Neuro-physiological basis of sensations Visual senses Muscle movement sensations, static sensations

Muscle - movement sensations, static sensations
Musculoskeletal senses are called motor senses, and they include senses of weight, resistance, and movement of organs. Their organs consist of body muscles, tendons, and joints. There are peripheral branches of sensory nerves in the composition of organs, under their influence movement and static sensations arise.
The physical cause of muscle-movement sensations is the mechanical pressure of things affecting the muscles and body movements.
Static senses are called senses of body position in space and sense of balance.
The vestibular apparatus in the inner ear acts as a receptor for knowing the position of the body in space and maintaining balance. The vestibular apparatus consists of the semicircular canals of the auditory canal, and sensory nerve networks control the movement and position of the body in space. They are composed of small limestone crystals floating in the endolymph, which are of particular importance in maintaining the body's balance.
Organic senses
Receptors of organic senses are located in internal organs, esophagus, stomach, intestines, blood vessels, lungs, etc. Processes in internal organs are triggers of organic sensory receptors.
They include;
a) Pain sensations;
b) sensations of thirst ;
c) unpleasant feelings;
g) feeling hungry.
The change in the sensitivity of the analyzers under the influence of habituation to the sescendents in the activity is called adaptation . In this case, the general law is as follows: sensitivity increases when moving from strong to weak sescendents, and decreases when moving from weak to strong ones. The degree of adaptation of different analyzer systems is not the same: high adaptation is observed in tactile, temperature, smell and vision senses, weak adaptation is observed in auditory and pain sensations. Among them, olfactory and tactile analyzers are quickly adapted . Complete adaptation to the smell of iodine occurs after one minute . after three seconds, the pressure sensor will reflect 1/5 of the power of the sescant . It takes 45 minutes to fully adapt to the darkness .
In the textbook published under the editorship of  AVPetrovsk iy, three different types of adaptation phenomena are given : adaptation in the complete disappearance of sensation due to the continuous influence of the sedative ; Adaptation in the reduction of sensation under the influence of a strong sedative . These two types of adaptation are combined under the term " negative adaptation " , because as a result, the sensitivity of the analyzers decreases ; The increase in sensitivity under the influence of a weak stimulant is also called adaptation . This type of adaptation is called positive adaptation . This type includes , for example , dark adaptation, which is observed in the increase in the sensitivity of the vision analyzer under the influence of darkness .
The phenomenon of adaptation can be explained by peripheral changes in the activity of the receptor that occur under the continuous influence of the sequestrant . It is known that under the influence of light, the dark red color of vision in the rods of the retina fades . In the dark, on the contrary, the red color is restored, which increases sensitivity .
The adaptation phenomenon is also explained by the processes that take place in the central departments of the analyzers . As a result of long-term excitation, the cerebral cortex undergoes internal protective braking that reduces sensitivity . The development of inhibition causes a strong excitation of other foci, which contributes to an increase in sensitivity in new conditions . 
Adaptation has a biological value that is appropriate for the purpose . It participates in the reflection of weak sescants and protects the analyzers from the effects of strong sescants .
The intensity of sensations depends not only on the strength of the sensitizer and the level of receptor adaptation , but also on the effects on other sense organs at a certain time . The change in the sensitivity of the analyzer due to the activity of another analyzer is called sensitivity interaction . The change in sensitivity is explained by the bark communication between the analyzers, the law of simultaneous induction at a high level. According to IP Pavlov , a weak sescendent creates an easily spreading (irradiating) excitation process in the cortex of the large hemispheres . As a result of the irradiation of the excitation process, the sensitivity of the other analyzer increases . On the other hand, under the influence of a strong sescensing agent, an excitation process tends to accumulate . According to the law of mutual induction, this situation leads to braking of other analyzers in the central sections and a decrease in sensitivity .
The law of interaction of senses is as follows : weak sensitizers in one system of analyzers increase the sensitivity of another system, and strong sensitizers reduce it . For example , a weak sense of taste (sour) increases the sensitivity of sight , and there is an interaction between the senses of hearing and sight . The interaction of the analyzers, as well as the increase in sensitivity as a result of regular exercises, is called sensitization . According to the type of sensitization, AR Luria distinguishes two sides of increased sensitivity .As the first one is continuous, consistent and depends on the stable changes occurring in the organism, the age of the object is definitely connected with the change of sensitivity . Studies have shown that the intensity of sensory sensitivity increases with age, reaching its peak in the  20s and 30s , and then gradually declines . According to the type of sensitization, the second side of the increase in sensitivity has a temporary nature and depends on the physiological, as well as psychological effects that affect the state of the subject .
In the interaction of the senses , synesthesia , that is, the formation of the same sensory analyzer characteristic of other analyzers under the influence of stimulation, is also observed . For example , a person can develop color sensations under the influence of sounds , and certain color combinations in turn affect temperature sensitivity . It is known to everyone that we evaluate loud sounds with " bright " colors , and low ones with " dark " colors .
Synesthesia enhances the emotional tone of the senses . The phenomenon of anesthesia applies to all  modalities . It should be noted that synesthesia is expressed individually . There are people who have a clear ability to synesthesia, while others do not have it at all . AR Luria studied in detail the famous mnemonist Sh.N , described in his work . Synesthesia is expressed very clearly in this person . He saw all voices painted, and in many cases the voice of the person who addressed him, for example, " he described it as yellow and scattered . The sounds he heard evoked in him visions of different colors (from pale yellow to purple). Perceived colors were felt by him as " loud " or " muted ", " salty " or " crunching " sounds . Thus , the phenomenon of synesthesia is evidence of the regular interaction of the system of analyzers of the human organism, the integrity of the emotional reflection of the objective world . ^[2]
In psychophysiology, two types of thresholds are distinguished: the threshold of absolute sensitivity and the threshold of discrimination.