The concept was introduced by the American psychologist W.B. Cannon in relation to any processes that change the initial state or a series of states, initiating new processes aimed at restoring the initial conditions. The mechanical homeostat is the thermostat. The term is used in physiological psychology to describe a number of complex mechanisms operating in the autonomic nervous system to regulate factors such as body temperature, biochemistry, blood pressure, fluid balance, metabolism, and so on. for example, a change in body temperature initiates a variety of processes such as shivering, increasing metabolism, increasing or retaining heat until normal temperature is reached. Examples of homeostatic psychological theories are balance theory (Heider, 1983), congruence theory (Osgood, Tannenbaum, 1955), cognitive dissonance theory (Festinger, 1957), symmetry theory (Newcomb, 1953) and others. an approach that assumes the fundamental possibility of the existence of balance states within a single whole (see heterostasis).
HOMEOSTASIS
Homeostasis) - maintaining a balance between opposing mechanisms or systems; the basic principle of physiology, which should also be considered the basic law of mental behavior.
HOMEOSTASIS
homeostasis The tendency of organisms to maintain their permanent state. According to Cannon (1932), the originator of the term: "Organisms, composed of matter characterized by the highest degree of volatility and instability, have somehow mastered the means of maintaining permanence and maintaining stability under conditions that should reasonably be regarded as absolutely destructive." Freud's PLEASURE PRINCIPLE and Fechner's CONSTANT PRINCIPLE used by him are usually considered as psychological concepts analogous to the physiological concept of homeostasis, i.e. they suggest that there is a programmed tendency to maintain psychological VOLTAGE at a constant optimal level, similar to the tendency for the body to maintain a constant blood chemistry, temperature, etc.
HOMEOSTASIS
a mobile equilibrium state of a system, maintained by its counteraction to disturbing external and internal factors. Maintaining the constancy of various physiological parameters of the body. The concept of homeostasis was originally developed in physiology to explain the constancy of the internal environment of the body and the stability of its basic physiological functions. This idea was developed by the American physiologist W. Cannon in his doctrine of the wisdom of the body as an open system that continuously maintains stability. Receiving signals about changes that threaten the system, the body turns on devices that continue to work until it is possible to return it to an equilibrium state, to the previous values of the parameters. The principle of homeostasis passed from physiology to cybernetics and other sciences, including psychology, acquiring a more general meaning of the principle of a systematic approach and self-regulation based on feedback. The idea that every system strives to maintain stability was transferred to the interaction of the organism with the environment. Such a transfer is typical, in particular:
1) for neobehaviorism, which believes that a new motor reaction is fixed due to the release of the body from a need that has violated its homeostasis;
2) for the concept of J. Piaget, who believes that mental development occurs in the process of balancing the body with the environment;
3) for K. Levin's field theory, according to which motivation arises in a non-equilibrium "system of stresses";
4) for Gestalt psychology, which notes that if the balance of the components of the mental system is disturbed, it seeks to restore it. However, the principle of homeostasis, explaining the phenomenon of self-regulation, cannot reveal the source of changes in the psyche and its activity.
HOMEOSTASIS
Greek homeios - similar, similar, statis - standing, immobility). The mobile, but stable balance of any system (biological, mental), due to its opposition to internal and external factors that violate this balance (see Cannon's thalamic theory of emotions. The principle of G. is widely used in physiology, cybernetics, psychology, it explains the adaptive ability Mental G. maintains optimal conditions for the functioning of the brain and nervous system in the process of life.
HOMEOSTASIS(IS)
from the Greek homoios - similar + stasis - standing; letters, meaning "to be in the same state").
1. In the narrow (physiological) sense, G. - the processes of maintaining the relative constancy of the main characteristics of the internal environment of the body (for example, the constancy of body temperature, blood pressure, blood sugar, etc.) in a wide range of environmental conditions. A large role in G. is played by the joint activity of the vegetative n. c, hypothalamus and brain stem, as well as the endocrine system, while partly neurohumoral regulation G. It is carried out "autonomously" from the psyche and behavior. The hypothalamus "decides" at what G.'s violation it is necessary to turn to the highest forms of adaptation and start the mechanism of biological motivation of behavior (see the Drive reduction hypothesis, Needs).
The term "G." introduced Amer. physiologist Walter Cannon (Cannon, 1871-1945) in 1929, however, the concept of the internal environment and the concept of its constancy were developed much earlier than fr. physiologist Claude Bernard (Bernard, 1813-1878).
2. In a broad sense, the concept of "G." apply to a variety of systems (biocenoses, populations, individuals, social systems, etc.). (B. M.)
