PHYSIOLOGY OF METABOLISM AND ENERGY

Metabolism in the body. Plastic and energetic role of nutrients

Constant exchange of substances and energy between the body and the environment is a necessary condition for its

existence and reflects their unity. The essence of this exchange is that the nutrients entering the body after digestive transformations are used as plastic material. The energy generated during these transformations replenishes the body's energy costs. Synthesis of complex specific substances of the body from

simple compounds absorbed into the blood from the digestive canal is called assimilation or anabolism. The breakdown of body substances into final products, accompanied by the release of energy, is called dissimilation or catabolism. These two processes are inextricably linked. “Assimilation ensures the accumulation of energy, and the energy released during dissimilation is necessary for the synthesis of substances. Anabolism and catabolism are combined into a single process with the help of ATP and NADP. With their help, the energy generated as a result of dissimilation is transferred for assimilation processes. Proteins are mainly plastic material They are part of cell membranes, organelles. Protein molecules are constantly renewed. But this renewal occurs not only due to food proteins, but also through the reutilization of the body’s own proteins. formed in the body. The end products of protein breakdown are nitrogen-containing compounds such as urea, uric acid, creatinine. The state of protein metabolism is assessed by nitrogen balance. This is the ratio of the amount of nitrogen received from food proteins and excreted from the body with nitrogen-containing metabolic products. Protein contains about. 16 g of nitrogen. Therefore, the release of 1 g of nitrogen indicates the breakdown of 6.25 g of protein in the body. If the amount of nitrogen released is equal to the amount absorbed by the body, nitrogen equilibrium occurs. If there is more nitrogen input than nitrogen output, this is called a positive nitrogen balance. Nitrogen retention occurs in the body. A positive nitrogen balance is observed during body growth, during recovery from a serious illness accompanied by weight loss and after prolonged fasting. When the amount of nitrogen excreted by the body is greater than that taken in, a negative nitrogen balance occurs. Its occurrence is explained by the breakdown of the body's own proteins. It occurs during fasting, lack of essential amino acids in food, impaired digestion and absorption of protein, and serious illnesses. The amount of protein that fully meets the body's needs is called the protein optimum. The minimum, ensuring only the preservation of nitrogen balance - a protein minimum. WHO recommends a protein intake of at least 0.75 g per kg of body weight per day. The energy role of proteins is relatively small.

Body fats are triglycerides, phospholipids and sterols. They also have a certain plastic role, since phospholipids, cholesterol, and fatty acids are part of cell membranes and organelles. Their main role is energetic. The oxidation of lipids releases the greatest amount of energy, so about half of the body's energy expenditure is provided by lipids. In addition, they are an energy accumulator in the body, because they are stored in fat depots and used as needed. Fat depots make up about 15% of body weight. Covering internal organs, adipose tissue also performs a plastic function. For example, perinephric fat helps to fix the kidneys and protect them from mechanical stress. Lipids are sources of water because the oxidation of 100 g of fat produces about 100 g of water. A special function is performed by brown fat, located along large vessels. The polypeptide contained in its fat cells inhibits the re-synthesis of ATP at the expense of lipids. As a result, heat production sharply increases. Essential fatty acids - linoleic, linolenic and arachidonic - are of great importance. They are not formed in the body. Without them, the synthesis of cell phospholipids, the formation of prostaglandins, etc. is impossible. In their absence, the growth and development of the body is delayed.

Carbohydrates mainly play an energy role as they serve as the main source of energy for cells.

The needs of neurons are met exclusively by glucose. Carbohydrates are stored as glycogen in the liver

and muscles. Carbohydrates have a certain plastic significance. Glucose is necessary for the formation of nucleotides

and synthesis of some amino acids.

Methods for measuring the body's energy balance

The relationship between the amount of energy entering the body with food and the energy released by the body during

the external environment is called the energy balance of the organism. There are 2 methods for determining the allocated

body energy.

1. Direct calorimetry. The principle of direct calorimetry is based on the fact that all types of energy are ultimately converted into heat. Therefore, with direct calorimetry, the amount of heat released by the body into the environment per unit of time is determined. For this purpose, special chambers with good thermal insulation and a system of heat exchange pipes are used, in which water circulates and is heated.

2. Indirect calorimetry. It consists in determining the ratio of carbon dioxide released and oxygen absorbed per unit of time. Those. full gas analysis. This ratio is called the respiratory coefficient (RQ). US02 DK=-U02

The value of the respiratory coefficient is determined by what substance is oxidized in the cells of the body. For example, there are a lot of oxygen atoms in a carbohydrate molecule, so less oxygen goes into their oxidation and their respiratory coefficient is 1. There is much less oxygen in a lipid molecule, so the respiratory coefficient during their oxidation is 0.7. The respiratory coefficient of proteins is 0.8. With a mixed diet, its value is 0.85-0.9. The respiratory quotient becomes greater than 1 during heavy physical work, acidosis, hyperventilation, and the body's conversion of carbohydrates into fats. It happens to be less than 0.7 when fats turn into carbohydrates. Based on the respiratory coefficient, the caloric equivalent of oxygen is calculated, i.e. the amount of energy released by the body when consuming 1 liter of oxygen. Its value also depends on the nature of the oxidized substances. For carbohydrates it is 5 kcal, proteins 4.5 kcal, fats 4.7 kcal. Indirect calorimetry in the clinic is performed using “Metatest-2” and “Spirolite” devices.

The amount of energy entering the body is determined by the amount and energy value of nutrients. Their energy value is determined by burning them in a Berthelot bomb in an atmosphere of pure oxygen. In this way the physical caloric coefficient is obtained. For proteins it is 5.8 kcal/g, carbohydrates 4.1 kcal/g, fats 9.3 kcal/g. For calculations, the physiological caloric coefficient is used. For carbohydrates and fats it corresponds to physical value, and for proteins it is 4.1 kcal/g. Its lower value for proteins is explained by the fact that in the body they are broken down not into carbon dioxide and water, but into nitrogen-containing products. BX

The amount of energy expended by the body to perform vital functions is called basal metabolism. This is energy expenditure to maintain a constant body temperature, the functioning of internal organs, the nervous system, and glands. Basal metabolism is measured by direct and indirect calorimetry methods under basic conditions, i.e. lying down with relaxed muscles, at a comfortable temperature, on an empty stomach. According to the surface law, formulated in the 19th century by Rubner and Richet, the magnitude of the fundamental is directly proportional to the surface area of ​​the body. This is due to the fact that the greatest amount of energy is spent on maintaining a constant body temperature. In addition, the amount of basal metabolism is influenced by gender, age, environmental conditions, nutritional status, and the state of the endocrine glands and nervous system. Men's basal metabolic rate is 10% higher than women's. In children, its value relative to body weight is greater than in adulthood, but in the elderly, on the contrary, it is less. In cold climates or in winter it increases and decreases in summer. In hyperthyroidism it increases significantly, and in hypothyroidism it decreases. On average, the basal metabolic rate for men is 1700 kcal/day, and for women 1550.

General energy metabolism

General energy metabolism is the sum of basal metabolism, work gain and the energy of the specifically dynamic action of food. Work gain is the energy expenditure for physical and mental work. Based on the nature of production activities and energy consumption, the following groups of workers are distinguished:

1. Persons of mental work (teachers, students, doctors, etc.). Their energy consumption is 2200-3300 kcal/day.

2. Workers engaged in mechanized labor (assemblers on a conveyor belt). 2350-3500 kcal/day.

3. Persons engaged in partially mechanized labor (drivers). 2500-3700 kcal/day. .

1. Those engaged in heavy non-mechanized labor (loaders). 2900-4200 kcal/day. A specifically dynamic effect of food is energy consumption for the absorption of nutrients. This effect is most pronounced in proteins, less so in fats and carbohydrates. In particular, proteins increase energy metabolism by 30%, and fats and carbohydrates by 15%. Physiological basis of nutrition.

2. Power modes. IN Depending on age, gender, profession, the consumption of proteins, fats and carbohydrates should be:

In the last century, Rubner formulated the law of isodynamics, according to which food substances can be interchanged in their energy value. However, it is of relative importance, since proteins that perform a plastic role cannot be synthesized from other substances. The same applies to essential fatty acids. Therefore, a balanced diet of all nutrients is required. In addition, it is necessary to take into account the digestibility of food. This is the ratio of nutrients absorbed and excreted in feces. Animal products are the easiest to digest. Therefore, animal protein should make up at least 50% of the daily protein diet, and fats should not exceed 70% of the fat.

By diet we mean the frequency of food intake and the distribution of its calorie content for each meal. With three meals a day, breakfast should account for 30% of the daily calorie intake, lunch 50%, dinner 20%. With a more physiological four meals a day, for breakfast 30%, lunch 40%, afternoon snack 10%, dinner 20%. The interval between breakfast and lunch is no more than 5 hours, and dinner should be at least 3 hours before bedtime. Meal times should be constant.

Exchange of water and minerals

The water content in the body is on average 73%. The body's water balance is maintained by equalizing the water consumed and excreted. The daily water requirement is 20-40 ml/kg body weight. About 1200 ml of water comes with liquids, 900 ml with food and 300 ml is formed during the oxidation of nutrients. The minimum water requirement is 1700 ml. With a lack of water, dehydration occurs and if its amount in the body decreases by 20%, death occurs. Excess water is accompanied by water intoxication with central nervous system stimulation and convulsions.

