space, etc.
Under the influence of walking, the process of maturation of the speech motor apparatus is also accelerated, the prerequisites for which are the gradual development of the child's voice and articulation (voice modulation, in crying and screaming, cooing and babble). Obviously, a sharp increase in impulses from the movement of the whole body during walking is a condition that contributes to the formation of the most subtle and differentiated system of speech movements.
Initially, each element of walking is trained, and this training is carried out due to the division of a separate movement into all its component parts. In the process of formation and strengthening of a motor skill, a complex of separate movements is synthesized and generalized. Thus, for example, a “single step” arises, which is the distance between any phase of the movement of the right leg, or, conversely, a single step is the result of the existing coordination of the movements of both legs, i.e., the synthesis of these movements. But the creation of such a synthesis was preceded by a higher cortical
analysis of the separate movements of the ankle and hip joints and all other parts of the body involved in walking.
"Single step" is a sensual measure of the space in which a person moves at one speed or another. The moment of step acceleration changes the ratio of the phases of movement of both legs, the difference between them, causes an urgent reaction through the muscular-articular sensations, from the side of the cerebral cortex, which ensures the balance of the body and the preservation of the center of gravity as a necessary condition for the normal position of the body during movement in space. It is wrong to think that only the legs carry out the act of walking. The whole body takes part in this act, and the coordination of the movements of individual parts of the body is conditioned reflex from beginning to end.
During walking, there are interrelated vertical movements of the head, the center of gravity of the body, the shoulder and hip joints. These changes are associated with moments of inertia, torque of the portable leg relative to the hip and knee joints of the supporting leg. The movements of the ankle joint of the portable (at the moment) and supporting (also at the moment) legs are, as it were, the resulting quantity relative to the totality of body movements.
This generalized nature of the movements in walking determines the position that in walking there is no such sharp permanent functional inequality between both limbs, which exists between the hands. However, in the process of walking, there is a variable functional inequality in the "double step", which is the name of the combination of periods of support and leg transfer. The duration of the support of the leg and the transfer of the leg (per 1 m of the path) is 0.37 sec for the support and 0.20-0.22 sec for the transfer of the leg during normal walking. The alternation for each leg of periods of support and transfer eliminates the constancy of functional inequality, but creates at each individual moment a difference in signals from moving legs, of which at a particular moment in time one is in static (support), the other is in dynamic tension.
When walking, there are conjugate hand movements. The hand of one side moves to the opposite one;! to the movement of the leg of the same side (for example, the right arm moves back when the right leg moves forward). The elbow angle develops more and flexes less during normal walking due to the change in successive positions of the shoulder and forearm. In race walking, the elbow
angle closer to a right. During normal walking, the angle of the knee joint does not exceed 80°. Vertical movements of the shoulder and hip joints occur simultaneously and in the same direction.
The result of all these changes is the formation of angles of the moving ankle joint.
The ankle angle has the largest value before the start of the leg transfer, and the smallest value - at the end of a single support. For normal walking, the maximum value of the ankle joint is 128-132°. and the minimum is 90-103 °. Each act of walking, therefore, is carried out by a system of coordinated in time and space movements of all parts of the body, which determine the ratio of dynamic and static stress in the human musculoskeletal system. The basis of such coordination is an urgent systemic reaction of the cortex to a multitude of signals from all parts of the motor apparatus. The differentiation of these signals forms the basis of the distinctive sensitivity of the musculoskeletal system.
The exceptional sensitization of this form of sensitivity is evidenced by the facts of the high development of the technique of sports and military walking, running, football games, swimming, and skiing. Puni's study of the culture of muscle-joint sensations in skiers showed an increase in this sensitivity in masters of skiing by 1 "/2-2 times compared with ordinary skiers. The same was noted in relation to the masters of running, jumping, etc.
Working posture of the human body
Walking is not the only general act of the motor apparatus in which the entire human motor analyzer takes part. Another such common and most time-consuming motor act is the working posture of the human body. , i
The natural state of the human body is the state of vigorous activity. This natural state finds its fullest expression in human labor, productive activity. The working person carries out the child normally inherent in the human body.
pregnancy.