homeostasis
homeostasis) In order to survive and move freely in changing and often hostile environmental conditions, complex organisms need to maintain their internal environment relatively constant. This inner constancy was called "G" by Walter B. Cannon. Cannon described his findings as examples of steady state maintenance in open systems. In 1926, he proposed the term "G" for such a steady state. and proposed a system of postulates relating to its nature, which was subsequently expanded in preparation for the publication of a review of the homeostatic and regulatory mechanisms known by that time. The organism, Cannon argued, through homeostatic reactions is able to maintain the stability of the intercellular fluid (fluid matrix), thus controlling and regulating. body temperature, blood pressure, and other parameters of the internal environment, the maintenance of which within certain limits is necessary for life. G. tzh is maintained in relation to the levels of supply of substances necessary for the normal functioning of cells. The concept of G. proposed by Kennon appeared in the form of a set of provisions concerning the existence, nature and principles of self-regulating systems. He emphasized that complex living beings are open systems formed from changing and unstable components, constantly subject to disturbing external influences due to this openness. Thus, these ever-changing systems must nevertheless maintain constancy with respect to the environment in order to maintain conditions favorable to life. Correction in such systems should occur continuously. Therefore, G. characterizes rather than an absolutely stable state. The concept of an open system has challenged all traditional notions of an adequate unit of organism analysis. If the heart, lungs, kidneys, and blood, for example, are parts of a self-regulating system, then their action or function cannot be understood from a study of each of them individually. A full understanding is possible only on the basis of knowing how each of these parts operates in relation to others. The concept of an open system also challenges all traditional views on causality, offering instead of a simple sequential or linear causality, a complex reciprocal determination. Thus, G. has become a new perspective both for considering the behavior of various kinds of systems, and for understanding people as elements of open systems. See also Adaptation, General Adaptation Syndrome, General Systems, Lens Model, Soul-Body Relationship Question R. Enfield
HOMEOSTASIS
the general principle of self-regulation of living organisms, formulated by Cannon in 1926. Perls emphasizes the importance of this concept in his work "The Gestalt Approach and Eye Witness to Therapy", begun in 1950, completed in 1970 and published after his death in 1973.
homeostasis
The process by which the body maintains balance in its internal physiological environment. Through homeostatic impulses, the urge to eat, drink and regulate body temperature occurs. For example, a decrease in body temperature initiates many processes (such as shivering) that help restore normal temperature. Thus, homeostasis initiates other processes that act as regulators and restore the optimal state. As an analogue, you can bring a central heating system with thermostatic control. When the room temperature drops below the values set in the thermostat, it turns on the steam boiler, which pumps hot water into the heating system, raising the temperature. When the temperature in the room reaches a normal level, the thermostat turns off the steam boiler.
HOMEOSTASIS
homeostasis) is the physiological process of maintaining the constancy of the internal environment of the body (ed.), in which various parameters of the body (for example, blood pressure, body temperature, acid-base balance) are maintained in balance, despite changes in environmental conditions. - Homeostatic.
homeostasis
Word formation. Comes from the Greek. homoios - similar + stasis - immobility.
Specificity. The process by which a relative constancy of the internal environment of the body is achieved (constancy of body temperature, blood pressure, blood sugar concentration). As a separate mechanism, neuropsychic homeostasis can be distinguished, due to which the preservation and maintenance of optimal conditions for the functioning of the nervous system in the process of implementing various forms of activity is ensured.
HOMEOSTASIS
Literally translated from Greek means the same state. American physiologist W.B. Cannon introduced this term to refer to any process that changes an existing condition or set of circumstances and, as a result, initiates other processes that perform regulatory functions and restore the original state. The thermostat is a mechanical homeostat. This term is used in physiological psychology to refer to a number of complex biological mechanisms that operate through the autonomic nervous system, regulating factors such as body temperature, body fluids and their physical and chemical properties, blood pressure, water balance, metabolism, etc. For example, a decrease in body temperature initiates a number of processes, such as shivering, piloerection, and an increase in metabolism, which cause and maintain a high temperature until a normal temperature is reached.
HOMEOSTASIS
from the Greek homoios - similar + stasis - state, immobility) - a type of dynamic balance, characteristic of complex self-regulating systems and consisting in maintaining parameters essential for the system within acceptable limits. The term "G." proposed by the American physiologist W. Cannon in 1929 to describe the state of the human body, animals and plants. Then this concept became widespread in cybernetics, psychology, sociology, etc. The study of homeostatic processes involves the selection of: 1) parameters, significant changes in which disrupt the normal functioning of the system; 2) the limits of the permissible change of these parameters under the influence of the conditions of the external and internal environment; 3) a set of specific mechanisms that begin to function when the values of variables go beyond these boundaries (B. G. Yudin, 2001). Each conflict reaction of any of the parties in the event of the emergence and development of a conflict is nothing more than the desire to maintain its G. The parameter, the change of which triggers the conflict mechanism, is the damage predicted as a consequence of the actions of the opponent. The dynamics of the conflict and the pace of its escalation are regulated by feedback: the reaction of one side of the conflict to the actions of the other side. For the last 20 years Russia has been developing as a system with lost, blocked or extremely weakened feedback. Therefore, the behavior of the state and society in the conflicts of the given period, which destroyed the national economy of the country, is irrational. The application of G.'s theory to the analysis and regulation of social conflicts can significantly increase the effectiveness of the work of domestic conflictologists.
