As is known, 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 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 an integral 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 regulating intra- and intercellular relationships have, in some cases, 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 arise 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 common name homeostasis. However, back in 1878, C. Bernard wrote that everything life processes have only one goal - maintaining the constancy of living conditions in our internal environment. Similar statements are found in the works of many researchers of the 19th and first half of the 20th centuries. (E. Pfluger, S. Richet, Frederic (L.A. Fredericq), I.M. Sechenov, I.P. Pavlov, K.M. Bykov and others). The works of L.S. were of great importance for the study of the problem of homeostasis. Stern (with colleagues), 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) equilibrium in the body - the principle of equilibrium is not applicable to complex physiological and biochemical processes occurring in living systems. It is also incorrect to contrast homeostasis with rhythmic fluctuations in the internal environment. Homeostasis in a broad sense covers issues of the cyclic and phase course 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 flexible, changing depending on individual age, gender, social, professional and other conditions.
Of particular importance for the life of the body is the constancy of the composition of the blood - the fluid matrix of the body, as W. Cannon puts it. The stability of its active reaction (pH) is well known, osmotic pressure, the ratio of electrolytes (sodium, calcium, chlorine, magnesium, phosphorus), glucose content, the number of formed elements, and so on. For example, blood pH, as a rule, does not go beyond 7.35-7.47. Even severe disorders of acid-base metabolism with pathology of acid accumulation in tissue fluid, for example in diabetic acidosis, have very little effect on the active blood reaction. 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 under certain 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 concentration of sodium ions in the internal environment is the most constant. The content of other electrolytes also varies within narrow limits. Availability large quantity osmoreceptors in tissues and organs, including in the central nervous formations (hypothalamus, hippocampus), and a coordinated system of regulators of water metabolism and ion composition allows the body to quickly eliminate shifts in the osmotic pressure of the blood 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 normal condition 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 blood→tissue fluid, tissue fluid→blood.
Especially important has a constancy of the internal environment for the activity of the central nervous system: even minor chemical and physico-chemical changes that occur in the cerebrospinal fluid, glia and pericellular spaces can cause sharp violation 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 optimal blood pressure levels. At the same time upper limit blood pressure level is determined by the functionality of baroreceptors vascular system body, and the lower limit is the body's needs for blood supply.
The most advanced homeostatic mechanisms in the body of higher animals and humans include thermoregulation processes; In homeothermic animals, temperature fluctuations in the internal parts of the body do not exceed tenths of a degree during the most dramatic changes in temperature in the environment.
Different researchers explain the general biological mechanisms underlying homeostasis in different ways. Yes, W. Cannon special meaning attributed 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 known ideas about the essence of the principles of homeostasis (I. M. Sechenov, I. P. Pavlov, A. D. Speransky and others). However, neither the principle of dominance (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 idea of homeostasis is not entirely legitimately 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 perspective of cybernetics is Ashby’s attempt (W. R. Ashby, 1948) to construct a self-regulating device that models 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 in the form of 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 determined by the activity of the “inputs”.
In practice, researchers and clinicians are faced with questions of assessing the adaptive (adaptive) or compensatory capabilities of the body, their regulation, strengthening and mobilization, and predicting the body's responses to disturbing influences. Some states of vegetative instability, caused by insufficiency, excess or inadequacy of regulatory mechanisms, are considered “diseases of homeostasis”. With a certain convention, these may include functional disorders normal activities of the body associated with its aging, forced restructuring 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 physiol. In experiments and in wedges, practice, a variety of dosed functional tests are used (cold, heat, adrenaline, insulin, mesaton and others) with the determination of the biological ratio in the blood and urine 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 biological system it is possible to establish a stationary course of physical and chemical processes, that is, homeostasis. 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 this point of view, the main causes of the disorder are non-enzymatic reactions occurring in membranes that are unusual for normal life; in most cases this is chain reactions oxidation involving free radicals, arising in cell phospholipids. These reactions lead to damage structural elements cells and dysfunction of regulation. Factors that cause disruption of homeostasis also include agents that cause radical formation - ionizing radiation, infectious toxins, certain foods, nicotine, as well as lack of vitamins and so on.
One of the main factors that stabilize the homeostatic state and functions of membranes are bioantioxidants, which inhibit the development of oxidative radical reactions.