The condition for each labor act (production operation, designing on drawings or writing, etc.), which is performed by hands, is the general working posture of the human body. Such a working posture is the position of the whole body (when working at the machine, workers, when
B. G. Ananiev
writing and reading, drawing, working with instruments, etc.), necessary for the normal and active work of the hands and senses (especially the eyes). It is known that the working posture, as well as the working movements of the hands, is brought up, trained by a whole system of exercises. So, for example, a child is taught not only rational finger movements when learning to write, write, or play the piano, but also how to hold the body, in what position the shoulder and elbow joints should be, how the child should keep his legs under the desk, etc. e. For "writing or listening in the lesson, a working posture should be developed in which long-term work of the brain and hands could be ensured without fatigue. It has been established that maintaining a long working posture is a lot of neuromuscular work, in which work plays a leading role human motor analyzer. Compared to the arm moving during labor, the general position of the body seems at first glance motionless, at rest. But this is only an appearance. In reality, the working posture is continuously maintained, and the necessary static tension of the muscles of the head, neck, body, Ukhtomsky called the working position operational rest or stationary work of the human body. At work, muscular-articular impulses continuously enter the brain both from those parts of the motor apparatus that provide the working posture, and from those that carry out the labor process itself. As Ukhtomsky pointed out, “behind such a work or posture one has to assume the excitation of not a single point, but a whole group of centers,”4 which he called “a constellation or constellation of nerve centers.” He showed that a certain interaction of nerve centers lies at the basis of stationary work, namely, the persistent excitation of one of them while the others are inhibited (the case of negative induction of nervous processes). But in this case, there is not a simple suppression of impulses from the inhibitory motor apparatus, but their use by the center that is dominant at the moment in the form of an increase in excitation in it due to accumulated excitations from inhibited points. During a labor action, such a dominant nerve center is that part of the motor analyzer that regulates the work of the hands. The remaining parts of the motor analyzer increase the excitation of this "manual" part of the motor analyzer, being themselves inhibited. At the same time, motor inhibition of other parts of the body does not at all mean the cessation of sensory
4A. A. Ukhtomsky. Sobr. cit., vol. I, p. 200.
(muscle-articular sensations) impulses from motor-inhibited parts of the body. On the contrary, the impulses coming from them excite the entire motor analyzer and especially that part of it that acts in accordance with the objective requirements of the external environment.
Ukhtomsky formulated his well-known principle of dominance in the following way. general view: "Sufficiently stable excitation flowing in the centers at the moment acquires the significance of a dominant factor in the work of other centers: the accumulation of excitation in oneself from distant sources but inhibits the ability of other receptors to respond to impulses that are directly related to them."5 To understand the mechanism working posture it is especially important to take into account the most important feature of the dominant, namely its inertia. Et: 1 "inertia is manifested in the fact that "once called dom 1" anta is able to steadfastly hold on to the centers for some time and be reinforced both in its elements of excitation and in its elements of inhibition by various and distant stimuli. 6 And this means that the inertia of the working posture is conditioned reflexively carried out due to the action of signals from the usual working environment of labor actions (workshop, office, class, etc.). In other words, together with the working movements of the hands, the working posture forms an integral dynamic stereotype of the temporal connections of the activity process.
The muscular-articular sensations of a person in the process of work are of a dual nature: sensations of active movements of the hands and sensations of passive movements of the rest of the body. With STOM, the inclination of the head and body, the extent of movements of individual joints, their duration, the amount of movement of the arm relative to the center of gravity of the body and the midpoint of the body of the body, etc. are reflected. Accurate recording of body movements while sitting at work shows continuous oscillations of the whole body body gravity.
The cerebral cortex, receiving impulses from all parts of the motor analyzer, continuously redistributes muscle energy between parts of the motor apparatus. ensuring the preservation of human performance, especially actively working hands.
Musculoskeletal sensations of working movements
The most diverse, accurate, clearly perceived muscle-articular sensations are the sensations of
5 Ibid., p. 198.
6 Ibid., p. 202.
side movements carried out joint work both hands. It is no coincidence that general ideas about muscle feeling developed precisely in the study of sensations obtained during the labor movements of the hands and the process of active touch-feeling. In fact, we have already mentioned them earlier, with a general description of muscular-articular sensations. Here we will touch on some special and additional materials.
Studies have shown high exercise capacity, therefore, sensitization of the sensation of heaviness and effort, i.e., overcoming the resistance of the external body when working with it, as well as a reflection of its elastic properties. Such sensitization especially takes place during work with weighing, with the determination of gravity, elastic properties, and dimensions of bodies during work.
An experienced seller accurately calculates the preparation of products when weighing, making very slight mistakes; the workers of the procurement workshops achieve great savings in materials not only due to the eye, but also due to the developed distinctive muscular-articular sensitivity. It is especially characteristic in this case to overcome the differences that arise when feeling heaviness by simultaneously weighing with both hands. Without special training, this usually results in an illusion or a perceptual error, consisting (especially in actions with open eyes) in the fact that each of the hands gives unequal readings. At the same time, as Khachapuridze from Uznadze's laboratory showed, the left hand of right-handed people often overestimates the actual heaviness of an even figure. During training, this illusion is removed, both hands give identical or close readings. Differences in the muscular-articular sensations of both hands are especially evident with active touch or palpation with both hands at the same time. Initially, from one object, two separate images of the right and left sides arise, corresponding to the work of the hands. Such a doubling of the image does not occur with alternate actions of the hands at different times, but only with simultaneous ones, which indicates the difficulty of developing a general rhythm of movement and simultaneous equal excitation of both hands.
