Sensitivity is the ability of a living organism to react to various stimuli coming from the external or internal environment. Investigation of sensitivity is playing a major role in determining the state of the nervous system of the body. However, the issue of sensitivity is of great theoretical, philosophical importance, connected with the theory of knowledge. By underlying sensitivity sensations resulting from effects on the body of different stimuli, is cognition of the surrounding world, which was formulated in a brilliant speech Century I. Lenin, who stressed that "... the feeling is really a direct link of consciousness with the outside world, is the transformation of energy external irritation in fact consciousness." (C. I. Lenin, SOBR. cit., ed. 5, I. 18, page 46.)
To understand the physiological mechanisms of sensitivity of particular importance is the teaching of I. P. Pavlov about the analyzer (see), in which there are peripheral Department - receptor apparatus, provodnikova and brain departments, mainly cortisol end of the analyzer. In basis sensitivity lies dynamic interaction of different parts of the system or that of the analyzer. In his peripheral target organ, the so-called receptor (see), born pulse propagating in the Central nervous system.
The main biological importance receptor devices is that they are capable of responding to the emergence of agitation in the irritants as a source of relevant experience pain, tactile, temperature, etc. For the origin of the feeling you want irritation that Specifies the receptor, had sufficient intensity. Minimum power of irritation that can cause the feeling is called threshold power threshold. The higher the intensity and longer duration of irritation, the faster overcome the threshold, the more intense the feeling. Anxiety receptor is determined not only by the absolute intensity of stimulation, but the number of simultaneously irritated receptors or as repeated irritation - law summation receptor stimulation. On the other hand, the excitability of the receptor and its threshold depend on the impact of the CNS and from the sympathetic innervation. Normal height threshold of different receptors is not the same.
For the correct and objective analysis of sensitive irritation and including that part of it which has no equivalent in the form of sensations, of great importance is the opportunity of reception of the electric potential, accompanying the emergence of pulses in the receptor apparatus in connection with the relevant irritation.
Receptors depending on their location divided by the SOMATO - and vicerrector. Refer to the first exteroreceptors, which are divided into distancerelated perceiving irritation at a distance (for example, visual, auditory, and others), kontaktirati perceiving irritation by contact with external object and located in the skin and mucous membranes, and proprioreceptors - in deep tissues (muscles, tendons, joints), and also in the ear labyrinth. Vicerrector - end-sensitive devices of various visceral organs, vessels and other Histological studies show the originality and complexity of the structure of finite sensitive devices. These features peripheral receptor apparatus served as starting points for clinical classification of sensitivity.
In this basis, the majority of authors marks quality, character irritation (injection, heat, touch, etc.)associated with the subjective feelings of irritation (pain and other), the scope of the impact of irritation (skin, muscle, etc). Accordingly, there are certain types 4.1. Skin, or exteroceptive, surface sensitivity - pain, tactile, thermal (heat and cold). Varieties of these species sensitivity: electric - sensations caused by different types of electric current; itching is a variety of tactile sensitivity; a sense of humidity - regrette (it is based on a combination of tactile sensations with temperature). 2. Proprioceptive, deep sensitivity - Batistuta. These include muscular-articular sensitivity or sensitivity of position of a body in space; vibration - parestesia; a feeling of pressure - parestesia. 3. Interoceptive, vegetative-visceral covering the sensitivity of the internal organs, blood vessels and so on Separately allocate complex kinds of sensitivity, dominated by more complex analytic processes - discriminatory, two-dimensional spatial, stereognosis. Classification Ged (see Ged zone), all the sensitivity to be divided on Protopriest associated with the visual hill - more primitive, ancient, and apocriticus - a newer, more complex defined by the cerebral cortex. Provisions Ged not confirmed by the modern data, though these terms are used in the clinic.
Specific differentiation of sensitivity associated with the structural and physiological features of the peripheral nerve fibers. Emerging in the receptor apparatus sensitive impulses are different structure of fibers with different speed depending on the severity of the myelin layer and different frequencies note the fluctuations of the electric potential. Structural differences reflect physiological and different functional significance of nerve fibers. So, fiber groups And with thick of the myelin sheath, supporting rapid pulse, providing in-depth and sensitivity. Fiber groups In thin myelin sheath, with a slower pulse, conduct pain, temperature and sensitivity and bezmalinovic fibers, slowly conducting impulses - diffuse non-localized pain.