Age-related features of homeostasis in children
Age characteristics homeostasis in children. Constancy of the internal environment of the body and relative stability physical and 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 whom 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 turns out to be more intense than in adults. Every age period characterized specific features mechanisms of homeostasis and their regulation. Therefore, in children, much more often than in adults, severe disturbances of homeostasis occur, often life-threatening. These disorders are most often associated with the immaturity of the homeostatic functions of the kidneys, with disorders of the gastrointestinal tract or respiratory function of the lungs.
The growth of a child, expressed in an increase in the mass of its 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 fluid volume (volume regulation) provides compensation for deviations in water balance within fairly narrow limits. High degree tissue hydration in newborns and children early age determines the child’s need for water (per unit body weight) is significantly higher than that of adults. Loss of water or its limitation quickly leads 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 volumoregulation system - do not provide water savings. The limiting factor of regulation is the immaturity of the renal tubular system. Key Feature neuroendocrine control of homeostasis in newborns and young children consists of relatively high secretion and renal excretion of aldosterone, which has direct influence on the state of tissue hydration and renal tubular function.
Regulation of osmotic pressure of blood plasma and extracellular fluid in children is also limited. The osmolarity of the internal environment fluctuates over a wider range (±50 mOsm/L) than in adults (±6 mOsm/L). This is due to the larger body surface area per 1 kg of weight and, consequently, to more significant water losses during respiration, as well as the immaturity of the renal mechanisms of urine concentration in children. Disturbances of homeostasis, 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 disease or nocturnal 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 osmotic pressure of the extracellular fluid was the sodium concentration, 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, carrying out homeostatic therapy by administering glucose-salt solutions requires monitoring not only the sodium content in the serum or blood plasma, but also changes in the total osmolarity of the extracellular fluid. The concentration of sugar and urea is of great importance in maintaining the general osmotic pressure in the internal environment. The content of these osmotically active substances and their effect on water-salt metabolism can increase sharply in many pathological conditions. Therefore, in case of any disturbances in homeostasis, it is necessary to determine the concentration of sugar and urea. Due to the above, in young children, when the water-salt and protein regimes are disturbed, a state of latent hyper- or hypoosmosis, hyperazotemia can 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 oxygen saturation of the blood, 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. Due to the peculiarities of homeostasis, newborns often experience disorders that border between physiological and pathological.
Restructuring of the neuroendocrine system during puberty is also associated with changes in homeostasis. However, the functions executive bodies(kidneys, lungs) reach at this age maximum degree maturity, therefore severe syndromes or diseases of homeostasis are rare, more often we're talking about about compensated changes in metabolism, which can only be detected with a biochemical blood test. In the clinic, to characterize homeostasis in children, it is necessary to examine the following indicators: hematocrit, total osmotic pressure, content of sodium, potassium, sugar, bicarbonates and urea in the blood, as well as blood pH, pO 2 and pCO 2.
Features of homeostasis in old and senile age
Features of homeostasis in old 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 the blood pressure level in young people 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. With the aging of the body, the constancy of the most important physiological functions is maintained in conditions of decreasing reliability and a reduction in the possible range physiological changes homeostasis. Maintaining relative homeostasis with significant structural, metabolic and functional changes is achieved by the fact that simultaneously not only extinction, disruption and degradation occurs, but also the development of specific adaptive mechanisms. Due to this, a constant level of blood sugar, blood pH, osmotic pressure, cell membrane potential, and so on is maintained.
Of significant importance in maintaining homeostasis during the aging process are 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.
As the body ages, the functioning of the heart, pulmonary ventilation, gas exchange, renal function, secretion of the digestive glands, function of the endocrine glands, metabolism and others change significantly. These changes can be characterized as homeoresis - a natural trajectory (dynamics) of changes in metabolic rate and physiological functions with age over time. Stroke value age-related changes is very important for characterizing the aging process of a person and determining his biological age.
In old age and old age, the general potential of adaptive mechanisms decreases. Therefore, in old age, under increased loads, stress and other situations, the likelihood of failure of adaptation mechanisms and disruption of homeostasis increases. This 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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2. Learning objectives:
Know the essence of homeostasis, the physiological mechanisms of maintaining homeostasis, the basics of homeostasis regulation.