The leading role of muscular-articular sensations in active touch is evidenced by the fact that it is the same during shutdowns; It is quite possible to accurately recognize the shape and elasticity of the objects being felt. -,
Zaporozhets showed / that with closed eyes and with the help of a “tool” (stick, pencil, etc.), that is, without the participation of skin sensitivity, a person can accurately recognize
size, shape, elastic properties of external objects. From the data of Yarmolenko and Pantsyrnaya it follows that under such conditions, tracing the contour of an object with a pointer with the right hand gives an accurate reflection of the contour. A special adaptation is required on the left hand side in order for it to give similar results in right-handed people.
The right, leading hand in right-handers is characterized by a higher distinctive sensitivity in recognizing the subject and spatio-temporal properties of the objects being felt. But at the same time, the static tension of the left hand or its partial dynamic tension enhances the distinctive work of the right hand.
Sensitization of the acuteness of the muscular-articular sensations of the right hand was established in the study of various types of Puni sports equipment. This is especially true for fencing. Pugni's experiments give an accurate idea of the increase in the sharpness of these sensations and the aiming ability of the right hand. They showed that the sharpness of muscular-articular sensations increases unevenly. After 3"/g months of fencing lessons, this sharpness increased by 25% with movements in the wrist joint, and by 40% with movements in the elbow joint.
If at the beginning of training in fencing technique the deviation from the target (fencing blow) in millimeters was 35, then after 3 "/2 months of exercises it was only 8.6 mm. The number of accurate hits on the target increased by 81.3%. At the same time, as Puni showed , the sensitization of the acuity of the muscular-articular feeling is influenced by such factors as the density of the fencing battle, interaction with a strong or weak opponent, etc.
Science has similar data regarding sensitization in other sports and shooting.
The leading role of the cerebral cortex in the sensitization of active movements is especially evident in the restoration of disturbed motor systems. So, Leontiev and Zaporozhets showed that the restructuring of the cerebral cortex after amputation of one or both hands gradually leads to sensitization of the remaining hand stumps or a two-finger hand artificially created from the stump (the so-called Krukenberg hand). Industrial training (occupational therapy) and remedial gymnastics, correctly physiologically and psychologically substantiated, provide a high rate of recovery of movements. In this case, the formation of a difference in the muscular-articular sensations of both hands plays an important role. Shenk summarized the valuable experience of such a functional education of two-armed disabled people, showing the possibility
the possibility of versatile substitutions of the motor functions of the hands, etc.
It has been established that between the muscular-articular sensations from the process of walking or working posture, on the one hand, and the sensations of working movements, on the other hand, there are relations of mutual induction, especially negative induction. The most conducive to accurate hand movements is operational rest and cessation of walking, in which the distinguishing work of both hands is enhanced.
In turn, similar inductive relations are formed between the working movements and speech movements (articulate speech) of a person.
The forms of muscular-articular sensitivity considered by us in the state of walking, working posture and working movements are carried out by the first signal system, although the second signal system plays a very important role in the sensitization and development of the entire human motor apparatus.
Even Lesgaft, in his teaching on physical education, emphasized the meaning of the word and the verbal explanation of the nature of movements in physical education. The experience of physical education fully confirmed this position of Lesgaft, and at the same time Pavlov's position on the influence of the second signal system on the work of all human analyzers, including the motor one, accelerating and rationalizing the development of muscular-articular sensitivity.
Feelings of speech movements
Sensations of speech movements are a condition for the formation of motor differentiation in the pronunciation of consonants and vowels. This differentiation is formed by -. sedately, and in conditions of closing connections between the auditory analysis of audible someone else's speech and the movements of all individual parts of the speech-motor apparatus (from the respiratory apparatus to the teeth and lips). A particularly important role is played by the differentiation of the position of the tongue in relation to the palate and teeth. At first, the child has a physiological tongue-tied tongue, in which the child still incorrectly performs: -ti movements (they do not separate from each other, similar positions of the tongue are mixed, etc.), which is removed in the process of educating the child's speech. An exceptional role in this process is played by the differentiation of muscle sensations during movements necessary for the pronunciation of similar vowels and similar consonant sounds. After the formation of such a differentiation, it becomes possible to synthesize speech movements, it with it and connected, continuous verbal speech, and then connected
new construction of words in a sentence based on mastering grammatical rules.
This exclusive role of muscle sensations can be easily and clearly detected when eliminating defects in oral speech by means of special speech therapy exercises, in which the movements of the tongue are quiet, smooth and are provided by the cultivation of a subtle distinction between muscle sensations when the teacher sets up various sounds of the articulatory apparatus. Speech movements, together with speech hearing, initially determine the movements of the writing hand.
As shown by Blinkov, Luria, and others, articulatory movements accompany and reinforce the differentiated movements of the squeaking hand. The most complex muscle sensations in the act of writing should also be attributed to speech movements. "Speech movements in the act of reading also include muscle sensations from the movement of the gaze, i.e., the visual axes of the eyes. Thus, speech movements also capture a large area of interconnected movements of the speech motor apparatus, hands and eyes, with a particularly increasing value of the overall working posture of the human body. The entire this complex of movements and sensations of movements is formed at the level of the second signal system and is determined by the social nature of the sound structure of a given language.
