regulation in biological systems

From Big Medical Encyclopedia

REGULATION in biological systems — set of the processes aimed at maintenance of a certain structure of biological system at providing the necessary modes of its functioning and at achievement by system of definite purposes. The principles P. extend also on social, technical, etc. systems.

Often the term «regulation» is identified with the term «management». In particular, at the description of biological systems terms «management» and «regulation» often act as synonyms, and the second of them is more preferably used. At the same time in technical literature of R. is considered, as a rule, as a special case of management when the purpose of functioning of system is limited to stabilization of an adjustable signal in an object, i.e. maintenance of its equality a nek-swarm to the set size.

Fig. 1. General scheme of system of regulation: the system consists of two subsystems — the regulating subsystem (R) and an object of management (O). Managing influences are developed in the regulating subsystem on the basis of information on the purposes of management, the revolting influences (for example, about a condition of the environment) and about a condition of an object of management, received by means of a feed-back (it is specified by an arrow from About to P).

The system of regulation (fig. 1) in a habit view is divided into two subsystems — managing and managed. The managed subsystem usually is called object of management, the managing director — the regulating subsystem, or the regulator. Obtaining information on the purposes of management, the revolting influences and on a condition of an object, the regulator develops control signals, to-rye arrive on object of management and change its state in the necessary direction. The revolting influences are understood as any signals or hindrances breaking a functional linkage between the signals arriving on the actuation device and the signals informing on a condition of an object of management.

This general scheme effectively describes management in systems of any nature, however in the analysis of biological systems it is necessary to consider that both an object, and the regulator represent very difficult, being in interaction specific complexes.

The principles of creation of control systems and pattern of course of processes in them are studied by the theory of automatic control (TAC). Originally it developed as purely technical science — the theory of automatic control (TAC), for a cut the problem of stabilization in simple one-planimetric systems, i.e. a problem of automatic control is characteristic. This task enters TAU as a component of a problem of ensuring due functioning of complex multicircuit systems in the changing conditions of the environment. After the American scientist — the creator of cybernetics N. Wiener stated the idea about a community of management processes in the equipment, economy and live organisms, scope of the TAU methods sharply extended. In the most habit view management in complex systems irrespective of their nature is studied in to cybernetics (see).

In biosystems (see. Biological system ), life activity to-rykh is based on a continuous metabolism, creation of a stock and an expenditure of energy, effective use of energy resources is possible only in the presence of enough perfect systems of regulation. The river in them is carried out at all levels of the organization — from cellular to a complete organism and nadorganizmenny systems (ecosystems, the biosphere in general). Specific mechanisms P. are characteristic of each of these levels though they have also many common features. Apparently, mechanisms P. at the level of a complete organism, and also its separate physiological systems and bodies are most effective and various. Complexity and R.'s perfection at this level is defined by what here gets the leading role nervous system (see), on to-ruyu the main functions of management in an organism lay down. The difficult mechanisms P. coordinating processes of life activity and behavior of a complete organism are combined also with the simplest mechanisms of an autoregulyation of separate variables entering as elements uniform system P. in an organism (see. Biological system, an autoregulyation in biological systems ).

Fig. 2. The simplified flowchart of flows of substances, energy and information in an organism of an animal. Receiving incentives and indignations from the environment, the organism answers them with the corresponding reactions (it is designated by shooters). All elements of an organism (managing and executive) receive energy from the power system (PS) according to the requirements, and the managing system (MS) defines what processes and with what speed shall go to ES to support the necessary mode of functioning of systems of an organism.

In fig. 2 the scheme of flows of the movement of substances, energy and information is provided in an organism of an animal, in it two main components are allocated: object of management, the Crimea is a power system — the set of the metabolic processes proceeding in cells of an organism, providing requirements of all bodies and fabrics for substances and energy and managing system, defines edges what metabolic processes and with what speed shall proceed in an organism.

Mechanisms P. in biosystems are divided on passive and active. Passive mechanisms of CDC «are built in» the general control system, their regulating action is defined, according to L. Bertalanffy, by «interaction of the elements making system». Passive R. is peculiar to many physiological systems. In particular, decrease in body temperature in cold conditions leads to reduction of temperature difference between a body surface and Wednesday. And as heat waste due to heat conductivity, convections and radiation owing to physical laws is defined by this difference, rates of heatlosses automatically decrease. Passive character of the «built-in» mechanisms such means that at the set organization of live system their managing action is carried out «passively» at the expense of the functioning systems without special expense of metabolic energy.