Study the main types of homeostasis. Know the age-related features of homeostasis
3. Questions for self-preparation for mastering this topic:
1) Definition of homeostasis
2) Types of homeostasis.
3) Genetic homeostasis
5) Homeostasis of the internal environment of the body
6) Immunological homeostasis
7) Mechanisms of regulation of homeostasis: neurohumoral and endocrine.
8) Hormonal regulation of homeostasis.
9) Organs involved in the regulation of homeostasis
10) General principle of homeostatic reactions
11) Species specificity of homeostasis.
12) Age-related features of homeostasis
13) Pathological processes accompanied by disruption of homeostasis.
14) Correction of body homeostasis – main task doctor
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4. Type of lesson: extracurricular
5. Duration of the lesson– 3 hours.
6. Equipment. Electronic presentation “Lectures on biology”, tables, dummies
Homeostasis(gr. homoios - equal, stasis - state) - the ability of an organism to maintain the constancy of the internal environment and the main features of its inherent organization, despite the variability of parameters external environment and the action of internal disturbing factors.
The homeostasis of each individual is specific and determined by its genotype.
Organism - open dynamic system. The flow of substances and energy observed in the body determines self-renewal and self-reproduction at all levels from molecular to organismal and population.
In the process of metabolism with food, water, and during gas exchange, various chemical compounds, which after transformations are likened to the chemical composition of the organism and are included in its morphological structures. After a certain period, the absorbed substances are destroyed, releasing energy, and the destroyed molecule is replaced by a new one, without violating the integrity of the structural components of the body.
Organisms are in a constantly changing environment, despite this, the main physiological indicators continue to be carried out within certain parameters and the body maintains a stable state of health for a long time, thanks to self-regulation processes.
Thus, the concept of homeostasis is not associated with the stability of processes. In response to the action of internal and external factors, some changes in physiological indicators occur, and the inclusion of regulatory systems ensures the maintenance of a relative constancy of the internal environment. Regulatory homeostatic mechanisms function at the cellular, organ, organismal and supraorganismal levels.
In evolutionary terms, homeostasis is the hereditarily fixed adaptations of the body to normal environmental conditions.
The following main types of homeostasis are distinguished:
1) genetic
2) structural
3) homeostasis of the liquid part of the internal environment (blood, lymph, interstitial fluid)
4) immunological.
Genetic homeostasis- preservation of genetic stability due to the strength of the physical and chemical bonds of DNA and its ability to recover after damage (DNA repair). Self-reproduction - fundamental property living, it is based on the process of DNA reduplication. The very mechanism of this process, in which a new DNA strand is built strictly complementarily around each of the constituent molecules of the two old strands, is optimal for the accurate transmission of information. The accuracy of this process is high, but errors can still occur during reduplication. Disruption of the structure of DNA molecules can also occur in its primary chains without connection with reduplication under the influence of mutagenic factors. In most cases, the cell genome is restored, damage is corrected, thanks to reparation. When repair mechanisms are damaged, genetic homeostasis is disrupted at both the cellular and organismal levels.
An important mechanism preservation of genetic homeostasis is the diploid state of somatic cells in eukaryotes. Diploid cells are characterized by greater stability of functioning, because the presence of two genetic programs in them increases the reliability of the genotype. Stabilization complex system genotype is provided by the phenomena of polymerization and other types of gene interaction. Regulatory genes that control the activity of operons play a major role in the process of homeostasis.
Structural homeostasis- this is the constancy of morphological organization at all levels of biological systems. It is advisable to highlight the homeostasis of a cell, tissue, organ, and body systems. Homeostasis of underlying structures ensures the morphological constancy of higher structures and is the basis of their life activity.
The cell, as a complex biological system, is characterized by self-regulation. The establishment of homeostasis in the cellular environment is ensured by membrane systems, which are associated with bioenergetic processes and regulation of the transport of substances into and out of the cell. In the cell, processes of change and restoration of organelles are continuously taking place, and the cells themselves are destroyed and restored. Restoration of intracellular structures, cells, tissues, organs during the life of the body occurs due to physiological regeneration. Restoration of structures after damage - reparative regeneration.