Speech kinesthesias are the "basal component" (Pavlov) of the second signaling system. However, the systematic study of this component is just beginning. In recent years, valuable data on the mechanisms of speech have been obtained, especially in a series of works by Zhinkin.7
7H. I. Zhinkin. Mechanisms of speech. M., ed. APN RSFSR, 1958.
FEELING BALANCE AND ACCELERATION (STATIC-DYNAMIC FEELINGS)
The position of the human body in space as a source
sensations
The historical, social and labor transformation of human nature has placed the human organism in a new relationship with the surrounding space of the outside world. Walking upright and the vertical position of the body in relation to the horizontal plane of the Earth, labor actions of the hands, articulate speech and new functions of all analyzers - all these are products of social and labor changes in the human body, developed in the process of social and labor influence of man on the outside world. In each act of such influence, the human body itself experiences many irritations from the outside world and the changing internal environment of the body. In any of his actions, a person moves in space, while maintaining the balance of his body, and thereby his constant vertical position in relation to the horizontal plane of the Earth. This movement occurs in various forms - translational, rotational, oscillatory, etc. The human brain continuously receives signals about various changes in body position, the brain ensures the restoration of the body in any form of movement. Each of the integral movements of the human body occurs at a different speed, and the acceleration of movement occurs with variable time values.
Thanks to the production of means of production, society receives more and more new means of transportation and accelerates
niya movement of a person in space. Even in ancient times, people used horse traction as a means of transportation and acceleration of movement. From horse traction to the most advanced technology of rail and trackless, water and air transport, the technique of movement and acceleration has passed a difficult historical path. Modern transport technology changes the nature of signaling the balance of the body in the process of movement. A person in the conditions of modern transport technology moves with ever greater accelerations, and a person experiences these accelerations with a relatively stationary body position. Thus, a pilot or a passenger in an airplane, a driver or a passenger in a car, etc., experience not only a change in the balance of the body in the narrow sense of the word (for example, when the car body moves vertically when climbing to a height or when the plane lands), but also the acceleration of the car in the same plane of horizontal movement. If in the first case there is also a change in the general muscle tone and intense muscle and joint signaling, then in the second case there are special sensations of acceleration that are not reducible to muscle and joint sensations. These sensations are static sensations or sensations of the general position of the body in the process of
movement.
We can say that the progress of transport technology has brought to life a special development of these sensations, closely related to the muscular-articular feeling and visual orientation in space. As we will see later, a person is aware of the balance of the body insofar as it is disturbed, changes when the position of the body changes. A person feels acceleration insofar as it is not continuously constant, but variable, that is, he feels a change in speeds (from high to low and vice versa), and the contrasting ratios of positions and accelerations play the most important role in these sensations. So, a person experiences static sensations with a sharp change in the horizontal position to a vertical one (for example, quickly jumping out of bed) or with a sharp change
acceleration.
A constant position of the body and a constant speed are usually not felt by a person, since the brain regulation of these states is carried out automatically, unconditionally-reflexively, by the lower parts of the central nervous system. Signals about the position of the body and accelerations reach the koza of the brain in a generalized form and in cases where an urgent reaction of the human body is required to a change in the position of the body in accordance with the requirements of its activity.
Receptors for static-dynamic sensations (vestibular,
In the inner ear, not only is the auditory receptor located, but also there are receptors for accelerating the movement of the body and its position in space. The inner ear consists of three main sections: the vestibule, the semicircular canals, and the cochlea. The latter, that is, the cochlea, is, as already known, the auditory receptor. The vestibule and semicircular canals form the vestibular apparatus, which is a receptor for static sensations. It is the window of the vestibular nerve and one of the main parts of the VIII ear-brain nerve. The vestibular apparatus itself consists of two groups of red
tori. The first is a set of hair cells, ___ „.,
covering the surface of the semicircular canals in the inner ear. These channels contain the zndolimph fluid, which moves when the position of a person in space changes (when the vertical position changes to a horizontal one, when the body is tilted, etc.). These movements of the endolymph irritate the hair cells of the semicircular canals, and it is believed that this irritation is not only mechanical in nature, but is also characterized by a certain electrical phenomenon (action current). Bjrosoft group of receptors are otoliths, or auditory pebbles, located on the threshold of the inner ear.
The activity of both groups of vestibular receptors is interconnected. It is assumed, however, that the receptor function of the semicircular canals specifically consists in signaling the acceleration of body movements. To study the excitability of the semicircular canals in the clinic, methods of mechanical and caloric (thermal) stimulation are used. The method of mechanical irritation consists in a rotational test. This test is performed on a special revolving chair. The person is slowly rotated (one full rotation in 2 sec) in this chair, and after 10 rotations out-. abruptly interrupted. In this case, two kinds of phenomena / with opposite spatial signs arise: 1) nistagmus, or involuntary convulsive tremulous movements of the eyeballs, and it takes place in the direction opposite to the former movement, and 2) reflex inclination of the head and torso in the same direction , which is the former movement.
