Homeostasis and its manifestations at different levels of organization of biosystems. Age-related features of homeostasis

Homeostasis

Homeostasis, homeorez, homeomorphosis - characteristics of the state of the body. The systemic essence of the organism is manifested primarily in its ability to self-regulate in continuously changing environmental conditions. Since all organs and tissues of the body consist of cells, each of which is a relatively independent organism, the state of the internal environment of the human body is of great importance for its normal functioning. For the human body - a land creature - the environment consists of the atmosphere and the biosphere, while it interacts to a certain extent with the lithosphere, hydrosphere and noosphere. At the same time, most cells of the human body are immersed in a liquid environment, which is represented by blood, lymph and intercellular fluid. Only the integumentary tissues directly interact with the human environment; all other cells are isolated from the outside world, which allows the body to largely standardize the conditions of their existence. In particular, the ability to maintain a constant body temperature of about 37 ° C ensures the stability of metabolic processes, since all biochemical reactions that constitute the essence of metabolism are very dependent on temperature. It is equally important to maintain a constant tension of oxygen, carbon dioxide, concentration of various ions, etc. in the liquid media of the body. Under normal conditions of existence, including during adaptation and activity, small deviations of these kinds of parameters arise, but they are quickly eliminated, and the internal environment of the body returns to a stable norm. The great French physiologist of the 19th century. Claude Bernard argued: “The constancy of the internal environment is an indispensable condition for a free life.” Physiological mechanisms that ensure the maintenance of a constant 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 maintaining the constancy of any characteristics of a complex system is the main goal of any management.

Another remarkable researcher, K. Waddington, drew attention to the fact that the body is capable of maintaining not only the stability of its internal state, but also the relative constancy of dynamic characteristics, i.e., the course of processes over time. This phenomenon, by analogy with homeostasis, was called homeorez. 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) a “development channel” during its dynamic transformations. In particular, if a child, due to illness or a sharp deterioration in living conditions caused by social reasons (war, earthquake, etc.), lags significantly behind his normally developing peers, this does not mean that such a lag is fatal and irreversible. If the period of unfavorable events ends and the child receives conditions adequate for development, then both in growth and in the level of functional development he soon catches up with his peers and in the future does not differ significantly from them. This explains the fact that children who have suffered a serious illness at an early age often grow into healthy and well-proportioned adults. Homeorez plays a crucial role both in controlling ontogenetic development and in adaptation processes. Meanwhile, the physiological mechanisms of homeoresis have not yet been sufficiently studied.

The third form of self-regulation of body constancy is homeomorphosis - the ability to maintain a constant form. This characteristic is more characteristic of an adult organism, since growth and development are incompatible with the immutability of form. Nevertheless, if we consider short periods of time, especially during periods of growth inhibition, then the ability to homeomorphosis can be found in children. The point is 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 of the previous generation. Special physiological mechanisms prevent significant changes in body weight under conditions of fasting or overeating. In particular, during fasting, the digestibility of nutrients sharply increases, and during overeating, on the contrary, most of the proteins, fats and carbohydrates supplied with food are “burned” without any benefit to the body. It has been proven (N.A. Smirnova) that in an adult, sharp and significant changes in body weight (mainly due to the amount of fat) in any direction are sure signs of failure of adaptation, overexertion and indicate functional ill-being 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 different substances. During the life of the body's cells, the concentration of these substances can change significantly, which means a change in the internal environment. It would be unthinkable if the body's control systems were forced to monitor the concentration of all these substances, i.e. have many sensors (receptors), continuously analyze the current state, make control decisions and monitor their effectiveness. Neither the information nor the energy resources of the body would be sufficient for such a mode of controlling all parameters. Therefore, the body is limited to monitoring a relatively small number of the most significant indicators, which must be maintained at a relatively constant level for the well-being of the vast majority of body cells. These most strictly homeostasis parameters are thereby transformed into “biological constants,” and their immutability is ensured by sometimes quite significant fluctuations in other parameters that are not classified as homeostasis. Thus, the levels of hormones involved in the regulation of homeostasis can change in the blood tens of times depending on the state of the internal environment and the influence of external factors. At the same time, homeostasis 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 constant level various physiological systems of the body are responsible, we should mention body temperature, blood glucose level, H+ ion content in body fluids, partial tension of oxygen and carbon dioxide in tissues.

Disease as a sign or consequence of homeostasis disorders. Almost all human diseases are associated with disruption of homeostasis. For example, in many infectious diseases, as well as in the case of inflammatory processes, temperature homeostasis in the body is sharply disrupted: fever (fever) occurs, sometimes life-threatening. The reason for this disruption of homeostasis may lie both in the characteristics of the neuroendocrine reaction and in disturbances in the activity of peripheral tissues. In this case, the manifestation of the disease - elevated temperature - is a consequence of a violation of homeostasis.

Typically, febrile conditions are accompanied by acidosis - a violation of the acid-base balance and a shift in the reaction of body fluids to the acidic side. Acidosis is also characteristic of all diseases associated with deterioration of the cardiovascular and respiratory systems (heart and vascular diseases, inflammatory and allergic lesions of the bronchopulmonary system, etc.). Acidosis often accompanies the first hours of a newborn’s life, especially if he did not begin to breathe normally immediately after birth. To eliminate this condition, the newborn is placed in a special chamber with a high oxygen content. Metabolic acidosis during heavy muscle activity can occur in people of any age and manifests itself in shortness of breath and increased sweating, as well as muscle soreness. 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.

Diseases that lead to disruption of water-salt homeostasis are very dangerous, for example 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 disruption of water-salt homeostasis. As a result of some of these diseases, alkalosis may develop - an excessive increase in the concentration of alkaline substances in the blood and an increase in pH (a shift to the alkaline side).

In some cases, minor but long-term disturbances in homeostasis can cause the development of certain diseases. Thus, 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 of which a person develops diabetes. Excessive consumption of table and other mineral salts, hot seasonings, etc., which increase the load on the excretory system, is also dangerous. The kidneys may not be able to cope with the abundance of substances that need to be removed from the body, resulting in a disruption of water-salt homeostasis. One of its manifestations is edema - the accumulation of fluid in the soft tissues of the body. The cause of edema usually lies either in the insufficiency of the cardiovascular system, or in impaired renal function and, as a consequence, mineral metabolism.