Homeostasis of the liquid part of the internal environment- constancy of the composition of blood, lymph, tissue fluid, osmotic pressure, total concentration of electrolytes and concentration of individual ions, content of nutrients in the blood, etc. These indicators, even with significant changes in environmental conditions, are maintained at a certain level, thanks to complex mechanisms.
For example, one of the most important physicochemical parameters of the internal environment of the body is acid-base balance. The ratio of hydrogen and hydroxyl ions in the internal environment depends on the content in body fluids (blood, lymph, tissue fluid) of acids - proton donors and buffer bases - proton acceptors. Typically, the active reaction of the medium is assessed by the H+ ion. The pH value (the concentration of hydrogen ions in the blood) is one of the stable physiological indicators and varies within a narrow range in humans - from 7.32 to 7.45. The activity of a number of enzymes, membrane permeability, protein synthesis processes, etc. largely depend on the ratio of hydrogen and hydroxyl ions.
The body has various mechanisms that ensure the maintenance of acid-base balance. Firstly, these are the buffer systems of blood and tissues (carbonate, phosphate buffers, tissue proteins). Hemoglobin also has buffering properties; it binds carbon dioxide and prevents its accumulation in the blood. The maintenance of a normal concentration of hydrogen ions is also facilitated by the activity of the kidneys, since a significant amount of metabolites that have an acidic reaction are excreted in the urine. If the listed mechanisms are insufficient, the concentration of carbon dioxide in the blood increases, and a slight shift in pH occurs to the acidic side. In this case, the respiratory center is excited, pulmonary ventilation increases, which leads to a decrease in carbon dioxide content and normalization of the concentration of hydrogen ions.
The sensitivity of tissues to changes in the internal environment varies. Thus, a pH shift of 0.1 in one direction or another from the norm leads to significant disturbances in the functioning of the heart, and a deviation of 0.3 is life-threatening. The nervous system is especially sensitive to decreased oxygen levels. Fluctuations in the concentration of calcium ions exceeding 30%, etc., are dangerous for mammals.
Immunological homeostasis- maintaining the constancy of the internal environment of the body by preserving the antigenic individuality of the individual. Immunity is understood as a way of protecting the body from living bodies and substances that carry signs of genetically foreign information (Petrov, 1968).
Alien genetic information carry bacteria, viruses, protozoa, helminths, proteins, cells, including modified cells of the body itself. All of these factors are antigens. Antigens are substances that, when introduced into the body, can trigger the formation of antibodies or another form of immune response. Antigens are very diverse, most often they are proteins, but there are also large molecules lipopolysaccharides, nucleic acids. Inorganic compounds(salts, acids), simple organic compounds (carbohydrates, amino acids) cannot be antigens, because have no specificity. Australian scientist F. Burnet (1961) formulated the position that the main significance of the immune system is to recognize “self” and “foreign”, i.e. in maintaining the constancy of the internal environment - homeostasis.
Immune system has a central (red bone marrow, thymus gland) and peripheral (spleen, lymph nodes) link. Defensive reaction carried out by lymphocytes formed in these organs. Type B lymphocytes, when encountering foreign antigens, differentiate into plasma cells, which release specific proteins into the blood - immunoglobulins (antibodies). These antibodies, combining with the antigen, neutralize them. This reaction is called humoral immunity.
Type T lymphocytes provide cellular immunity by destroying foreign cells, such as transplant rejection, and mutated cells of one's own body. According to calculations given by F. Bernet (1971), in each genetic change of dividing human cells, about 10 - 6 spontaneous mutations accumulate within one day, i.e. on the cellular and molecular levels processes are continuously occurring that disrupt homeostasis. T lymphocytes recognize and destroy mutant cells of their own body, thus providing the function of immune surveillance.
The immune system controls the genetic constancy of the body. This system, consisting of anatomically separated organs, represents a functional unity. The property of immune defense has reached its highest development in birds and mammals.
Regulation of homeostasis carried out by the following organs and systems (Fig. 91):
1) central nervous system;
2) the neuroendocrine system, which includes the hypothalamus, pituitary gland, and peripheral endocrine glands;
3) diffuse endocrine system (DES), represented by endocrine cells located in almost all tissues and organs (heart, lung, gastrointestinal tract, kidneys, liver, skin, etc.). The bulk of DES cells (75%) are concentrated in the epithelium of the digestive system.