Homeostasis (Greek homoios - the same, similar, stasis - stability, balance) is a set of coordinated reactions that maintain or restore the constancy of the internal environment of the body. In the middle of the nineteenth century, the French physiologist Claude Bernard introduced the concept of the internal environment, which he considered as a collection of body fluids. This concept was expanded by the American physiologist Walter Cannon, who meant by the internal environment the totality of fluids (blood, lymph, tissue fluid) that are involved in metabolism and maintaining homeostasis. The human body adapts to constantly changing environmental conditions, but the internal environment remains constant and its indicators fluctuate within very narrow limits. Therefore, a person can live in various environmental conditions. Some physiological parameters are regulated especially carefully and finely, for example, body temperature, blood pressure, glucose, gases, salts, calcium ions in the blood, acid-base balance, blood volume, its osmotic pressure, appetite, and many others. Regulation is carried out according to the principle of negative feedback between the receptors f , which detect changes in the indicated indicators and control systems. Thus, a decrease in one of the parameters is captured by the corresponding receptor, from which impulses are sent to one or another brain structure, at the command of which the autonomic nervous system turns on complex mechanisms to equalize the changes that have occurred. The brain uses two main systems to maintain homeostasis: autonomic and endocrine. Recall that the main function of the autonomic nervous system is to maintain the constancy of the internal environment of the body, which is carried out due to a change in the activity of the sympathetic and parasympathetic parts of the autonomic nervous system. The latter, in turn, is controlled by the hypothalamus, and the hypothalamus by the cerebral cortex. The endocrine system regulates the function of all organs and systems through hormones. Moreover, the endocrine system itself is under the control of the hypothalamus and pituitary gland. Homeostasis (Greek homoios - the same and stasis - state, immobility)
As our understanding of normal, and even more pathological, physiology became more complex, this concept was refined as homeokinesis, i.e. mobile equilibrium, the balance of constantly changing processes. The body is woven from millions of "homeokinesics". This huge living galaxy determines the functional status of all organs and cells that are bound by regulatory peptides. Like the world economic and financial system - many firms, industries, factories, banks, stock exchanges, markets, shops ... And between them - "convertible currency" - neuropeptides. All body cells constantly synthesize and maintain a certain, functionally necessary, level of regulatory peptides. But when deviations from "stationarity" occur, their biosynthesis (in the body as a whole or in its individual "loci") either increases or weakens. Such fluctuations occur constantly when it comes to adaptive reactions (getting used to new conditions), work performance (physical or emotional actions), the state of pre-illness - when the body "turns on" increased protection against functional imbalance. The classic case of maintaining balance is the regulation of blood pressure. There are groups of peptides between which there is constant competition - to increase / decrease pressure. In order to run, climb a mountain, bathe in a sauna, perform on stage, and finally think, a functionally sufficient increase in blood pressure is necessary. But as soon as the work is over, the regulators come into action, ensuring the “calming” of the heart and normal pressure in the vessels. Vasoactive peptides constantly interact to "allow" to increase the pressure to such and such a level (no more, otherwise the vascular system will go "peddling"; a well-known and bitter example is a stroke) and so that after the end of the physiologically necessary work
As you know, a living cell is a mobile, self-regulating system. Its internal organization is supported by active processes aimed at limiting, preventing or eliminating shifts caused by various influences from the environment and the internal environment. The ability to return to the original state after a deviation from a certain average level, caused by one or another "disturbing" factor, is the main property of the cell. A multicellular organism is a holistic organization, the cellular elements of which are specialized to perform various functions. Interaction within the body is carried out by complex regulatory, coordinating and correlating mechanisms with the participation of nervous, humoral, metabolic and other factors. Many individual mechanisms that regulate intra- and intercellular relationships, in some cases, have mutually opposite (antagonistic) effects that balance each other. This leads to the establishment of a mobile physiological background (physiological balance) in the body and allows the living system to maintain relative dynamic constancy, despite changes in the environment and shifts that occur during the life of the organism.
The term "homeostasis" was proposed in 1929 by the physiologist W. Cannon, who believed that the physiological processes that maintain stability in the body are so complex and diverse that it is advisable to combine them under the general name of homeostasis. However, back in 1878, K. Bernard wrote that all life processes have only one goal - to maintain the constancy of living conditions in our internal environment. Similar statements are found in the works of many researchers of the 19th and the first half of the 20th century. (E. Pfluger, S. Richet, L.A. Fredericq, I.M. Sechenov, I.P. Pavlov, K.M. Bykov and others). The works of L.S. Stern (with collaborators), devoted to the role of barrier functions that regulate the composition and properties of the microenvironment of organs and tissues.
The very idea of homeostasis does not correspond to the concept of stable (non-fluctuating) balance in the body - the principle of balance is not applicable to complex physiological and biochemical processes occurring in living systems. It is also wrong to oppose homeostasis to rhythmic fluctuations in the internal environment. Homeostasis in a broad sense covers the issues of cyclic and phase flow of reactions, compensation, regulation and self-regulation of physiological functions, the dynamics of the interdependence of nervous, humoral and other components of the regulatory process. The boundaries of homeostasis can be rigid and plastic, vary depending on individual age, gender, social, professional and other conditions.
Of particular importance for the life of the organism is the constancy of the composition of the blood - the liquid basis of the body (fluid matrix), according to W. Cannon. The stability of its active reaction (pH), osmotic pressure, ratio of electrolytes (sodium, calcium, chlorine, magnesium, phosphorus), glucose content, number of formed elements, and so on are well known. So, for example, blood pH, as a rule, does not go beyond 7.35-7.47. Even severe disorders of acid-base metabolism with a pathology of acid accumulation in the tissue fluid, for example, in diabetic acidosis, have very little effect on the active reaction of the blood. Despite the fact that the osmotic pressure of blood and tissue fluid is subject to continuous fluctuations due to the constant supply of osmotically active products of interstitial metabolism, it remains at a certain level and changes only in some severe pathological conditions.
Maintaining a constant osmotic pressure is of paramount importance for water metabolism and maintaining ionic balance in the body (see Water-salt metabolism). The greatest constancy is the concentration of sodium ions in the internal environment. The content of other electrolytes also fluctuates within narrow limits. The presence of a large number of osmoreceptors in tissues and organs, including in the central nervous formations (hypothalamus, hippocampus), and a coordinated system of regulators of water metabolism and ionic composition allows the body to quickly eliminate shifts in the osmotic blood pressure that occur, for example, when water is introduced into the body .
Despite the fact that blood represents the general internal environment of the body, the cells of organs and tissues do not directly come into contact with it.
