Mechanisms for maintaining homeostasis, reliability and compensation of functions. Homeostasis - what is it? Homeostasis concept

Homeostasis is a process that occurs independently in the body and is aimed at stabilizing the state of human systems when changing internal conditions(change in temperature, pressure) or external (change in climate, time zone). This name was proposed by the American physiologist Cannon. Subsequently, homeostasis began to be called the ability of any system (including environment) to maintain your internal constancy.

Concept and characteristics of homeostasis

Wikipedia characterizes this term as the desire to survive, adapt and develop. In order for homeostasis to be correct, the coordinated work of all organs and systems is needed. In this case, all the person’s parameters will be normal. If some parameter in the body is not regulated, this indicates disturbances in homeostasis.

The main characteristics of homeostasis are as follows:

• analysis of the possibilities of adapting the system to new conditions;
• desire to maintain balance;
• inability to predict in advance the results of indicator regulation.

Feedback

Feedback is the actual mechanism of homeostasis. This is how the body reacts to any changes. The body functions continuously throughout a person's life. However separate systems must have time to rest and recover. During this period, the work of individual bodies slows down or stops altogether. This process is called feedback. An example of this is a break in the functioning of the stomach, when food does not enter it. This break in digestion ensures that acid production stops due to the actions of hormones and nerve impulses.

There are two types of this mechanism, which will be described below.

Negative Feedback

This type of mechanism is based on the fact that the body reacts to changes, trying to direct them in the opposite direction. That is, it strives again for stability. For example, if carbon dioxide accumulates in the body, the lungs begin to work more actively, breathing becomes more frequent, due to which excess carbon dioxide is removed. And it is also thanks to negative feedback that thermoregulation is carried out, due to which the body avoids overheating or hypothermia.

Positive Feedback

This mechanism is exactly the opposite of the previous one. In the case of its action, the change in the variable is only enhanced by the mechanism, which removes the body from a state of equilibrium. This is a fairly rare and less desirable process. An example of this would be the presence of electrical potential in nerves, which, instead of reducing the effect, leads to its increase.

However, thanks to this mechanism, development and transition to new states occur, which means it is also necessary for life.

What parameters does homeostasis regulate?

Despite the fact that the body constantly tries to maintain the values ​​of parameters important for life, they are not always stable. Body temperature will still vary within a small range, as will heart rate or blood pressure. The task of homeostasis is to maintain this range of values, as well as to help the body function.

Examples of homeostasis are the removal of waste from the human body by the kidneys, sweat glands, gastrointestinal tract, as well as the dependence of metabolism on diet. A little more detail about the adjustable parameters will be discussed below.

Body temperature

The most striking and simple example of homeostasis is maintaining normal body temperature. Overheating of the body can be avoided by sweating. Normal temperature is the range from 36 to 37 degrees Celsius. An increase in these values ​​can be triggered by inflammatory processes, hormonal and metabolic disorders, or any diseases.

A part of the brain called the hypothalamus is responsible for controlling body temperature. Failure signals are received there temperature regime, which can also be expressed in rapid breathing, an increase in the amount of sugar, and an unhealthy acceleration of metabolism. All this leads to lethargy, a decrease in the activity of organs, after which the systems begin to take measures to regulate temperature indicators. A simple example The body's thermoregulatory response is sweating.

It is worth noting that this process also works when body temperature drops excessively. This way the body can warm itself by breaking down fats, which releases heat.

Water-salt balance

Water is necessary for the body, and everyone knows this well. There is even a norm for daily fluid intake of 2 liters. In fact, each body needs its own amount of water, and for some it may exceed the average value, while for others it may not reach it. However, no matter how much water a person drinks, the body will not accumulate all the excess liquid. Water will remain at the required level, while all excess will be eliminated from the body due to osmoregulation carried out by the kidneys.

Blood homeostasis

In the same way, the amount of sugar is regulated, namely glucose, which is important element blood. A person cannot be completely healthy if the sugar level is far from normal. This indicator is regulated by the functioning of the pancreas and liver. When the glucose level exceeds the norm, the pancreas acts, producing insulin and glucagon. If the amount of sugar becomes too low, glycogen from the blood is processed into it with the help of the liver.

Normal pressure

Homeostasis is also responsible for normal blood pressure in the body. If it is disrupted, signals about this will come from the heart to the brain. The brain reacts to the problem and, with the help of impulses, helps the heart reduce high blood pressure.