Practically in all biosystems on internal mechanisms P. the external mechanisms consisting of the special elements which are structurally allocated from system are imposed. These mechanisms are active as implementation of managing functions by them demands from system of additional metabolic expenses. In particular, mechanisms of c. N of page, reacting to decrease in body temperature, increase rate of heat production and by means of vascular reactions reduce rates of a thermolysis that in general leads to preservation of a heat balance and prevents fall of temperature of a body. The characteristic response of system to fall of temperature of the environment leads to increase in an expense of metabolic energy which goes for implementation of process of active thermal controls (see).

The main means of achievement of goals of R. is feed-back (see), being that the output, adjustable signal of a condition of an object of management comes back on an entrance of system — to the actuation device. Rather smaller role in biosystems is played by a so-called feedforward, at a cut the regulator develops managing influences directly on the basis of information on indignation (see fig. 1).

By means of managing mechanisms in biosystems variables of two types — or quantities or concentration (levels) of nek-ry substances, or speeds (rates) of course of these or those processes, including — speeds of biochemical reactions can be regulated. Both rates of these processes, and levels of maintenance of substances in an organism are regulated by the whole system of mechanisms through certain executive bodies. So, oxidizing processes in fabrics are controlled purposeful changes of respiratory volume, vital capacity of lungs, volume of reserve air, depth of a breath, respiration rate, stroke output of heart, heart rate, rate of volume flow of a blood-groove, size of vascular resistance, amount of hemoglobin in blood, sizes of oxygen capacity of blood, an erythrogenesis etc.

R. in physiological systems of an organism is directed to achievement of a number of results (see. Functional systems ). The river is carried out by mobilization of reserves and reasonable change of speed of the adjustable processes directed to compensation of speed of a consumption of substances on average for some span here. Maintenance of constancy of levels of substances means preservation of internal conditions, stability of internal environment of an organism, i.e. homeostasis (see).

For the first time two specified purposes P. in an organism were compared by I. M. Sechenov, to-ry wrote that «Arrival and a consumption of mineral substances are equal among themselves, and it is, of course, the guarantee for the fact that the content of these substances in an organism is constant».

Fig. 3. Graphic representation of typical dependence of controlled variables of internal environment of an organism on external conditions: 1 — area of environmental conditions in which mechanisms of management provide both a stationary disbalance in system and a homeostasis (the plateau on a curve means relative constancy of internal environment). At an exit out of borders of this area (2) the homeostasis of system is broken since variables of internal environment can change at change of external conditions. At hit in extreme conditions (3) mechanisms of management are not able to provide stationarity any more, and life is possible only during a short time slice — up to exhaustion of the reserves of the substances necessary for ensuring life activity which are saved up in an organism (it is designated by a dotted line).

Results of activity of regulatory mechanisms in an organism are illustrated by fig. 3, on Krom characteristic dependence of variables of internal environment of a live organism on external conditions is given. Such dependence is known for change of temperature, concentration of oxygen in blood and fabrics, osmotic concentration and other variables internal environment of an organism (see). The better the system of regulation is organized, the area of a homeostasis on each of the interconnected variables is wider, the better within this area constancy of internal environment is maintained.

As hierarchically even more high aim of R. it is possible to call the maximum increase in efficiency and the best quality of functioning. Often at the formalized description of processes of R. in biosystems this purpose is defined as achievement of an optimality of system.

New perspectives in theoretical and practical application of the theory of R. in biosystems it is connected with emergence of new type of the biocybernetic managed systems — artificial organs (see) and active systems of individual protective equipment (see. Space suit ). Intensively methods P. of the mode of sugar of blood (a so-called artificial pancreas) develop, hemosorptions (cm), the most difficult problem of creation of artificial heart is solved. Implementation in practice of thermal protective equipment with active cooling or heating begins. At management of complex systems of such and artificial organs there is a new type of biocybernetic systems, in to-rykh all set of physiological mechanisms P. closely interacts with artificial (technical) means and control units.

See also System , Management .

Bibliography: Novoseltsev V. N. Theory of management and biosystem, M., 1978; Sechenov I. M. Chosen works, page 34, M., 1958; The Theory of systems and biology, the lane with English, under the editorship of V. I. Krinsky, page 7, M., 1971; In e-talanffy of L. General system theory, N. Y., 1969; Milsum J. H. a. Outer-bridge J. S. Homeostasis, control theory and cybernetics, in book: Med. engineering, ed. by Ch. D. Ray, p. 90, Chicago, 1974.

Century of H. Novoseltsev.