In multicellular organisms, each organ has its own internal environment (microenvironment) corresponding to its structural and functional features, and the normal state of organs depends on the chemical composition, physicochemical, biological and other properties of this microenvironment. Its homeostasis is determined by the functional state of histohematic barriers and their permeability in the directions of blood→tissue fluid, tissue fluid→blood.
Of particular importance is the constancy of the internal environment for the activity of the central nervous system: even minor chemical and physicochemical shifts that occur in the cerebrospinal fluid, glia, and pericellular spaces can cause a sharp disruption in the course of life processes in individual neurons or in their ensembles. A complex homeostatic system, including various neurohumoral, biochemical, hemodynamic and other regulatory mechanisms, is the system for ensuring the optimal level of blood pressure. At the same time, the upper limit of the level of arterial pressure is determined by the functionality of the baroreceptors of the vascular system of the body, and the lower limit is determined by the body's needs for blood supply.
The most perfect homeostatic mechanisms in the body of higher animals and humans include the processes of thermoregulation; in homoiothermic animals, fluctuations in temperature in the internal parts of the body during the most dramatic changes in temperature in the environment do not exceed tenths of a degree.
Various researchers explain the mechanisms of a general biological nature that underlie homeostasis in different ways. So, W. Cannon attached special importance to the higher nervous system, L. A. Orbeli considered the adaptive-trophic function of the sympathetic nervous system to be one of the leading factors of homeostasis. The organizing role of the nervous apparatus (the principle of nervism) underlies the well-known ideas about the essence of the principles of homeostasis (I. M. Sechenov, I. P. Pavlov, A. D. Speransky and others). However, neither the dominant principle (A. A. Ukhtomsky), nor the theory of barrier functions (L. S. Stern), nor the general adaptation syndrome (G. Selye), nor the theory of functional systems (P. K. Anokhin), nor the hypothalamic regulation of homeostasis (N. I. Grashchenkov) and many other theories do not completely solve the problem of homeostasis.
In some cases, the concept of homeostasis is not quite rightly used to explain isolated physiological states, processes, and even social phenomena. This is how the terms “immunological”, “electrolyte”, “systemic”, “molecular”, “physico-chemical”, “genetic homeostasis” and the like appeared in the literature. Attempts have been made to reduce the problem of homeostasis to the principle of self-regulation. An example of solving the problem of homeostasis from the standpoint of cybernetics is Ashby's attempt (W. R. Ashby, 1948) to design a self-regulating device that simulates the ability of living organisms to maintain the level of certain quantities within physiologically acceptable limits. Some authors consider the internal environment of the body as a complex chain system with many "active inputs" (internal organs) and individual physiological indicators (blood flow, blood pressure, gas exchange, etc.), the value of each of which is due to the activity of the "inputs".
In practice, researchers and clinicians face the questions of assessing the adaptive (adaptive) or compensatory capabilities of the body, their regulation, strengthening and mobilization, predicting the body's response to disturbing influences. Some states of vegetative instability, caused by insufficiency, excess or inadequacy of regulatory mechanisms, are considered as “diseases of homeostasis”. With a certain conventionality, they can include functional disturbances in the normal functioning of the body associated with its aging, forced restructuring of biological rhythms, some phenomena of vegetative dystonia, hyper- and hypocompensatory reactivity under stressful and extreme influences, and so on.
To assess the state of homeostatic mechanisms in fiziol. experiment and in a wedge, practice various dosed functional tests are applied (cold, thermal, adrenaline, insulin, mezaton and others) with definition in blood and urine of a parity of biologically active substances (hormones, mediators, metabolites) and so on.
Biophysical mechanisms of homeostasis
Biophysical mechanisms of homeostasis. From the point of view of chemical biophysics, homeostasis is a state in which all processes responsible for energy transformations in the body are in dynamic equilibrium. This state is the most stable and corresponds to the physiological optimum. In accordance with the concepts of thermodynamics, an organism and a cell can exist and adapt to such environmental conditions under which it is possible to establish a stationary course of physicochemical processes, that is, homeostasis, in a biological system. The main role in establishing homeostasis belongs primarily to cellular membrane systems, which are responsible for bioenergetic processes and regulate the rate of entry and release of substances by cells.
From these positions, the main causes of the disturbance are non-enzymatic reactions that are unusual for normal life activity, occurring in membranes; in most cases, these are chain reactions of oxidation involving free radicals that occur in cell phospholipids. These reactions lead to damage to the structural elements of cells and disruption of the regulatory function. Factors that cause homeostasis disorders also include agents that cause radical formation - ionizing radiation, infectious toxins, certain foods, nicotine, as well as a lack of vitamins, and so on.
One of the main factors stabilizing the homeostatic state and functions of membranes are bioantioxidants, which inhibit the development of oxidative radical reactions.
Age features of homeostasis in children
Age features of homeostasis in children. The constancy of the internal environment of the body and the relative stability of physico-chemical parameters in childhood are provided with a pronounced predominance of anabolic metabolic processes over catabolic ones. This is an indispensable condition for growth and distinguishes the child's body from the body of adults, in which the intensity of metabolic processes is in a state of dynamic equilibrium. In this regard, the neuroendocrine regulation of the homeostasis of the child's body is more intense than in adults. Each age period is characterized by specific features of homeostasis mechanisms and their regulation. Therefore, in children much more often than in adults, there are severe violations of homeostasis, often life-threatening. These disorders are most often associated with the immaturity of the homeostatic functions of the kidneys, with disorders of the functions of the gastrointestinal tract or respiratory function of the lungs.