Homeostasis(from Greek homoios- similar, identical and status- immobility) is the ability of living systems to resist changes and maintain the constancy of the composition and properties of biological systems.

The term “homeostasis” was proposed by W. Cannon in 1929 to characterize the states and processes that ensure the stability of the body. The idea of ​​the existence of physical mechanisms aimed at maintaining the constancy of the internal environment was expressed in the second half of the 19th century by C. Bernard, who considered the stability of physical and chemical conditions in the internal environment as the basis for the freedom and independence of living organisms in a continuously changing external environment. The phenomenon of homeostasis is observed at different levels of organization of biological systems.

Manifestation of homeostasis at different levels of organization of biological systems.

Restorative processes are carried out constantly and at different structural and functional levels of the organization of the individual - molecular genetic, subcellular, cellular, tissue, organ, organismal.

On molecular genetic level DNA replication occurs (its molecular repair, synthesis of enzymes and proteins that perform other (non-catalytic) functions in the cell, ATP molecules, for example, in mitochondria, etc. Many of these processes are included in the concept metabolism cells.

At the subcellular level restoration of various intracellular structures occurs (mainly we are talking about cytoplasmic organelles) through neoplasm (membranes, plasmalemma), assembly of subunits (microtubules), division (mitochondria).

Cellular level of regeneration implies restoration of the structure and, in some cases, functions of the cell. Examples of regeneration at the cellular level include restoration of a nerve cell process after injury. In mammals, this process occurs at a rate of 1 mm per day. Restoration of the functions of a cell of a certain type can be carried out through the process of cellular hypertrophy, that is, an increase in the volume of the cytoplasm and, consequently, the number of organelles (intracellular regeneration of modern authors or regenerative cellular hypertrophy of classical histology).

At the next level - tissue or cell-population (level of cellular tissue systems - see 3.2) replenishment of lost cells of a certain direction of differentiation occurs. Such replenishment is caused by changes in cellular material within cell populations (cellular tissue systems), which results in the restoration of tissue and organ functions. Thus, in humans, the lifespan of intestinal epithelial cells is 4-5 days, platelets - 5-7 days, erythrocytes - 120-125 days. At the indicated rates of death of red blood cells in the human body, for example, about 1 million red blood cells are destroyed every second, but the same amount is formed again in the red bone marrow. The possibility of restoring cells worn out during life or lost as a result of injury, poisoning or a pathological process is ensured by the fact that in the tissues of even a mature organism, cambial cells are preserved, capable of mitotic division with subsequent cytodifferentiation. These cells are now called regional or resident stem cells (see 3.1.2 and 3.2). Since they are committed, they are capable of giving rise to one or more specific cell types. Moreover, their differentiation into a specific cell type is determined by signals coming from the outside: local, from the immediate environment (the nature of intercellular interactions) and distant (hormones), causing selective expression of specific genes. Thus, in the epithelium of the small intestine, cambial cells are located in the bottom zones of the crypts. Under certain influences, they are capable of giving rise to cells of the “marginal” absorptive epithelium and some single-celled glands of the organ.

Regeneration on organ level has the main task of restoring the function of an organ with or without reproducing its typical structure (macroscopic, microscopic). In the process of regeneration at this level, not only transformations occur in cell populations (cellular tissue systems), but also morphogenetic processes. In this case, the same mechanisms are activated as during the formation of organs in embryogenesis (the period of development of the definitive phenotype). What has been said rightfully makes it possible to consider regeneration as a particular variant of the development process.

Structural homeostasis, mechanisms of its maintenance.

Types of homeostasis:

 Genetic homeostasis . The genotype of the zygote, when interacting with environmental factors, determines the entire complex of variability of the organism, its adaptive ability, that is, homeostasis. The body reacts to changes in environmental conditions specifically, within the limits of a hereditarily determined reaction norm. The constancy of genetic homeostasis is maintained on the basis of matrix syntheses, and the stability of the genetic material is ensured by a number of mechanisms (see mutagenesis).

 Structural homeostasis. Maintaining the constancy of the composition and integrity of the morphological organization of cells and tissues. The multifunctionality of cells increases the compactness and reliability of the entire system, increasing its potential capabilities. The formation of cell functions occurs through regeneration.

Regeneration:

1. Cellular (direct and indirect division)

2. Intracellular (molecular, intraorganoid, organoid)

A biological system of any complexity, from subcellular structures of functional systems and the whole organism, is characterized by the ability to self-organize and self-regulate. The ability to self-organize is manifested by a variety of cells and organs in the presence of a general principle of elementary structure (membranes, organelles, etc.). Self-regulation is ensured by mechanisms inherent in the very essence of living things.

The human body consists of organs that, to perform their functions, are most often combined with others, thereby forming functional systems. For this, structures of any level of complexity, from molecules to the whole organism, require regulatory systems. These systems ensure the interaction of various structures already in a state of physiological rest. They are especially important in an active state when the body interacts with a changing external environment, since any changes require an adequate response from the body. In this case, one of the mandatory conditions for self-organization and self-regulation is the preservation of the constant conditions of the internal environment characteristic of the body, which is denoted by the concept of homeostasis.

Rhythm of physiological functions. Physiological processes of life, even under conditions of complete physiological rest, proceed with varying activity. Their strengthening or weakening occurs under the influence of a complex interaction of exogenous and endogenous factors, which is called “biological rhythms”. Moreover, the periodicity of fluctuations of various functions varies within extremely wide limits, ranging from a period of up to 0.5 hours up to multi-day and even multi-year periods.

Concept of homeostasis

The efficient functioning of biological processes requires certain conditions, most of which must be constant. And the more stable they are, the more reliably the biological system functions. These conditions must first of all include those that help maintain a normal level of metabolism. This requires the supply of initial metabolic ingredients and oxygen, as well as the removal of final metabolites. The efficiency of metabolic processes is ensured by a certain intensity of intracellular processes, determined primarily by the activity of enzymes. At the same time, enzymatic activity also depends on such seemingly external factors as, for example, temperature.

