General pathogenesis

The damaging effect of rays of the solar spectrum

The action of ultraviolet radiation

Ultraviolet (UV) radiation to penetrate skin and conjunctiva of the eye to a depth of several tenths of a millimeter. Nevertheless, its effect is not limited to local variations, but extends to the entire body.

Biological properties of UV radiation different in wavelength dependence. In this regard, the entire UV range is divided into three areas: area A (longwave) - 400-320 nm; area B (medium wave) - 320-280 nm; аrea C (short-wave) - 280-200 nm.

Area A also called fluorescence (for ability to cause luminescence of some substances, such as in fluorescent lamps), or in connection with suntan chromogenic effect: under the influence of UV radiation generated from the amino acid tyrosine melanin, which organism is a protective agent against excessive UV radiation.

Area B (after brief exposure to UV light in small doses) is characterized by a strong general stimulating effect. General stimulating mechanism of the photochemical action of UV radiation is associated with the ability to initiate its atoms to increase their reactivity. In general this leads to increased activity of chemical reactions in the cells, which stimulates the metabolic and trophic processes. Ultimately, the enhanced growth and tissue regeneration, increases the body's resistance to the action of infectious and toxic agents, improves physical and mental performance. UV radiation in the range 315-265 nm region in have vitamin formation antirachitic action: under its influence from the 7.8-dehydrocholesterol synthesized vitamin D3 (cholecalciferol).

Area C has a strong bactericidal effect, the maximum of which is at the wavelength of 254 nm.

Disposable excessive UV exposure causes skin absent suntan its photochemical burns, accompanied by the development of erythema and Blistering skin reactions, fever, headache, a common painful condition. It may be the conjunctiva eye disease (photoelectric ophthalmia) manifested its redness and swelling, burning sensation, and "sand" in the eyes, watery eyes, pronounced photophobia. Photoelectric ophthalmia phenomena can be observed both from direct sunlight and from the scattered and reflected (from snow, sand in the desert), as well as when working with artificial sources of UV radiation, such as welding.

The pathogenic effect of excess disposable UV irradiation (photochemical burn) associated with the activation of free radical (superoxide) oxidation of lipids, resulting in damage to the membranes, the disintegration of the protein molecules, cell death in general.

Excessive UV radiation can provoke the exacerbation of certain chronic diseases (rheumatism, gastric ulcer, tuberculosis and others.). With intensive UV irradiation due to increased melanin formation and degradation of proteins in the body increases the need of essential amino acids, vitamins, and other calcium salts. Excessive exposure to UV radiation in the range of wavelengths 280-200 nm (region C) may cause inactivation cholecalciferol to its conversion into indifferent (suprasterine) and even harmful (toxisterin) substances that must be taken into account when preventive UV irradiation.

Prolonged excessive UV exposure can promote the formation of peroxide compounds and epoxy substances having a mutagenic effect, and induce the occurrence of basal cell and squamous cell skin cancer, particularly in people with fair skin.

UV radiation is enhanced by so-called photosensitizing. These include dyes (methylene blue, rose bengal), cholesterol, and porphyrins, as well as contact photosensitizing (perfumes, lotions, lipsticks, creams and other cosmetics).

There have been cases of hypersensitivity to UV radiation – photoallergy. For example, in people with high blood porphyrins due to violation of hemoglobin transformations (for example, hematoporphyria) even after short-term exposure to the sun can cause burns and severe state of intoxication toxic products irradiated porphyrin. Especially high sensitivity to UV radiation have xeroderma pigmentosum patients. The resulting effect of UV irradiation on the skin burns open areas of these patients in the 50% pass in carcinoma.

The general effect of UV radiation in conjunction with the thermal effect of the sun's rays (infrared rays heats the deeper tissues) manifests itself in the form of so-called heat stroke. The action of UV radiation on the nervous system is mediated through the skin capillaries in the irradiated blood cholesterol and proteins. There is the excitement of the autonomic centers of the hypothalamus and basal ganglia, increased body temperature, increased blood pressure and continue to fall, drowsiness, collapse and death from paralysis of the respiratory center. Sunstroke often occurs with prolonged stay on the beach.

Pathogenic effect of low temperatures. Hypothermia

As a result of the low temperatures in the human body, a number of general and local reactions, which may cause a cold, reduction of body temperature, local changes in the tissues (frostbite) and freezing body end. The occurrence and severity of changes in the body depend upon cooling to the ambient temperature and the nature of its effect (air and water), air flow velocity (air) and moisture, the insulation properties of the thermal protection of the organism, and other factors. There are general and local cooling of the body.

