The regulation of body functions

As already mentioned, a feature of every living organism is that it is a self-regulating system that responds to these pressures as a whole. This is achieved by the interaction of all its cells, tissues, organs and systems, links and vzaimopodchinennostyu all the processes occurring in them. None cell the body does not change without change and not any others. Changing the function of any organ in some degree alter the activity of other organs. It is the interaction of the most clearly expressed in the functional limits of their systems. This system consists of organs, which provides the overall activity of the adaptation to specific environmental conditions.
Relationship functions and reactions of the body — the unity and integrity of it — due to the presence of two mechanisms of regulation and correlation, ie, matching functions. One of them — the humoral or chemical mechanism of the regulation — is phylogenetically ancient. It is based on the fact that in various cells and organs in the metabolic process produces a variety of their chemical nature and physiological action of chemicals — products fission and fusion. Some of these products have a high physiological activity, ie, in very low concentrations, can cause significant changes in body functions. Entering the interstitial fluid and then into the blood, they are carried by the moving blood around the body and can affect the cells and tissues distant from those in which they are formed. The action of chemical stimuli, circulating in the blood, is addressed to all the cells, more specifically, chemical stimuli have a specific address. However, they are not the same effect on different cells: some cells are more sensitive to a chemical irritants, others — for others. Is selective sensitivity to chemical irritants. Included in different parts of the chain of metabolic processes, various chemical stimuli act differently.
A particular case of chemical regulation functions is hormonal regulation, carried out the endocrine glands.
Second, physiologically younger, that is late to develop in the evolution of living beings, the mechanism of regulation of body functions is nervous mechanism. It combines, agrees and regulates the activity of various cells, tissues and organs, adapting it to the external conditions of life of the organism. Changes in the activity and status of some cells and organs through the nervous system caused by reflex changes in the function of other cells and organs. This control mechanism is superior, first, because the interaction of cells in the nervous system is much faster than the humoral-chemical, and secondly, because the nerve impulses are always "mean" some "destination" (on neural spikes are directed only to specific cells or groups of cells).
Nervous regulation appears to change the activity of the cells to maintain a constant level of activity and a change in the intensity of the exchange of peace. The influence of the nervous system on the metabolism is regarded as an expression of its special trophic function.
Both the regulatory mechanism related. Different chemical compounds formed in the body and affect the nerve cells, changing their status. Thus, the nervous system affect the hormones produced by the endocrine glands. On the other hand, the humoral regulation is subject to a certain degree of nervous. For example, the formation and release of most hormones are carried out under the controlling influence of the nervous system. Because of this nervous system affects the function of a number of bodies, not only directly by sending nerve impulses, but also indirectly through humoral and chemical stimuli produced in the cells of the body and enter the blood under the influence of nerve impulses.
The nervous system and the chemical interaction of cells and organs provided essential feature of an organism — self-regulation of physiological functions, leading to self-sustained conditions required by the body for its existence. Any shift in the external or internal environment of the body out of its activities, has the effect the restoration of the constancy of conditions of existence, that is, the restoration of homeostasis. The more developed organism, the better development of his self-control functions, the better and more stable homeostasis.
Self-regulation is only possible because there are feedbacks between the regulated process and control system. Of the many examples that could be cited to illustrate the feedback, confine myself to two. The first example of the intermediate nerve centers of the brain, altering the secretion of hormones of the adrenal cortex (mineralocorticoid), regulate the exchange of sodium, allowing a constant concentration in the blood. This can only be achieved as a result of the shift of the sodium concentration changes the state of the nerve centers that increase or decrease the secretion of adrenal hormones. Second example: muscular movements are carried out under the influence of impulses coming to the muscles of the central nervous system. In turn, every muscle contraction results in a flow of impulses from the muscles to the nerve centers that bring them information about the intensity of the contractile process and alter their activity.
Thus, there is a circular interaction between the regulators and the regulated processes.

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