Stability in most conditions is necessary at any structural and functional level, starting from an individual biochemical reaction, cell, and ending with complex functional systems of the body. In real life, these conditions can often be violated. The appearance of changes is reflected in the state of biological objects and the flow of metabolic processes in them. In addition, the more complex the structure of a biological system, the greater deviations from standard conditions it can withstand without significant disruption of vital functions. This is due to the presence in the body of appropriate mechanisms aimed at eliminating the changes that have arisen. For example, the activity of enzymatic processes in a cell decreases by 2-3 times with every 10 °C decrease in temperature. At the same time, warm-blooded animals, due to the presence of thermoregulation mechanisms, maintain a constant internal temperature over a fairly wide range of changes in external temperature. As a result, the stability of this condition for the occurrence of enzymatic reactions at a constant level is maintained. And for example, a person who also has intelligence, having clothes and housing, can exist for a long time at an external temperature significantly below 0 ° C.

In the process of evolution, adaptive reactions were formed aimed at maintaining constant conditions of the organism’s external environment. They exist both at the level of individual biological processes and the entire organism. Each of these conditions is characterized by corresponding parameters. Therefore, systems for regulating the constancy of conditions control the constancy of these parameters. And if these parameters deviate from the norm for some reason, regulatory mechanisms ensure their return to the original level.

The universal property of a living thing to actively maintain the stability of body functions, despite external influences that can disrupt IT, is called homeostasis.

The state of a biological system at any structural and functional level depends on a complex of influences. This complex consists of the interaction of many factors, both external to it and those that are inside or formed as a result of processes occurring in it. The level of exposure to external factors is determined by the corresponding state of the environment: temperature, humidity, illumination, pressure, gas composition, magnetic fields, etc. However, the body can and should maintain the degree of influence of not all external and internal factors at a constant level. Evolution has selected those that are more necessary for the preservation of life, or those for the maintenance of which appropriate mechanisms have been found.

Homeostasis parameter constants They do not have clear constancy. Their deviations from the average level in one direction or another in a kind of “corridor” are also possible. Each parameter has its own limits of maximum possible deviations. They also differ in the time during which the body can withstand a violation of a specific homeostasis parameter without any serious consequences. At the same time, the mere deviation of a parameter beyond the “corridor” can cause the death of the corresponding structure - be it a cell or even an organism as a whole. So, normally the pH of the blood is about 7.4. But it can fluctuate between 6.8-7.8. The human body can withstand the extreme degree of deviation of this parameter without harmful consequences for only a few minutes. Another homeostatic parameter - body temperature - in some infectious diseases can increase to 40 ° C and above and remain at this level for many hours and even days. Thus, some body constants are quite stable - - hard constants others have a wider range of vibrations - plastic constants.

Changes in homeostasis can occur under the influence of any external factors, and can also be of endogenous origin: the intensification of metabolic processes tends to change the parameters of homeostasis. At the same time, activation of regulatory systems easily ensures their return to a stable level. But, if at rest in a healthy person these processes are balanced and the recovery mechanisms function with a reserve of power, then in the event of a sharp change in living conditions, during illnesses they turn on with maximum activity. The improvement of homeostasis regulation systems is also reflected in evolutionary development. Thus, the absence of a system for maintaining a constant body temperature in cold-blooded animals, causing the dependence of life processes on variable external temperature, sharply limited their evolutionary development. However, the presence of such a system in warm-blooded animals ensured their settlement throughout the planet and made such organisms truly free creatures with high evolutionary potential.

In turn, each person has individual functional capabilities of the homeostasis regulation systems themselves. This largely determines the severity of the body’s reaction to any influence, and ultimately affects life expectancy.

Cellular homeostasis . One of the unique parameters of homeostasis is the “genetic purity” of the cell populations of the body. The body's immune system monitors normal cell proliferation. If it is disrupted or the reading of genetic information is impaired, cells appear that are foreign to the given organism. The mentioned system destroys them. We can say that a similar mechanism also combats the entry of foreign cells (bacteria, worms) or their products into the body. And this is also ensured by the immune system (see section C - “Physiological characteristics of leukocytes”).

Mechanisms of homeostasis and their regulation

Systems that control the parameters of homeostasis consist of mechanisms of varying structural complexity: both relatively simple elements and rather complex neurohormonal complexes. Metabolites are considered one of the simplest mechanisms, some of which can locally influence the activity of enzymatic processes and various structural components of cells and tissues. More complex mechanisms (neuroendocrine) that carry out interorgan interaction are activated when simple ones are no longer enough to return the parameter to the required level.

Local autoregulation processes with negative feedback occur in the cell. For example, during intense muscular work, NEP suboxides and metabolic products accumulate in the skeletal muscles through a relative deficiency of 02. They shift the pH of sarcoplasm to the acidic side, which can cause the death of individual structures, the entire cell, or even the organism. When pH decreases, the conformational properties of cytoplasmic proteins and membrane complexes change. The latter causes a change in the pore radius, an increase in the permeability of membranes (partitions) of all subcellular structures, and a disruption of ion gradients.

The role of body fluids in homeostasis. The body's fluids are considered the central link in maintaining homeostasis. For most organs this is blood and lymph, and for the brain it is blood and cerebrospinal fluid (CSF). Blood plays a particularly important role. In addition, the liquid media for a cell are its cytoplasm and intercellular fluid.

Functions of liquid media The maintenance of homeostasis is quite varied. Firstly, liquid media provide metabolic processes with tissues. They not only bring substances necessary for life to cells, but also transport metabolites from them, which otherwise can accumulate in cells in high concentrations.

Secondly, liquid media have their own mechanisms necessary to maintain certain parameters of homeostasis. For example, buffer systems mitigate the shift in acid-base state when acids or bases enter the blood.

thirdly, liquid media take part in the organization of the homeostasis control system. There are also several mechanisms here. Thus, due to the transport of metabolites, distant organs and systems (kidneys, lungs, etc.) are involved in the process of maintaining homeostasis. In addition, metabolites contained in the blood, acting on the structures and receptors of other organs and systems, can trigger complex reflex responses and hormonal mechanisms. For example, thermoreceptors respond to “hot” or “cold” blood and accordingly change the activity of organs involved in the formation and transfer of heat.