Rotation excites both vestibular apparatuses (right and left ears), but the apparatus that was opposite to the side of movement is more excited. Therefore, left-sided nystagmus occurs when rotating to the right
and is determined by the left vestibular apparatus. Right-sided nystagmus occurs during left rotation and is caused by the right vestibular apparatus. By the size of the intensity and duration of nystagmus during rotation in one direction or the other, it is judged which side is affected. With a caloric test, you can examine the semicircular canals of each ear separately. For this purpose, water is slowly poured into the external auditory canal without pressure (temperature 15-20 or 40-45 ° heat). The cooling of the semicircular canals causes the movement of endolymph in them, irritating the hair cells. As a result, nystagmus occurs in the opposite direction and the deviation of the head and outstretched arms, as well as a fall towards the ear irritated by cooling. With the defeat of one vestibular apparatus on the irritated side, neither nystagmus nor other reactions are obtained. With an increase in its excitability, nystagmus and other reactions are intensified and longer.
The relay function of the semicircular canals is manifested in the signaling of the general movement of the body and its acceleration. Volume signs of this function are nystagmus and reflex movements of the head, neck, torso and arms.
The reflex function of the otoliths, apparently, consists in the primary analysis of changes in the position of the body in relation to the plane of support. In order to study the receptor functions of otoliths, a movable table is used, the slope of which can vary (according to a certain measuring scale in degrees). A person is placed on such a table (in a sitting, standing, lying position), his reactions to a sudden movement of the support plane, a change in the position of his body are studied. As can be seen, the functions of the vestibular receptors come into play especially under such conditions when the human body itself is relatively immobile, but either the direction of the plane of the external support of the human body changes, or the speed of movement of this support. With this apparent immobility of the human body under conditions of a moving support, there is movement of the endolymph in the semicircular canals and movement of the otoliths. It is established that this movement is performed aperiodically. From both vestibular apparatuses, somewhat identical signals about a change in balance come to the brain. This difference in signals is an important condition for the formation of static sensations. Although the vestibular receptors themselves are located in the internal environment of the body, the signaling of these receptors, which occurs when the inner ear changes under the influence of external stimuli, has the character of signaling about external changes in the human body~]G~bktyar~* Zhatsche his space.
Therefore, as Bekhterev first established, the vestibular function is an integral part of the orientation of a person "e ~ ka in the" Tphospace of the outside world and plays an important role in "7pt; g: lysator" work of the human cerebral cortex.
vestibular nerves
In the depths of the internal auditory meatus there is a special ganglion (an accumulation of nerve cells), consisting of cells of the peripheral nerve of the otoliths and semicircular canals. \ From here, from the internal auditory meatus, fibers from this:! the ganglion and the auditory nerve go together to form the eighth pair of ear-brain nerves. Upon entering the hindbrain, they are divided] into two branches: vestibular and auditory. The vestibular branch branches in three directions, ending, respectively, in each of them. The first branch has an ending; inside from the so-called rope body in the auditory region of the cerebral hemispheres, the second - in the nucleus! Ankylosing spondylitis, located between the bottom of the IV cerebral ventricle and the posterior cerebellar peduncle, the third is in the nucleus of Deidets. From the nucleus of Deidets, the axons of the cells are sent to the spin | noah brain, ending at the peripheral motor 1 nerve. From the first two branches (in the auditory tubercle and Bekhterev's nucleus I), the fibers of the vestibular nerve go through the posterior 1 cerebellar pedicle to the so-called cerebellar vermis and to | nuclei of the oculomotor nerve located in the middle |
Muscle tone is one of the physiological properties of the human body. The nature of this condition has not yet been established, but there are several theories that experts adhere to. Muscle tension at rest can change under the influence of external factors or diseases of the nervous system. There are two types of pathology: hypertonicity and hypotonicity. In the article we will consider in detail their symptoms and treatment.
The value of muscle tone
Tonic muscle tension is a normal physiological state of the human body, which is carried out at the reflex level. Without it, it would be impossible to perform many movements, as well as maintain the position of the body. Muscle tone keeps the body in readiness for active action. This is its main purpose.
What is the mechanism of muscle work with normal tone? If all the fibers of the tissue are involved in the movement, then at rest they replace each other. While some are tense, others are resting. Interestingly, the process is directly affected by the psycho-emotional state of a person. For example, a decrease in muscle tone leads to a decrease in performance and is observed mainly during sleep. The condition is accompanied by natural calmness: excessive excitement is significantly reduced.
The regulation of muscle tone is carried out with the help of alpha and gamma motor neurons, afferent fibers and spindles. The impulses come from the brain. The cerebellum, the midbrain (the red nucleus, the black substance, the quadrigemina) are responsible for maintaining muscle tone. If the neurons responsible for tonic tension are damaged, its disturbances occur: hypotension or hypertension of the muscles.