Total cooling - a violation of the heat balance in the body, leading to a decrease in body temperature (hypothermia). Hypothermia occurs:

1. With enhanced impact of heat and normal heat production;

2. While reducing heat production and the normal impact of heat;

3. A combination of these factors.

Most often found in warm-blooded animals the first version of hypothermia, so the phase compensation reaction directed primarily at the heat transfer restriction: reflex occurs spasm of vessels in the skin, reduces sweating, breathing slows down. Further included thermoregulatory mechanisms to increase heat production: there is muscular shivering (chills), strengthens the processes of glycogenolysis in the liver and muscles, increased blood glucose, increased basal metabolic rate.

With long-term effect of low-temperature phase of developing decompensation. Body temperature decreases, stops muscle tremors, reduced oxygen consumption and metabolic rate, dilate the peripheral blood vessels. As a result, the braking function of the cerebral cortex and subcortical structures of oppression and bulbar centers decreases blood pressure, slows the heart rate progressively weakens and becomes less respiratory rate, there is a gradual extinction of all life functions. Death occurs from paralysis of the respiratory center.

The oppression of the central nervous system when supercooling may have protective value that is associated with a reduction in the sensitivity of nerve cells to oxygen deficiency. Reduced metabolism in tissues reduces the body's need for oxygen. It is also known that hypothermia increases resistance to poisoning, infection, and some other adverse environmental effects. Artificial temperature decrease (hibernation) of the body, under anesthesia achieved by physical effects used in medical practice (particularly in cardiac and neurosurgery) in order to reduce the body's need for oxygen and prevent temporary brain ischemia.

Local effect of low temperatures can cause frostbite of varying severity, pathogenesis of which is associated with changes in tissue colloidal state intracapillary impaired blood flow and blood rheology.

Pathogenic effects of heat. Overheating. Heatstroke.

The action of heat can cause burns, burn disease and hyperthermia.

Burns (thermal) - Local (local) damage to tissues by increasing their temperature within 45-50 °C and higher as a result of the action of flame, hot liquids, steam, heated solids. Depending on the depth of tissue damage are four degrees of burns: 1) skin redness (erythema); 2) the formation of bubbles; 3a) a partial or complete necrosis of the Malpighian (sprout) layer of the skin; Zbigniew) complete necrosis of the skin during the whole of its thickness; 4) necrosis of the skin and deeply lying tissues.

The mechanism of burns associated with an inflammatory response at the site of action of thermal agent and coagulation proteins, leading to cell death and tissue necrosis.

Burn disease - versatile functional disorders of the internal organs and systems of the whole organism, caused extensive (more than 10-15% of the body surface) and deep burns. In the development of burn disease is divided into four periods:

1. Burn shock;

2. General toxemia - the result of auto-intoxication decomposition products tissue formed at the site of burn (denatured protein, biologically active amines, polypeptides, and others). And the production of specific autoantibodies burn. Additionally, in animal and human skin burn autoantigen was found absent in healthy people and in other tissues character the damage;

3. Septic (accession infection);

4. Convalescence (recovery).

Overheating (hyperthermia) - passive temporary increase in body temperature due to the accumulation of excess heat in the body (with a loss of heat transfer processes and a high ambient temperature operation environment).

To maintain the normal body temperature at the maximum level of heat (work) and enters the body of 100-150 kcal / hr of heat by thermal radiation heat transfer is required in the total environment of about 500-600 kcal / hr.

When aligning the skin and the ambient temperature (average 33 ° C), the heat output from the body surface due to convection and heat radiation stops. At higher ambient temperature, the heat output is only possible due to the evaporation of sweat from the skin surface. Termination of office or evaporation of sweat (high humidity, water-resistant clothing, etc.) can lead to overheating even at 33-34 ° C. Overheating contribute to water shortages in the body and lack of replenishment of its losses through sweat.

Increased body temperature is accompanied by a dramatic increased frequency of respiratory movements, caused by irritation of the respiratory center of the heated blood (PN Veselkin), shortness of breath develops heat. Further notes quickening heart rate and increased blood pressure. Due to the loss of water through sweating occurs blood clots, disturbed electrolyte metabolism, increased hemolysis, there are phenomena of intoxication decay products of hemoglobin. Damage to the various tissues is also accompanied by the accumulation of toxic products of their decomposition. In connection with the destruction VII, VIII, X and other plasma clotting factors is disrupted.

