PHYSIOLOGICAL LAWS

Nervous impact on the cardiovascular system weakens. In contrast the role of the humoral factors (the liquid medium of the body - lymph, blood, bile, etc.) yields higher significance in the elderly. The total amount of water in the muscles is reduced. It is proved reduction in the intracellular and increase of the extracellular water. In muscles of old animals is demonstrated increased content of sodium, chloride and calcium and reduced - of potassium, magnesium, phosphorus and nitrogen. The concentration of potassium and sodium ions in the muscle fibers in old age is amended. The concentration of potassium ions is reduced and the ions of sodium are increased. In young age, the potassium content in the muscle fiber is significant but sodium is lower. In old age is reduced the synthesis of acetylcholine which is participating in the mechanism of transmission of neuromuscular pulse. The process of excitement is carried out in delayed manner in the muscle fibers. The amount of mitochondria also decreased while the rest are often subjected to dystrophic changes. The protective properties of the skin in older people decreases, resulting in the commonly observed infections. There is an increased sensitivity of the skin to some drugs. Could be sensed thickening of the corneous layer (stratum corneum, keratosis). Increases the pain threshold. Could be observed disorders of a thermoregulatory reflexes. Frequently responses are uneven. Reduces the secretion of saliva and its enzyme activity is decreased. Functional expression of these changes is the dryness of the mouth. Following single administration of small doses of thyroxine (a hormone secreted by the thyroid gland) in old animals are observed pronounced changes in the quantities of gas exchange, excretion of nitrogen in urine and cholesterol level in the blood as compared to young animals. Widely known is the fact that the tolerance of the organism to carbohydrates with age is lowered. After menopause due to the decreased excretion of estrogens and pregnanediol occur atrophic changes (reduced or interrupted blood supply) in the organs of the reproductive system. Prominent disease states, such as osteoporosis of the bones, impaired lipid metabolism, increased rate of progression of atherosclerosis and the like are oftenly associated with reduced production of estrogen. Tissue sensitivity to hormones in old age is greatly enhanced. In the process of aging is disturbed the metabolism of testosterone. Studies of long-living people and centenarians showed that in old age is developed anemia from hypoplastic type (as a result of improper functioning of the bone marrow) thereby assuming an "extinction" of hematopoiesis (blood formation). Platelets are restored in the lower limit of the range. As regards the overall blood coagulability most scientists noted an increased potential for blood clotting. For growing hypercoagulation convincingly evidence the thromboelastograms which acquire "thrombophilic" type. In the plasma of the blood in the elderly is marked an increase in the protein fractions - alpha, beta and gamma globulins and the content of albumin is reduced. Blood glucose increases. The concentration of cholesterol also increases up to the age of 60 then slowly decreases. There are found normal characteristics of the blood cell and hemoglobin levels typical of people in the active age. The levels of total cholesterol and total protein in the blood serum in centenarians do not differ significantly from those in adulthood. It is noted a reduction of the alkaline reserve in the blood in old age. The organs having absolute and relative weight which grows to the old age are the blood vessels, the heart and the lungs. Absolute share of other organs increases to a certain age in parallel with the body and their relative share begins to fall almost from the day of birth - brain, liver, kidneys, thymus gland, spleen and some other organs.

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