It is now known that a number of hormones are simultaneously present in the central nerve structures and endocrine cells of the gastrointestinal tract. Thus, the hormones enkephalins and endorphins are found in nerve cells and endocrine cells of the pancreas and stomach. Chocystokinin was detected in the brain and duodenum. Such facts gave rise to the hypothesis that there is a single system of chemical information cells in the body. The peculiarity of nervous regulation is the speed of onset of the response, and its effect is manifested directly in the place where the signal arrives through the corresponding nerve; the reaction is short-lived.
In the endocrine system, regulatory influences are associated with the action of hormones carried in the blood throughout the body; the effect is long-lasting and non-local.
The integration of nervous and endocrine regulatory mechanisms occurs in the hypothalamus. The general neuroendocrine system allows for the implementation of complex homeostatic reactions associated with the regulation of visceral functions of the body.
The hypothalamus also has glandular functions, producing neurohormones. Neurohormones, entering the anterior lobe of the pituitary gland with the blood, regulate the release of pituitary tropic hormones. Tropic hormones directly regulate the functioning of the endocrine glands. For example, thyroid-stimulating hormone from the pituitary gland stimulates the thyroid gland, increasing the level of thyroid hormone in the blood. When the concentration of the hormone increases above the norm for a given organism, the thyroid-stimulating function of the pituitary gland is inhibited and the activity of the thyroid gland is weakened. Thus, to maintain homeostasis, it is necessary to balance the functional activity of the gland with the concentration of the hormone in the circulating blood.
This example shows general principle homeostatic reactions: deviation from baseline --- signal --- switching on regulatory mechanisms based on the feedback principle --- correction changes (normalization).
Some endocrine glands are not directly dependent on the pituitary gland. These are the islets of the pancreas that produce insulin and glucagon, the adrenal medulla, the pineal gland, the thymus, and the parathyroid glands.
The thymus occupies a special position in the endocrine system. It produces hormone-like substances that stimulate the formation of T-lymphocytes, and a relationship is established between immune and endocrine mechanisms.
The ability to maintain homeostasis is one of the the most important properties a living system in a state of dynamic equilibrium with environmental conditions. The ability to maintain homeostasis varies among different species; it is high in higher animals and humans, which have complex nervous, endocrine and immune regulatory mechanisms.
In ontogenesis, each age period is characterized by the characteristics of metabolism, energy and homeostasis mechanisms. In a child’s body, the processes of assimilation prevail over dissimilation, which determines growth and weight gain; the mechanisms of homeostasis are not yet mature enough, which leaves an imprint on the course of both physiological and pathological processes.
With age, metabolic processes and regulatory mechanisms improve. IN mature age the processes of assimilation and dissimilation, the system of normalization of homeostasis provide compensation. With aging, the intensity of metabolic processes decreases, the reliability of regulatory mechanisms weakens, the function of a number of organs fades, and at the same time new specific mechanisms develop that support the preservation of relative homeostasis. This is expressed, in particular, in an increase in the sensitivity of tissues to the action of hormones along with a weakening of nervous effects. During this period, adaptive features are weakened, so increased workload and stressful conditions can easily disrupt homeostatic mechanisms and often become the cause of pathological conditions.
Knowledge of these patterns is necessary for the future doctor, since the disease is a consequence of a violation of the mechanisms and ways of restoring homeostasis in humans.
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The term "homeostasis" is most often used in biology. Multicellular organisms need to maintain a constant internal environment to exist. Many ecologists are convinced that this principle also applies to the external environment. If the system is unable to restore its balance, it may eventually cease to function.
Complex systems - such as the human body - must have homeostasis in order to remain stable and exist. These systems not only must strive to survive, they also have to adapt to environmental changes and evolve.
Properties of homeostasis
Homeostatic systems have the following properties:
- Instability system: testing how best to adapt.
- Striving for balance: all internal, structural and functional organization systems helps maintain balance.
- Unpredictability: The resulting effect of a certain action can often be different from what was expected.
- Regulation of the amount of micronutrients and water in the body - osmoregulation. Carried out in the kidneys.
- Removal of waste products from the metabolic process - excretion. It is carried out by exocrine organs - kidneys, lungs, sweat glands and gastrointestinal tract.