All the impulses that arise in peripheral device overall sensitivity, fall mainly through the rear spinal roots in the Central nervous system, where and experience. The occurrence of any feeling is determined by the process afferention, distribution of specific impulse from the appropriate receptor on certain conduction paths. In response to that, or other irritation activate all the relevant departments of the analyzer and the usual sense, respectively mind sensitivity is always the result of a complex interaction of different mechanisms until cortical, which determine, by I. P. Pavlov, analysis and synthesis of incoming pulses. Of great importance for a proper understanding of the Central mechanisms of sensitivity has given its multifaceted interactions with reticular formation, this sort ascending activating the so-called non-specific system of the brain. It is important that the reticular formation and descending has regulatory effect on peripheral receptor apparatus and process afferention in sensitive ways. Thus, sensitivity, which previously was considered only as a result of unilateral afferention, passive holding of a receptor of excitement in the Central direction, acts as a complex system with double bonds, with an active influence on the flow of sensitive pulse and constant regulation of the level of excitability of various localization links sensitivity through facilitating and inhibiting influence. All the values are certain prerequisites for the correct estimation of cortical-subcortical relationships in the mechanism of sensitivity.

Sensitivity - the property of a living organism, which is expressed in the perception of stimuli from the environment and from its own tissues and organs. There are exteroceptive sensitivity (surface), proprioceptive sensitivity (deep) and interoceptive, or vegetative-visceral sensitivity (from internal organs, blood vessels and so on). There are also complex kinds of sensitivity (stereognosis and others). The perception of irritation in humans exists only if the inseparable connection of the receptor, i.e. peripheral parts sensitive analyzer (see), with its cortical Department. The relationship between these departments parser goes through trejdingovuju chain of neurons.
Depending on which of the neurons breach occurs, clinically will be observed this or that type of sensitivity disorders, the nature of which is based diagnostics damage. For this determination, you need to know anatomy course sensitive pathways and distribution of peripheral neurons.
Each segment of the spinal cord is connected through the rear roots with strictly corresponding skin segment. Irritation of skin segments are on different peripheral nerves (for example, neck and shoulder and lumbar-sacral plexus), so when the defeat of the posterior roots picture of the fallout of sensitivity is different from precipitation sensitivity observed in the peripheral nerves (Fig). It gives the right to talk about the frustration of sensitivity in peripheral and radicular type, i.e. about the siege of nerve impulses in the trunk of a peripheral nerve or in a particular rear root of the spinal cord, which is celebrated with neuritis, radiculitis. With radicular type drop sensitivity coincides and segmental type drop sensitivity with the defeat of the posterior horn of any segment of the spinal cord. However well they are different, as segmental type falls sensitivity dissociate type, i.e., only pain and temperature sensitivity, and stored deep sensitivity. This is because fiber rear of the spine at the entrance to the spinal cord is disconnected. Fiber, which impulses are transmitted from the muscles and joints, without going into the back horn, on the back of the stakes go up to level oblong brain to switch to the second neuron making the transition to the opposite side and reaching vision of the hill, where now the third neuron brings momentum to the back and front of the Central brains of the big hemispheres of a brain. Thus, deep sensitivity is transmitted on the rear pillars same side. Zadnekamernye fiber transmission of pain and temperature sensitivity, come into gelatin rolandovna the substance of the posterior horn of the same segment of the spinal cord, where it switches to the second neuron, rising up, goes ahead of the Central canal of the spinal cord to the opposite side and is on the side column of the spinal cord, forming Spino-thalamic the way, comes to the optic of the hill, and then in the third neuron impulses reach back Central gyrus, i.e. cortical part of skin analyzer. Thus, segmental type of sensitivity disorders, or otherwise Sudarikova type of sensitivity disorders, will be identified in those cases where the patient on certain skin segments drops of pain and temperature sensitivity and deep is not disturbed. For example, during those of syringomyelia (see) is well known for such areas to loss of sensation in the form of jackets or olukordi, and in patients in these areas of the body often there are traces of previously obtained painless burns.

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