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 are composed of cells, each of which is a relatively independent organism, the state internal environment 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 human body immersed in a liquid medium, which is represented by blood, lymph and intercellular fluid. Only integumentary tissues directly interact with human environment 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 everything biochemical reactions, which constitute the essence of metabolism, depend very strongly on temperature. It is equally important to maintain a constant oxygen tension in the body fluids, carbon dioxide, the concentration of various ions, etc. AT normal conditions existence, including during adaptation and activity, there are small deviations of such parameters, 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 prerequisite 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 main goal any management.

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 dynamic characteristics, i.e., the course of processes in time. This phenomenon, by analogy with homeostasis, was called homeoresis. It is of particular importance for a growing and developing organism and consists 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 the child, due to illness or sharp deterioration conditions of life caused by social causes (war, earthquake, etc.), significantly lags behind their 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 level functional development he soon catches up with his peers and in the future does not differ significantly from them. This explains the fact that those who underwent at an early age serious illness children often grow up into healthy and proportionally built adults. Homeoresis plays a crucial role both in the management ontogenetic development and in adaptation processes. Meanwhile physiological mechanisms homeoresis is not yet well understood.

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, location and, accordingly, functional properties the previous generation. Special physiological mechanisms prevent significant changes in body weight in conditions of starvation or overeating. In particular, during starvation, the digestibility sharply increases. nutrients, and when overeating, on the contrary, most of proteins, fats and carbohydrates coming from 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 many sensors (receptors), continuously analyze Current state make management decisions and monitor their effectiveness. Neither information nor energy resources the organism would not 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 need to be maintained at a relatively constant level for the sake of well-being. absolute majority 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 exposure to 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 organism should be called body temperature, blood glucose level, content of H+ ions in body fluids, partial voltage 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, for many infectious diseases, and also in the case 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 the 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 prolonged violations homeostasis can lead to the development of certain diseases. So, there is evidence that 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 cardio-vascular system, or in violations of the kidneys and, as a result, mineral metabolism.

Homeostasis is the ability of the human body to adapt to changing conditions of the external and internal environment. The stable operation of homeostasis processes guarantees a person a comfortable state of health in any situation, maintaining the constancy of vitality. important indicators organism.

Homeostasis from a biological and ecological point of view

In homeostasis apply to any multicellular organisms. At the same time, environmentalists often pay attention to the balance external environment. It is believed that this is the homeostasis of the ecosystem, which is also subject to change and is constantly rebuilt for further existence.

If the balance in any system is disturbed and it is not able to restore it, then this leads to a complete cessation of functioning.

Man is no exception, homeostatic mechanisms play an important role in daily life, and the permissible degree of change in the main indicators of the human body is very small. With unusual fluctuations in the external or internal environment, a malfunction in homeostasis can lead to fatal consequences.

What is homeostasis and its types

Every day a person is exposed to various factors environment, but in order for the main biological processes in the body continued to work stably, their conditions should not change. It is in maintaining this stability that the main role of homeostasis lies.

It is customary to distinguish three main types:

1. Genetic.
2. Physiological.
3. Structural (regenerative or cellular).

For a full-fledged existence, a person needs the work of all three types of homeostasis in a complex, if one of them fails, this leads to backfire for good health. Well-coordinated work of processes will allow you to ignore or endure the most common changes with minimal inconvenience and feel confident.

This type of homeostasis is the ability to maintain a single genotype within one population. At the molecular-cellular level, a single genetic system is maintained, which carries a certain set of hereditary information.

The mechanism allows individuals to interbreed, while maintaining the balance and uniformity of a conditionally closed group of people (population).

Physiological homeostasis

This type of homeostasis is responsible for maintaining optimal condition main vital signs:

• body temperature.
• Blood pressure.
• Digestive stability.

The immune, endocrine and nervous systems are responsible for its proper functioning. In the event of an unforeseen failure in the operation of one of the systems, this immediately affects the well-being of the whole organism, leads to a weakening of protective functions and the development of diseases.

Cellular homeostasis (structural)

This species is also called "regeneration", which probably best describes the functional features.

The main forces of such homeostasis are aimed at restoring and healing damaged cells of the internal organs of the human body. It is these mechanisms that correct work allow the body to recover from illness or injury.

The main mechanisms of homeostasis develop and evolve together with a person, better adapting to changes in the external environment.

Functions of homeostasis

In order to correctly understand the functions and properties of homeostasis, it is best to consider its action on specific examples.

So, for example, when playing sports, human breathing and pulse quicken, which indicates the body's desire to maintain internal balance under changed environmental conditions.