The growth of the child, expressed in an increase in the mass of his cells, is accompanied by distinct changes in the distribution of fluid in the body (see Water-salt metabolism). The absolute increase in the volume of extracellular fluid lags behind the rate of overall weight gain, so the relative volume of the internal environment, expressed as a percentage of body weight, decreases with age. This dependence is especially pronounced in the first year after birth. In older children, the rate of change in the relative volume of extracellular fluid decreases. The system for regulating the constancy of the volume of liquid (volume regulation) provides compensation for deviations in the water balance within fairly narrow limits. A high degree of tissue hydration in newborns and young children determines a significantly higher need for water than in adults (per unit body weight). Loss of water or its limitation quickly lead to the development of dehydration due to the extracellular sector, that is, the internal environment. At the same time, the kidneys - the main executive organs in the system of volume regulation - do not provide water savings. The limiting factor of regulation is the immaturity of the tubular system of the kidneys. The most important feature of the neuroendocrine control of homeostasis in newborns and young children is the relatively high secretion and renal excretion of aldosterone, which has a direct impact on the state of tissue hydration and the function of the renal tubules.
Regulation of the osmotic pressure of blood plasma and extracellular fluid in children is also limited. The osmolarity of the internal environment varies over a wider range (±50 mosm/l) than in adults ±6 mosm/l). This is due to the greater body surface per 1 kg of weight and, consequently, more significant water loss during respiration, as well as the immaturity of the renal mechanisms of urine concentration in children. Homeostasis disorders, manifested by hyperosmosis, are especially common in children during the neonatal period and the first months of life; at older ages, hypoosmosis begins to predominate, associated mainly with gastrointestinal or night diseases. Less studied is the ionic regulation of homeostasis, which is closely related to the activity of the kidneys and the nature of nutrition.
Previously, it was believed that the main factor determining the value of the osmotic pressure of the extracellular fluid is the concentration of sodium, but more recent studies have shown that there is no close correlation between the sodium content in the blood plasma and the value of the total osmotic pressure in pathology. The exception is plasmatic hypertension. Therefore, homeostatic therapy by administering glucose-salt solutions requires monitoring not only the sodium content in serum or plasma, but also changes in the total osmolarity of the extracellular fluid. Of great importance in maintaining the total osmotic pressure in the internal environment is the concentration of sugar and urea. The content of these osmotically active substances and their effect on water-salt metabolism can increase sharply in many pathological conditions. Therefore, for any violations of homeostasis, it is necessary to determine the concentration of sugar and urea. In view of the foregoing, in children of early age, in violation of the water-salt and protein regimes, a state of latent hyper- or hypoosmosis, hyperazotemia may develop (E. Kerpel-Froniusz, 1964).
An important indicator characterizing homeostasis in children is the concentration of hydrogen ions in the blood and extracellular fluid. In the antenatal and early postnatal periods, the regulation of acid-base balance is closely related to the degree of blood oxygen saturation, which is explained by the relative predominance of anaerobic glycolysis in bioenergetic processes. Moreover, even moderate hypoxia in the fetus is accompanied by the accumulation of lactic acid in its tissues. In addition, the immaturity of the acidogenetic function of the kidneys creates the prerequisites for the development of "physiological" acidosis. In connection with the peculiarities of homeostasis in newborns, disorders often occur that stand on the verge between physiological and pathological.
The restructuring of the neuroendocrine system in puberty is also associated with changes in homeostasis. However, the functions of the executive organs (kidneys, lungs) reach their maximum degree of maturity at this age, so severe syndromes or homeostasis diseases are rare, but more often we are talking about compensated changes in metabolism, which can only be detected by a biochemical blood test. In the clinic, to characterize homeostasis in children, it is necessary to examine the following indicators: hematocrit, total osmotic pressure, sodium, potassium, sugar, bicarbonates and urea in the blood, as well as blood pH, pO 2 and pCO 2.
Features of homeostasis in the elderly and senile age
Features of homeostasis in the elderly and senile age. The same level of homeostatic values in different age periods is maintained due to various shifts in the systems of their regulation. For example, the constancy of blood pressure at a young age is maintained due to a higher cardiac output and low total peripheral vascular resistance, and in the elderly and senile - due to a higher total peripheral resistance and a decrease in cardiac output. During the aging of the body, the constancy of the most important physiological functions is maintained in conditions of decreasing reliability and reducing the possible range of physiological changes in homeostasis. Preservation of relative homeostasis with significant structural, metabolic and functional changes is achieved by the fact that at the same time not only extinction, disturbance and degradation occurs, but also the development of specific adaptive mechanisms. Due to this, a constant level of sugar in the blood, blood pH, osmotic pressure, cell membrane potential, and so on are maintained.
Changes in the mechanisms of neurohumoral regulation, an increase in the sensitivity of tissues to the action of hormones and mediators against the background of a weakening of nervous influences, are essential in maintaining homeostasis during the aging process.
With the aging of the body, the work of the heart, pulmonary ventilation, gas exchange, renal functions, secretion of the digestive glands, the function of the endocrine glands, metabolism, and others change significantly. These changes can be characterized as homeoresis - a regular trajectory (dynamics) of changes in the intensity of metabolism and physiological functions with age over time. The value of the course of age-related changes is very important for characterizing the aging process of a person, determining his biological age.
In the elderly and senile age, the general potential of adaptive mechanisms decreases. Therefore, in old age, with increased loads, stress and other situations, the likelihood of disruption of adaptive mechanisms and homeostasis disturbances increase. Such a decrease in the reliability of homeostasis mechanisms is one of the most important prerequisites for the development of pathological disorders in old age.
