SELF-CONTROL OF PHYSIOLOGICAL FUNCTIONS

From Big Medical Encyclopedia

SELF-CONTROL OF PHYSIOLOGICAL FUNCTIONS — one of mechanisms of maintenance of life activity of an organism on rather fixed level.

Page f. t. it is inherent in all forms of the organization of life activity and arose in the course of evolution as result of adaptation to action of the environment. The general regulatory mechanisms of various physiological nature (neurohumoral, endocrine, immunological, etc.) directed to achievement and maintenance were developed by such way homeostasis (see).

In 1932 I. P. Pavlov wrote that the live organism is system, in the highest degree self-regulating, supporting itself, recovering, correcting and even improving. He assumed existence of two levels C. f. t.: the lowest (at the level of subcrustal structures of a brain) and the highest (with the defining participation of a cerebral cortex). In 1933 — 1935 M. M. Zavadovsky on the basis of studying of humoral mechanisms of regulation in the growing organism put forward the all-biological principle of regulation of developments and a homeostasis «a plus-minus interaction». In his opinion, development is carried out on the basis of interaction of an organism and the environment, and development of bodies happens on the basis of contradictory interaction of at least two bodies. The developing animal, in his opinion, represents self-regulating system with high degree of stability, in a cut regulation is inherent in all organism and each link separately. In addition to the mutually contradictory relations between bodies, M. M. Zavadovsky emphasized existence of relationship like «plus — plus» and «minus — minus», to-rye provide harmonious development of an organism. Investigating generally patterns of humoral regulation, he attached great value to nervous control and relationship of an organism with external environment.

In 1935 P. K. Anokhin entered idea of the functional system which is in his opinion, the specific device C. f. t. at all levels of life activity and for all adaptive functions of an organism also formulated its main patterns (see. Functional systems ). It proved a concept of the return, or authorizing, afferentation, i.e. obligatory at any action of the impulsation going from receptors of an organism to c. N of page and informing on result of the made action which is answering or not answering the planned purpose (see. Feed-back ). At further development of the mechanism of comparison the last received the name acceptor of result of action (see).

During the research of a role of an afferentation in implementation of locomotory acts (run, walking, jumps etc.) N. A. Bernstein put forward the idea about touch corrections, according to a cut continuous partnership of a flow of the afferent alarm system of control or correctional value is a necessary component of motor reactions. According to N. A. Bernstein, each case of the arranged reaction represents continuous cyclic process of interaction of an organism with changeable conditions of surrounding or internal environment of an organism. At the same time the huge role is played by a control and correctional afferentation.

Thus, already in the forties 20 century different leading role of afferent influences in S.'s processes f was revealed. t. organism. Later, under the influence of the ideas cybernetics (see), the term «feed-back» applied in the beginning during creation of technical control devices, and then postponed and on the biologist, objects became more standard.

Emergence of life on Earth was connected with emergence and maintenance at molecular level of labile equilibrium in the steady organization that as a result, according to I. I. Shmalgauzen, led to acquisition of new quality live — self-reproduction. Lives of any cell are the cornerstone the reversible processes of synthesis and disintegration of substances happening to participation of enzymes. Preservation of a mobile stable state and ability to its recovery is provided with the regulating mechanisms in the cell (a so-called cytogenetic homeostasis). The activating interaction of components in any functional system, a so-called positive feed-back, leads to the coordinated consecutive development of the system. In case one of components renders the action stimulating, and braking another, a negative feed-back is shown and labile equilibrium is established. All processes of formation of a germ, since the moment of fertilization of an ovum, crushing, a differentiation etc., are carried out at mutual stimulation of separate components thanks to what progressive development is reached. The result of morphogenesis is controlled by means of metabolites, to-rye are means of a feed-back from cytoplasm of the developing components to specific structures of a kernel cells (see).

The main condition of preservation of life of a metaphyte is stability of its main internal constants. The indicators of a homeostasis defining normal life activity of an organism concern to them (levels of osmotic and blood pressure, concentration of sugar and mineral substances in blood, a ratio of partial tension of oxygen and carbonic acid, pH of blood, body temperature etc.). Any deviation of values of these constants from initial levels is the initial push «starting» S.'s processes f. t. on achievement of the level of this or that indicator, initial or close to it.