Diagnosis in adults
A change in tone can occur for various reasons. Most often, these are diseases of the nervous system or a complex psycho-emotional state. A neuropathologist or orthopedist deals with the problem of muscle tone disorders. To correctly diagnose, conduct an examination. Muscle tension is assessed in a relaxed state and during passive movements using special tests: dropping the head, supination-pronation, swinging the legs, shaking the shoulders, and others.
Examination is quite difficult: not every patient can completely relax. At the same time, the qualification of the doctor is also important - the speed of passive movements affects the assessment of the condition. External factors can also distort the results: muscle tone changes under the influence of temperature and mental state. The most difficult situations require re-examination.
Tonus in children up to a year
In the womb, the fetus is located very closely, so all the muscles are in constant tension. After birth, the baby has physiological hypertonicity. In this case, the head is thrown back, and the legs and arms are brought to the body.
Which muscles are tense is affected by the position of the baby in the womb and in the birth process. For example, with facial presentation, there is an increased tone of the neck (the newborn throws his head back). In the “forward buttocks” position, the child’s legs are spread apart, forming an angle of 90 ° between them. Lying on the bed, the baby tries to take the usual fetal position.
Diagnosis of tone in babies
When conducting an examination, a pediatrician or neuropathologist assesses the state of the child's muscle tone according to the following signs:
- At 1 month, the baby, lying on his stomach, tries to raise his head and holds it for a few seconds. Legs make bending movements, as if crawling. If you put your hand under your feet, he will push off from it.
- By 3 months, the child holds his head confidently. If you raise it in a vertical position, the legs will make movements, as when walking. The child can lean on the foot. If you put him on his back and pull the handles, he will be pulled up by his own strength.
- Up to 6 months, the baby rolls over from his stomach to his back, tries to get on all fours, holds small objects in his hands.
- By the age of one, the child sits confidently, tries to walk with support, and develops on his own.
If the baby cannot perform one of the listed actions due to excessive tension or, conversely, muscle weakness, they speak of pathology. Additionally, the doctor evaluates the symmetry of the tone. To do this, alternately bend and unbend the arms and legs of the child. They also observe active movements in different positions of the body. A deviation from the norm is hypotonicity, hypertonicity, which persists even during sleep, and muscle dystonia.
Types of hypertonicity and the causes of its development
Increased muscle tone can manifest itself in different ways. Experts distinguish:
- Spasticity - develops due to craniocerebral and spinal injuries, meningitis, encephalopathy, cerebral palsy, multiple sclerosis, stroke. It is characterized by uneven distribution of hypertonicity, when only certain muscle groups are subjected to spasm.
- Rigidity is a sharp increase in the tone of skeletal muscles, which occurs as a result of diseases of the nervous system, the poisoning effect of certain poisons.
- Gegenhalten - a sharply increasing muscle resistance during passive movements of any type. It occurs in connection with the defeat of the mixed or corticospinal tracts in the frontal regions of the brain.
- Myotonia - characterized by slow relaxation of tense muscles after active movements.
- Psychogenic hypertension - during a seizure, a "hysterical arc" is formed.
In children, the cause of the development of hypertonicity is birth trauma, hypoxia in childbirth, damage to the nervous system and brain, meningitis, excessive excitability or hyperactivity.
Symptoms of hypertonicity
Hypertension of the muscles is expressed in their excessive tension in a relaxed state. The disease can be identified by the following signs:
- decreased motor function, muscle stiffness;
- seals;
- feeling of constant tension;
- soreness;
- spasms;
- significant muscle resistance during passive movements;
- in children, tearfulness, increased nervous excitability, increased muscle resistance when repeating flexion-extensor movements;
- in a vertical position with support on the legs, the baby presses the feet, standing on tiptoe;
- slowing down the motor development of the child (does not sit down, does not crawl, does not walk at the right age).
It is not difficult to notice hypertonicity in an adult or a child, especially in the middle and severe stages. The gait changes, actions are carried out stiffly, with great difficulty. At the same time, babies are clamped and tense, often scream and sleep poorly, react painfully to any, even minor, noise. After eating, profuse regurgitation occurs.
Causes and symptoms of muscle hypotension
Weak muscle tone is characterized by low tissue tension in a relaxed state, which makes it difficult to actuate them. This happens mainly due to damage or disease of the spinal cord, cerebellum or extrapyramidal disorders and cerebellar damage. There are also attacks, during which the muscle tone temporarily decreases. This occurs in the acute phase of a stroke or in a midbrain tumor.
Weak muscle tone in children is less common than hypertension. Its appearance can be triggered by prematurity, slow development of the brain, damage to peripheral nerves during the birth process, birth defects, Down syndrome, rickets.
Symptoms of muscle hypotonia in babies are:
- lethargy, overly relaxed state;
- respiratory failure, inability to swallow, suck;
- weak motor activity;
- excessive sleepiness, poor weight gain.