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A biological system of any complexity, from subcellular structures of functional systems and the whole organism, is characterized by the ability to self-organize and self-regulate. The ability for self-organization is manifested by a variety of cells and organs in the presence of a general principle of elementary structure (membranes, organoids, etc.). Self-regulation is provided by mechanisms inherent in the very essence of the living.
The human body consists of organs that most often combine with others to perform their functions, thereby forming functional systems. For this, structures of any level of complexity, ranging from molecules to the whole organism, require regulation systems. These systems ensure the interaction of various structures already in a state of physiological rest. They are especially important in the active state when the organism interacts with a changing external environment, since any changes require an adequate response of the organism. In this case, one of the prerequisites for self-organization and self-regulation is the preservation of the constant conditions of the internal environment inherent in the body, which is denoted by the concept of homeostasis.
Rhythm of physiological functions. Physiological processes of vital activity, even in conditions of complete physiological rest, proceed with different activity. Their strengthening or weakening occurs under the influence of a complex interaction of exogenous and endogenous factors, which is called "biological rhythms". Moreover, the frequency of fluctuations of various functions varies over an extremely wide range, ranging from a period of up to 0.5 hours up to multi-day and even multi-year ones.
The concept of homeostasis
The efficient functioning of biological processes requires certain conditions, most of which must be constant. And the more stable they are, the more reliably the biological system functions. To these conditions, first of all, it is necessary to include those that contribute to the preservation of a normal level of metabolism. This requires the supply of initial ingredients of metabolism and oxygen, as well as the removal of final metabolites. The efficiency of metabolic processes is ensured by a certain intensity of intracellular processes, primarily due to the activity of enzymes. At the same time, enzymatic activity also depends on such seemingly external factors as, for example, temperature.
Stability in most conditions is necessary at any structural and functional level, ranging from a single biochemical reaction, a cell, to complex functional systems of the body. In real life, these conditions can often be violated. The appearance of changes is reflected in the state of biological objects, the flow of metabolic processes in them. In addition, the more complex the biological system is, the larger deviations from standard conditions it can withstand without significant disruption of vital activity. This is due to the presence in the body of appropriate mechanisms aimed at eliminating the changes that have arisen. So, for example, the activity of enzymatic processes in a cell decreases by 2-3 times with a decrease in temperature for every 10 °C. At the same time, warm-blooded animals, due to the presence of thermoregulation mechanisms, keep the internal temperature constant over a fairly wide range of changes in the external one. As a result, the stability of this condition is maintained for the enzymatic reactions to proceed at a constant level. And for example, a person who also has a mind, having clothes and housing, can exist for a long time at an external temperature significantly below 0 ° C.
In the process of evolution, the formation of adaptive reactions took place, aimed at maintaining constant conditions of the external environment of the organism. They exist both at the level of individual biological processes and the whole organism. Each of these conditions is characterized by corresponding parameters. Therefore, systems for regulating the constancy of conditions control the constancy of these parameters. And if these parameters deviate from the norm for some reason, regulation mechanisms ensure their return to the initial level.
The universal property of a living being to actively maintain the stability of body functions, despite external influences that can disrupt it, is called homeostasis.
The state of a biological system of any structural and functional level depends on a complex of influences. This complex consists of the interaction of many factors, both external in relation to it, and those that are inside or are formed as a result of the processes occurring in it. The level of influence of external factors is determined by the corresponding state of the environment: temperature, humidity, illumination, pressure, gas composition, magnetic fields, and the like. However, the body can and should maintain the degree of influence of far from all external and internal factors at a constant level. Evolution has selected those of them that are more necessary for the preservation of life, or those for the maintenance of which appropriate mechanisms have been found.
Homeostasis parameter constants They do not have a clear consistency. Their deviations from the average level in one direction or another in a kind of "corridor" are also possible. Each parameter has its own limits for the maximum possible deviations. They also differ in the time during which the body can withstand a violation of a particular parameter of homeostasis without any serious consequences. At the same time, the deviation of the parameter outside the "corridor" itself can cause the death of the corresponding structure - be it a cell or even an organism as a whole. So, normal blood pH is about 7.4. But it can fluctuate between 6.8-7.8. The human body can withstand the extreme degree of deviations of this parameter without harmful consequences only for a few minutes. Another homeostatic parameter - body temperature - in some infectious diseases can rise to 40 ° C and above and stay at this level for many hours and even days. Thus, some body constants are quite stable - - hard constants, others have a wider range of fluctuations - plastic constants.
Changes in homeostasis can occur under the influence of any external factors, as well as be of endogenous origin: the intensification of metabolic processes tends to change the parameters of homeostasis. At the same time, the activation of regulatory systems easily ensures their return to a stable level. But, if at rest in a healthy person these processes are balanced and the recovery mechanisms function with a reserve of power, then in the event of a sharp change in the conditions of existence, in case of diseases, they turn on with maximum activity. Improvement of homeostasis regulation systems is also reflected in evolutionary development. Thus, the absence of a system for maintaining a constant body temperature in cold-blooded animals, having determined the dependence of life processes on a variable external temperature, sharply limited their evolutionary development. However, the presence of such a system in warm-blooded animals ensured their spread throughout the planet and made such organisms truly free beings with a high evolutionary potential.
In turn, each person has individual functional capabilities of the homeostasis regulation systems themselves. This largely determines the severity of the body's reaction to any impact, and ultimately affects life expectancy.
Cellular homeostasis . One of the peculiar parameters of homeostasis is the "genetic purity" of the body's cell populations. The body's immune system "monitors" the normal proliferation of cells. In the event of its violation or violation of the reading of genetic information, cells appear that are alien to the given organism. The mentioned system destroys them. We can say that a similar mechanism also carries out the fight against the entry into the body of foreign cells (bacteria, worms) or their products. And this is also provided by the immune system (see section C - "Physiological characteristics of leukocytes").