Sodium, potassium, calcium, chlorine are necessary for the normal functioning of all cells, in particular providing mechanisms for the formation of membrane potential and action potentials. The daily requirement for sodium and potassium is 2-3 g, calcium 0.8 g, chlorine 3-5 g. A large amount of calcium is found in the bones. In addition, it is needed for blood clotting and regulation of cellular metabolism. The bulk of phosphorus is also concentrated in the bones. At the same time, it is part of membrane phospholipids and participates in metabolic processes. The daily requirement for it is 0.8 g. Most of the iron is contained in hemoglobin and myoglobin. It ensures the binding of oxygen. Fluoride is part of tooth enamel. Sulfur in proteins and vitamins. Zinc is a component of a number of enzymes. Cobalt and copper are essential for erythropoiesis. The need for all these microelements ranges from tens to hundreds of mg per day.

Regulation of metabolism and energy

The highest nerve centers for the regulation of energy metabolism and metabolism are located in the hypothalamus. They influence these processes through the autonomic nervous system and the hypothalamic-pituitary system. The sympathetic department of the ANS stimulates the processes of dissimilation, parasympathetic assimilation. It also contains centers for regulating water-salt metabolism. But the main role in the regulation of these basic processes belongs to the endocrine glands. In particular, insulin and glucagon regulate carbohydrate and fat metabolism. Moreover, insulin inhibits the release of fat from the depot. Adrenal glucocorticoids stimulate the breakdown of proteins. Somatotropin, on the contrary, enhances protein synthesis. Mineralocorticoids sodium potassium. The main role in the regulation of energy metabolism belongs to thyroid hormones. They sharply intensify it. They are also the main regulators of protein metabolism. Significantly increases energy metabolism and adrenaline. A large amount of it is released during fasting.

THERMOREGULATION

Phylogenetically, two types of body temperature regulation have emerged. In cold-blooded or poikilothermic organisms, the metabolic rate is low, and therefore heat production is low. They are unable to maintain a constant body temperature and it depends on the ambient temperature. Harmful temperature changes are compensated by changes in behavior (hibernation). In warm-blooded animals, the intensity of metabolic processes is very high and there are special mechanisms of thermoregulation. Therefore, they have a level of activity independent of the ambient temperature. Isothermia ensures high adaptability of warm-blooded animals. In humans, daily temperature fluctuations are 36.5-36.9°C. The highest human body temperature is at 16:00. Lowest at 4 o'clock. his body is very sensitive to changes in body temperature. When it decreases to 27-3 0°C, severe

impairment of all functions, and at 25° cold death occurs (there are reports of preservation of viability at 18° C). For rats, the lethal temperature is 12° C (special methods 1° C). When body temperature rises to 40°, severe disturbances also occur. At 42° heat death can occur. For humans, the temperature comfort zone is 18-20°. There are also heterothermic living creatures that can temporarily reduce their body temperature (hibernating animals).

Thermoregulation is a set of physiological processes of heat generation and heat transfer that ensure the maintenance of normal body temperature. Thermoregulation is based on the balance of these processes. Regulation of body temperature by changing metabolic rate is called chemical thermoregulation. Thermogenesis enhances involuntary muscle activity in the form of trembling and voluntary motor activity. The most active heat generation occurs in working muscles. With heavy physical work it increases by 500%. Heat formation increases with the intensification of metabolic processes, this is called non-shivering thermogenesis and is provided by brown fat. Its cells contain many mitochondria and a special peptide that stimulates the breakdown of lipids with the release of heat. Those. the processes of oxidation and phosphorylation are separated.

Heat transfer serves to release excess heat generated and is called physical thermoregulation. >"0na is carried out through heat radiation, through which 60% of the heat is released, convection (15%),

thermal conductivity (3 °/o), evaporation of water from the surface of the body and from the lungs (20%). The balance of the processes of heat generation and heat transfer is ensured by nervous and humoral mechanisms. When body temperature deviates from normal values, thermoreceptors in the skin, blood vessels, internal organs, and upper respiratory tract are excited. These receptors are processes of sensory neurons, as well as thin fibers of type C. There are more cold receptors in the skin than thermal ones and they are located more superficially. Nerve impulses from these neurons travel through the spinothalamic tracts to the hypothalamus and cerebral cortex. A feeling of cold or warmth is formed. The thermoregulation center is located in the posterior hypothalamus and the prepoptic area of ​​the anterior hypothalamus. The posterior neurons mainly provide chemical thermoregulation. Front physical. There are three types of neurons in this center. The first are temperature-sensitive neurons. They are located in the prepoptic area and respond to changes in the temperature of the blood passing through the brain. The same neurons are present in the spinal cord and medulla oblongata. The second group are interneurons and receive information from temperature receptors and thermoreceptor neurons. These neurons serve to maintain the set point, i.e. a certain body temperature. One part of these neurons receives information from cold ones, the other from thermal peripheral receptors and thermoreceptor neurons. The third type of neurons is efferent. They are located in the posterior hypothalamus and provide regulation of heat generation mechanisms. The thermoregulation center exerts its influence on effector mechanisms through the sympathetic and somatic nervous systems and endocrine glands. When body temperature rises, thermal receptors of the skin, internal organs, blood vessels and thermoreceptor neurons of the hypothalamus are excited. Impulses from them travel to interneurons, and then to effector neurons. Effector neurons are the sympathetic centers of the hypothalamus. As a result of their excitation, sympathetic nerves are activated, which dilate the blood vessels of the skin and stimulate sweating. When cold receptors are excited, the opposite picture is observed. The frequency of nerve impulses going to the skin vessels and sweat glands decreases, the vessels narrow, and sweating is inhibited. At the same time, the blood vessels of the internal organs dilate. If this does not lead to the restoration of temperature homeostasis, other mechanisms are activated. Firstly, the sympathetic nervous system enhances catabolic processes, and therefore heat production. Norepinephrine released from the endings of sympathetic nerves stimulates lipolysis processes. Brown fat plays a special role in this. This phenomenon is called non-shivering thermogenesis. Secondly, nerve impulses begin to travel from the neurons of the posterior hypothalamus to the motor centers of the midbrain and medulla oblongata. They are excited and activate a-motoneurons of the spinal cord. Involuntary muscle activity occurs in the form of cold tremors. The third way is to strengthen voluntary motor activity. The corresponding change in behavior, which is provided by the cortex, is of great importance. Of the humoral factors, adrenaline, norepinephrine and thyroid hormones are of greatest importance. The first two hormones cause a short-term increase in heat production due to increased lipolysis and glycolysis. When adapting to long-term cooling, the synthesis of thyroxine and triiodothyronine increases. They significantly increase energy metabolism and heat production by increasing the number of enzymes in mitochondria.

A decrease in body temperature is called hypothermia, an increase is called hyperthermia. Hypothermia occurs when you are overcooled. Hypothermia of the body or brain is used clinically to prolong the viability of the human body or brain during resuscitation measures. Hyperthermia occurs during heat stroke, when the temperature rises to 40-41°. One of the violations of thermoregulation mechanisms is fever. It develops as a result of increased heat generation and decreased heat transfer. Heat transfer decreases due to narrowing of peripheral blood vessels and decreased sweating. Heat generation increases due to the effect of bacterial and leukocyte pyrogens, which are lipopolysaccharides, on the thermoregulation center of the hypothalamus. This effect is accompanied by feverish trembling. During the recovery period, normal temperature is restored due to the dilation of blood vessels in the skin and heavy sweating.

PHYSIOLOGY OF EXCRETION PROCESSES

Kidney functions. Mechanisms of urine formation The renal parenchyma secretes the cortex and medulla. The structural unit of the kidney is the nephron. Each kidney has about a million nephrons. Each nephron consists of a vascular glomerulus, located in the Shumlyansky-Bowman capsule, and a renal tubule. The afferent arteriole approaches the capillaries of the glomerulus, and the efferent arteriole departs from it. The diameter of the afferent arteriole is greater than that of the efferent one. The glomeruli located in the cortical layer are classified as cortical, and in deep in the kidneys - juxtamedullary. From the Shumlyansky-Bowman capsule, the proximal convoluted canadian passes into the loop of Henle. In turn, it passes into the distal convoluted urinary canadian, which opens into the collecting duct. Urine formation occurs through several mechanisms.

1. Glomerular ultrafiltration. The capillary glomerulus located in the cavity of the capsule consists of 20-40 capillary loops. Filtration occurs through the capillary endothelial layer, the basement membrane and the inner layer of the capsule epithelium. The main role belongs to the basement membrane. It is a network formed by thin collagen fibers that act as a molecular sieve. Ultrafiltration is carried out due to high blood pressure in the capillaries of the glomerulus - 70 - 80 mmHg. Its large value is due to the difference in diameter of the afferent and efferent arterioles. Blood plasma with all low molecular weight substances dissolved in it, including low molecular weight proteins, is filtered into the capsule cavity. Under physiological conditions, large proteins and other large colloidal plasma particles are not filtered. The proteins remaining in the plasma create an oncotic pressure of 25-30 mmHg, which keeps some of the water from filtering into the capsule cavity. In addition, it is hampered by the hydrostatic pressure of the filtrate located in the capsule of 10-20 mmHg. Therefore, the filtration rate is determined by the effective filtration pressure. Normally it is: Reff.=Rdk. -(Roem.- Rhydr.)= 70 - (25 + 10) = 35 mmHg. The glomerular filtration rate is 110-120 ml/min. Therefore, 180 liters of filtrate or primary urine are formed per day. 2. Tubular reabsorption. All the resulting primary urine enters the tubules and loop of Henle, where 178 liters of water and substances dissolved in it are reabsorbed. Not all of them return to the blood along with the water. Based on their ability to reabsorb, all substances in primary urine are divided into three groups:

1. Threshold. Normally they are completely reabsorbed. These are glucose and amino acids.

2. Low threshold. Partially reabsorbed. For example, urea.

3. Non-threshold. They are not reabsorbed. Creatinine, sulfates. The last 2 groups create osmotic pressure and provide tubular diuresis, i.e. retention of a certain amount of urine in the tubules. Reabsorption of glucose and amino acids occurs in the proximal convoluted tubule and is carried out using the sodium transport system. They are transported against a concentration gradient. In diabetes mellitus, the blood glucose level rises above the excretion threshold and glucose appears in the urine. In renal diabetes, the glucose transport system in the tubular epithelium is disrupted and it is excreted in the urine, despite normal levels in the blood. Reabsorption of other threshold and non-threshold substances occurs by diffusion. Obligate reabsorption of essential ions and water occurs in the proximal tubule, the loop of Henle. Optional in the distal tubule. They form a rotary-countercurrent system, since mutual exchange of ions occurs in them. In the proximal tubule and descending limb of the loop of Henle, active transport of large amounts of sodium ions occurs. It is carried out by sodium-potassium ATPase. Following sodium, large amounts of water are passively reabsorbed into the intercellular space. In turn, this water promotes additional passive reabsorption of sodium into the blood. At the same time, bicarbonate anions are also reabsorbed. In the descending limb of the loop and the distal tubule, a relatively small amount of sodium is reabsorbed, followed by water. In this part of the nephron, sodium ions are reabsorbed through coupled sodium-proton and sodium-potassium exchange. Chlorine ions are transferred here from urine to tissue fluid using active chlorine transport. Low molecular weight proteins are reabsorbed in the proximal convoluted tubule.