Violation of muscle tone in the direction of its decrease can be observed in adulthood. Various diseases usually lead to this: muscle dystrophy, sepsis, rickets, meningitis, Sandifer's syndrome. The condition is accompanied by physical weakness, reduced resistance to passive movements. When flexed, the joints unbend on their own, the muscles feel soft to the touch.
Muscular dystonia in adults and children
With muscle dystonia, uneven tone is observed. At the same time, there are signs of both hypotension and hypertension. The main symptoms of dystonia in children and adults are:
- excessive tension of certain muscles and relaxation of others;
- spastic contractions;
- legs or arms;
- fast or slow movements of certain parts of the body.
The condition develops due to genetic, infectious diseases, birth trauma, severe intoxication.
Treatment
Muscle tone is important to normalize in time, especially in childhood. The progression of symptoms leads to impaired movement, scoliosis, cerebral palsy, and delayed development. There are several treatment methods:
- massage with muscle tone gives good results, for this the muscles are stroked, kneaded, stretched, their strength is trained, making physiological movements (flexion-extension);
- therapeutic gymnastics, including in water;
- physiotherapy: electrophoresis, ultrasound, treatment with heat, water and mud;
- in difficult cases, medications are used, among which vitamins of group B, dibazol, mydocalm can be prescribed.
With hypertonicity, the muscles try to relax with the help of stroking, healing injuries, light massage, stretching. With hypotension, on the contrary, they stimulate motor movements by performing muscle tone exercises. significantly improves the patient's condition.
Violation of muscle tone is a common problem in children of the first year of life and adults with diseases of the nervous system. It is quite easy to treat with the help of massages, less often - medicines. Mobility returns to normal, and there is no trace of the problem. The main thing is to start treatment on time, preventing serious violations and deviations in the development of the skeleton and muscles.
Different parts of the central nervous system (CNS) from the spinal cord to the cerebral cortex are responsible for the regulation of postures and movements. Each neural mechanism involved in the regulation of phasic (dynamic) and postural (static) muscle activity is called propulsion or motor system . We can talk about the motor system of the spinal cord, the motor system of the brain stem, subcortical structures, the cerebellum and the cerebral cortex.
Accordingly, three main levels or "floors" of the organization of movements can be distinguished:
First level - spinal
The second level is the stem
The third level is the highest - subcortical and cortical.
Reflex mechanisms underlie the operation of motor centers at different levels and the entire system as a whole. Each motor level is a center of closure and association (integration) of motor reflexes of varying degrees of complexity. The lower motor levels are the centers of relatively simple motor reflexes evoked by strictly defined stimuli and carried out through constant reflex pathways. At higher levels, there is a closure and integration of more complex reflex reactions. At higher levels, interneuronal connections are even more complex. Due to the interaction between various central structures, a wide variety of motor reactions is possible.
At the same time, a clear pattern can be traced in the work of the motor centers - the subordination of the underlying centers to the overlying ones. When controlling movements, the higher motor centers exert influence on the lower motor centers subordinate to them, which cause a restructuring in their work. The nature of the restructuring at the lower level is set by the higher level in accordance with the requirements of the upcoming movement.
All motor systems work through the mandatory use of sensory information. At each moment in time, they must receive information about the position of the head and body in space and how the movement is performed.
Each moving center, at whatever level it is, receives its own share of sensory information. Neurons of local motor systems use sensory information from receptors in muscles, tendons, and joints, from superficial and deep skin receptors, and from interoreceptors in internal organs. The motor centers of the trunk, along with this information, also use signals from the vestibular, visual and auditory receptors in their activities. The motor cortex receives the sum of the necessary information from the sensory cortex, and, in addition, from the associative areas of the cortex, which have already integrated all types of sensory information. The continuous flow of sensory information in a timely manner provides each motor structure with operational feedback, i.e. information about how a particular movement is performed, what is the position of the head and body in space, whether the intended goal is achieved or not; in accordance with these data, the movements performed are constantly adjusted. A special role belongs to the information coming from the receptors of the muscles and the vestibular apparatus.
Let's move on to their consideration.
vestibular apparatus is a peripheral part of the vestibular analyzer. It is located inside the pyramid of the temporal bone and consists of a bone labyrinth, inside of which there is a membranous labyrinth repeating its shape. Between the walls of the membranous and bony labyrinth is a fluid - perilymph. The cavity of the membranous labyrinth is filled with endolymph. The labyrinth consists of two parts that perform different functions - the cochlea, in which the organ of hearing is located, and the vestibule, in which the vestibular apparatus is located.
vestibular apparatus consists of two sections - the uterus and the sac, containing the so-called otolith device, and three semicircular canals (Fig. 1A).
Figure 1. Vestibular apparatus.
A - semicircular canals, B - scheme of the scallop of the labyrinth
In the region of the maculae (spots) of the uterus and sac, near the so-called ampullae, there is a sensory epithelium containing receptors, which is covered with a jelly-like mass. This mass cushions the sensory cells and contains deposits of calcium carbonate in the form of small calcite crystals. Due to the presence of these stony inclusions, it is called otolithic membrane.