Mechanisms of homeostasis and their regulation
The systems that control the parameters of homeostasis consist of mechanisms of varying structural complexity: both with relatively simple elements and rather complex neurohormonal complexes. One of the simplest mechanisms is metabolites, some of which can locally affect the activity of enzymatic processes, various structural components of cells and tissues. More complex mechanisms (neuroendocrine), which carry out interorgan interaction, are connected when simple ones are no longer enough to return the parameter to the required level.
Local processes of autoregulation with negative feedback take place in the cell. Thus, for example, during intensive muscular work in the skeletal muscles, through a relative deficiency of 02, NEP suboxide and metabolic products accumulate. They shift the pH of sarcoplasm to the acidic side, which can lead to the death of individual structures, the entire cell or even the organism. With a decrease in pH, the conformational properties of cytoplasmic proteins and membrane complexes change. The latter is caused by a change in the pore radius, an increase in the permeability of membranes (partitions) of all subcellular structures, and a violation of ionic gradients.
The role of body fluids in homeostasis. The body fluids are considered to be the central link in maintaining homeostasis. For most organs, this is blood and lymph, and for the brain, it is blood and cerebrospinal fluid (CSF). Blood plays an especially important role. In addition, liquid media for a cell are its cytoplasm and intercellular fluid.
Functions of liquid media In maintaining homeostasis are quite diverse. Firstly, liquid media provide metabolic processes with tissues. They not only bring substances necessary for vital activity to the cells, but also transport metabolites from them, which otherwise can accumulate in cells in high concentrations.
Secondly, liquid media have their own mechanisms necessary to maintain certain parameters of homeostasis. For example, buffer systems soften the shift in the acid-base state when acids or bases enter the bloodstream.
thirdly, liquid media take part in the organization of the homeostasis control system. There are also several mechanisms here. So, due to the transportation of metabolites, distant organs and systems (kidneys, lungs, etc.) are connected to the process of maintaining homeostasis. In addition, metabolites contained in the blood, acting on the structures and receptors of other organs and systems, can trigger complex reflex responses and hormonal mechanisms. For example, thermoreceptors react to "hot" or "cold" blood and accordingly change the activity of the organs involved in the formation and delivery of heat.
Receptors are also located in the walls of blood vessels themselves. They are involved in the regulation of the chemical composition of blood, its volume, pressure. With irritation of vascular receptors, reflexes begin, the efector link of which are the organs and systems of the body. The great importance of blood in maintaining homeostasis has become the basis for the formation of a special system of homeostasis of many parameters of the blood itself, its volume. For their preservation, there are complex mechanisms included in a single system of regulation of body homeostasis.
The above can be clearly illustrated by the example of intense muscular activity. During its execution, metabolic products in the form of lactic, pyruvic, acetoacetic and other acids come out of the muscles into the bloodstream. Acidic metabolites are first neutralized by the alkaline reserves of the blood. In addition, they activate blood circulation and respiration through reflex mechanisms. The connection of these body systems, on the one hand, improves the flow of 02 to the muscles, and therefore reduces the formation of underoxidized products; on the other hand, it helps to increase the release of CO2 through the lungs, many metabolites through the kidneys, sweat glands.
homeostasis
Homeostasis, homeoresis, homeomorphosis - characteristics of the state of the body. The system essence of the organism is manifested primarily in its ability to self-regulate in continuously changing environmental conditions. Since all organs and tissues of the body consist of cells, each of which is a relatively independent organism, the state of the internal environment of the human body is of great importance for its normal functioning. For the human body - a land creature - the environment is the atmosphere and the biosphere, while it interacts to a certain extent with the lithosphere, hydrosphere and noosphere. At the same time, most of the cells of the human body are immersed in a liquid medium, which is represented by blood, lymph and intercellular fluid. Only integumentary tissues directly interact with the human environment, all other cells are isolated from the outside world, which allows the body to largely standardize the conditions for their existence. In particular, the ability to maintain a constant body temperature of about 37 ° C ensures the stability of metabolic processes, since all the biochemical reactions that make up the essence of metabolism are very temperature dependent. It is equally important to maintain a constant tension of oxygen, carbon dioxide, concentration of various ions, etc. in the liquid media of the body. Under normal conditions of existence, including during adaptation and activity, small deviations of such parameters occur, but they are quickly eliminated, the internal environment of the body returns to a stable norm. Great French physiologist of the 19th century. Claude Bernard said: "The constancy of the internal environment is a prerequisite for a free life." The physiological mechanisms that ensure the maintenance of the constancy of the internal environment are called homeostatic, and the phenomenon itself, which reflects the body's ability to self-regulate the internal environment, is called homeostasis. This term was introduced in 1932 by W. Cannon, one of those physiologists of the 20th century, who, along with N.A. Bernstein, P.K. Anokhin and N. Wiener, stood at the origins of the science of control - cybernetics. The term "homeostasis" is used not only in physiological, but also in cybernetic research, since it is precisely the maintenance of the constancy of any characteristics of a complex system that is the main goal of any control.