The definition of homeostasis characterizes not only correct work systems of one organism, but can also apply to entire populations. Depending on this, there are different types of homeostasis, described below.

Ecological homeostasis

This species is present in a community provided with the necessary living conditions. It arises through the action of a positive feedback mechanism, when organisms that begin to inhabit an ecosystem quickly multiply, thereby increasing their numbers. But such rapid settlement can lead to even faster destruction of the new species in the event of an epidemic or a change in conditions to less favorable ones. Therefore, organisms need to adapt and stabilize, which occurs due to negative feedback. Thus, the number of inhabitants decreases, but they become more adaptable.

Biological homeostasis

This type is just typical for individual individuals, whose body strives to maintain internal balance, in particular, by regulating the composition and quantity of blood, intercellular substance and other fluids necessary for the normal functioning of the body. At the same time, homeostasis does not always require keeping parameters constant; sometimes it is achieved through adaptation and adaptation of the body to changed conditions. Because of this difference, organisms are divided into two types:

• conformational - these are those who strive to preserve values ​​(for example, warm-blooded animals whose body temperature should be more or less constant);
• regulatory, which adapt (cold-blooded, having different temperatures depending on conditions).

In this case, the homeostasis of each organism is aimed at compensating for costs. If warm-blooded animals do not change their lifestyle when the ambient temperature drops, then cold-blooded animals become lethargic and passive so as not to waste energy.

Besides, biological homeostasis includes the following subtypes:

• cellular homeostasis is aimed at changing the structure of the cytoplasm and enzyme activity, as well as the regeneration of tissues and organs;
• homeostasis in the body is ensured by regulating temperature, concentration of substances necessary for life, and removing waste.

Other types

In addition to use in biology and medicine, this term has found application in other areas.

Maintaining Homeostasis

Homeostasis is maintained thanks to the presence in the body of so-called sensors that send impulses to the brain containing information about body pressure and temperature, water-salt balance, blood composition and other important factors. normal life parameters. As soon as some values ​​begin to deviate from the norm, a signal about this is sent to the brain, and the body begins to regulate its indicators.

This complex adjustment mechanism incredibly important to life. Normal condition human health is maintained by the correct balance of chemicals and elements in the body. Acids and alkalis are necessary for stable operation digestive system and other organs.

Calcium is a very important structural material, without the right amount of which a person will not have healthy bones and teeth. Oxygen is essential for breathing.

Toxins that enter the body can disrupt the smooth functioning of the body. But to prevent harm to health, they are eliminated thanks to the work of the urinary system.

Homeostasis works without any effort on the part of the person. If the body is healthy, the body will regulate all processes itself. If people are hot, the blood vessels dilate, which results in redness of the skin. If it's cold, you'll shiver. Thanks to such responses of the body to stimuli, human health is maintained at the desired level.

Homeostasis (Greek homoios - same, similar, stasis - stability, balance) is a set of coordinated reactions that ensure the maintenance or restoration of the constancy of the internal environment of the body. In the mid-nineteenth century, the French physiologist Claude Bernard introduced the concept of the internal environment, which he considered as a collection of body fluids. This concept was expanded by the American physiologist Walter Cannon, who meant by the internal environment the entire set of fluids (blood, lymph, tissue fluid) that are involved in metabolism and maintaining homeostasis. The human body adapts to constantly changing environmental conditions, but the internal environment remains constant and its indicators fluctuate within very narrow limits. Therefore, a person can live in different environmental conditions. Some physiological parameters are regulated especially carefully and subtly, for example, body temperature, blood pressure, glucose, gases, salts, calcium ions in the blood, acid-base balance, blood volume, its osmotic pressure, appetite, and many others. Regulation is carried out on the principle of negative feedback between receptors f, which detect changes in these indicators and control systems. Thus, a decrease in one of the parameters is captured by the corresponding receptor, from which impulses are sent to one or another structure of the brain, at the command of which the autonomic nervous system turns on complex mechanisms for equalizing the changes that have occurred. The brain uses two main systems to maintain homeostasis: autonomic and endocrine. Let us remind you that main function The autonomic nervous system is the preservation of the constancy of the internal environment of the body, which is carried out due to changes in the activity of the sympathetic and parasympathetic parts of the autonomic nervous system. The latter, in turn, is controlled by the hypothalamus, and the hypothalamus by the cerebral cortex. The endocrine system regulates the function of all organs and systems through hormones. Moreover, the endocrine system itself is under the control of the hypothalamus and pituitary gland. Homeostasis (Greek homoios - identical and stasis - state, immobility)