3. Tubular secretion and excretion. They occur in the proximal part of the tubules. This is the transport into the urine of substances from the blood and tubular epithelial cells that cannot be filtered. Active secretion is carried out by three transport systems. The first transports organic acids, for example para-aminohippuric acid. The second is organic grounds. The third is ethylenediaminetetraacetate (EDTA). Excretion of weak acids and bases occurs by non-ionic diffusion. This is their transfer in an undissociated state. To carry out the excretion of weak acids, it is necessary that the reaction of the tubular urine be alkaline, and for the excretion of alkalis to be acidic. Under these conditions, they are in a non-dissociated state and the rate of their release increases. In this way, protons and ammonium cations are also secreted. Daily diuresis is 1.5-2 liters. The final urine has a slightly acidic reaction with pH = 5.0 - 7.0. Specific gravity not less than 1.018. Protein no more than 0.033 g/l. Sugar, ketone bodies, urobilin, bilirubin are absent. Red blood cells, leukocytes, epithelium are single cells in the field of view. Columnar epithelium 1. Bacteria no more than 50,000 per ml. Regulation of urine formation.

The kidneys have a high ability for self-regulation. The lower the osmotic pressure of the blood, the more pronounced the filtration processes and the weaker the reabsorption and vice versa. Nervous regulation is carried out through sympathetic nerves innervating the renal arterioles. When they are excited, the efferent arterioles narrow, the blood pressure in the glomerular capillaries, and as a result, the effective filtration pressure increases, and glomerular filtration accelerates. Also, sympathetic nerves enhance the reabsorption of glucose, sodium and water. Humoral regulation is carried out by a group of factors.

1. Antidiuretic hormone (ADH). It begins to be released from the posterior lobe of the pituitary gland when the osmotic pressure of the blood increases and the osmoreceptor neurons of the hypothalamus are excited. ADH interacts with receptors in the epithelium of the collecting ducts, which increase the content of cyclic adenosine monophosphate in them; cAMP activates protein kinases, which increase the permeability of the epithelium of the distal tubules and collecting ducts to water. As a result, water reabsorption increases and it is stored in the vascular bed.

2. Aldosterone. Stimulates the activity of sodium-potassium ATPase and therefore increases the reabsorption of sodium, but at the same time the excretion of potassium and protons in the tubules. As a result, the content of potassium and protons in the urine increases. With a lack of adosterone, the body loses sodium and water.

3. Natriuretic hormone or atriopeptide. It is formed mainly in the left atrium when it is stretched, as well as in the anterior lobe of the pituitary gland and chromaffin cells of the adrenal glands. It enhances filtration and reduces sodium reabsorption. As a result, the excretion of sodium and chlorine by the kidneys increases and daily diuresis increases.

4. Parathyroid hormone and calcitonin. Parathyroid hormone enhances the reabsorption of calcium, magnesium and reduces the reabsorption of phosphate. Calcitonin reduces the reabsorption of these ions.

5. Renin-angiotensin-aldosterone system. Renin is a protease that is produced by the juxtaglomerular cells of the arterioles of the kidneys. Under the influence of renin, angiotensin I is cleaved from the blood plasma protein a2-globulin-angiotensin. Angiotensin I is then converted by renin into angiotensin II. This is the most powerful vasoconstrictor. The formation and release of renin by the kidneys is caused by the following factors:

a) Decreased blood pressure.

b) Decrease in circulating blood volume.

c) upon stimulation of the sympathetic nerves innervating the renal vessels. Under the influence of renin, the arterioles of the kidneys narrow and the permeability of the glomerular capillary wall decreases. As a result, the filtration rate decreases. At the same time, angiotensin II stimulates the release of aldosterone by the adrenal glands. Aldosterone enhances tubular sodium reabsorption and water reabsorption. Water and sodium retention occurs in the body. The action of angiotensin is accompanied by increased synthesis of antidiuretic hormone of the pituitary gland. An increase in water and sodium chloride in the vascular bed, with the same content of plasma proteins, leads to the release of water into the tissues. Renal edema develops. This occurs against the background of high blood pressure.

6. Kallikrein-kinin system. It is a renin-angiotensin antagonist. With a decrease in renal blood flow, the enzyme kallikrein begins to be produced in the epithelium of the distal tubules. It converts inactive plasma proteins kininogens into active kinins. In particular, bradykinin. Kinins dilate renal vessels, increase the rate of glomerular ultrafiltration and reduce the intensity of reabsorption processes. Diuresis increases.

7. Prostaglandins. They are synthesized in the renal medulla by prostaglandin synthetases and stimulate the excretion of sodium and water. Violations of the excretory function of the kidneys occur in acute or chronic renal failure. Nitrogen-containing metabolic products accumulate in the blood - uric acid, urea, creatinine. The content in it increases

potassium and sodium decreases. Acidosis occurs. This occurs against the background of increased blood pressure, edema and decreased daily diuresis. The end result of kidney failure is uremia. One of its manifestations is the cessation of urine formation anuria. Non-excretory functions of the kidneys:

1. Regulation of the constancy of the ionic composition and volume of the intercellular fluid of the body. The basic mechanism for regulating blood volume and intercellular fluid is a change in sodium content. As its amount in the blood increases, water intake increases and water retention occurs in the body. Those. a positive sodium and water balance is observed. In this case, the isotonicity of body fluids is maintained. With a low sodium chloride content in the diet, sodium excretion from the body predominates, i.e. there is a negative sodium balance. But thanks to the kidneys, a negative water balance is established and/ water excretion begins to exceed its consumption. In these cases, after 2-3 weeks a new sodium-water balance is established. But the excretion of sodium and water by the kidneys will be either more or less than the original. With an increase in circulating blood volume (CBV) or hypervolemia, arterial and effective filtration pressure increases. At the same time, natriuretic hormone begins to be released in the atria. As a result, sodium and water excretion by the kidneys increases. With a decrease in circulating blood volume or hypovolemia, blood pressure drops, effective filtration pressure decreases, and a number of additional mechanisms are activated to ensure the conservation of sodium and water in the body. There are peripheral osmoreceptors in the vessels of the liver, kidneys, heart and carotid sinuses, and osmoreceptor neurons in the hypothalamus. They respond to changes in blood osmotic pressure. Impulses from them go to the center of osmoregulation, located in the area of ​​the supraoptic and paraventricular nuclei. The sympathetic nervous system is activated. The blood vessels, including those of the kidneys, narrow. At the same time, the formation and release of antidiuretic hormone by the pituitary gland begins. Adrenaline and norepinephrine released by the adrenal glands also constrict the afferent arterioles. As a result, filtration in the kidneys decreases and reabsorption increases. At the same time, the renin-angiotensin system is activated. During this same period, a feeling of thirst develops. The ratio of sodium and potassium ions is regulated by mineralocorticoids, calcium and phosphorus by parthormone and calcitonin.

2. Participation in the regulation of systemic blood pressure. They carry out this function by maintaining a constant volume of circulating blood, as well as the renin-angiotensin and kallikrein-kinin systems.

3. Maintaining acid-base balance. When the blood reaction shifts to the acidic side, acid anions and protons are excreted in the tubules, but sodium ions and bicarbonate anions are simultaneously reabsorbed. During alkalosis, alkali cations and bicarbonate anions are excreted.

1. Regulation of hematopoiesis. They produce erythropoietin. It is an acidic glycoprotein consisting of protein and heterosaccharide. The production of erythropoietin is stimulated by low oxygen tension in the blood.

2. Urinary excretion

Urine is constantly produced in the kidneys and flows through the collecting ducts into the pelvis, and then through the ureters into the bladder. The filling rate of the bladder is about 50 ml/hour. During this time, called the filling period, urination is either difficult or impossible. When 200-300 ml of urine accumulates in the bladder, a urination reflex occurs. There are stretch receptors in the wall of the bladder. They are excited and impulses from them travel through the afferent fibers of the pelvic parasympathetic nerves to the urination center. It is located in the 2-4 sacral segments of the spinal cord. The impulses travel to the thalamus and then to the cortex. The urge to urinate occurs, and the period of emptying the bladder begins. From the center of urination, along the efferent parasympathetic pelvic nerves, impulses begin to flow to the smooth muscles of the bladder wall. They contract and the pressure in the bladder increases. At the base of the bladder, these muscles form the internal sphincter. Due to the special direction of the smooth muscle fibers in it, their contraction leads to passive opening of the sphincter. At the same time, the external urinary sphincter, formed by the striated muscles of the perineum, opens. They are innervated by the branches of the pudendal nerve. The bladder empties. With the help of the bark, the onset and course of the urination process is regulated. At the same time, it can be observed

psychogenic urinary incontinence. When more than 500 ml of urine accumulates in the bladder, a protective reaction of involuntary urination may occur. Disorders, cystitis, urinary retention.