In experiences with a hemodynamometry and registration of activity of baroreceptors it was established that maintenance of constant level of function always is a consequence of interaction of two forces: breaking this level and recovering it. As a result of such ratio homeostatic indicators, as a rule, are returned to initial level. So, recovery of a fixed level blood pressure (see) occurs because depressory reactions (see) are normal stronger pressor reactions (see).

Practically all constants of an organism continuously fluctuate about fixed levels. There are constants «rigid» (e.g., indicators of sugar of blood or osmotic pressure) allowing only insignificant deviations from the level, and the constant «plastic» (e.g., the level of blood pressure or nutrients in blood) varying in quite big range and for a long time. The considerable variations of level of blood pressure inherent to the healthy person are normal, have defined fiziol. sense. E.g., during the strengthened muscular work rise in blood pressure provides supply with blood of the working muscles, and in extreme conditions — a brain, heart etc. However in all cases of such changes of indicators of blood pressure as a result of S. f. t. its normal values are recovered.

One more principle C. f is established. t. — the principle of multicoherent regulation which is that the aberration of any indicator in multicoherent system leads to redistribution of values of all adjustable indicators. In other words, at action of the revolting factor, napr, at inhalation transition of adjustable indicators happens an animal of carbon dioxide gas (naira., pH, rs02, r02 in liquor, blood and fabric of a respiratory center) on new level owing to what the minimum of shift of each of them is supported, though does not occur return to former indicators.

Thus, from positions of the theory of functional systems, the net result of action is that factor, to-ry creates specific functional system. Its device can be very difficult, including processes S. f. t. both in an organism, and in the environment. In particular, at depletion of blood nutrients, «hungry» blood irritates the centers of a hypothalamus and brings a number of structures of a brain into generalized excitement that is expressed in formation appetite (see), and then and feelings of hunger (see. Hunger as physiological phenomenon ). Questing and satisfying of hunger therefore there is «a touch saturation», and then recovery of the broken constants of blood to datum level begins.

The first in S. f. t. the receptors of fabrics and bodies informing in the beginning on shifts in levels of these or those vital constants then about step-by-step results of action and, at last, about parameters of final adaptive effect begin to participate in an organism. Characteristic property of all peripheral and intra central receptors of various modality is their specific sensitivity r: to changes of certain constants, as provides their relative constancy. This property developed in the course of long evolution and fixed by heredity remains throughout all life. At the same time structure of components C. f. t. it can widely vary and be interchanged at change of ways of achievement of net adaptive result. Information on results of perfect action is the final stage of the behavioural act, signaling in c. N of page about effect of the made action. In case of achievement of the result corresponding to a purpose the following stage of behavior is terminated and begins. At discrepancy of result of action with the planned purpose «is started» approximate and research reaction (see), search and implementation of the corresponding actions for achievement of the goal.

In S. f. t. all levels of c participate. N of page. So, change of a breath p an exhalation is provided with a respiratory center of a myelencephalon (see. Respiratory center ). Stretching of alveoluses as a result of intake of air in them causes excitement of the receptors which are stuffed up in their walls, a cut on vagus nerves is transmitted to inspiratory neurons of a myelencephalon. In the course of expansion of alveoluses the frequency of an impulsation increases; at achievement of critical frequency (70 — 100 imp / sec.) it brakes activity of inspiratory and causes excitement of expiratory neurons. The breath is replaced by an exhalation. In turn, activity of expiratory neurons slows down activity of inspiratory neurons. However rhythmic activity of a respiratory center is defined by overlying structures of a brainstem. Section of a brain at the level of a trunk leads to sharp disturbances of breath and animals quickly perish from acidosis; animals with section of a brain above chetverokholmiya can live much longer without noticeable signs of disturbance of breath, but in the conditions of absolute rest. This fact says that direct regulation of gas composition of blood is carried out at the level of a brainstem. At last, process of reduction of volume of inhaled air in compliance with requirements of an organism during any adaptive activity is provided with the regulating mechanisms of the highest departments of c. N of page.