As our ideas about normal, and even more so pathological, physiology became more complex, this concept was clarified as homeokinesis, i.e. moving equilibrium, balance of constantly changing processes. The body is woven from millions of “homeokinesics”. This huge living galaxy determines the functional status of all organs and cells that communicate with regulatory peptides. Like the global economic and financial systems - many firms, industries, factories, banks, exchanges, markets, shops... And between them - “convertible currency” - neuropeptides. All cells of the body constantly synthesize and maintain a certain, functionally necessary, level of regulatory peptides. But when deviations from “stationarity” occur, their biosynthesis (in the body as a whole or in its individual “loci”) either increases or decreases. Such fluctuations occur constantly if we're talking about about adaptive reactions (getting used to new conditions), performing work (physical or emotional actions), the state of pre-illness - when the body “turns on” increased protection against disruption of the functional balance. A classic case of maintaining balance is the regulation of blood pressure. There are groups of peptides between which there is constant competition - to increase / decrease pressure. In order to run, climb a mountain, steam in a sauna, perform on stage, and finally think, a functionally sufficient increase in blood pressure is necessary. But as soon as the work is over, regulators come into effect, ensuring “calmation” of the heart and normal pressure in the blood vessels. Vasoactive peptides constantly interact to “allow” the pressure to increase to such and such a level (no more, otherwise the vascular system will go “out of whack”; a well-known and bitter example is a stroke) and so that after the completion of physiologically necessary work

Topic 4.1. Homeostasis

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 a constant 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.

General patterns of homeostasis. 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.

Normalization of physiological parameters is carried out on the basis of the property of irritability. The ability to maintain homeostasis varies among various types. As organisms become more complex, this ability progresses, making them more independent of fluctuations in external conditions. This is especially evident in higher animals and humans, who have complex nervous, endocrine and immune regulatory mechanisms. The influence of the environment on the human body is mainly not direct, but indirect due to the creation of an artificial environment, the success of technology and civilization.

In the systemic mechanisms of homeostasis, the cybernetic principle of negative feedback operates: with any disturbing influence, nervous and endocrine mechanisms, which are closely interconnected, are activated.

Genetic homeostasis at the molecular genetic, cellular and organismal levels is aimed at maintaining balanced system genes containing all the biological information of the organism. The mechanisms of ontogenetic (organismal) homeostasis are fixed in the historically established genotype. At the population-species level, genetic homeostasis is the ability of a population to maintain the relative stability and integrity of hereditary material, which is ensured by the processes of reduction division and free crossing of individuals, which contributes to the conservation genetic balance allele frequencies.

Physiological homeostasis associated with the formation and continuous maintenance of specific physicochemical conditions in the cell. The constancy of the internal environment of multicellular organisms is maintained by the systems of respiration, circulation, digestion, excretion and is regulated by the nervous and endocrine systems.

Structural homeostasis is based on regeneration mechanisms that ensure morphological constancy and integrity of the biological system at different levels of organization. This is expressed in the restoration of intracellular and organ structures through division and hypertrophy.

Violation of the mechanisms underlying homeostatic processes is considered a “disease” of homeostasis.

Studying the patterns of human homeostasis is of great importance for choosing effective and rational methods of treating many diseases.

Target. Have an idea of ​​homeostasis as a property of living things that ensures self-maintenance of the stability of the organism. Know the main types of homeostasis and the mechanisms of its maintenance. Know the basic patterns of physiological and reparative regeneration and the factors that stimulate it, the importance of regeneration for practical medicine. Know the biological essence of transplantation and its practical significance.

Work 2. Genetic homeostasis and its disorders

Study and rewrite the table.

End of table.