Overvoltage mechanisms of thermal regulation leads to their depletion, accompanied by inhibition of the central nervous system, respiratory depression, cardiac function, blood pressure reduction, and ultimately - to the profound hypoxia.

Acute hyperthermia with a rapid rise in body temperature and prolonged exposure to high ambient temperatures can cause heat stroke.

Death at a heatstroke occurs from paralysis of the respiratory center.

etiological factor	Hyperthermia body and blood	I stage		II stage
		Stimulation of the cerebral cortex (delusions, hallucinations)		Inhibition of the cerebral cortex, loss of consciousness
		Excitation of the bulbar respiratory center	Thermal shortness of breath	Stop breathing movements. The paralysis of the respiratory center
Ambient temperature 50 ° C		The excitation of the heart muscle and its sympathetic innervation	Tachycardia
		Excitation of the vasomotor center	Reducing arterioles (hypertension)	Inhibition of the vasomotor center, lowering blood pressure, collapse
Temperature 40 ° C, humidity 80%		Violation of thermoregulation, increased heat production and heat	The sharp increase in blood temperature (up to 41-43 ° C)	The continuation of heat and fever after death
		Concentration of of blood	Increased blood viscosity, albuminosis, polycythemia

Sunstroke. The cause and pathogenesis of sunstroke.

Sunstroke, as a form of hyperthermia states, it has some differences from hyperthermia both because of, and in the mechanisms of development.

Cause. The cause of sunstroke sunstroke is a direct effect of solar radiation on the body. Most pathogenic effect, among others, provides the infrared part of solar radiation, i.e. radiative heat. Last, unlike the conductive and convective heat-foot, and heats both superficial and profound tissue. In addition, the infrared radiation acting on the whole body, and rapidly heats the tissue of the brain in which neurons are located the center of thermoregulation. In this regard, sunstroke developing fleeting and fraught with fatal.

Pathogenesis. The pathogenesis of sunstroke sunstroke - a combination of hyperthermia and the actual mechanisms of sunstroke.

Leading are the various CNS.

1. Increasing arterial hyperemia of the brain.

Causes:

- An increase in temperature of the brain under the influence of infrared (heat) radiation from sunlight.

- BAS produced directly in the brain tissue: kinins, adenosine, acetylcholine, and others. Long term effects of heat and various vasodilators reduces neuronal and myogenic tone of the walls of the arterioles to the development of pathological (!) Form of arterial hyperemia neyromioparaliticheskomu mechanism. Arterial hyperemia leads to an increase in blood supply to the tissue. For the brain, located in the confined space of the skull bone, which means its compression.

2. Increase (in terms of arterial hyperemia), and lymph formation of filling excess lymph lymphatic vessels, which leads to an increase in compression of the brain substance.

3. Progressive venous congestion of the brain. Its cause is the compression of the brain, including the occupants of the veins and sinuses. In turn, venous congestion leads to the development of cerebral hypoxia, cerebral edema and small focal brain hemorrhage. The result is a focal symptoms in a variety of neurogenic disorders of sensitivity, movement and autonomic functions.

4. Growing errors of metabolism, energy supply and plastic processes in the neurons of the brain. It potentiates decompensation mechanisms of thermoregulation, disorders of the cardiovascular system, respiratory, endocrine glands, blood and other organ systems. In severe changes in the brain of the victim loses consciousness, coma develops. Given the intensive growth of hyperthermia and disturbances of vital activity, sunstroke is fraught with a high probability of death (due to the dysfunction of the CVS and the respiratory system), as well as development of paralysis, nervous disorders, sensitivity and trophism.
The damaging effects of ionizing radiation

General characteristics of the damaging effects of ionizing radiation

Acting on the body ionizing radiation sources may be both external and internal. Man is exposed to ionizing radiation in the working environment, working with X-ray equipment, nuclear reactors and particle accelerators (Betatrons, cyclotrons, synchrotrons, linear accelerators), with radioactive isotopes, mining and processing of radioactive ores. In clinical practice, patients receive radiation therapy for therapeutic purposes. Finally, radiation may be due to the use of nuclear weapons and accidental releases of nuclear technology product companies in the environment.

The source of internal radiation can be radioactive substances entering the body with food, water, through the skin. Perhaps the combined effect of external and internal exposure.

Ionizing radiation, having the ability to cause ionization of atoms and molecules that are characterized by high biological activity. By their nature, all ionizing radiation is divided into electromagnetic (X-rays and gamma rays that accompany the radioactive decay) and corpuscular (charged particle: a helium nucleus - a-rays, electrons - p-rays, protons, pions and neutrons, do not carry an electrical charge).