Receptors are also located in the walls of blood vessels themselves. They participate in the regulation of the chemical composition of blood, its volume, and pressure. With irritation of vascular receptors, reflexes begin, the effector part of which is the organs and systems of the body. The great importance of blood in maintaining homeostasis became the basis for the formation of a special homeostasis system for many parameters of the blood itself and its volume. To preserve them, there are complex mechanisms that are included in a unified system for regulating the body’s homeostasis.

The above can be clearly illustrated using the example of intense muscle activity. During its execution, metabolic products in the form of lactic, pyruvic, acetoacetic and other acids are released from the muscles into the bloodstream. Acidic metabolites are first neutralized by alkaline blood reserves. In addition, they activate blood circulation and breathing through reflex mechanisms. Connecting these body systems, on the one hand, improves the supply of 02 to the muscles, and therefore reduces the formation of under-oxidized products; on the other hand, it helps to increase the release of CO2 through the lungs, many metabolites through the kidneys, and sweat glands.

The body as an open self-regulating system.

A living organism is an open system that has a connection with the environment through the nervous, digestive, respiratory, excretory systems, etc.

In the process of metabolism with food, water, and gas exchange, various chemical compounds enter the body, which undergo changes in the body, enter the structure of the body, but do not remain permanently. Assimilated substances decompose, release energy, and decomposition products are removed into the external environment. The destroyed molecule is replaced by a new one, etc.

The body is an open, dynamic system. In a constantly changing environment, the body maintains a stable state for a certain time.

The concept of homeostasis. General patterns of homeostasis in living systems.

Homeostasis – the property of a living organism to maintain the relative dynamic constancy of its internal environment. Homeostasis is expressed in the relative constancy of the chemical composition, osmotic pressure, and the stability of basic physiological functions. Homeostasis is specific and determined by genotype.

Preservation of the integrity of the individual properties of the organism is one of the most general biological laws. This law is ensured in the vertical series of generations by reproduction mechanisms, and throughout the life of an individual by homeostasis mechanisms.

The phenomenon of homeostasis is an evolutionarily developed, hereditarily fixed adaptive property of the body to normal environmental conditions. However, these conditions may be outside the normal range for a short or long period of time. In such cases, adaptation phenomena are characterized not only by the restoration of the usual properties of the internal environment, but also by short-term changes in function (for example, an increase in the rhythm of cardiac activity and an increase in the frequency of respiratory movements with increased muscle work). Homeostasis reactions can be aimed at:

maintaining known levels of steady state;

elimination or limitation of harmful factors;

development or preservation of optimal forms of interaction between the organism and the environment in the changed conditions of its existence. All these processes determine adaptation.

Therefore, the concept of homeostasis means not only a certain constancy of various physiological constants of the body, but also includes processes of adaptation and coordination of physiological processes that ensure the unity of the body not only normally, but also under changing conditions of its existence.

The main components of homeostasis were identified by C. Bernard, and they can be divided into three groups:

A. Substances that provide cellular needs:

Substances necessary for energy production, growth and recovery - glucose, proteins, fats.

NaCl, Ca and other inorganic substances.

Oxygen.

Internal secretion.

B. Environmental factors affecting cellular activity:

Osmotic pressure.

Temperature.

Hydrogen ion concentration (pH).

B. Mechanisms ensuring structural and functional unity:

Heredity.

Regeneration.

Immunobiological reactivity.

The principle of biological regulation ensures the internal state of the organism (its content), as well as the relationship between the stages of ontogenesis and phylogenesis. This principle has proven to be widespread. During its study, cybernetics arose - the science of purposeful and optimal control of complex processes in living nature, in human society, and industry (Berg I.A., 1962).

A living organism is a complex controlled system where many variables of the external and internal environment interact. Common to all systems is the presence input variables, which, depending on the properties and laws of behavior of the system, are transformed into weekend variables (Fig. 10).

Rice. 10 - General scheme of homeostasis of living systems

Output variables depend on the input and laws of system behavior.

The influence of the output signal on the control part of the system is called feedback , which is of great importance in self-regulation (homeostatic reaction). Distinguish negative Andpositive feedback.

Negative feedback reduces the influence of the input signal on the output value according to the principle: “the more (at the output), the less (at the input).” It helps restore system homeostasis.

At positive feedback, the magnitude of the input signal increases according to the principle: “the more (at the output), the more (at the input).” It enhances the resulting deviation from the initial state, which leads to a disruption of homeostasis.

However, all types of self-regulation operate according to the same principle: self-deviation from the initial state, which serves as an incentive to turn on correction mechanisms. Thus, normal blood pH is 7.32 – 7.45. A pH shift of 0.1 leads to cardiac dysfunction. This principle was described by Anokhin P.K. in 1935 and called the feedback principle, which serves to carry out adaptive reactions.

General principle of the homeostatic response(Anokhin: “Theory of functional systems”):

deviation from the initial level → signal → activation of regulatory mechanisms based on the feedback principle → correction of the change (normalization).

So, during physical work, the concentration of CO 2 in the blood increases → pH shifts to the acidic side → the signal enters the respiratory center of the medulla oblongata → centrifugal nerves conduct an impulse to the intercostal muscles and breathing deepens → CO 2 in the blood decreases, pH is restored.

Mechanisms of regulation of homeostasis at the molecular genetic, cellular, organismal, population-species and biosphere levels.

Regulatory homeostatic mechanisms function at the gene, cellular and system (organismal, population-species and biosphere) levels.

Gene mechanisms homeostasis. All phenomena of homeostasis in the body are genetically determined. Already at the level of primary gene products there is a direct connection - “one structural gene - one polypeptide chain.” Moreover, there is a collinear correspondence between the nucleotide sequence of DNA and the amino acid sequence of the polypeptide chain. The hereditary program for the individual development of an organism provides for the formation of species-specific characteristics not in constant, but in changing environmental conditions, within the limits of a hereditarily determined reaction norm. The double helicity of DNA is essential in the processes of its replication and repair. Both are directly related to ensuring the stability of the functioning of the genetic material.