PHYSIOLOGY OF METABOLISM AND ENERGY. BALANCED DIET.

Lecture plan.

1. The concept of metabolism in the body of animals and humans. Sources of energy in the body.

The human body is an open thermodynamic system, which is characterized by the presence of metabolism and energy.

Metabolism and energythis is a set of physical, biochemical and physiological processes of transformation of substances and energy in the human body and the exchange of substances and energy between the body and the environment. These processes occurring in the human body are studied by many sciences: biophysics, biochemistry, molecular biology, endocrinology and, of course, physiology.

Metabolism and energy metabolism are closely interrelated, however, in order to simplify the concepts, they are considered separately.

Metabolism (metabolism)a set of chemical and physical transformations that occur in the body and ensure its vital activity in conjunction with the external environment.

In metabolism, there are two directions of processes in relation to the structures of the body: assimilation or anabolism and dissimilation or catabolism.

Assimilation (anabolism) a set of processes for creating living matter. These processes consume energy.

Dissimilation (catabolism) a set of processes of decay of living matter. As a result of dissimilation, energy is reproduced.

The life of animals and humans is a unity of the processes of assimilation and dissimilation. The factors connecting these processes are two systems:

• ATP ADP (ATP - adenosine triphosphate, ADP adenosine diphosphate;
• NADP (oxidized) NADP (reduced), where NADP nicotine amide diphosphate.

The mediation of these connections between the processes of assimilation and dissimilation is ensured by the fact that the ATP and NADP molecules act as universal biological energy accumulators, its carrier, a kind of “energy currency” of the body. However, before energy is accumulated in the molecules of ATP and NADP, it must be extracted from the nutrients that enter the body with food. These nutrients are the proteins, fats and carbohydrates you know. It should also be added that nutrients perform not only the function of energy suppliers, but also the function of suppliers of building material (plastic function) for cells, tissues and organs. The role of various nutrients in meeting the plastic and energy needs of the body is not the same. Carbohydrates primarily perform an energy function; the plastic function of carbohydrates is insignificant. Fats equally perform energy and plastic functions. Proteins are the main building material for the body, but under certain conditions they can also be sources of energy.

Sources of energy in the body.

As noted above, the main sources of energy in the body are nutrients: carbohydrates, fats and proteins. The release of energy contained in nutrients in the human body occurs in three stages:

Stage 1. Proteins are broken down into amino acids, carbohydrates into hexoses, for example, glucose or fructose, fats into glycerol and fatty acids. At this stage, the body mainly spends energy on the breakdown of substances.

Stage 2. Amino acids, hexoses and fatty acids are converted during biochemical reactions into lactic and pyruvic acids, as well as acetyl coenzyme A. At this stage, up to 30% of potential energy is released from nutrients.

Stage 3. With complete oxidation, all substances are broken down to CO 2 and N 2 A. At this stage, in the Krebs metabolic cauldron, the remaining energy is released, about 70%.However, not all of the released energy is accumulated into the chemical energy of ATP. Some of the energy is dispersed into the environment. This heat is called primary heat ( Q 1) . The energy accumulated by ATP is subsequently spent on various types of work in the body: mechanical, electrical, chemical and active transport. In this case, part of the energy is lost in the form of so-called secondary heat Q2. See diagram 1.

H 2 O + CO 2 + Q 1 + ATP

Scheme 1. Sources of energy in the body, the results of complete oxidation of nutrients and types of heat generated in the body.

It should be added that the amount of food substances released during oxidation does not depend on the number of intermediate reactions, but depends on the initial and final state of the chemical system. This position was first formulated by Hess (Hess’s law).

You will consider these processes in more detail during lectures and classes that will be taught to you by teachers from the Department of Biochemistry.

Energy value of nutrients.

The energy value of nutrients is assessed using special devices - oxycalorimeters. It has been established that with complete oxidation of 1 g of carbohydrates, 4.1 kcal is released (1 kcal = 4187 J), 1 g of fat - 9.45 kcal, 1 g of protein - 5.65 kcal. It should be added that some of the nutrients entering the body are not absorbed. For example, on average, about 2% of carbohydrates, 5% of fats and up to 8% of proteins are not digested. In addition, not all nutrients in the body are broken down into the final products carbon dioxide (carbon dioxide) and water. For example, part of the products of incomplete breakdown of proteins in the form of urea is excreted in the urine.

Taking into account the above, it can be noted that the real energy value of nutrients is somewhat lower than that established under experimental conditions. The real energy value of 1 g of carbohydrates is 4.0 kcal, 1 g of fat is 9.0 kcal, 1 g of protein is 4.0 kcal.

1. Basic concepts and definitions of the physiology of metabolism and energy.

An integral (general) characteristic of the energy metabolism of the human body is the total energy expenditure or gross energy expenditure.

Gross energy expenditure body - the totality of the body’s energy expenditure during the day under the conditions of its normal (natural) existence. Gross energy expenditure includes three components: basal metabolism, the specific dynamic effect of food and work gain. Gross energy expenditure is estimated in kJ/kg/day or kcal/kg/day (1 kJ=0.239 kcal).

BX.

The study of basic metabolism began with the work of scientists from the University of Tartu Bidder and Schmidt ( Bidder and Schmidt, 1852).

BX the minimum level of energy expenditure necessary to maintain the vital functions of the body.

The idea of ​​basal metabolism as the minimum level of energy expenditure by the body also imposes a number of requirements on the conditions under which this indicator should be assessed.

Conditions under which basal metabolism should be assessed:

1. a state of complete physical and mental rest (preferably in a lying position);
2. ambient comfort temperature (18-20 degrees Celsius);
3. 10 12 hours after the last meal to avoid an increase in energy metabolism associated with food intake.

Factors influencing basal metabolism.

Basal metabolism depends on age, height, body weight and gender.

Effect of age to the main exchange.

The highest basal metabolic rate per 1 kg. Body weight in newborns (50-54 kcal/kg/day), the lowest in older people (after 70 years, the basal metabolism averages 30 kcal/kg/day). The basal metabolism reaches a constant level at the time of puberty at 12-14 years of age and remains stable until 30-35 years of age (about 40 kcal/kg/day).

Effect of height and weight body for basal metabolism.

There is an almost linear, direct relationship between body weight and basal metabolism - the greater the body weight, the higher the level of basal metabolism. However, this dependence is not absolute. With an increase in body weight due to muscle tissue, this relationship is almost linear, however, if the increase in body weight is associated with an increase in the amount of adipose tissue, this relationship becomes nonlinear.

Since body weight, other things being equal, depends on height (the greater the height, the greater the body weight), there is a direct relationship between height and basal metabolism; the greater the height, the greater the basal metabolism.

Considering the fact that height and body weight affect the total body area, M. Rubner ( M.Rubner) formulated a law according to which the basal metabolism depends on the area of ​​the body: the larger the body area, the greater the basal metabolism. However, this law practically ceases to work in conditions when the ambient temperature is equal to body temperature. In addition, unequal skin hairiness significantly changes the heat exchange between the body and the environment and therefore Rubner’s law also has limitations under these conditions.

Influence genderto the level of basal metabolism.

In men, the level of basal metabolism is 5-6% higher than in women. This is explained by the different ratio of fat and muscle tissue per 1 kg of body weight, as well as different levels of metabolism due to differences in the chemical structure of sex hormones and their physiological effects.

Specific dynamic action of food.

The term specific dynamic action of food was first introduced into scientific use by M. Rubner in 1902.

The specific dynamic effect of food is an increase in the energy metabolism of the human body associated with food intake. The specific dynamic effect of food is the energy expenditure of the body on the mechanisms of utilization of ingested food. This effect in changing energy metabolism is observed from the moment of preparation for meals, during meals and lasts 10-12 hours after meals. The maximum increase in energy metabolism after eating is observed after 3 3.5 hours. Special studies have shown that from 6 to 10% of its energy value is spent on food disposal.

Work increase.

Work gain is the third component of the body's gross energy expenditure.The work gain is part of the body's energy expenditure on muscular activity in the environment. During heavy physical work, the body's energy expenditure can increase by 2 times compared to the level of basal metabolism.

1. Methods for studying energy metabolism in humans.

To study energy metabolism in humans, a number of methods have been developed under the general name calorimetry.

METHODS OF CALORIMETRY

Direct Indirect

Direct calorimetry methodsmethods for directly measuring the heat produced by the body under certain conditions. The principle of the method is based on the fact that the higher the energy metabolism in the body, the greater the amount of heat dissipated in the environment. In this regard, if the biological object under study is placed in a heat-insulating room containing a heat-absorbing substance, the initial and, after a certain period of time, the final temperature are measured, and also knowing the specific heat capacity of the heat-absorbing substance and its mass, it is possible to calculate the amount of heat dissipated by the body ( Q) according to a well-known formula.

Q = c x m x  t, where

c specific heat capacity of the heat-absorbing substance;

m mass of heat-absorbing substance;

 t temperature shift.

The disadvantages of the method are its complexity, relatively long implementation time and the inability to use in natural conditions, incl. in real production conditions.

Methods of indirect calorimetry.

Indirect calorimetry methods are based on an indirect assessment of the body's energy expenditure. Methods of indirect calorimetry include the method of food rations, the time-table method, and the analysis of gases of inhaled and exhaled air.

Food ration methodis based on the proposition that energy metabolism can be assessed by knowing the ratio of nutrients in consumed food products and their energy value. This method is very inaccurate, since it does not take into account the individual digestibility of nutrients, the degree of their breakdown in the body, and therefore their energy effect.

