From Big Medical Encyclopedia

EXTRAORDINARY IRRITANT (a synonym a pathogenic irritant) — the factor of surrounding or internal environment causing pathological changes of life activity.

The term «extraordinary irritant» was used for the first time by I. P. Pavlov in the works on physiology of century of N of for designation «extraordinary, very big intensity or highly an unusual type of external irritations», to-rye can cause various acute disorders of nervous processes (braking of earlier developed conditioned reflexes, «destruction» of conditioned reflexes and process of braking, reaction of passive protection, catalepsy, «tetanus», «hypnosis») when the irritant has «huge force at a meeting with which there is no rescue neither in fight, nor in flight». At repeated influence of Ch. of river can lead to chronic morbid conditions of a cerebral cortex; in other cases, on the contrary, gradually to become indifferent for an organism. At animals against the background of diffuse braking of a cerebral cortex of Ch. of river can sometimes not strengthen process of braking, and have opposite effect, to-ry And. II. Pavlov connected with primary impact of an irritant on a subcortex and the secondary activating influence of the last on bark.

The properties of an irritant characterizing its «chrezvychaynost», I. P. Pavlov considered the unusual nature of the influence menacing with destruction, destruction of an organism or doing it explicit harm, very big intensity of irritants indifferent in character (e.g., light, sound, vibration, etc.), an element of suddenness of irritation. For организма^ the most usual influences can become extraordinary if they synchronized action of other unconditional irritants having the extreme, menacing character earlier.

Investigating the reasons of nervous and mental disorders at people, I. P. Pavlov came to conclusion that such frustration can be also caused by Ch. river. The same force majeure at one persons lead to heavy disturbances and at the same time for other persons «with stronger nervous system» are left without effects. Thus, idea that «chrezvychaynost» of an irritant can depend not only on its objective properties, but also on features («force») of cortical cells of the individual was formulated, on to-rye this irritant influences. At the same time matter as inborn constitutional features of a nervous system (its types), and its functional state at the time of Ch.'s influence by the river.

Further representations And. G1. Pavlova about Ch. rubles gained versatile development and considerably formed a basis of modern fundamental concepts of the general pathology. The concept «extraordinary irritant» gained more general sense and approached the concept «pathogenic irritant», or «a disease-producing irritant». Rubles began to carry to Ch. not only the influences of the environment influencing an organism, but also different internal causes (the centers of a necrosis, hemorrhage, gallstones, the expressed shifts of physical and chemical parameters of internal environment, etc.).

Irritants, usual by the nature, but exceeding the limit of the range of physiological adaptive opportunities of an organism on intensity (very high and low temperatures, mechanical influences, acute psychoemotional overloads, etc.) can be extraordinary. The usual irritant can become extraordinary also in connection with the excessive duration of impact on an organism or disturbance of natural biorhythms (long sound irritation or complete silence, loneliness, stay in the dark or on light, vibration, a hypokinesia, changes of external temperature, dust content of air, a chronic psychological overstrain, etc.). In the conditions of continuous impact on an organism even subthreshold but the force of influence can gain Ch.'s character of river.

Results of impact of irritants on an organism to a large extent depend on conditions, in to-rykh they work. So, the same elevated temperature of the environment at low humidity can not cause any disorders of life activity, and in the conditions of high humidity becomes extraordinary for an organism and leads to a hyperthermia and a thermal shock (see). In other cases of a condition soften pathogenic action of an irritant, up to its full elimination.

Properties of the organism which is affected by this or that irritant — its reactivity (see Reactivity of an organism) and resistance are of exclusively great importance (see Resistance of an organism). Depending on specific, age, sexual, constitutional, individual reactivity the same irritants can act as extraordinary and cause heavy disturbances of vital processes up to death of an organism, and in other cases not to influence an organism or to cause only poorly expressed frustration. Sometimes changed reactivity of an organism leads to the fact that the most usual irritants gain pathogenic properties. This dependence is especially brightly shown on the example of various allergic reactions (see the Allergy). Can be extraordinary on the manifestation and such irritants of the environment, to-rye in normal conditions do not cause pathological effect, but cause emergence of the last at incomplete clinical recovery. Then there can be pathological effects or a recurrence which are shown in a varying degree.

Reactivity of an organism has no essential value only when the organism is affected exclusive, the extreme destroying or disturbing factors, on the properties or intensity surpassing the highest degree of body resistance and its ability to adaptation.

Bibliography: Anokhin P. K. Sketches

on physiology of functional systems, M., 1975; D and in and d e N to about in S. N. Neurosises, L., 1963; To wasps P. G. Fiziologiya's bale of the central nervous system, Kiev, 1977; Kryzhanovskiyg, N. Determinant structures in pathology of a nervous system, M., 1980; General physiology of a nervous system, under the editorship of P. G. Co-styuka and A. I. Roytbak, L., 1979; Pavlov I. P. Complete works, t. 1 — 6, M. — L., 1951 — 1952; The Philosopher

sky and social problems of medicine, under the editorship of G. I. Tsaregorodtsev, M., 1966; Hananashvili M. M. Experimental pathology of higher nervous activity, M., 1978. N. I. Losev.