From a genetic point of view, one can distinguish between elementary and systemic manifestations of homeostasis. Examples of elementary manifestations of homeostasis include: gene control of thirteen blood coagulation factors, gene control of histocompatibility of tissues and organs, allowing transplantation.

The transplanted area is called transplant. The organism from which tissue is taken for transplantation is donor , and who is being transplanted - recipient . The success of transplantation depends on the body's immunological reactions. There are autotransplantation, syngeneic transplantation, allotransplantation and xenotransplantation.

Autotransplantation – tissue transplantation from the same organism. In this case, the proteins (antigens) of the transplant do not differ from those of the recipient. There is no immunological reaction.

Syngeneic transplantation carried out in identical twins who have the same genotype.

Allotransplantation – transplantation of tissues from one individual to another belonging to the same species. The donor and recipient differ in antigens, which is why higher animals experience long-term engraftment of tissues and organs.

Xenotransplantation – the donor and recipient belong to different types of organisms. This type of transplantation is successful in some invertebrates, but in higher animals such transplants do not take root.

During transplantation, the phenomenon is of great importance immunological tolerance (histocompatibility). Suppression of the immune system in the case of tissue transplantation (immunosuppression) is achieved by: suppression of the activity of the immune system, irradiation, administration of antilymphatic serum, adrenal hormones, chemicals - antidepressants (imuran). The main task is to suppress not just immunity, but transplantation immunity.

Transplant immunity determined by the genetic constitution of the donor and recipient. Genes responsible for the synthesis of antigens that cause a reaction to transplanted tissue are called tissue incompatibility genes.

In humans, the main genetic histocompatibility system is the HLA (Human Leukocyte Antigen) system. Antigens are quite fully represented on the surface of leukocytes and are detected using antisera. The structure of the system in humans and animals is the same. A common terminology has been adopted to describe genetic loci and alleles of the HLA system. Antigens are designated: HLA-A 1; HLA-A 2, etc. New antigens that have not been definitively identified are designated W (Work). Antigens of the HLA system are divided into 2 groups: SD and LD (Fig. 11).

Antigens of the SD group are determined by serological methods and are determined by the genes of 3 subloci of the HLA system: HLA-A; HLA-B; HLA-C.

Rice. 11 - HLA is the main genetic system of human histocompatibility

LD - antigens are controlled by the HLA-D sublocus of the sixth chromosome, and are determined by the method of mixed cultures of leukocytes.

Each of the genes that control human HLA antigens has a large number of alleles. Thus, the HLA-A sublocus controls 19 antigens; HLA-B – 20; HLA-C – 5 “working” antigens; HLA-D – 6. Thus, about 50 antigens have already been discovered in humans.

Antigenic polymorphism of the HLA system is the result of the origin of some from others and the close genetic connection between them. Identity of the donor and recipient by HLA antigens is necessary for transplantation. Transplantation of a kidney identical in 4 antigens of the system ensures a survival rate of 70%; 3 – 60%; 2 – 45%; 1 – 25% each.

There are special centers that conduct the selection of donor and recipient for transplantation, for example, in Holland - “Eurotransplant”. Typing based on HLA system antigens is also carried out in the Republic of Belarus.

Cellular mechanisms homeostasis are aimed at restoring tissue cells and organs in the event of a violation of their integrity. The set of processes aimed at restoring destroyed biological structures is called regeneration. This process is characteristic of all levels: renewal of proteins, components of cell organelles, entire organelles and the cells themselves. Restoring organ functions after injury or nerve rupture and wound healing are important for medicine from the point of view of mastering these processes.

Tissues, according to their regenerative ability, are divided into 3 groups:

Tissues and organs that are characterized by cellular regeneration (bones, loose connective tissue, hematopoietic system, endothelium, mesothelium, mucous membranes of the intestinal tract, respiratory tract and genitourinary system.

Tissues and organs that are characterized by cellular and intracellular regeneration (liver, kidneys, lungs, smooth and skeletal muscles, autonomic nervous system, endocrine, pancreas).

Fabrics that are characterized predominantly intracellular regeneration (myocardium) or exclusively intracellular regeneration (central nervous system ganglion cells). It covers the processes of restoration of macromolecules and cellular organelles by assembling elementary structures or by dividing them (mitochondria).

In the process of evolution, 2 types of regeneration were formed physiological and reparative .

Physiological regeneration - This is a natural process of restoration of body elements throughout life. For example, restoration of erythrocytes and leukocytes, replacement of skin epithelium, hair, replacement of milk teeth with permanent ones. These processes are influenced by external and internal factors.

Reparative regeneration – is the restoration of organs and tissues lost due to damage or injury. The process occurs after mechanical injuries, burns, chemical or radiation injuries, as well as as a result of illnesses and surgical operations.

Reparative regeneration is divided into typical (homomorphosis) and atypical (heteromorphosis). In the first case, an organ that was removed or destroyed regenerates, in the second, another develops in the place of the removed organ.

Atypical regeneration more common in invertebrates.

Hormones stimulate regeneration pituitary gland And thyroid gland . There are several methods of regeneration:

Epimorphosis or complete regeneration - restoration of the wound surface, completion of the part to the whole (for example, the regrowth of a tail in a lizard, limbs in a newt).

Morphollaxis – reconstruction of the remaining part of the organ into a whole, only smaller in size. This method is characterized by the reconstruction of a new one from the remains of an old one (for example, restoration of a limb in a cockroach).

Endomorphosis – restoration due to intracellular restructuring of tissue and organ. Due to the increase in the number of cells and their size, the mass of the organ approaches the original one.

In vertebrates, reparative regeneration occurs in the following form:

Full regeneration – restoration of the original tissue after its damage.

Regenerative hypertrophy , characteristic of internal organs. In this case, the wound surface heals with a scar, the removed area does not grow back and the shape of the organ is not restored. The mass of the remaining part of the organ increases due to an increase in the number of cells and their sizes and approaches the original value. This is how the liver, lungs, kidneys, adrenal glands, pancreas, salivary, and thyroid glands regenerate in mammals.