Timing-tabular methodis based on timing human activity during a given period of time in order to identify the proportion of certain actions that have a certain energy “price”. The energy “price” of certain actions is estimated using special tables, which are compiled on the basis of a large number of studies of the energy metabolism of human activity.

Methods for analyzing gases of inhaled and exhaled air.

The main part of energy in the body of animals and humans is reproduced during the oxidation of nutrients with the participation of oxygen (O 2 ) to final products carbon dioxide (CO 2) and water (H 2 ABOUT). At the same time, during the oxidation of certain nutrients, an unequal amount of energy is released, due to their unequal energy value. Thus, knowing the amount of oxygen consumed and carbon dioxide released, one can evaluate the body’s energy metabolism. To assess energy metabolism by analyzing the concentration of gases in exhaled air, at the first stage, the respiratory coefficient is calculated. Respiratory coefficient (RK) is the ratio of the volume of carbon dioxide released to the volume of oxygen absorbed during the same time.

DK = V CO 2 / V O 2

Studies have shown that DC typically ranges from 0.7 to 1.0. DC acquires its maximum value during the oxidation of carbohydrates:

C 6 H 12 O 6 + 6O 2 = 6CO 2 + 6H 2 0 + Q

Since the volume of a gram of a molecule of any gas is the same, DC in this case is equal to:

DK = 6СО 2 / 6О 2 = 1.0

DC of fats is 0.7; DC of proteins is about 0.8; The DC of mixed food is 0.85.

A certain respiratory coefficient corresponds to a certain caloric equivalent of oxygen (CEO 2). KEO 2 for the corresponding recreation center are found using special tables.

Caloric oxygen equivalent is the amount of energy released during the oxidation of nutrients in 1.0 liter of oxygen. Knowing KEO2 and the volume of oxygen consumed, you can easily calculate the total amount of energy released under given conditions

A = KEO 2 x V O 2 / 1000

This method is quite simple, reliable and, therefore, widely used in medicine to assess human energy metabolism.

5. The concept of rational nutrition. Rules for preparing food rations.

The term balanced nutrition literally means smart eating. Since the nutritional factor largely determines the level of individual health, in today’s lecture we will touch on some principles of rational human nutrition.

First principle rational nutrition principle of energy adequacy.

In accordance with this principle, the energy value of nutrients included in the food consumed must correspond to the gross energy expenditure of the body. With an increase in the gross energy expenditure of the body in connection with production activities (an increase in work gain), the energy value of the food received must necessarily increase.

Second principle rational nutrition the principle of optimal balance of nutrients included in the food intake. Today, in the Russian school of nutritional physiology, it is generally accepted that the optimal ratio between proteins, fats and carbohydrates obtained from food is the ratio 1: 1: 4. This ratio indicates that, in quantitative terms, proteins are in a rational diet should be 1 part, fats - 1part, and carbohydrates - 4 parts.

Third principle rational nutrition states that the food consumed in biological terms should be complete, i.e. Essential amino acids, saturated and unsaturated fatty acids, vitamins, dietary fiber, and all necessary mineral salts must be supplied with food in full. In practical terms, this issue is resolved as follows: proteins must be not only of animal origin, but also of plant origin (55% should be proteins of animal origin, 45% proteins of plant origin). Proteins of plant origin are found in the fruits of legumes. It is necessary that 60% of fats in the diet come from vegetable fats (sunflower, olive and other vegetable oils), and 40% from animal fats. This requirement is due to the fact that vegetable fats contain unsaturated fatty acids. To provide the diet with vitamins and mineral salts, it is necessary to include a sufficient amount of raw fruits and vegetables.

Fourth principlerational nutrition requires optimal frequency of meals and optimal distribution of the volume of food consumed throughout the day. The most optimal is considered to be four meals a day, including breakfast, lunch, afternoon snack and dinner. At the same time, 20-25% of the total volume of food should be consumed during breakfast, based on its calorie content, 40-45% during lunch, 5-10% during the afternoon snack, 15-20% during dinner.

Fifth principle rational nutrition requires taking into account the national, cultural and religious traditions of the population, for which a specialist in the field of rational nutrition develops a diet.

Metabolism and energy, or metabolism, - a set of chemical and physical transformations of substances and energy that occur in a living organism and ensure its vital activity. Metabolism of matter and energy constitutes a single whole and is subject to the law of conservation of matter and energy.

Metabolism consists of the processes of assimilation and dissimilation. Assimilation (anabolism)- the process of absorption of substances by the body, during which energy is consumed. Dissimilation (catabolism)- the process of decomposition of complex organic compounds that occurs with the release of energy.

The only source of energy for the human body is the oxidation of organic substances supplied with food. When food products are broken down into their final elements - carbon dioxide and water - energy is released, part of which goes into mechanical work performed by muscles, the other part is used for the synthesis of more complex compounds or accumulates in special high-energy compounds.

Macroergic compounds are substances whose breakdown is accompanied by the release of a large amount of energy. In the human body, the role of high-energy compounds is performed by adenosine triphosphoric acid (ATP) and creatine phosphate (CP).

PROTEIN METABOLISM.

Proteins(proteins) are high-molecular compounds built from amino acids. Functions:

Structural or plastic function is that proteins are the main component of all cells and intercellular structures. Catalytic or enzymatic The function of proteins is their ability to accelerate biochemical reactions in the body.

Protective function proteins manifests itself in the formation of immune bodies (antibodies) when a foreign protein (for example, bacteria) enters the body. In addition, proteins bind toxins and poisons that enter the body, and ensure blood clotting and stop bleeding in case of wounds.

Transport function involves the transfer of many substances. The most important function of proteins is the transmission hereditary properties , in which nucleoproteins play a leading role. There are two main types of nucleic acids: ribonucleic acids (RNA) and deoxyribonucleic acids (DNA).

Regulatory function proteins is aimed at maintaining biological constants in the body.

Energy role Proteins are responsible for providing energy for all life processes in the body of animals and humans. When 1 g of protein is oxidized, on average, energy is released equal to 16.7 kJ (4.0 kcal).

Protein requirement. The body constantly breaks down and synthesizes proteins. The only source of new protein synthesis is food proteins. In the digestive tract, proteins are broken down by enzymes into amino acids and are absorbed in the small intestine. From amino acids and simple peptides, cells synthesize their own protein, which is characteristic only of a given organism. Proteins cannot be replaced with other nutrients, since their synthesis in the body is possible only from amino acids. At the same time, protein can replace fats and carbohydrates, i.e., be used for the synthesis of these compounds.

Biological value of proteins. Some amino acids cannot be synthesized in the human body and must be supplied with food in finished form. These amino acids are commonly called irreplaceable, or vitally necessary. These include: valine, methionine, threonine, leucine, isoleucine, phenylalanine, tryptophan and lysine, and in children also arginine and histidine. A lack of essential acids in food leads to disturbances in protein metabolism in the body. Nonessential amino acids are mainly synthesized in the body.

Proteins containing all the necessary amino acids are called biologically complete. The highest biological value of proteins is milk, eggs, fish, and meat. Biologically deficient proteins are those that lack at least one amino acid that cannot be synthesized in the body. Incomplete proteins are proteins from corn, wheat, and barley.

Nitrogen balance. Nitrogen balance is the difference between the amount of nitrogen contained in human food and its level in excreta.

Nitrogen balance- a condition in which the amount of nitrogen excreted is equal to the amount entered into the body. Nitrogen balance is observed in a healthy adult.

Positive nitrogen balance- a condition in which the amount of nitrogen in the body’s secretions is significantly less than its content in food, that is, nitrogen retention in the body is observed. A positive nitrogen balance is observed in children due to increased growth, in women during pregnancy, during intense sports training leading to an increase in muscle tissue, during the healing of massive wounds or recovery from serious illnesses.

Nitrogen deficiency(negative nitrogen balance) is observed when the amount of nitrogen released is greater than its content in the food entering the body. Negative nitrogenbalance is observed during protein starvation, feverish conditions, and disorders of the neuroendocrine regulation of protein metabolism.

Protein breakdown and urea synthesis. The most important nitrogenous products of protein breakdown, which are excreted in urine and sweat, are urea, uric acid and ammonia.

FAT METABOLISM.

Fats are divided on simple lipids(neutral fats, waxes), complex lipids(phospholipids,glycolipids, sulfolipids) and steroids(cholesterol andetc.). The bulk of lipids in the human body are represented by neutral fats. Neutral fats Human food is an important source of energy. When 1 g of fat is oxidized, 37.7 kJ (9.0 kcal) of energy is released.

The daily requirement of an adult for neutral fat is 70-80 g, for children 3-10 years old - 26-30 g.

Energy-neutral fats can be replaced with carbohydrates. However, there are unsaturated fatty acids - linoleic, linolenic and arachidonic, which must necessarily be contained in the human diet, they are called Not replaceable bold acids.

Neutral fats that make up food and human tissues are represented mainly by triglycerides containing fatty acids - palmitic,stearic, oleic, linoleic and linolenic.

The liver plays an important role in fat metabolism. The liver is the main organ in which the formation of ketone bodies (beta-hydroxybutyric acid, acetoacetic acid, acetone) occurs. Ketone bodies are used as a source of energy.

Phospho- and glycolipids are found in all cells, but mainly in nerve cells. The liver is practically the only organ that maintains the level of phospholipids in the blood. Cholesterol and other steroids can be obtained from food or synthesized in the body. The main site of cholesterol synthesis is the liver.

In adipose tissue, neutral fat is deposited in the form of triglycerides.

Formation of fats from carbohydrates. Excessive intake of carbohydrates from food leads to the deposition of fat in the body. Normally, in humans, 25-30% of carbohydrates in food are converted into fats.

