The term "homeostasis" was proposed in 1929 by the American physiologist W. Cannon, who believed that the physiological mechanisms that support the constancy of the internal environment in the body, so complex and diverse that it is desirable to combine under the name of homeostasis.

What is homeostasis

Homeostasis - a movable relative constancy of the internal fluid (such as blood, lymph, intercellular fluid), and the stability of the basic physiological functions (the cardiovascular system, respiratory system, temperature regulation, metabolism) of the human body and animals. The mechanisms to maintain homeostasis at an optimal level, called homeostatic.

Every cell in the human body is a self-regulating mobile system. Its internal organization is supported by active processes aimed at limiting or eliminating shifts which are caused by various external and internal factors. The main property of all cells - the ability to go back to the original normal state after any exposure to it.

The human body is composed of a plurality of cells which are combined with each other to perform various functions. Interaction between such associations cells perform different systems - the nervous, endocrine, immune, metabolic (metabolism). Sometimes these systems have on the cells of the opposite effect, which balance each other, creating a relatively constant temperature or moving the physiological background. This background can be changed within certain limits under the influence of different factors, but normally he always returns to its original state.

The boundaries of homeostasis may vary depending on individual (genetic) characteristics of the organism, age, gender, living and working conditions of man.

Homeostasis of blood

The constancy of the blood maintains all the other functions of the body. By definition U.Kennona blood - a liquid base body. Blood has a strong acidity (Ph 7, 35 - 7, 47), a relatively constant osmotic pressure and the ratio contained in the plasma (the liquid part of blood) electrolytes (potassium, sodium, calcium, chloride, magnesium, phosphorus), fluctuating within certain limits sugar , the number of different blood cells.

Even major pathological processes with acid accumulation in the tissue fluid is not significantly alter blood Ph. The situation is similar to the osmotic blood pressure: it is exposed to constant fluctuations, as in blood products continuously receives intermediate metabolism influencing osmotic pressure, however, these oscillations do not exceed the limits of normal. Significant changes in the osmotic pressure can be expressed only under pathological conditions.

Microenvironment of internal organs

In humans, there is a general internal environment - the blood, but the cells of organs and tissues it is not directly in contact. Each individual body has its own internal environment (microenvironment), which corresponds to its structure and functions. The normal state of each organ depends on the state of this particular microenvironments, its individual properties and the permeability of the microenvironment in the directions of the blood in the microenvironment (interstitial fluid) of the body and vice versa.

Especially important is consistency microenvironment for the central nervous system. Even minor changes encountered, e.g., in the cerebrospinal fluid may cause severe patient's condition.

Homeostatic mechanisms

There are many homeostatic mechanisms. One of the most complex mechanisms of this type of system is the maintenance of normal blood pressure (BP). The upper (systolic) blood pressure depends on the level of functionality of baroreceptors (nerve cells that react to changes in pressure), blood vessel walls, and the bottom (diastolic) blood pressure - from the blood supply to the body's needs.

By homeostatic mechanisms include processes and regulation of core body temperature: temperature fluctuations inside the body, even at very significant changes in the environment do not exceed a few tenths of a degree.

Immunological system provides immunological homeostasis, not allowing "outsider" in the form of different microorganisms enter the body. The autonomic nervous system is also involved in the maintenance of homeostasis, leveling various influences, such as stress.

To assess the state of human homeostasis are different functional assays (cold, heat, adrenaline) with determination of blood and urine ratios of the active compounds (hormones, metabolites, neurotransmitters - substances, which are transmitted by nerve impulses).

Galina Romanenko

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