Intracellular compensatory hyperplasia cell ultrastructures. In this case, a scar is formed at the site of damage, and restoration of the original mass occurs due to an increase in the volume of cells, and not their number based on the proliferation (hyperplasia) of intracellular structures (nervous tissue).

Systemic mechanisms are provided by the interaction of regulatory systems: nervous, endocrine and immune .

Nervous regulation carried out and coordinated by the central nervous system. Nerve impulses entering cells and tissues not only cause excitement, but also regulate chemical processes and the exchange of biologically active substances. Currently, more than 50 neurohormones are known. Thus, the hypothalamus produces vasopressin, oxytocin, liberins and statins, which regulate the function of the pituitary gland. Examples of systemic manifestations of homeostasis are maintaining a constant temperature and blood pressure.

From the standpoint of homeostasis and adaptation, the nervous system is the main organizer of all body processes. The basis of adaptation is the balancing of organisms with environmental conditions, according to N.P. Pavlov, reflex processes lie. Between different levels of homeostatic regulation there is a private hierarchical subordination in the system of regulation of internal processes of the body (Fig. 12).

Rice. 12. - Hierarchical subordination in the system of regulation of internal processes of the body.

The most primary level consists of homeostatic systems at the cellular and tissue levels. Above them are peripheral nervous regulatory processes such as local reflexes. Further in this hierarchy are systems of self-regulation of certain physiological functions with various “feedback” channels. The top of this pyramid is occupied by the cerebral cortex and the brain.

In a complex multicellular organism, both direct and feedback connections are carried out not only by nervous, but also by hormonal (endocrine) mechanisms. Each of the glands included in the endocrine system influences other organs of this system and, in turn, is influenced by the latter.

Endocrine mechanisms homeostasis according to B.M. Zavadsky, this is a mechanism of plus-minus interaction, i.e. balancing the functional activity of the gland with the concentration of the hormone. With a high concentration of the hormone (above normal), the activity of the gland is weakened and vice versa. This effect is carried out through the action of the hormone on the gland that produces it. In a number of glands, regulation is established through the hypothalamus and the anterior pituitary gland, especially during a stress reaction.

Endocrine glands can be divided into two groups according to their relation to the anterior lobe of the pituitary gland. The latter is considered central, and the other endocrine glands are considered peripheral. This division is based on the fact that the anterior lobe of the pituitary gland produces so-called tropic hormones, which activate some peripheral endocrine glands. In turn, the hormones of the peripheral endocrine glands act on the anterior lobe of the pituitary gland, inhibiting the secretion of tropic hormones.

The reactions that ensure homeostasis cannot be limited to any one endocrine gland, but involve all glands to one degree or another. The resulting reaction takes on a chain course and spreads to other effectors. The physiological significance of hormones lies in the regulation of other functions of the body, and therefore the chain nature should be expressed as much as possible.

Constant disturbances in the body's environment contribute to maintaining its homeostasis over a long life. If you create living conditions in which nothing causes significant changes in the internal environment, then the organism will be completely unarmed when it encounters the environment and will soon die.

The combination of nervous and endocrine regulatory mechanisms in the hypothalamus allows for complex homeostatic reactions associated with the regulation of the visceral function of the body. The nervous and endocrine systems are the unifying mechanism of homeostasis.

An example of a general response of nervous and humoral mechanisms is a state of stress that develops under unfavorable living conditions and there is a threat of disruption of homeostasis. Under stress, a change in the state of most systems is observed: muscular, respiratory, cardiovascular, digestive, sensory organs, blood pressure, blood composition. All these changes are a manifestation of individual homeostatic reactions aimed at increasing the body's resistance to unfavorable factors. The rapid mobilization of the body's forces acts as a protective reaction to stress.

With “somatic stress,” the problem of increasing the overall resistance of the body is solved according to the scheme shown in Figure 13.

Rice. 13 - Scheme for increasing the overall resistance of the body during

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: The entire internal, structural and functional organization of systems contributes to maintaining 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:

1. Negative feedback, expressed as a reaction in which the system responds in a way that reverses 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).
2. Positive feedback, which is expressed in increasing changes 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 a much larger action potential. Blood clotting and events at birth can be cited as 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 a large volcanic eruption - the state of homeostasis of the previous forest climax ecosystem was destroyed, as was all life on that 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 , one hundred years after the eruption destroyed 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). As an ecosystem approaches climax, such species are replaced by more complex climax species that, 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 contributes to 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, the tropical tree reduces light access 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. Likewise, such forests contribute to ecological processes such as the regulation of microclimates or hydrological cycles of an 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.

3) tissues characterized primarily or exclusively by intracellular regeneration (myocardium and ganglion cells of the central nervous system)

In the process of evolution, 2 types of regeneration were formed: physiological and reparative.

Homeostasis in the human body

Various factors affect the ability of body fluids to support life. These include parameters such as temperature, salinity, acidity and concentration of nutrients - glucose, various ions, oxygen, and waste - carbon dioxide and urine. Since these parameters influence the chemical reactions that keep the body alive, there are built-in physiological mechanisms to maintain them at the required level.

Homeostasis cannot be considered the cause of these unconscious adaptation processes. It should be perceived as a general characteristic of many normal processes acting together, and not as their root cause. Moreover, there are many biological phenomena that do not fit this model - for example, anabolism.

Other areas

The concept of “homeostasis” is also used in other areas.