Formation of fats from proteins. Proteins are plastic materials. Only under extreme circumstances are proteins used for energy purposes. The conversion of protein to fatty acids most likely occurs through the formation of carbohydrates.

CARBOHYDRATE METABOLISM.

The biological role of carbohydrates for the human body is determined primarily by their energy function. The energy value of 1 g of carbohydrates is 16.7 kJ (4.0 kcal). Carbohydrates are a direct source of energy for all cells of the body and perform plastic and support functions.

The daily carbohydrate requirement of an adult is approximately 0.5 kg. The main part of them (about 70%) is oxidized in tissues to water and carbon dioxide. About 25-28% of dietary glucose is converted into fat and only 2-5% of it is synthesized into glycogen - the body's reserve carbohydrate.

The only form of carbohydrates that can be absorbed are monosaccharides. They are absorbed mainly in the small intestine and are transported by the bloodstream to the liver and tissues. Glycogen is synthesized from glucose in the liver. This process is called glycogenesis. Glycogen can be broken down into glucose. This phenomenon is called glycogenolysis. In the liver, new formation of carbohydrates is possible from the products of their breakdown (pyruvic or lactic acid), as well as from the breakdown products of fats and proteins (keto acids), which is designated as glyconeogenesis. Glycogenesis, glycogenolysis and glyconeogenesis are closely interrelated processes occurring in the liver that ensure optimal blood sugar levels.

In the muscles, just likeIn the liver, glycogen is synthesized. The breakdown of glycogen is one of the sources of energy for muscle contraction. When muscle glycogen breaks down, the process proceeds to the formation of pyruvic and lactic acids. This process is called glycolysis. During the rest phase, glycogen re-synthesis occurs from lactic acid in muscle tissue.

Brain contains small reserves of carbohydrates and requires a constant supply of glucose. Glucose in brain tissue is predominantly oxidized, and a small part of it is converted into lactic acid. The energy expenditure of the brain is covered exclusively by carbohydrates. A decrease in the supply of glucose to the brain is accompanied by changes in metabolic processes in the nervous tissue and impaired brain function.

Formation of carbohydrates from proteins and fats (glyconeogenesis). As a result of the transformation of amino acids, pyruvic acid is formed; during the oxidation of fatty acids, acetyl coenzyme A is formed, which can be converted into pyruvic acid, a precursor of glucose. This is the most important general pathway for carbohydrate biosynthesis.

There is a close physiological relationship between the two main sources of energy - carbohydrates and fats. An increase in blood glucose increases the biosynthesis of triglycerides and reduces the breakdown of fats in adipose tissue. Less free fatty acids enter the blood. If hypoglycemia occurs, the process of triglyceride synthesis is inhibited, fat breakdown is accelerated, and free fatty acids enter the blood in large quantities.

WATER-SALT EXCHANGE.

All chemical and physical-chemical processes occurring in the body are carried out in an aquatic environment. Water performs the following important functions in the body: functions: 1) serves as a solvent for food and metabolism; 2) transports substances dissolved in it; 3) reduces friction between contacting surfaces in the human body; 4) participates in the regulation of body temperature due to high thermal conductivity and high heat of evaporation.

The total water content in the adult human body is 50 —60% from its mass, that is, reaches 40—45 l.

It is customary to divide water into intracellular, intracellular (72%) and extracellular, extracellular (28%). Extracellular water is located inside the vascular bed (as part of blood, lymph, cerebrospinal fluid) and in the intercellular space.

Water enters the body through the digestive tract in the form of liquid or water contained in densefood products. Some of the water is formed in the body itself during the metabolic process.

When there is an excess of water in the body, there is general overhydration(water poisoning), with a lack of water, metabolism is disrupted. Losing 10% of water leads to the condition dehydration(dehydration), death occurs when 20% of water is lost.

Along with water, minerals (salts) also enter the body. Near 4% The dry mass of food should consist of mineral compounds.

An important function of electrolytes is their participation in enzymatic reactions.

Sodium ensures the constancy of the osmotic pressure of the extracellular fluid, participates in the creation of bioelectric membrane potential, and in the regulation of the acid-base state.

Potassium provides osmotic pressure of intracellular fluid, stimulates the formation of acetylcholine. A lack of potassium ions inhibits anabolic processes in the body.

Chlorine is also the most important anion in the extracellular fluid, ensuring constant osmotic pressure.

Calcium and phosphorus are found mainly in bone tissue (over 90%). The calcium content in plasma and blood is one of the biological constants, since even minor changes in the level of this ion can lead to severe consequences for the body. A decrease in the level of calcium in the blood causes involuntary muscle contractions, convulsions, and death occurs due to respiratory arrest. An increase in calcium content in the blood is accompanied by a decrease in the excitability of nervous and muscle tissue, the appearance of paresis, paralysis, and the formation of kidney stones. Calcium is necessary for building bones, so it must be supplied to the body in sufficient quantities through food.

Phosphorus participates in the metabolism of many substances, as it is part of high-energy compounds (for example, ATP). The deposition of phosphorus in the bones is of great importance.

Iron is part of hemoglobin and myoglobin, which are responsible for tissue respiration, as well as enzymes involved in redox reactions. Insufficient intake of iron into the body disrupts hemoglobin synthesis. A decrease in hemoglobin synthesis leads to anemia (anemia). The daily iron requirement of an adult is 10-30 mcg.

Iodine is found in the body in small quantities. However, its significance is great. This is due to the fact that iodine is part of the thyroid hormones, which have a pronounced effect on all metabolic processes, growthand development of the organism.

Education and energy consumption.

The energy released during the breakdown of organic substances accumulates in the form of ATP, the amount of which in the tissues of the body is maintained at a high level. ATP is found in every cell of the body. The largest amount is found in skeletal muscles - 0.2-0.5%. Any cell activity always coincides exactly in time with the breakdown of ATP.

The destroyed ATP molecules must be restored. This occurs due to the energy that is released during the breakdown of carbohydrates and other substances.

The amount of energy expended by the body can be judged by the amount of heat it gives off to the external environment.

Methods for measuring energy expenditure (direct and indirect calorimetry).

Respiratory coefficient.

Direct calorimetry is based on the direct determination of heat released during the life of the body. A person is placed in a special calorimetric chamber, in which the entire amount of heat given off by the human body is taken into account. The heat generated by the body is absorbed by water flowing through a system of pipes laid between the walls of the chamber. The method is very cumbersome and can be used in special scientific institutions. As a result, they are widely used in practical medicine. indirect method calorimetry. The essence of this method is that the volume of pulmonary ventilation is first determined, and then the amount of absorbed oxygen and released carbon dioxide. The ratio of the volume of carbon dioxide released to the volume of oxygen absorbed is called respiratory quotient . The value of the respiratory coefficient can be used to judge the nature of oxidized substances in the body.

Upon oxidation carbohydrates respiratory quotient is 1 because for complete oxidation of 1 molecule glucose 6 molecules of oxygen are required to reach carbon dioxide and water, and 6 molecules of carbon dioxide are released:

С 6 Н12О 6 +60 2 =6С0 2 +6Н 2 0

The respiratory coefficient for protein oxidation is 0.8, for fat oxidation - 0.7.

Determination of energy consumption by gas exchange. Quantityheat released in the body when 1 liter of oxygen is consumed - caloric equivalent of oxygen - depends on what substances oxygen is used to oxidize. Caloric equivalent oxygen during the oxidation of carbohydrates is equal to 21,13 kJ (5.05 kcal), proteins— 20.1 kJ (4.8 kcal), fat - 19.62 kJ (4.686 kcal).

Energy consumption in humans is determined as follows. The person breathes for 5 minutes through a mouthpiece placed in the mouth. The mouthpiece, connected to a bag made of rubberized fabric, has valves. They are arranged like this What man breathes freely atmospheric air, and exhales air into the bag. Using gas hours measure the volume of exhaled breath air. The gas analyzer's readings determine the percentage of oxygen and carbon dioxide in the air inhaled and exhaled by a person. The amount of oxygen absorbed and carbon dioxide released, as well as the respiratory quotient, are then calculated. Using the appropriate table based on the respiratory coefficient, the caloric equivalent of oxygen is determined and energy consumption is determined.

Basal metabolism and its significance.

BX- the minimum amount of energy necessary to maintain the normal functioning of the body in a state of complete rest, excluding all internal and external influences that could increase the level of metabolic processes. Basic metabolism is determined in the morning on an empty stomach (12-14 hours after the last meal), in a supine position, with complete muscle relaxation, in temperature comfort conditions (18-20 ° C). The basic metabolism is expressed by the amount of energy released by the body (kJ/day).

In a state of complete physical and mental peace the body consumes energy to: 1) constantly occurring chemical processes; 2) mechanical work performed by individual organs (heart, respiratory muscles, blood vessels, intestines, etc.); 3) constant activity of the glandular-secretory apparatus.

Basic metabolism depends on age, height, body weight, and gender. The most intense basal metabolism per 1 kg of body weight is observed in children. As body weight increases, basal metabolism increases. The average basal metabolic rate for a healthy person is approximately 4.2 kJ (1 kcal) per 1 hour per 1 kg of weight body.

In terms of energy consumption at rest, body tissues are heterogeneous. Internal organs consume energy more actively, muscle tissue less actively.

The intensity of basal metabolism in adipose tissue is 3 times lower than in the rest of the cellular mass of the body. Thin people produce more heat per kgbody weight than full.

Women have a lower basal metabolism than men. This is due to the fact that women have less mass and body surface area. According to Rubner's rule, basal metabolism is approximately proportional to the surface of the body.

Seasonal fluctuations in the value of basal metabolism were noted - it increased in spring and decreased in winter. Muscular activity causes an increase in metabolism in proportion to the severity of the work performed.