- Regulation of body temperature. Lowering temperature through sweating, various thermoregulatory reactions.
- Regulation of blood glucose levels. Mainly carried out by the liver, insulin and glucagon secreted by the pancreas.
- Regulation of the level of basal metabolism depending on the diet.
It is important to note that although the body is in equilibrium, its physiological state can be dynamic. Many organisms exhibit endogenous changes in the form of circadian, ultradian, and infradian rhythms. Thus, even when in homeostasis, body temperature, blood pressure, heart rate and most metabolic indicators are not always at a constant level, but change over time.
Homeostasis mechanisms: feedback
When a change in variables occurs, there are two main types of feedback to which the system responds:
- Negative feedback, expressed in a reaction in which the system responds in such a way as to reverse the direction of change. Since feedback serves to maintain the constancy of the system, it allows homeostasis to be maintained.
- For example, when the concentration of carbon dioxide in the human body increases, a signal comes to the lungs to increase their activity and exhale more carbon dioxide.
- Thermoregulation is another example of negative feedback. When body temperature rises (or falls), thermoreceptors in the skin and hypothalamus register the change, triggering a signal from the brain. This signal, in turn, causes a response - a decrease in temperature (or increase).
- Positive feedback, which is expressed in increasing the change in a variable. It has a destabilizing effect and therefore does not lead to homeostasis. Positive feedback is less common in natural systems, but it also has its uses.
- For example, in nerves, a threshold electrical potential causes the generation of much greater potential actions. Blood clotting and events at birth are other examples of positive feedback.
Stable systems require combinations of both types of feedback. Whereas negative feedback allows a return to a homeostatic state, positive feedback is used to move to an entirely new (and perhaps less desirable) state of homeostasis, a situation called “metastability.” Such catastrophic changes can occur, for example, with an increase in nutrients in clear-water rivers, leading to a homeostatic state of high eutrophication (algae overgrowth of the riverbed) and turbidity.
Ecological homeostasis
In disturbed ecosystems, or subclimax biological communities - such as the island of Krakatoa, after strong eruption volcano c - the state of homeostasis of the previous forest climax ecosystem was destroyed, like all life on this island. Krakatoa, in the years following the eruption, went through a chain of ecological changes in which new species of plants and animals succeeded each other, leading to biodiversity and the resulting climax community. Ecological succession on Krakatoa took place in several stages. The complete chain of successions leading to climax is called preseria. In the Krakatoa example, the island developed a climax community with eight thousand different species recorded in 100 years after the eruption wiped out life on it. The data confirm that the situation remains in homeostasis for some time, with the emergence of new species very quickly leading to the rapid disappearance of old ones.
The case of Krakatoa and other disturbed or intact ecosystems shows that initial colonization by pioneer species occurs through positive feedback reproductive strategies in which species disperse, producing as many offspring as possible, but with little investment in the success of each individual. . In such species there is rapid development and equally rapid collapse (for example, through an epidemic). When an ecosystem approaches climax, such species are replaced by more complex climax species, which, through negative feedback adapt to the specific conditions of their environment. These species are carefully controlled by the potential carrying capacity of the ecosystem and follow a different strategy - producing fewer offspring, the reproductive success of which is invested more energy in the microenvironment of its specific ecological niche.
Development begins with the pioneer community and ends with the climax community. This climax community forms when flora and fauna come into balance with the local environment.
Such ecosystems form heterarchies, in which homeostasis at one level promotes homeostatic processes at another complex level. For example, the loss of leaves from a mature tropical tree provides space for new growth and enriches the soil. Equally, a tropical tree reduces the access of light to lower levels and helps prevent invasion by other species. But trees also fall to the ground and the development of the forest depends on the constant change of trees and the cycle of nutrients carried out by bacteria, insects, and fungi. Similarly, such forests contribute to ecological processes such as the regulation of microclimates or hydrological cycles of the ecosystem, and several different ecosystems may interact to maintain homeostasis of river drainage within a biological region. Bioregional variability also plays a role in the homeostatic stability of a biological region, or biome.
Biological homeostasis
Homeostasis acts as a fundamental characteristic of living organisms and is understood as maintaining the internal environment within acceptable limits.