When moving to a country with a climate that is significantly different from the usual, for some time you can feel unwell. Depending on the general health of a person, the mechanisms of homeostasis allow to adapt to new living conditions. For some, acclimatization is not felt and the internal balance quickly adjusts, while others have to wait a little before the body adjusts its performance.

In conditions elevated temperature the person becomes hot and starts sweating. This phenomenon is considered direct evidence of the functioning of self-regulation mechanisms.

In many ways, the work of the main homeostatic functions depends on heredity, the genetic material transmitted from the older generation of the family.

Based on the examples given, it is clearly possible to trace the main functions:

• Energy.
• Adaptive.
• Reproductive.

It is important to pay attention to the fact that in old age, as well as in infancy the stable work of homeostasis requires special attention, due to the fact that the reaction of the main regulatory systems during these periods of life is slow.

properties of homeostasis

Knowing about the basic functions of self-regulation, it is also useful to understand what properties it has. Homeostasis is a complex interrelation of processes and reactions. Among the properties of homeostasis are:

• Instability.
• Striving for balance.
• Unpredictability.

Mechanisms are in constant change, testing conditions in order to choose the best option for adapting to them. This is the property of instability.

Balance is the main goal and property of any organism, it constantly strives for it, both structurally and functionally.

In some cases, the reaction of the body to changes in the external or internal environment can become unexpected, lead to restructuring of vital important systems. The unpredictability of homeostasis can cause some discomfort, which does not indicate a further detrimental effect on the state of the body.

How to improve the functioning of the mechanisms of the homeostatic system

From the point of view of medicine, any disease is evidence of a malfunction in homeostasis. External and internal threats constantly affect the body, and only coherence in the work of the main systems will help to cope with them.

The weakening of the immune system does not happen for no reason. Modern medicine has a wide range of tools that can help a person maintain their health, regardless of what caused the failure.

Changing weather conditions, stressful situations, injuries - all this can lead to the development of diseases of varying severity.

In order for the functions of homeostasis to work correctly and as quickly as possible, it is necessary to monitor general condition your health. To do this, you can consult a doctor for an examination to determine your vulnerabilities and choose a set of therapy to eliminate them. Regular diagnostics will help to better control the basic processes of life.

In this case, it is important to independently follow simple recommendations:

• Avoid stressful situations to protect the nervous system from constant overexertion.
• Monitor your diet, do not overload yourself with heavy foods, avoid mindless starvation, which will allow digestive system easier to do your job.
• Choose suitable vitamin complexes to reduce the impact of seasonal weather changes.

vigilant attitude towards own health will help homeostatic processes to timely and correctly respond to any changes.

In the organism of higher animals, adaptations have been developed that counteract many influences of the external environment, providing relatively constant conditions for the existence of cells. This is essential for the life of the whole organism. We illustrate this with examples. The cells of the body of warm-blooded animals, that is, animals with a constant body temperature, function normally only within narrow temperature limits (in humans, within 36-38 °). A temperature shift beyond these limits leads to disruption of cell activity. At the same time, the body of warm-blooded animals can normally exist with much wider fluctuations in the temperature of the external environment. For example, polar bear can live at a temperature of - 70 ° and + 20-30 °. This is due to the fact that in the whole organism its heat exchange with the environment is regulated, i.e. heat generation (intensity, chemical processes occurring with the release of heat) and heat transfer. So, at a low ambient temperature, heat generation increases, and heat transfer decreases. Therefore, with fluctuations in external temperature (within certain limits), the constancy of body temperature is maintained.

The functions of body cells are normal only with a relative constancy of osmotic pressure, due to the constancy of the content of electrolytes and water in the cells. Changes in osmotic pressure - its decrease or increase - lead to sharp violations of the functions and structure of cells. The organism as a whole can exist for some time both with excessive intake and with deprivation of water, and with large and small amounts of salts in food. This is due to the presence in the body of adaptations that contribute to maintaining
constancy of the amount of water and electrolytes in the body. In case of excessive intake of water, significant amounts of it are quickly excreted from the body by excretory organs (kidneys, sweat glands, skin), and with a lack of water, it is retained in the body. In the same way, the excretory organs regulate the content of electrolytes in the body: they quickly remove excess amounts of them or keep them in the body fluids with insufficient intake of salts.

The concentration of individual electrolytes in the blood and tissue fluid, on the one hand, and in the protoplasm of cells, on the other, is different. The blood and tissue fluid contain more sodium ions, and the protoplasm of cells contains more potassium ions. The difference in the concentration of ions inside the cell and outside it is achieved by a special mechanism that keeps potassium ions inside the cell and does not allow sodium ions to accumulate in the cell. This mechanism, the nature of which is not yet clear, is called the sodium-potassium pump and is associated with the process of cell metabolism.