Significant changes in the basal metabolism are caused by dysfunctions of organs and systems of the body. With increased thyroid function, malaria, typhoid fever, tuberculosis, accompanied by fever, the basal metabolism increases.

Energy expenditure during physical activity.

During muscular work, the body's energy expenditure increases significantly. This increase in energy costs constitutes a work increase, which is greater the more intense the work.

Compared to sleep, energy expenditure increases by 3 times when walking slowly, and by more than 40 times when running short distances during competition.

During short-term exercise, energy is consumed through the oxidation of carbohydrates. During prolonged muscular exercise, the body breaks down mainly fats (80% of all necessary energy). In trained athletes, the energy of muscle contractions is provided exclusively by fat oxidation. For a person engaged in physical labor, energy costs increase in proportion to the intensity of work.

NUTRITION.

Replenishment of the body's energy costs occurs through nutrients. Food should contain proteins, carbohydrates, fats, mineral salts and vitamins in small quantities and in the correct ratio. Digestibilitynutrients dependson the individual characteristics and condition of the body, on the quantity and quality of food, the ratio of its various components, and the method of preparation. Plant foods are less digestible than animal products because plant foods contain more fiber.

A protein diet promotes the absorption and digestibility of nutrients. When carbohydrates predominate in food, the absorption of proteins and fats is reduced. Replacing plant products with products of animal origin enhances metabolic processes in the body. If you give proteins from meat or dairy products instead of vegetable ones, and wheat bread instead of rye bread, then the digestibility of food products increases significantly.

Thus, in order to ensure proper human nutrition, it is necessary to take into account the degree of absorption of foods by the body. In addition, food must necessarily contain all essential (essential) nutrients: proteins and essential amino acids, vitamins,highly unsaturated fatty acids, minerals and water.

The bulk of food (75-80%) consists of carbohydrates and fats.

Diet- the quantity and composition of food products needed by a person per day. It must replenish the body’s daily energy expenditure and include all nutrients in sufficient quantities.

To compile food rations, it is necessary to know the content of proteins, fats and carbohydrates in foods and their energy value. Having this data, it is possible to create a scientifically based diet for people of different ages, genders and occupations.

Diet and its physiological significance. It is necessary to follow a certain diet and organize it correctly: constant hours of meals, appropriate intervals between them, distribution of the daily diet during the day. You should always eat at a certain time, at least 3 times a day: breakfast, lunch and dinner. Breakfast's energy value should be about 30% of the total diet, lunch - 40-50%, and dinner - 20-25%. It is recommended to have dinner 3 hours before bedtime.

Proper nutrition ensures normal physical development and mental activity, increases the performance, reactivity and resistance of the body to environmental influences.

According to the teachings of I.P. Pavlov on conditioned reflexes, the human body adapts to a certain time of eating: appetite appears and digestive juices begin to be released. Proper intervals between meals ensure a feeling of fullness during this time.

Eating three times a day is generally physiological. However, four meals a day are preferable, which increases the absorption of nutrients, in particular proteins, there is no feeling of hunger in the intervals between individual meals and a good appetite is maintained. In this case, the energy value of breakfast is 20%, lunch - 35%, afternoon snack - 15%, dinner - 25%.

Balanced diet. Nutrition is considered rational if the need for food is fully satisfied in quantitative and qualitative terms, and all energy costs are reimbursed. It promotes proper growth and development of the body, increases its resistance to harmful influences of the external environment, promotes the development of the functional capabilities of the body and increases the intensity of work. Rational nutrition involves the development of food rations and diets in relation to various populations and living conditions.

As already indicated, the nutrition of a healthy person is based on daily food rations. The patient's diet and diet is called a diet. Each diet has certain components of the diet and is characterized by the following characteristics: 1) energy value; 2) chemical composition; 3) physical properties (volume, temperature, consistency); 4) power mode.

Regulation of metabolism and energy.

Conditioned reflex changes in metabolism and energy are observed in humans in pre-start and pre-working states. Athletes before the start of a competition, and a worker before work, experience an increase in metabolism and body temperature, an increase in oxygen consumption and the release of carbon dioxide. Can cause conditioned reflex changes in metabolism, energy and thermal processes people have verbal stimulus.

Nervous influence metabolic and energy systems processes in the body carried out in several ways:

Direct influence of the nervous system (through the hypothalamus, efferent nerves) on tissues and organs;

Indirect influence of the nervous system throughpituitary gland (somatotropin);

Indirectinfluence of the nervous system through tropic hormones pituitary gland and peripheral glands of the internal secretion;

Direct influencenervous system (hypothalamus) on the activity of the endocrine glands and through them on metabolic processes in tissues and organs.

The main department of the central nervous system, which regulates all types of metabolic and energy processes, is hypothalamus. A pronounced influence on metabolic processes and heat generation is exerted by internal glands secretion. Hormones of the adrenal cortex and thyroid gland in large quantities increase catabolism, i.e., the breakdown of proteins.

The body clearly demonstrates the close interconnected influence of the nervous and endocrine systems on metabolic and energy processes. Thus, excitation of the sympathetic nervous system not only has a direct stimulating effect on metabolic processes, but also increases the secretion of thyroid and adrenal hormones (thyroxine and adrenaline). Due to this, metabolism and energy are further enhanced. In addition, these hormones themselves increase the tone of the sympathetic nervous system. Significant changes in metabolism And heat exchange occurs when there is a deficiency of endocrine gland hormones in the body. For example, a lack of thyroxine leads to a decrease in basal metabolism. This is due to a decrease in oxygen consumption by tissues and a decrease in heat generation. As a result, body temperature decreases.

Hormones of the endocrine glands are involved in the regulation of metabolism And energy, changing the permeability of cell membranes (insulin), activating the body's enzyme systems (adrenaline, glucagon, etc.) and influencing on their biosynthesis (glucocorticoids).

Thus, the regulation of metabolism and energy is carried out by the nervous and endocrine systems, which ensure the body’s adaptation to the changing conditions of its environment.

Metabolism in the body. Plastic rf energy role

nutrients

The constant exchange of substances and energy between the organism and the environment is a necessary condition for its existence and reflects them

unity. The essence of this exchange is that the nutrients entering the body, after digestive transformations, are used as plastic material. The energy generated in this case replenishes the body's energy costs. The synthesis of complex body-specific substances from simple compounds absorbed into the blood is called assimilation or anabolism. The breakdown of body substances into final products, accompanied by the release of energy, is called dissimilation or catabolism. These processes are inextricably linked. Assimilation ensures the accumulation of energy, and the energy released during dissimilation is necessary for the synthesis of substances. Anabolism and catabolism are combined into a single process with the help of ATP and NADP. Through them, the energy generated as a result of dissimilation is transferred for assimilation processes.

Proteins are basically plastic material. They are part of cell membranes and organelles. Protein molecules are constantly renewed. But this renewal occurs not only due to food proteins, but also through the reutilization of one’s own proteins. However, of the 20 amino acids that form proteins, 10 are essential. Those. they cannot be formed in the body. The end products of protein breakdown are nitrogen-containing compounds such as urea, uric acid, and creatinine. Therefore, the state of protein metabolism can be determined by nitrogen balance. This is the ratio of the amount of nitrogen supplied with food proteins and excreted from the body with nitrogen-containing metabolic products. 100 g of protein contains about 16 g of nitrogen. Therefore, the release of 1 g of nitrogen indicates the breakdown of 6.25 g of protein in the body. If the amount of nitrogen released is equal to the amount absorbed by the body, nitrogen equilibrium occurs. If there is more nitrogen in than nitrogen out, it is called a positive nitrogen balance. Nitrogen retention occurs in the body. A positive nitrogen balance is observed during the growth of the body, during recovery from a serious illness and after prolonged fasting. When the amount of nitrogen excreted by the body is greater than that taken in, a negative nitrogen balance occurs. Its occurrence is explained by the predominant breakdown of the body's own proteins. It occurs during fasting, lack of essential amino acids in food, impaired digestion and absorption of protein, and serious illnesses. The amount of protein that fully meets the body's needs is called the protein optimum. The minimum, ensuring only the preservation of nitrogen balance - a protein minimum. WHO recommends a protein intake of at least 0.75 g per kg of body weight per day. The energy role of proteins is relatively small.

Body fats are triglycerides and phospholipids. and sterols. Their main role is energetic. The oxidation of lipids releases the greatest amount of energy, so about half of the body's energy expenditure is provided by lipids. They are also an energy accumulator in the body, because they are deposited in fat depots and are used as needed. Fat depots make up about 15% of body weight. Fats have a certain plastic role, since phospholipids, cholesterol, and fatty acids are part of cell membranes and organelles. In addition, they cover the internal organs. For example, perinephric fat helps to fix the kidneys and protect them from mechanical stress. Lipids are also sources of endogenous water. When 100 g of fat is oxidized, about 100 g of water is formed. A special function is performed by brown fat, located along large vessels and between the shoulder blades. The polypeptide contained in its fat cells, when the body cools, inhibits the resynthesis of ATP due to lipids. As a result, heat production sharply increases. Essential fatty acids - linoleic, linolenic and arachidonic - are of great importance. Without them, the synthesis of cell phospholipids, the formation of prostaglandins, etc. is impossible. In their absence, the growth and development of the body is delayed.

Carbohydrates mainly play an energy role, as they serve as the main source of energy for cells. For example, the energy needs of neurons are met exclusively by glucose. They accumulate as glycogen in the liver and muscles. Carbohydrates have a certain plastic significance, since glucose is necessary for the formation of nucleotides and the synthesis of certain amino acids.

H Methods for measuring the body's energy balance

The relationship between the amount of energy received from food and the energy released into the external environment is called the energy balance of the body. There are 2 methods for determining the energy released by the body.