The internal environment of the body includes body fluids - blood plasma, lymph, intercellular substance and cerebrospinal fluid. Maintaining the stability of these fluids is vital for organisms, while its absence leads to damage to the genetic material.
With respect to any parameter, organisms are divided into conformational and regulatory. Regulatory organisms keep the parameter at a constant level, regardless of what happens in the environment. Conformational organisms allow the environment to determine the parameter. For example, warm-blooded animals maintain a constant body temperature, while cold-blooded animals exhibit a wide range of temperatures.
This is not to say that conformational organisms do not have behavioral adaptations that allow them to regulate a given parameter to some extent. Reptiles, for example, often sit on heated rocks in the morning to raise their body temperature.
The benefit of homeostatic regulation is that it allows the body to function more efficiently. For example, cold-blooded animals tend to become lethargic when low temperatures, while warm-blooded animals are almost as active as ever. On the other hand, regulation requires energy. The reason why some snakes can only eat once a week is that they expend much less energy to maintain homeostasis than mammals.
Cellular homeostasis
Regulation of the chemical activity of the cell is achieved through a number of processes, among which changes in the structure of the cytoplasm itself, as well as the structure and activity of enzymes, are of particular importance. Autoregulation depends on
The term “homeostasis” comes from the word “homeostasis”, which means “the power of stability”. Many people don’t hear about this concept often, or even at all. However, homeostasis is an important part of our lives, harmonizing contradictory conditions among themselves. And this is not just a part of our life, homeostasis - important function our body.
If we define the word homeostasis, the meaning of which is the regulation of the most important systems, then this is the ability that coordinates various reactions, allowing us to maintain balance. This concept applies to both individual organisms and entire systems.
In general, homeostasis is often discussed in biology. In order for the body to function properly and perform the necessary actions, it is necessary to maintain a strict balance in it. This is necessary not only for survival, but also so that we can properly adapt to environmental changes and continue to develop.
It is possible to identify the types of homeostasis necessary for a full-fledged existence - or, more precisely, the types of situations when this effect manifests itself.
- Instability. At this moment, we, namely our inner self, diagnose changes and, based on this, make decisions to adapt to new circumstances.
- Equilibrium. All ours internal forces aimed at maintaining balance.
- Unpredictability. We can often surprise ourselves by taking action we didn't expect.
All these reactions are determined by the fact that every organism on the planet wants to survive. The principle of homeostasis helps us understand the circumstances and accept important decision to maintain balance.
Unexpected decisions
Homeostasis has taken a strong place not only in biology. This term is also actively used in psychology. In psychology, the concept of homeostasis implies our response to external conditions. Nevertheless, this process closely links the adaptation of the body and individual mental adaptation.
Everything in this world strives for balance and harmony, and individual relationships with the environment tend toward harmonization. And this happens not only on the physical level, but also on the mental level. You can give the following example: a man laughs, but then he was told a very sad story, laughter is no longer appropriate. The body and emotional system are driven by homeostasis, calling for correct reaction, – and your laughter is replaced by tears.
As we see, the principle of homeostasis is based on close connection between physiology and psychology. However, the principle of homeostasis associated with self-regulation cannot explain the sources of change.
The homeostatic process can be called the process of self-regulation. And this whole process occurs on a subconscious level. Our body has needs in many areas, but psychological contacts play an important role. Feeling the need to contact other organisms, a person shows his desire for development. This subconscious desire in turn reflects a homeostatic drive.
Very often such a process in psychology is called instinct. In fact, this is a very correct name, because all our actions are instincts. We cannot control our desires, which are dictated by instinct. Often our survival depends on these desires, or with their help the body requires what it needs. at the moment is sorely lacking.
Imagine the situation: a group of deer is grazing not far from a sleeping lion. Suddenly the lion wakes up and roars, the fallow deer scatter. Now imagine yourself in the place of the doe. The instinct of self-preservation worked in her - she ran away. She must run very fast to save her life. This is psychological homeostasis.
But some time passes, and the doe begins to lose steam. Even though there might be a lion chasing after her, she would stop because the need to breathe was at the moment more important than the need to run. This is an instinct of the body itself, physiological homeostasis. Thus, the following types of homeostasis can be distinguished:
- Coercive.
- Spontaneous.
