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the ability of biologic systems to automatically adjust and maintain at comparatively constant levels various physiological and other biologic parameters. The controlling factors do not act on the regulated system from without but originate within the system itself. The process of self-regula-tion is frequently cyclic in nature. The deviation of any vital factor from its constant level stimulates the mobilization of the apparatus that restore it. The particular mechanisms of self-regulation vary considerably at different levels of the organization of living matter—from the molecular to the supraorganismic.
An example of self-regulation at the molecular level is an enzyme reaction in which the final product influences the activity of the enzyme. In this biochemical system, a certain concentration of the reaction product is automatically maintained. Several examples of self-regulation at the cellular level include the self-assembly of cellular organelles from biologic macromole-cules, the self-organization of different kinds of cells followed by the formation of orderly cellular associations, the maintenance of a certain transmembrane potential in excitable cells, and the regular temporal and spatial succession ion flows during the excitation of a cellular membrane.
Self-regulation is an important factor in cell division and differentiation. In mammals, for example, after part of the liver has been removed, the remaining part regenerates, automatically compensating for the loss: this is an instance of self-regulation at the organ level. The neural, humoral, and hormonal mechanisms have been studied thoroughly at the organism level. In man and other mammals these mechanisms adjust and maintain at a certain level various parameters of the internal environment, including temperature, blood and osmotic pressures, and blood sugar.
Neuroregulation is one of the principal mechanisms of the self-regulation of functions. The self-regulation of supraorganismic systems includes the regulation of population size, sex ratios, aging, and death. Supraorganismic systems include populations at the species level and biocenoses at the supraspecies level. The general patterns of self-regulation are studied by biological cybernetics. Regulation by disturbance and by deviation occurs in biological systems; the second mode differs from the first by the presence of feedback from the outputs of a system to its regulators.
Specialists differ in their interpretation of the concept of self-regulation. This is related to the differences existing between the biologic systems in which automatic regulation takes place. These systems include those in which the regulated parameters are constants and the result of regulation is stereotypical, for example, the stereotypical and therefore “senseless” behavior of insects under certain conditions. Automatic regulation is also characteristic of adaptive systems, for example, self-adjusting, self-organizing, and self-teaching systems, that automatically adapt to changing external conditions.
D. A. SAKHAROV