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An excerpt characterizing Homeostasis

Returning from Prince Andrei to Gorki, Pierre, having ordered the horseman to prepare the horses and wake him up early in the morning, immediately fell asleep behind the partition, in the corner that Boris had given him.
When Pierre fully woke up the next morning, there was no one in the hut. Glass rattled in the small windows. The bereitor stood pushing him aside.
“Your Excellency, your Excellency, your Excellency...” the bereitor said stubbornly, without looking at Pierre and, apparently, having lost hope of waking him up, swinging him by the shoulder.
- What? Began? Is it time? - Pierre spoke, waking up.
“If you please hear the firing,” said the bereitor, a retired soldier, “all the gentlemen have already left, the most illustrious ones themselves have passed a long time ago.”
Pierre quickly got dressed and ran out onto the porch. It was clear, fresh, dewy and cheerful outside. The sun, having just broken out from behind the cloud that was obscuring it, splashed half-broken rays through the roofs of the opposite street, onto the dew-covered dust of the road, onto the walls of the houses, onto the windows of the fence and onto Pierre’s horses standing at the hut. The roar of the guns could be heard more clearly in the yard. An adjutant with a Cossack trotted down the street.
- It's time, Count, it's time! - shouted the adjutant.
Having ordered his horse to be led, Pierre walked down the street to the mound from which he had looked at the battlefield yesterday. On this mound there was a crowd of military men, and the French conversation of the staff could be heard, and the gray head of Kutuzov could be seen with his white cap with a red band and the gray back of his head, sunk into his shoulders. Kutuzov looked through the pipe ahead along the main road.
Entering the entrance steps to the mound, Pierre looked ahead of him and froze in admiration at the beauty of the spectacle. It was the same panorama that he had admired yesterday from this mound; but now this entire area was covered with troops and the smoke of gunfire, and the slanting rays of the bright sun, rising from behind, to the left of Pierre, threw upon it in the clear morning air a piercing light with a golden and pink tint and dark, long shadows. The distant forests that completed the panorama, as if carved from some precious yellow-green stone, were visible with their curved line of peaks on the horizon, and between them, behind Valuev, cut through the great Smolensk road, all covered with troops. Golden fields and copses glittered closer. Troops were visible everywhere - in front, right and left. It was all lively, majestic and unexpected; but what struck Pierre most of all was the view of the battlefield itself, Borodino and the ravine above Kolocheya on both sides of it.
Above Kolocha, in Borodino and on both sides of it, especially to the left, where in the marshy banks Voina flows into Kolocha, there was that fog that melts, blurs and shines through when the bright sun comes out and magically colors and outlines everything visible through it. This fog was joined by the smoke of shots, and through this fog and smoke the lightning of the morning light flashed everywhere - now on the water, now on the dew, now on the bayonets of the troops crowded along the banks and in Borodino. Through this fog one could see a white church, here and there the roofs of Borodin's huts, here and there solid masses of soldiers, here and there green boxes and cannons. And it all moved, or seemed to move, because fog and smoke stretched throughout this entire space. Both in this area of ​​the lowlands near Borodino, covered with fog, and outside it, above and especially to the left along the entire line, through forests, across fields, in the lowlands, on the tops of elevations, cannons, sometimes solitary, constantly appeared by themselves, out of nothing, sometimes huddled, sometimes rare, sometimes frequent clouds of smoke, which, swelling, growing, swirling, merging, were visible throughout this space.
These smokes of shots and, strange to say, their sounds produced the main beauty of the spectacle.
Puff! - suddenly a round, dense smoke was visible, playing with purple, gray and milky white colors, and boom! – the sound of this smoke was heard a second later.
“Poof poof” - two smokes rose, pushing and merging; and “boom boom” - the sounds confirmed what the eye saw.
Pierre looked back at the first smoke, which he left as a round dense ball, and already in its place there were balls of smoke stretching to the side, and poof... (with a stop) poof poof - three more, four more were born, and for each, with the same arrangements, boom... boom boom boom - beautiful, firm, true sounds answered. It seemed that these smokes were running, that they were standing, and forests, fields and shiny bayonets were running past them. On the left side, across the fields and bushes, these large smokes were constantly appearing with their solemn echoes, and closer still, in the valleys and forests, small gun smokes flared up, not having time to round off, and in the same way gave their little echoes. Tah ta ta tah - the guns crackled, although often, but incorrectly and poorly in comparison with gun shots.
Pierre wanted to be where these smokes were, these shiny bayonets and cannons, this movement, these sounds. He looked back at Kutuzov and his retinue to compare his impressions with others. Everyone was exactly like him, and, as it seemed to him, they were looking forward to the battlefield with the same feeling. All faces now shone with that hidden warmth (chaleur latente) of feeling that Pierre had noticed yesterday and which he understood completely after his conversation with Prince Andrei.
“Go, my dear, go, Christ is with you,” said Kutuzov, without taking his eyes off the battlefield, to the general standing next to him.
Having heard the order, this general walked past Pierre, towards the exit from the mound.
- To the crossing! – the general said coldly and sternly in response to one of the staff asking where he was going. “Both I and I,” thought Pierre and followed the general in the direction.
The general mounted the horse that the Cossack handed to him. Pierre approached his rider, who was holding the horses. Having asked which was quieter, Pierre climbed onto the horse, grabbed the mane, pressed the heels of his outstretched legs to the horse’s belly and, feeling that his glasses were falling off and that he was unable to take his hands off the mane and reins, galloped after the general, exciting the smiles of the staff, from the mound looking at him.