Work 3. Repair mechanisms using the example of post-radiation restoration of DNA structure

Reparation or correction of damaged sections of one of the DNA strands is considered as limited replication. The most studied is the repair process when DNA strands are damaged by ultraviolet (UV) radiation. There are several enzyme repair systems in cells that were formed during evolution. Since all organisms have developed and exist under conditions of UV irradiation, cells have a separate light repair system, which is the most studied at present. When a DNA molecule is damaged by UV rays, thymidine dimers are formed, i.e. “crosslinks” between neighboring thymine nucleotides. These dimers cannot function as a template, so they are corrected by light repair enzymes found in cells. Excision repair restores damaged areas using both UV irradiation and other factors. This repair system has several enzymes: repair endonuclease

and exonuclease, DNA polymerase, DNA ligase. Post-replicative repair is incomplete, as it bypasses and the damaged section is not removed from the DNA molecule. Study the mechanisms of repair using the example of photoreactivation, excision repair and post-replicative repair (Fig. 1).

Rice. 1. Repair

Work 4. Forms of protection of the biological individuality of the organism

Study and rewrite the table.

Work 5. Blood-salivar barrier

The salivary glands have the ability to selectively transport substances from the blood into saliva. Some of them are excreted in saliva in higher concentrations, while others are released in lower concentrations than in blood plasma. The transition of compounds from blood to saliva is carried out in the same way as transport through any histo-blood barrier. The high selectivity of substances transferred from blood to saliva makes it possible to isolate the blood-salivar barrier.

Explain the process of saliva secretion in acinar cells salivary gland in Fig. 2.

Rice. 2. Saliva secretion

Work 6. Regeneration

Regeneration- this is a set of processes that ensure the restoration of biological structures; it is a mechanism for maintaining both structural and physiological homeostasis.

Physiological regeneration restores structures worn out during the normal functioning of the body. Reparative regeneration- this is the restoration of the structure after injury or after a pathological process. Regeneration ability

tion varies both among different structures and among different types living organisms.

Restoration of structural and physiological homeostasis can be achieved by transplanting organs or tissues from one organism to another, i.e. by transplantation.

Fill out the table using the material from the lectures and textbook.

Work 7. Transplantation as an opportunity to restore structural and physiological homeostasis

Transplantation- replacement of lost or damaged tissues and organs with one’s own or taken from another organism.

Implantation- organ transplantation from artificial materials.

Study and copy the table into your workbook.

Questions for self-study

1. Define the biological essence of homeostasis and name its types.

2. At what levels of organization of living things is homeostasis maintained?

3. What is genetic homeostasis? Reveal the mechanisms of its maintenance.

4. What is biological entity immunity? 9. What is regeneration? Types of regeneration.

10.At what levels structural organization does the body exhibit a regeneration process?

11. What is physiological and reparative regeneration (definition, examples)?

12. What are the types of reparative regeneration?

13. What are the methods of reparative regeneration?

14. What is the material for the regeneration process?

15. How is the process of reparative regeneration carried out in mammals and humans?

16. How is the reparative process regulated?

17. What are the stimulation options? recovery ability organs and tissues in humans?

18. What is transplantation and what is its significance for medicine?

19. What is isotransplantation and how does it differ from allo- and xenotransplantation?

20. What are the problems and prospects of organ transplantation?

21. What methods exist to overcome tissue incompatibility?

22. What is the phenomenon of tissue tolerance? What are the mechanisms to achieve it?

23. What are the advantages and disadvantages of implantation of artificial materials?

Test tasks

Choose one correct answer.

1. HOMEOSTASIS IS MAINTAINED AT THE POPULATION-SPECIES LEVEL:

1. Structural

2. Genetic

3. Physiological

4. Biochemical

2. PHYSIOLOGICAL REGENERATION PROVIDES:

1. Formation of a lost organ

2. Self-renewal at the tissue level

3. Tissue repair in response to damage

4. Restoring part of a lost organ

3. REGENERATION AFTER REMOVAL OF A LIVER LOBE

A PERSON GOES THE PATH:

1. Compensatory hypertrophy

2. Epimorphosis

3. Morpholaxis

4. Regenerative hypertrophy

4. TISSUE AND ORGAN TRANSPLANT FROM DONOR

TO THE RECIPIENT OF THE SAME SPECIES:

1. Auto- and isotransplantation

2. Allo- and homotransplantation

3. Xeno- and heterotransplantation

4. Implantation and xenotransplantation

Choose several correct answers.