Initial push of S. f. t. excitement of peripheral or central receptors, especially those is, to-rye are located in sinocarotid and aortal areas. It results from disturbance of a normal ratio of blood gases (C02 or 02). Excitement on aortal or sinokarotpdny nerves is transferred to a respiratory center and to higher departments of c. N of page. In them occurs afferent synthesis (see) all arriving information from the periphery and from various departments of a brain «decision» in the form of parcel in a respiratory center of excitement is also developed. The last defines expansion ratio of lungs for a breath of a certain air volume according to requirement of an organism at present (see. Lung ventilation ). Impulsation from pulmonary stretch receptors is the main return afferentation bringing to c. N of page information on final adaptive effect, i.e. on the degree of stretching of alveoluses necessary for satisfaction of need of an organism for oxygen. Reception from a nasal cavity and respiratory tracts — throats, a trachea and bronchial tubes, and also from respiratory muscles belongs to the return, step-by-step afferentation, edges informs central offices of S. f. t. about the sequence of the made actions necessary for net adaptive result. Here information on an air flow, on its pressure in pneumatic ways, about expansion ratio of bronchial tubes, reduction of respiratory muscles etc. belongs. All chemoreception of respiratory system (peripheral and central) which is adjusted on perception of changes of partial tension of oxygen and carbonic acid, and also pH in blood and fabrics represents obstanovochny, or extra-starting, an afferentation. In usual conditions of life it a relative and constant and, supporting a certain level of excitement in central offices of S. f. t., provides prestarting integration of all coming vozbuzhdeniye. Final synthesis of all factors defining purposeful behavior — i.e. starting incentives, the emotional state connected with dominating motivation (see), the life experience and a surrounding situation — is carried out by bark brain (see).

A big role in S. f. t. play also neurohumoral and hormonal influences (see. Neurohumoral regulation ). Mediators (see) — acetylcholine, catecholamines and other low-molecular biologically active agents — not only take part in humoral transfer of excitement of nervous cells, but also exert impact on metabolism of those cells where they are formed. Being local hormones, they participate in intracellular regulation of exchange; influencing permeability of membranes, maintain a certain value of transmembrane potential and define ion fluxes and activity of enzymes. At the heart of linkng of hormones with the specific receptors located on a cell membrane or in cytoplasm (see. Receptors, cellular receptors ), mechanisms of the return positive and negative communication lie. Possessing regulatory function and being allocated with cells of a certain gland, hormones regulate a metabolism in the target cells belonging to other fabric. So, the sex steroid hormones produced by ovaries and seed plants influence the hypothalamic mechanisms regulating the gonadotropic function of a front share of a hypophysis and departments of a hypothalamus connected with a sexual behavior. In this case hypothalamic cells are target cells of estrogen.

S.'s processes f. t. take place on all standards of living from molecular to nadvidovy. Studying of mechanisms C. f. t. at molecular level it was begun by H. E. Umbarger in 1956 during the studying of synthesis of a leucine and pyridine nucleotides. It is shown that in biokhimich. the process happening in acellular extracts or in living cell, a certain concentration of an end product is an inhibiting agent for all process. Intermediate products of biosynthesis do not possess similar action. Selectivity such provides an orientation of regulation, i.e. self-control of process of formation of an end product of reaction is carried out. The last, by the principle of the return negative communication, interacts with enzymes and, braking their activity, stops all biochemical process. There is a large amount of enzymes, interaction to-rykh with components of a cell leads to its progressive development and improvement that is defined as a positive feed-back. Thus, living cells have sensitive biochemical mechanisms, to-rye reveal and fill shifts of concentration of the substances breaking their stationary state.

Intraorganic S. f is rather well studied. t. So, the heart of a frog isolated from all humoral and nervous influences continues long time to function, i.e. there is an intraorganic self-control of cordial reductions. At long irritation of a vagus nerve heart of a frog or hematothermal animal leaves a condition of braking (a so-called phenomenon of an uskolzaniye). The mechanism of this type of self-control consists that acetylcholine which is allocated from the terminations of a vagus nerve interacts with holinoretseptor of a cardiac muscle and, changing structure of cellular protein, «starts» a chain of biochemical processes, as a result to-rykh heart stops. Believe that at the proceeding irritation of a nerve in a myocardium physiologically active agent of the makroergichesky nature is emitted, a cut, slowing down reaction of acetylcholine with receptors, strengthens cordial reductions. As a result heart leaves a condition of braking. Reactions of this kind in a cardiac muscle are established at long irritation of a cordial branch of a sympathetic nerve. The end product of biochemical process activates priming reaction between a mediator — adrenaline and an effector cell of a myocardium, i.e. reaction of interaction of adrenaline with an adrenoceptor. As a result heart stops or urezhat the reductions.