Body cells are very sensitive to shifts in the concentration of hydrogen ions. A change in the concentration of these ions in one direction or another sharply disrupts the vital activity of cells. The internal environment of the body is characterized by a constant concentration of hydrogen ions, which depends on the presence of so-called buffer systems in the blood and tissue fluid (p. 48) and on the activity of the excretory organs. With an increase in the content of acids or alkalis in the blood, they are quickly excreted from the body and in this way the constancy of the concentration of hydrogen ions in the internal environment is maintained.

Cells, especially nerve cells, are very sensitive to changes in blood sugar, an important nutrient. Therefore, the constancy of the sugar content in the blood is of great importance for the life process. It is achieved by the fact that with an increase in blood sugar levels in the liver and muscles, a polysaccharide, glycogen, deposited in the cells, is synthesized from it, and with a decrease in blood sugar levels, glycogen is broken down in the liver and muscles and grape sugar is released into the blood.

permanence chemical composition and physico-chemical properties of the internal environment is an important feature of organisms of higher animals. To designate this constancy, W. Cannon proposed a term that has become widespread - homeostasis. The expression of homeostasis is the presence of a number of biological constants, i.e. stable quantitative indicators characterizing normal condition organism. Such constant values ​​are: body temperature, osmotic pressure of blood and tissue fluid, the content of sodium, potassium, calcium, chlorine and phosphorus ions, as well as proteins and sugar, the concentration of hydrogen ions and a number of others.

Noting the constancy of the composition, physicochemical and biological properties of the internal environment, it should be emphasized that it is not absolute, but relative and dynamic. This constancy is achieved by the continuously performed work of a number of organs and tissues, as a result of which the shifts in the composition and physicochemical properties of the internal environment that occur under the influence of changes in the external environment and as a result of the vital activity of the organism are leveled.

The role of different organs and their systems in maintaining homeostasis is different. Thus, the digestive system ensures the flow of nutrients into the blood in the form in which they can be used by the cells of the body. The circulatory system carries out continuous movement blood and transport various substances in the body, as a result of which the nutrients, oxygen and various chemical compounds formed in the body itself enter the cells, and the decay products, including carbon dioxide, released by the cells, are transferred to the organs that remove them from the body. The respiratory organs provide oxygen to the blood and remove carbon dioxide from the body. The liver and a number of other organs carry out a significant number of chemical transformations - the synthesis and breakdown of many chemical compounds important in the life of cells. The excretory organs - kidneys, lungs, sweat glands, skin - remove the end products of the decay of organic substances from the body and maintain a constant content of water and electrolytes in the blood, and therefore in the tissue fluid and in the cells of the body.

The nervous system plays an important role in maintaining homeostasis. responsive to various changes external or internal environment, it regulates the activity of organs and systems in such a way that shifts and disturbances that occur or could occur in the body are prevented and leveled.

Thanks to the development of adaptations that ensure the relative constancy of the internal environment of the body, its cells are less susceptible to the changing influences of the external environment. According to Cl. Bernard, "the constancy of the internal environment is a condition for a free and independent life."

Homeostasis has certain limits. When the body stays, especially for a long time, in conditions that differ significantly from those to which it is adapted, homeostasis is disturbed and shifts incompatible with normal life can occur. So, with a significant change in external temperature in the direction of both its increase and decrease, the body temperature may rise or fall and overheating or cooling of the body may occur, leading to death. Similarly, with a significant restriction of the intake of water and salts into the body or a complete deprivation of these substances, the relative constancy of the composition and physico-chemical properties of the internal environment is disturbed after a while and life stops.

A high level of homeostasis occurs only at certain stages of the species and individual development. The lower animals do not have sufficiently developed adaptations to mitigate or eliminate the influences of changes in the external environment. So, for example, the relative constancy of body temperature (homeothermia) is maintained only in warm-blooded animals. In the so-called cold-blooded animals, the body temperature is close to the temperature of the external environment and represents variable(poikilothermia). A newborn animal does not have such a constancy of body temperature, composition and properties of the internal environment, as in an adult organism.

Even small violations of homeostasis lead to pathology, and therefore the determination of relatively constant physiological parameters, such as body temperature, blood pressure, composition, physicochemical and biological properties blood, etc., is of great diagnostic value.

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. The multicellular organism is holistic organization, cellular elements 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 environment and shifts that occur in the process of life of the organism.

The term "homeostasis" was proposed in 1929 by the physiologist W. Cannon, who believed that physiological processes, maintaining 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 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 active reaction 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. Availability a large number osmoreceptors in tissues and organs, including the central nerve 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.