Another remarkable researcher, K. Waddington, drew attention to the fact that the body is able to maintain not only the stability of its internal state, but also the relative constancy of dynamic characteristics, i.e., the flow of processes over time. This phenomenon, by analogy with homeostasis, was called homeoresis. It is of particular importance for a growing and developing organism and lies in the fact that the organism is able to maintain (within certain limits, of course) the "channel of development" in the course of its dynamic transformations. In particular, if a child, due to an illness or a sharp deterioration in living conditions caused by social causes (war, earthquake, etc.), lags significantly behind his normally developing peers, this does not mean that such a lag is fatal and irreversible. If the period of adverse events ends and the child receives adequate conditions for development, then both in terms of growth and the level of functional development, he soon catches up with his peers and in the future does not differ significantly from them. This explains the fact that children who have had a serious illness at an early age often grow up into healthy and proportionately built adults. Homeoresis plays an important role both in the management of ontogenetic development and in the processes of adaptation. Meanwhile, the physiological mechanisms of homeoresis are still insufficiently studied.
The third form of self-regulation of body constancy is homeomorphosis - the ability to maintain the invariance of the form. This characteristic is more characteristic of an adult organism, since growth and development are incompatible with the invariance of form. Nevertheless, if we consider short periods of time, especially during periods of growth inhibition, then in children it is possible to detect the ability to homeomorphosis. We are talking about the fact that in the body there is a continuous change of generations of its constituent cells. Cells do not live long (the only exception is nerve cells): the normal lifespan of body cells is weeks or months. Nevertheless, each new generation of cells almost exactly repeats the shape, size, arrangement and, accordingly, the functional properties of the previous generation. Special physiological mechanisms prevent significant changes in body weight in conditions of starvation or overeating. In particular, during starvation, the digestibility of nutrients increases sharply, and during overeating, on the contrary, most of the proteins, fats and carbohydrates that come with food are "burned" without any benefit to the body. It has been proven (N.A. Smirnova) that in an adult, sharp and significant changes in body weight (mainly due to the amount of fat) in any direction are sure signs of a breakdown in adaptation, overstrain and indicate a functional dysfunction of the body. The child's body becomes especially sensitive to external influences during periods of the most rapid growth. Violation of homeomorphosis is the same unfavorable sign as violations of homeostasis and homeoresis.
The concept of biological constants. The body is a complex of a huge number of a wide variety of substances. In the process of vital activity of body cells, the concentration of these substances can change significantly, which means a change in the internal environment. It would be unthinkable if the control systems of the body were forced to monitor the concentration of all these substances, i.e. have a lot of sensors (receptors), continuously analyze the current state, make management decisions and monitor their effectiveness. Neither the information nor the energy resources of the body would be enough for such a regime of control of all parameters. Therefore, the body is limited to monitoring a relatively small number of the most significant indicators that must be maintained at a relatively constant level for the well-being of the vast majority of body cells. These most rigidly homeostatic parameters thus turn into "biological constants", and their invariance is ensured by sometimes quite significant fluctuations of other parameters that do not belong to the category of homeostatic ones. Thus, the levels of hormones involved in the regulation of homeostasis can change tenfold in the blood, depending on the state of the internal environment and the impact of external factors. At the same time, homeostatic parameters change only by 10-20%.
The most important biological constants. Among the most important biological constants, for the maintenance of which at a relatively unchanged level, various physiological systems of the body are responsible, we should mention body temperature, blood glucose level, content of H + ions in body fluids, partial tension of oxygen and carbon dioxide in tissues.
Disease as a symptom or consequence of homeostasis disorders. Almost all human diseases are associated with a violation of homeostasis. So, for example, in many infectious diseases, as well as in the case of inflammatory processes, temperature homeostasis is sharply disturbed in the body: fever (fever), sometimes life-threatening, occurs. The reason for such a violation of homeostasis may lie both in the features of the neuroendocrine reaction, and in violations of the activity of peripheral tissues. In this case, the manifestation of the disease - fever - is a consequence of a violation of homeostasis.
Usually, feverish conditions are accompanied by acidosis - a violation of the acid-base balance and a shift in the reaction of body fluids to the acid side. Acidosis is also characteristic of all diseases associated with deterioration of the cardiovascular and respiratory systems (diseases of the heart and blood vessels, inflammatory and allergic lesions of the bronchopulmonary system, etc.). Often, acidosis accompanies the first hours of a newborn's life, especially if normal breathing did not begin immediately after birth. To eliminate this condition, the newborn is placed in a special chamber with a high oxygen content. Metabolic acidosis with heavy muscular exertion can occur in people of any age and manifests itself in shortness of breath and increased sweating, as well as painful sensations in the muscles. After completion of work, the state of acidosis can persist from several minutes to 2-3 days, depending on the degree of fatigue, fitness and the effectiveness of homeostatic mechanisms.
Very dangerous diseases that lead to a violation of water-salt homeostasis, such as cholera, in which a huge amount of water is removed from the body and tissues lose their functional properties. Many kidney diseases also lead to a violation of water-salt homeostasis. As a result of some of these diseases, alkalosis can develop - an excessive increase in the concentration of alkaline substances in the blood and an increase in pH (shift to the alkaline side).
In some cases, minor but long-term disturbances in homeostasis can cause the development of certain diseases. So, there is evidence that the excessive consumption of sugar and other sources of carbohydrates that disrupt glucose homeostasis leads to damage to the pancreas, as a result, a person develops diabetes. Also dangerous is the excessive consumption of table and other mineral salts, hot spices, etc., which increase the load on the excretory system. Kidneys May not cope with the abundance of substances that need to be removed from the body, resulting in a violation of water-salt homeostasis. One of its manifestations is edema - the accumulation of fluid in the soft tissues of the body. The cause of edema usually lies either in the insufficiency of the cardiovascular system, or in violations of the kidneys and, as a result, mineral metabolism.