In the whole organism of S. f. t. is the most difficult, happens to participation of numerous neuro and humoral, nervous and hormonal influences. An important role is played at the same time the physiologist, by parameters of the intracellular environment (see. Internal environment of an organism ). According to I. I. Shmalgauzen (1968), all process of an ontogeny of an individual consists in «transformation of hereditary information to system of vital bonds of a phenotype with external environment» and «any development of an individual is at least autoregulation and in a bigger smaller measure of a pla approaches autonomous development». In pre-and the post-natal periods of development of an individual there is a formation of a row of the vital functional systems to the device of self-control inherent to them, to-rye adapt an organism for the environment surrounding it (see. Sistemogenez ).

Since 70th 20 century the doctrine about populations of animals as about biological systems of nadorganizmenny level strenuously develops (see. Population ). It is shown that at vertebrate animals maintenance of population homeostasis, i.e. conditions of a dynamic equilibrium between population and the environment, is reached as a result of the difficult adaptive mechanisms operating by the principle of feed-backs. So, the lack of food or increase in animal numbers of any look in a certain territory lead to decrease in reproductive rates or increase of mortality among adult individuals. Fiziol. mechanisms of this phenomenon are very difficult: there is a change of the regulating role of closed glands, increase in stressful reactions, change of stereotypes of behavior etc. In particular, the role of predators as regulators of number of population is studied. Need to resist to predators leads to change of forms of behavior of pack. Seasonal changes of standard metabolism, body temperature, a physical activity, activity of closed glands etc. are known. In all these cases, in opinion And. Of Slonim (1971), the mechanism C. f takes place. t. Therefore, population as elementary unit of evolutionary process has ability to regulation of the number, structure of genes and phenotypes. Page f. t. in population leads to mutual stimulation of dependent processes therefore there is a progressive development of all population. The return orientation of process of self-control providing labile equilibrium in population is established. According to I. I. Shmalgauzen, «regulation of evolutionary process is carried out by means of the cyclic mechanism with a feed-back on the basis of comparison of the received results — phenotypes — in actual practice existence of population, i.e. in biogeocenoses». At the same time the phenotype (i.e. a specific organism with the organization, characteristic of it, and vital manifestations) is considered as the carrier of the return information. The last serves for comparison purposes fenotnp in population ceilings. This assessment comes to the end natural selection (see) that together with sexual process provides transformation of genetic structure of population. Positive assessment of phenotypes leads to increase in concentration of certain genes in population and to strengthening of their result in individuals of the next generations — i.e. to reproduction (regulation with a positive feed-back). Regulation with the return negative communication represents the stabilizing form of natural selection, at a cut there is an elimination of a phenotype and, therefore, reduction of concentration of the genes characterizing it. Maintenance of a stationary state of this population under certain conditions is result of existence. Fight for existence is considered as a control mechanism, in Krom an assessment is given to separate individuals, populations or types.

Thus, S.'s process f. t. in a cell, an organism, population and a look it is provided with existence of feed-backs, to-rye are a part of the main nodal mechanisms of functional systems, and process always has cyclic character.

In pathology, at an overstrain of mechanisms C. f. t. there is a disturbance of stability of these or those constants of an organism and, as a result, emergence of a number of defense adaptive reactions (see. Adaptation ). In particular, treat them vicarious processes (see) and compensatory processes (see), the using ways of mobilization of sa-moregulyatorny mechanisms, characteristic of norm. The principle «a plus-minus of interaction» of M. M. Zavadovsky was useful in interpretation of a pathogeny of a number of endocrine diseases (a hyperthyroidism, a myxedema, diabetes etc.). The big material showing use and value of this principle in clinic is saved up. Observations, testimonial are known that disturbance of implementation of the principle «a plus-minus of interaction» is the reason of development of dishormonal tumors.



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E. L. Golubeva.

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