AT 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 activities of the central nervous system: even minor chemical and physico-chemical 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 blood pressure. In this case, 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, temperature fluctuations in the internal parts of the body at the most abrupt changes ambient temperatures 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 widely famous performances 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 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 conditions, 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 point of view 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 parameters (blood flow, blood pressure, gas exchange, etc.), the value of each of which is determined by the activity of the "inputs".

In practice, researchers and clinicians face the issues 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 disorders of the normal activity of the body associated with its aging, forced restructuring biological rhythms, some phenomena of vegetative dystonia, hyper- and hypocompensatory reactivity during stressful and extreme exposure etc.

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 agents (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 this chain reactions oxidation involving free radicals produced in cellular phospholipids. These reactions lead to damage structural elements cells and regulatory dysfunction. 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 relative stability physical and chemical indicators 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 (volumoreregulation) provides compensation for deviations in water balance within fairly narrow limits. High degree of tissue hydration in newborns and children early age determines a significantly higher than in adults, the child's need for water (per unit of 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 neuroendocrine control of homeostasis in newborns and young children is the relatively high secretion and renal excretion of aldosterone, which has direct influence 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 fluctuates more than wide range(±50 mosm/l) than in adults ±6 mosm/l). It's connected with larger body surface per 1 kg of weight and, consequently, with more significant losses of water during respiration, as well as with 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.

It was previously 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 executive bodies(kidneys, lungs) reach the maximum degree of maturity at this age, so severe syndromes or diseases of homeostasis 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 supported by 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 physiological changes homeostasis. The 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, kidney 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 essential prerequisites development of pathological disorders in old age.

Are you categorically not satisfied with the prospect of irretrievably disappearing from this world? Do you wish to live another life? Start all over again? Fix the mistakes of this life? Implement unfulfilled dreams? Follow this link:

In biology, it is the maintenance of the constancy of the internal environment of the body.
Homeostasis is based on the body's sensitivity to the deviation of certain parameters (homeostatic constants) from a given value. Limits of permissible fluctuations of the homeostatic parameter ( homeostatic constant) can be wide or narrow. Narrow limits are: body temperature, blood pH, blood glucose. Wide limits are: blood pressure, body weight, the concentration of amino acids in the blood.
Special intraorganism receptors ( interoreceptors) respond to the deviation of homeostatic parameters from the given limits. Such interoreceptors are found inside the thalamus, hypothalamus, in vessels, and in organs. In response to the deviation of the parameters, they trigger restorative homeostatic reactions.

General mechanism of neuroendocrine homeostatic responses for internal regulation of homeostasis

The parameters of the homeostatic constant deviate, interoreceptors are excited, then the corresponding centers of the hypothalamus are excited, they stimulate the release of the corresponding liberins by the hypothalamus. In response to the action of liberins, hormones are released by the pituitary gland, and then, under their action, hormones of other endocrine glands are released. Hormones, released from the endocrine glands into the blood, change the metabolism and the mode of operation of organs and tissues. As a result, established new mode the work of organs and tissues shifts the changed parameters towards the previous set value and restores the value of the homeostatic constant. Such general principle restoration of homeostatic constants in case of their deviation.

2. In these functional nerve centers the deviation of these constants from the norm is determined. The deviation of the constants within the given limits is eliminated due to the regulatory capabilities of the functional centers themselves.

3. However, if any homeostatic constant deviates above or below allowable limits functional centers transmit excitation higher: in "need centers" hypothalamus. This is necessary in order to switch from the internal neurohumoral regulation of homeostasis to the external - behavioral.

4. Excitation of one or another need center of the hypothalamus forms the corresponding functional state, which is subjectively experienced as a need for something: food, water, warmth, cold or sex. There is an activating and inciting to action psycho-emotional state dissatisfaction.

5. To organize purposeful behavior, it is necessary to choose only one of the needs as a priority and create a working dominant to satisfy it. It is believed that leading role this is played by the tonsils of the brain (Corpus amygdoloideum). It turns out that on the basis of one of the needs that the hypothalamus forms, the amygdala creates a leading motivation that organizes purposeful behavior to satisfy only this one chosen need.

6. The next stage can be considered the launch of a preparatory behavior, or drive reflex, which should increase the likelihood of launching an executive reflex in response to a trigger stimulus. The drive reflex prompts the body to create a situation in which there will be an increased likelihood of finding an object suitable for satisfying the current need. This may be, for example, moving to a place rich in food, or water, or sexual partners, depending on the leading need. When, in the achieved situation, a specific object is found that is suitable for satisfying this dominant need, then it launches an executive reflex behavior aimed at satisfying the need with the help of this particular object.

© 2014-2018 Sazonov V.F. © 2014-2016 kineziolog.bodhy.ru..

Homeostasis Systems - A detailed educational resource on homeostasis.