5. NON-SPECIFIC FACTORS OF IMMUNE DEFENSE IN MAMMALS INCLUDE:

1. Barrier functions of the epithelium of the skin and mucous membranes

2. Lysozyme

3. Antibodies

4. Bactericidal properties of gastric and intestinal juice

6. CONSTITUTIONAL IMMUNITY IS DUE TO:

1. Phagocytosis

2. Lack of interaction between cellular receptors and antigen

3. Antibody formation

4. Enzymes that destroy foreign agents

7. MAINTENANCE OF GENETIC HOMEOSTASIS AT THE MOLECULAR LEVEL IS DUE TO:

1. Immunity

2. DNA replication

3. DNA repair

4. Mitosis

8. REGENERATIVE HYPERTROPHY IS CHARACTERISTIC:

1. Restoring the original mass of the damaged organ

2. Restoring the shape of the damaged organ

3. Increase in the number and size of cells

4. Scar formation at the site of injury

9. IN HUMAN IMMUNE SYSTEM ORGANS ARE:

2. Lymph nodes

3. Peyer's patches

4. Bone marrow

5. Bag of Fabritius

Match.

10. TYPES AND METHODS OF REGENERATION:

1. Epimorphosis

2. Heteromorphosis

3. Homomorphosis

4. Endomorphosis

5. Intercalary growth

6. Morpholaxis

7. Somatic embryogenesis

BIOLOGICAL

ESSENCE:

a) Atypical regeneration

b) Regrowth from the wound surface

c) Compensatory hypertrophy

d) Regeneration of the body from individual cells

e) Regenerative hypertrophy

f) Typical regeneration g) Restructuring of the remaining part of the organ

h) Regeneration of through defects

Literature

Main

Biology / Ed. V.N. Yarygina. - M.: graduate School, 2001. -

pp. 77-84, 372-383.

Slyusarev A.A., Zhukova S.V. Biology. - Kyiv: Higher school,

1987. - pp. 178-211.

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 provide interaction various structures already in a state of physiological rest. They are especially important in 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 was called " biological rhythms". Moreover, the frequency of oscillation various functions varies over an extremely wide range, ranging from a period of up to 0.5 hours up to many days and even many years.

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 contribute to the preservation normal level 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, such as temperature.

Stability in most conditions is necessary at any structural and functional level, from an individual biochemical reaction, cell, to complex functional systems 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. And for example, a person who also has intelligence, having clothes and housing, can long time exist at external temperatures well below 0 °C.

In the process of evolution, adaptive reactions were formed aimed at maintaining constant conditions external environment body. 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 living things to actively maintain the stability of body functions, despite external influences that can violate it are 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 and the like. 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 healthy person these processes are balanced and the recovery mechanisms function with a reserve of power, then in the case sudden change conditions of existence, during diseases they turn on with maximum activity. The improvement of homeostasis regulation systems is also reflected in evolutionary development. Thus, the lack of a support system constant temperature bodies in cold-blooded animals, having determined 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 is in to a large extent 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 central link in maintaining homeostasis is considered liquid media body. 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 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 the blood, its volume, and pressure. Reflexes begin with irritation of vascular receptors, the effector part of which is the organs and systems of the body. Great value blood in maintaining homeostasis became the basis for the formation of a special homeostasis system for many parameters of the blood itself, 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. Moreover, they are through reflex mechanisms activate blood circulation and breathing. 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.

2. Learning goals:

Know the essence of homeostasis, physiological mechanisms maintaining homeostasis, the basis 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

4) Structural 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 characteristics homeostasis

13) Pathological processes accompanied by disruption of homeostasis.

14) Correction of body homeostasis – main task doctor

__________________________________________________________________

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 the parameters of the 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 gas exchange, various chemical compounds enter the body from the environment, which, after transformations, become similar chemical composition 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 structural components 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 parameters occur, and the inclusion regulatory systems ensures the maintenance of 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 maintaining genetic homeostasis is the diploid state 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 of a complex genotype system is ensured 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 continuously occur, 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 the concentration of individual ions, content in the blood nutrients 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. Usually active reaction media are 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 to maintain 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.

The 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--- inclusion of regulatory mechanisms based on the feedback principle --- correction changes (normalization).

Some endocrine glands are not directly dependent on the pituitary gland. These are the pancreatic islets 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 most important properties of a living system that is 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 characterized by the characteristics of metabolism, energy and homeostasis mechanisms. IN children's body the processes of assimilation prevail over dissimilation, which determines growth and increase in body weight; 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, adaptation features are weakened, so increased load and stressful conditions can easily disrupt homeostatic mechanisms and often cause 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.