When the position of the head changes, the gelatinous mass containing the otoliths is displaced by its own weight, and the hair cells are excited. The receptors of the uterus and sac perceive the linear acceleration caused by the change in the speed of movement forward or backward, up or down. The most common form of linear acceleration is the acceleration due to gravity.
The semicircular canals (there are three of them) depart from the uterus at right angles. Their location is such that each of them responds to angular acceleration in one of three planes - frontal, sagittal and horizontal. In each channel there is an expanded section - an ampoule. The ampulla contains a receptor structure - a sensory comb or crista with sensitive hair cells. The cilia of these cells are covered with a jelly-like cap - cupula (Fig. 1B). The cupula protrudes into the lumen of the canal and is easily displaced by the movement of the endolymph filling the canal. Displacement of the cupula leads to excitation of the hair cells immersed in the endolymph. Hair cells respond to the angular acceleration that occurs when the head turns. When the head suddenly begins to rotate in any direction, the endolymph of the membranous semicircular canals, due to its inertia, remains motionless, while the walls of the semicircular canals themselves rotate. This causes a relative flow of fluid in the channels in the direction opposite to the rotation of the head and excitation of the receptor cells.
In humans, the sensitivity of the vestibular apparatus is very high. The otolithic apparatus perceives a linear acceleration equal to 2 cm/s 2 . The threshold for distinguishing the tilt of the head to the side is only 1 o, and forward-backward - 1.5-2 o. The receptors of the semicircular canals allow a person to notice an acceleration of rotation of 2-3 cm / s 2.
Information from the vestibular apparatus is sent as part of the vestibular nerve to the medulla oblongata, where it is addressed to the vestibular nuclei, and to the cerebellum. Thanks to the use of this information, any purposeful movement is performed in a position that is comfortable for the body, despite the influence of the forces of gravity.
The vestibular apparatus determines the orientation and movements mainly of the head. However, in order to determine the position of the body as a whole, it is necessary to have information about the position of the head relative to the body and different parts of the body relative to each other. This information is supplied muscle receptors (proprioceptors), thanks to which a person constantly feels the position of his limbs and the passive or active movement of the joints. In addition, it accurately determines the resistance to each of its movements.
Of particular importance in maintaining and regulating muscle tone are muscle spindles located among the muscle fibers, and Golgi tendon receptors located in the tendons (Fig. 2B).
muscle spindles . The muscle spindle is a small elongated structure, expanded in the middle due to the capsule and resembling a spinning spindle in shape (Fig. 2 B, C). In the connective tissue capsule of the spindle, on its terminal or polar parts, there are special muscle intrafusal fibers. They are called so because they are located inside the spindle, in contrast to the usual working muscle fibers, which are called extrafusal (from Latin fusus - spindle).
Thus, 2 groups of fibers can be distinguished in the composition of skeletal muscles: extrafusal and intrafusal. The extrafusal fibers form the bulk of the muscle and do all the work needed to move and maintain posture. And intrafusal fibers are modified muscle fibers that are part of the spindle and perform a receptor function.
Each intrafusal fiber consists of a central part, called the nuclear bag, and two peripheral sections, which are striated and have the ability to contract.
Muscle spindles are attached at one end to the extrafusal fibers of the muscle, and at the other end to the tendon of the muscle, thus, they are located in the muscle parallel to its extrafusal fibers (Fig. 2B). That is why they will respond to muscle stretching, since when the length of the muscle changes, the length of the muscle spindles will also change.
Figure 2. Proprioreceptors
In the central part of the muscle spindle, wrapping around the nuclear bag in the form of a spiral, there are stretch-sensitive nerve endings of sensory neurons. They serve as the main channel for transmitting information about changes in muscle length and the rate of its lengthening.
The motor innervation of the extrafusal muscle fibers is carried out by alpha motor neurons of the anterior horns of the spinal cord, and the innervation of intrafusal fibers is carried out by gamma motor neurons through gamma efferent (g-efferent) fibers. We'll talk more about this later.
Golgi tendon receptors . These receptors are located in the junction of muscle fibers with the tendon. Tendon receptors are encapsulated nerve endings that wrap around tendon bundles of collagen fibers at the junction of muscle fibers in them (Fig. 2A, B).
Both muscle spindles and tendon receptors are stretch receptors. However, their location in the muscle is different: the muscle spindles are connected to the extrafusal muscle fibers in parallel, and the tendon organs are connected in series. As a result, the nature of excitation of these two types of receptors, especially during contraction, will be different. It is believed that muscle spindles perceive mainly the length of the muscle, and tendon receptors - its tension.
Information from muscle spindles and tendon receptors is sent to the spinal cord and overlying centers.
After we got acquainted with the structure of muscle receptors, it is advisable to move on to studying the mechanisms of regulation of muscle length and tension, which will be considered together with the participation of the spinal cord that controls these processes.