1. Direct calorimetry. Its principle is based on the fact that all types of energy ultimately turn into heat. Therefore, with direct calorimetry, the amount of heat released by the body into the environment per unit of time is determined. For this purpose, special chambers with good thermal insulation and a system of thermal exchange pipes are used, through which water circulates and is heated.

2.Indirect calorimetry. It consists in determining the ratio of carbon dioxide released and oxygen absorbed per unit of time. This is a complete gas analysis. This ratio is called the respiratory coefficient (RQ).

Description of the presentation Physiology of metabolism and energy. Physiology of thermoregulation on slides

Physiology of metabolism and energy. Physiology of thermoregulation PREPARED BY: ALIMZHAN SERZHAN (39 -01)

Metabolism (metabolism) is a set of chemical reactions in living organisms that ensure their growth, development, and vital processes. Plastic metabolism or anabolism (assimilation) is the synthesis of organic substances (carbohydrates, fats, proteins), with the expenditure of energy. Energy metabolism or catabolism (dissimilation) is the breakdown of organic substances, with the release of energy. The final breakdown products are carbon, water, and ATP.

There are 4 stages of metabolism: 1. Hydrolysis of nutrients in the digestive tract - enzymatic breakdown of nutrients. 2. Absorption of the final products of hydrolysis into the blood and lymph. 3. Transport of nutrients and O2 into the cell - intracellular metabolism and energy. 4. Isolation of metabolic end products.

Cellular regulation is based on the characteristics of the interaction between the enzyme and the substrate. An enzyme as a biological catalyst changes the rate of a reaction by combining with a substrate and forming an enzyme-substrate complex. After changes have occurred in the substrate, the enzyme leaves this complex intact and begins a new cycle.

Humoral regulation Some hormones directly regulate the synthesis or breakdown of enzymes and the permeability of cell membranes, changing the content of substrates, cofactors and ionic composition in the cell.

Nervous regulation is carried out in various ways: - changing the intensity of functioning of the endocrine glands; direct activation of enzymes. The central nervous system, acting on cellular and humoral regulatory mechanisms, adequately changes the trophism of cells

Proteins (80 -100 g) The main source of protein for the body is food protein. The importance of proteins: Plastic role Energetic Motor function (actin, myosin). Enzymatic function (enzymes are proteins that provide the basic functions of the body: respiration, digestion, excretion. Regulation of protein metabolism - Regulation centers in the nuclei of the hypothalamus. The sympathetic nervous system enhances protein dissimilation. The parasympathetic nervous system enhances protein synthesis. Enhances protein synthesis - growth hormone, triiodothyroxine, thyroxine

Essential amino acids Valine (meat, mushrooms, dairy and grain products) Isoleucine (chicken meat, liver, eggs, fish) Leucine (meat, fish, nuts) Lysine (fish, eggs, meat, beans) Methionine (milk, beans, fish, beans) Threonine (dairy, eggs, nuts) Tryptophan (bananas, dates, chicken, dairy) Phenylalanine (beef, fish, eggs, milk) Arginine (pumpkin seeds, beef, pork, sesame) Histidine (beef, chicken, lentils) , salmon)

Conversion of proteins in the body Food proteins Digestive tract Blood amino acids Cells of various tissues Liver Transamination Deamination of amino acids. Liver amino acids Ammonia Keto acids Urea Oxidation Glycerol synthesis Fatty acid synthesis. Residual blood nitrogen. Kidneys. Urine nitrogen Liver enzymes Liver proteins. Blood plasma proteins

Regulation of protein metabolism Central regulatory mechanisms Hypothalamus Pituitary gland Pancreas Adrenal glands. Parasympathetic influences Sympathetic influences Somatotropic hormones Glucocorticoids In the liver Muscles, lymphoid tissue Anabolism Catabolism Thyroid hormones Insulin. Thyroid

Fats (80 -100 g) Plastic, energy role. Fats are absorbed from the intestines into the lymph and blood in the form of glycerol and fatty acids (forming micelles with bile acids). Regulation is carried out by the hypothalamus. The breakdown of fat occurs under the influence of adrenaline, norepinephrine, growth hormone, and thyroxine. Irritation of the sympathetic nervous system increases the breakdown of fat. Parasympathetic – promotes fat deposition.

Conversion of fats in the body Food fat (triglycerides) FOOD CHANNEL BLOOD LYMPHAS E R D C E L I P E T r iglycerides v i d e c h i l o m i c r o n about v. Short chain fatty acids Glycerol Long chain fatty acids

Carbohydrates (400 -500 g) The main source of energy comes in the form of di-polysaccharides, absorbed in the form of monosaccharides. Glycogen is synthesized from glucose in the liver. When blood glucose decreases, the breakdown of liver glucogen increases. Regulation of carbohydrate metabolism: Hyperglycemia causes irritation of the hypothalamus and cerebral cortex, the effect is realized through the autonomic nerves. The sympathetic nervous system enhances the breakdown of glycogen - glycolysis. The parasympathetic nervous system enhances the synthesis of glycogen from glucose - glycogenesis.

Food carbohydrates Food channel Blood carbohydrates Brain LIVER MUSCLE AT REST WORKING MUSCLE H 2 O + CO 2 Blood lactate. Metabolism of carbohydrates in the body Glycogen Pyruvic acid Lactic acid H 2 O + CO

Provided that all energy expenditure is replaced by carbohydrates and fats, that is, with a protein-free diet, approximately 331 mg of protein per 1 kg of body weight is destroyed per day. For a person weighing 70 kg, this is 23.2 g. M. Rubner called this value “wear coefficient”.

NITROGEN BALANCE The ratio of the amount of nitrogen taken in from food and excreted in urine and sweat is called nitrogen balance. The protein coefficient is the amount of protein that, when broken down, produces 1 gram of nitrogen. It is equal to 6.25 g. Positive nitrogen balance - when more protein comes in than is excreted. Negative nitrogen balance is when less protein is taken in than is excreted. Nitrogen balance - when the same amount of nitrogen enters with proteins as is excreted.

STANDARD CONDITIONS FOR DETERMINING BASIC METABOLISM: Basal metabolism is the minimum level of energy expenditure to maintain the vital functions of the body in conditions of relatively complete physical and emotional rest. In the morning, on an empty stomach. At a temperature of 25 -28 degrees Celsius. In a state of complete physical and mental rest, lying on your back.

Methods for determining basal metabolism Direct calorimetry method with complete gas analysis. Method of indirect calorimetry with incomplete gas analysis.

The importance of water for the body Participation in metabolic processes (hydrolysis, oxidation reactions, etc.); Promotes the removal of end products of metabolism; Provides support for temperature homeostasis; Mechanical role (reduces friction between internal organs, articular surfaces, etc.); Universal solvent.

Thermoregulation THERMOREGULATION is a physiological process that ensures the maintenance of a constant temperature in the body of warm-blooded animals and humans. Constancy of temperature is the result of self-regulation of the body, necessary for normal functioning. Body temperature depends on heat production and heat transfer.

Types of thermoregulation Homeothermic is the ability of a living creature to maintain a constant body temperature, regardless of the ambient temperature. Poikilothermic is an evolutionary adaptation of a species or (in medicine and physiology) a state of an organism in which the body temperature of a living creature varies widely depending on the temperature of the external environment. Heterothermic Homeothermic animals whose body temperature may decrease during hibernation or torpor

Mechanisms of Thermoregulation Chemical thermoregulation 1) increase in tissue metabolic processes, intense oxidation of proteins, fats and carbohydrates with the formation of heat 2) increase in the level of thyroid and adrenal hormones, enhancing basal metabolism and heat formation Physical thermoregulation 1) expansion of blood vessels of the skin 2) increase in blood flow to skin vessels 3) increased sweating 4) increased breathing and evaporation of water through the lungs, which allows the body to give off excess heat

Chemical thermoregulation Heat formation is associated with metabolism, with the oxidation of proteins, fats and carbohydrates. These are exothermic reactions. Heat formation in different organs: In muscles – 60-70%. In the liver, gastrointestinal tract – 20-30%. In the kidneys and other organs – 10-20%.

Physical thermoregulation Paths of heat transfer: Heat conduction (in contact with other objects). Convection is the transfer of heat by circulating air. Thermal radiation (radiation) is the emission of heat in the infrared range. Evaporation (from mucous membranes, through the lungs, sweating)

Isothermia is the constancy of body temperature and the internal environment of the body. Isothermia is one of the most important indicators of homeostasis. The constancy of body temperature is ensured by a functional system, which includes a number of heat-producing organs, as well as structures that provide heat transfer, as well as mechanisms that regulate their activity.

Regulation of isothermia Thermoreceptors: Peripheral (skin, mucous membranes, gastrointestinal tract). - cold receptors (Krause cones) - heat receptors (Ruffini corpuscles) Central (hypothalamus, midbrain, cerebral cortex) The anterior nuclei of the hypothalamus control physical thermoregulation. The posterior nuclei of the hypothalamus control chemical thermoregulation.

Human body temperature The temperature of individual parts of the human body is different. The lowest skin temperature is observed on the hands and feet, the highest - in the armpit. In a healthy person, the temperature in this area is 36-37° C. During the day, slight rises and falls in the human body temperature are observed in accordance with the daily biorhythm: the minimum temperature is observed at 2-4 o'clock in the morning, the maximum at 16-19 o'clock. Temperature muscle tissue at rest and at work can fluctuate within 7° C. The temperature of the internal organs depends on the intensity of metabolic processes. The most intensive metabolic processes occur in the liver, the temperature in the liver tissue is 38-38.5 ° C. The temperature in the rectum is 37-37.5 ° C. However, it can fluctuate within 4-5 ° C depending on the presence in her feces, blood filling her mucosa and other reasons.