The fact that the doe started running is a spontaneous psychological urge. She had to survive, and she ran. And the fact that she stopped to catch her breath was coercion. The body forced the animal to stop, otherwise life processes could be disrupted.
The importance of homeostasis is very important for any organism, both in psychological sense, and in the physical. A person can learn to live in harmony with himself and the environment without following only the urges of instincts. He only needs to correctly see and understand the world around him, as well as sort out his thoughts, placing priorities in the right order. Author: Lyudmila Mukhacheva
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 the body’s vital indicators.
Homeostasis from a biological and environmental point of view
In homeostasis apply to any multicellular organisms. At the same time, ecologists often pay attention to the balance of the external environment. It is believed that this is the homeostasis of the ecosystem, which also undergoes changes and is constantly rebuilt for continued 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 vital role in daily life, and the permissible degree of change in the basic indicators of the human body is very small. With unusual fluctuations in the external or internal environment, a failure in homeostasis can lead to fatal consequences.
Why is homeostasis needed and its types?
Every day a person is exposed to various factors environment, but in order for the basic biological processes in the body to continue to operate stably, their conditions must not change. It is in maintaining this stability that the main role of homeostasis lies.
It is customary to distinguish three main types:
- Genetic.
- Physiological.
- Structural (regenerative or cellular).
For a full-fledged existence, a person needs the work of all three types of homeostasis in combination; if one of them fails, this leads to unpleasant consequences for health. Coordinated work of processes will allow you not to notice 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, which carries a certain set of hereditary information.
The mechanism allows individuals to interbreed with each other, while maintaining balance and uniformity conditionally closed group people (populations).
Physiological homeostasis
This type homeostasis is responsible for maintaining the main vital signs in an optimal state:
- Body temperatures.
- Blood pressure.
- Digestive stability.
The immune, endocrine and nervous systems are responsible for its proper functioning. In the event of an unexpected failure in the operation of one of the systems, this immediately affects the well-being of the entire body, leading to weakening protective functions and the development of diseases.
Cellular homeostasis (structural)
This type is also called "regenerative", which probably best describes the functional features.
The main forces of such homeostasis are aimed at restoring and healing damaged cells internal organs human body. It is these mechanisms, when working properly, that allow the body to recover from illness or injury.
The basic mechanisms of homeostasis develop and evolve along 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 using specific examples.
For example, when playing sports, human breathing and heart rate increase, which indicates the body’s desire to maintain inner balance under changed environmental conditions.
When moving to a country with a climate significantly different from your usual one, you may feel unwell for some time. Depending on the general health of a person, homeostasis mechanisms allow adaptation to new living conditions. Some people do not feel acclimatization and the internal balance quickly adjusts, while others have to wait a little before the body adjusts its parameters.
In conditions of elevated temperature, a person becomes hot and sweats. This phenomenon is considered direct evidence of the functioning of self-regulation mechanisms.
In many ways, the work of basic homeostatic functions depends on heredity, genetic material passed on from the older generation of the family.
Based on the examples given, the main functions can be clearly seen:
- Energy.
- Adaptive.
- Reproductive.
It is important to pay attention to the fact that in old age, as well as in infancy, the stable functioning of homeostasis requires special attention, due to the fact that the reaction of the main regulatory systems is slow during these periods of life.
Properties of homeostasis
Knowing about the main 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.
The mechanisms are in constant change, testing conditions in order to choose the best option for adapting to them. This shows 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 body's reaction to changes in the external or internal environment may become unexpected and lead to restructuring of vital 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 a medical point of view, any disease is evidence of a malfunction in homeostasis. External and internal threats constantly impact the body, and only coherence in the operation of the main systems will help cope with them.
Weakening of the immune system does not occur without 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 the general state of your health. To do this, you can consult a doctor for an examination to identify your vulnerabilities and choose a set of therapy to eliminate them. Regular diagnostics will help to better control the basic processes of life.
It is important to follow these simple recommendations yourself:
- Avoid stressful situations to protect the nervous system from constant overstrain.
- Monitor your diet, do not overload yourself with heavy foods, and avoid pointless fasting, which will allow the digestive system to cope with its work more easily.
- Choose appropriate vitamin complexes to reduce the impact of seasonal weather changes.
A vigilant attitude towards your own health will help homeostatic processes respond promptly and correctly to any changes.