The damaging effect of different types of ionizing radiation depends on the value of the ionization density in the tissues and their penetrating power. The shorter path of photons in the tissues and particles, the more they caused ionization density and stronger damaging effect.
Penetration and density of ionization of various types of radiation with an energy of 2 MeV

Type radiation	Length, m	Density radiation, ions/mkl
α-radiation	0.01	6000
β-radiation	10	6
γ-radiation	about 600	0,1

Most ionizing power at the a-rays having a run length of biological tissues a few tens of micrometers, the lowest - in the y-rays have great penetrating power.

The biological effects of ionizing radiation of different types are not only determined by the total amount of absorbed energy, but also its distribution in the tissues. For comparative quantitative assessment of the biological effect of various types of radiation determined by their relative biological effectiveness (RBE). The greatest biological efficiency characterized as radiation, protons, fast neutrons, the RBE for which equals 10. As a criterion for determining the RBE used mortality rates, the degree of hematological and morphological changes in tissues and organs, the effect on the sex glands and OE in this regard, RBE is not constant.

The values for the relative biological effectiveness of different types of radiation

Type radiation	RBE
γ-wave and X-ray beam	1
β-particle and electron	1
α-particle and proton	10
thermal neutron	3
fast neutron (to 20 MeB)	10
Multiply charged ions and nuclear recoil	20

The biological effects are determined not only by the type and the amount of absorbed radiation dose, but also its capacity. The unit dose is the gray (Gy), and for comparative biological assessment of various types of radiation, a special unit - rem. The higher dose rate, the greater biological activity. The damaging effect of ionizing radiation for short irradiation is more pronounced than in long-term irradiation in the same dose. Irradiation can be single, fractional and time-consuming. When fractional (fractionated) and long-term exposure of the body damage caused by higher total doses. The severity of ionizing radiation also depends on the area of the exposed surface of the body (general and local), especially individual reactivity, age, sex and the functional state of the body prior to irradiation. It is believed that exercise, changes in body temperature and other influences affecting the metabolism, have a significant impact on the radioresistance. Young and pregnant animals are more sensitive to ionizing radiation.

Even in a variety of body tissues and cells differ in radiosensitivity. Along with radiosensitive tissues (bone marrow hematopoietic cells, reproductive glands, small intestinal mucosal epithelium) are stable, radioresistant (muscle, nerve and bone).
The mechanisms of action of ionizing radiation on living organisms. Common pathogenesis

Biological effects of ionizing radiation is reflected in the development of local radiation reactions (burns and cataracts) and special generalized process - radiation sickness. In the process of the damaging effect of radiation can be roughly divided into three stages: a) the primary action of ionizing radiation; b) the impact of radiation on cells; c) the effects of radiation on the whole organism.

The primary action of ionizing radiation on living tissue is manifested by ionization, excitation of atoms and molecules and thus the formation of free radicals, HO, HO2 and hydrogen peroxide (H2O2), the existence of which does not exceed 105-106 with (direct effect of radiation). The ionization and excitation of atoms and molecules of the irradiated tissue cause the trigger biological effects of radiation.

Free radicals cause chain reactions, react with the most reactive protein structures of enzyme systems (SH-groups) and translate them into inactive disulfide group (S = S).

Indirect (indirect) effects of radiation due to the radiation-chemical changes in the structure of DNA, enzymes, proteins, etc., caused by the water radiolysis products or substances dissolved in it, has a high biochemical activity and capable of causing an oxidation reaction on any links.

The oxidation of unsaturated fatty acids and phenols form lipid (peroxides, epoxides, aldehydes, ketones) and quinone primary radiotoxins that inhibit the synthesis of nucleic acids, which suppress the activity of various enzymes that increase the permeability of biological membranes, and alter the diffusion processes in the cell. This results in a violation of metabolic processes, functional and structural damage to the cells, organs and body systems.

The effect of ionizing radiation on cells

Ionizing radiations cause various cell responses - from the time delay breeding until their death. Even in 1906, L.Bergonie and I.Tribondeau noted that the radiosensitivity of tissues proportional to proliferative activity and inversely proportional to the degree of differentiation of its constituent cells. Radiosensitivity tissue cells can be arranged in the following descending order: lymphoid organs (lymph nodes, spleen, thymus), bone marrow, testes, ovaries, mucous membrane of the gastrointestinal tract, the skin and other epithelia.