The general, whom Pierre was galloping after, went down the mountain, turned sharply to the left, and Pierre, having lost sight of him, galloped into the ranks of the infantry soldiers walking ahead of him. He tried to get out of them, now to the right, now to the left; but everywhere there were soldiers, with equally preoccupied faces, busy with some invisible, but obviously important matter. Everyone looked at this fat man in a white hat with the same dissatisfied, questioning look, who for some unknown reason was trampling them with his horse.
- Why is he driving in the middle of the battalion! – one shouted at him. Another pushed his horse with the butt, and Pierre, clinging to the bow and barely holding the darting horse, jumped out in front of the soldier, where there was more space.
There was a bridge ahead of him, and other soldiers stood at the bridge, shooting. Pierre drove up to them. Without knowing it, Pierre drove to the bridge over Kolocha, which was between Gorki and Borodino and which the French attacked in the first action of the battle (having occupied Borodino). Pierre saw that there was a bridge in front of him and that on both sides of the bridge and in the meadow, in those rows of lying hay that he had noticed yesterday, soldiers were doing something in the smoke; but, despite the incessant shooting that took place in this place, he did not think that this was the battlefield. He did not hear the sounds of bullets screaming from all sides, or shells flying over him, he did not see the enemy who was on the other side of the river, and for a long time he did not see the dead and wounded, although many fell not far from him. With a smile never leaving his face, he looked around him.
- Why is this guy driving in front of the line? – someone shouted at him again.
“Take it left, take it right,” they shouted to him. Pierre turned to the right and unexpectedly moved in with the adjutant of General Raevsky, whom he knew. This adjutant looked angrily at Pierre, obviously intending to shout at him too, but, recognizing him, nodded his head to him.
- How are you here? – he said and galloped on.
Pierre, feeling out of place and idle, afraid to interfere with someone again, galloped after the adjutant.
- This is here, what? Can I come with you? - he asked.
“Now, now,” answered the adjutant and, galloping up to the fat colonel standing in the meadow, he handed him something and then turned to Pierre.
- Why did you come here, Count? - he told him with a smile. -Are you all curious?
“Yes, yes,” said Pierre. But the adjutant, turning his horse, rode on.
“Thank God here,” said the adjutant, “but on Bagration’s left flank there is a terrible heat going on.”
- Really? – asked Pierre. - Where is this?
- Yes, come with me to the mound, we can see from us. “But our battery is still bearable,” said the adjutant. - Well, are you going?
“Yes, I’m with you,” said Pierre, looking around him and looking for his guard with his eyes. Here, only for the first time, Pierre saw the wounded, wandering on foot and carried on stretchers. In the same meadow with fragrant rows of hay through which he drove yesterday, across the rows, his head awkwardly turned, one soldier lay motionless with a fallen shako. - Why wasn’t this raised? - Pierre began; but, seeing the stern face of the adjutant, looking back in the same direction, he fell silent.
Pierre did not find his guard and, together with his adjutant, drove down the ravine to the Raevsky mound. Pierre's horse lagged behind the adjutant and shook him evenly.
“Apparently you’re not used to riding a horse, Count?” – asked the adjutant.
“No, nothing, but she’s jumping around a lot,” Pierre said in bewilderment.
“Eh!.. yes, she’s wounded,” said the adjutant, “right front, above the knee.” Must be a bullet. Congratulations, Count,” he said, “le bapteme de feu [baptism by fire].
Having driven through the smoke through the sixth corps, behind the artillery, which, pushed forward, was firing, deafening with its shots, they arrived at a small forest. The forest was cool, quiet and smelled of autumn. Pierre and the adjutant dismounted from their horses and entered the mountain on foot.
- Is the general here? – asked the adjutant, approaching the mound.
“We were there now, let’s go here,” they answered him, pointing to the right.
The adjutant looked back at Pierre, as if not knowing what to do with him now.
“Don’t worry,” said Pierre. – I’ll go to the mound, okay?
- Yes, go, you can see everything from there and it’s not so dangerous. And I'll pick you up.
Pierre went to the battery, and the adjutant went further. They did not see each other again, and much later Pierre learned that this adjutant’s arm was torn off that day.
The mound that Pierre entered was the famous one (later known among the Russians under the name of the kurgan battery, or Raevsky’s battery, and among the French under the name la grande redoute, la fatale redoute, la redoute du center [the great redoubt, the fatal redoubt, the central redoubt ] a place around which tens of thousands of people were positioned and which the French considered the most important point of the position.
This redoubt consisted of a mound on which ditches were dug on three sides. In a place dug in by ditches there were ten firing cannons, stuck out into the opening of the shafts.
There were cannons lined up with the mound on both sides, also firing incessantly. A little behind the guns stood the infantry troops. Entering this mound, Pierre did not think that this place, dug in with small ditches, on which several cannons stood and fired, was the most important place in the battle.
To Pierre, on the contrary, it seemed that this place (precisely because he was on it) was one of the most insignificant places of the battle.
Entering the mound, Pierre sat down at the end of the ditch surrounding the battery, and with an unconsciously joyful smile looked at what was happening around him. From time to time, Pierre still stood up with the same smile and, trying not to disturb the soldiers who were loading and rolling guns, constantly running past him with bags and charges, walked around the battery. The guns from this battery fired continuously one after another, deafening with their sounds and covering the entire area with gunpowder smoke.
In contrast to the creepiness that was felt between the infantry soldiers of the cover, here, on the battery, where a small number of people busy with work are white limited, separated from others by a ditch - here one felt the same and common to everyone, as if a family revival.
The appearance of the non-military figure of Pierre in a white hat initially struck these people unpleasantly. The soldiers, passing by him, glanced sideways at his figure in surprise and even fear. The senior artillery officer, a tall, long-legged, pockmarked man, as if to watch the action of the last gun, approached Pierre and looked at him curiously.
A young, round-faced officer, still a complete child, apparently just released from the corps, very diligently disposing of the two guns entrusted to him, addressed Pierre sternly.
“Mister, let me ask you to leave the road,” he told him, “it’s not allowed here.”
The soldiers shook their heads disapprovingly, looking at Pierre. But when everyone was convinced that this man in a white hat not only did nothing wrong, but either sat quietly on the slope of the rampart, or with a timid smile, courteously avoiding the soldiers, walked along the battery under gunfire as calmly as along the boulevard, then Little by little, the feeling of hostile bewilderment towards him began to turn into affectionate and playful sympathy, similar to that which soldiers have for their animals: dogs, roosters, goats and in general animals living with military commands. These soldiers immediately mentally accepted Pierre into their family, appropriated them and gave him a nickname. “Our master” they nicknamed him and laughed affectionately about him among themselves.
One cannonball exploded into the ground two steps away from Pierre. He, cleaning the soil sprinkled with the cannonball from his dress, looked around him with a smile.
- And why aren’t you afraid, master, really! - the red-faced, broad soldier turned to Pierre, baring his strong white teeth.
-Are you afraid? – asked Pierre.
- How then? - answered the soldier. - After all, she will not have mercy. She will smack and her guts will be out. “You can’t help but be afraid,” he said, laughing.
Several soldiers with cheerful and affectionate faces stopped next to Pierre. It was as if they did not expect him to speak like everyone else, and this discovery delighted them.
- Our business is soldierly. But master, it’s so amazing. That's it master!
- In places! - the young officer shouted at the soldiers gathered around Pierre. This young officer, apparently, was fulfilling his position for the first or second time and therefore treated both the soldiers and the commander with particular clarity and formality.