In accordance with the laws of thermodynamics, the processes of metabolism and energy are associated with the generation of heat. In some animals (and humans), body temperature will remain at a constant level, which significantly exceeds the temperature of the environment due to the intensive heat production controlled by special regulatory mechanisms. It - homoothermal (warm-blooded) organisms. Another group of animals (fish, amphibians) is characterized by a significantly lower intensity of heat production, their body temperature only slightly exceeds the temperature of the medium and undergoes the same fluctuations ( poikilothermic, cold-blooded animals).
Heat production and body temperature. All chemical reactions in the body are temperature dependent. In poikilothermal, the intensity of energy processes increases in proportion to the external temperature in accordance with the Van Hoff rule. In homoothermal, this rule is masked by another effect (regulatory thermogenesis) and appears only with the blockade of thermoregulation (anesthesia, damage to the NS). Even after the blockade of the regulatory component, significant quantitative differences remain between the metabolic processes in cold-blooded and warm-blooded ones: at the same body temperature, the intensity of energy exchange per unit body weight in warm-blooded animals is 3 times greater. Anesthesia together with a decrease in body temperature can cause a noticeable decrease in the degree of oxygen consumption and a delay in tissue destruction processes - this is used in surgery.
Heat production and body size. The body temperature of most warm-blooded animals lies in the range of 36-39 ° C, despite significant differences in weight and size. In contrast, metabolic rate (M) is a power-law function of body weight (m): M \u003d km 0.75 . The coefficient k is approximately the same for both the mouse and the elephant. This law of the dependence of metabolism on body weight reflects the tendency to establish a correspondence between heat production and the rate of heat transfer to the environment. Heat loss per unit mass is greater, the greater the ratio between the surface and body volume, and this ratio decreases with increasing body size. In addition, in small animals, the insulating layer of the body is thinner. If you arrange in a decreasing intensity of metabolic processes of some animals in a row, you get the following: mouse, rabbit, dog, man, elephant.
Thermoregulatory thermogenesis. In the case when additional heat is necessary to maintain body temperature, it can be generated in the following ways:
1. Arbitrary activity of the muscular system.
2. Involuntary tonic or rhythmic (trembling) activity. These two pathways are called contractile thermogenesis.
3. Acceleration of metabolic processes not related to muscle contraction (do not reduce
thermal thermogenesis).
In an adult, trembling is the most significant involuntary manifestation of thermogenesis mechanisms. In a newborn, non-contractile thermogenesis is of greater importance (burning brown fat in a "metabolic cauldron"). Accumulations of brown fat with a large number of mitochondria are located between the shoulder blades, in the armpit. When the body cools, its temperature increases, blood flow increases. By increasing thermogenesis, body temperature is maintained at a constant level.
Environmental factors and thermal comfort. The influence of environmental temperatures on the body depends on at least four physical factors: air temperature, humidity, radiation temperature and air velocity (wind). These factors determine whether a person feels "temperature comfort" or is he hot or cold. The condition for comfort is that the body does not need to work with the mechanisms of thermoregulation: it does not require either trembling or sweating, and the blood flow in the peripheral regions maintains an average speed. This is the so-called thermoneutral zone.
These four factors are interchangeable to some extent.
The value of the comfort temperature for an easily dressed (shirt, underpants, long cotton trousers) seated person is 25-26 ° C with a humidity of 50% and equal air temperature and walls. For naked \u003d 28 ° C. In conditions of thermal comfort, the average skin temperature \u003d 34 ° C. As the physical work progresses, the comfort temperature drops. For easy cabinet work, it is 22 o C.
Discomfort increases with increasing average temperature and humidity of the skin (part of the body surface covered with sweat).
Heat dissipation.
1. The internal flow of heat. Less than half of all the heat generated inside the body spreads to the surface by passing through the tissue. Most comes by convection into the bloodstream. Blood has a high heat capacity. The limb blood flow is organized according to the principle of a rotary-countercurrent mechanism, which facilitates heat transfer between the vessels.
2. External heat flux. The heat is transferred to the outside by conducting, convection, radiation and evaporation. Heat transfer by conducting - when the body is in contact with a dense substrate. When body contact occurs with air - convection, radiation or evaporation. If the skin is warmer than air, the adjacent layer heats up and goes up, being replaced by colder air. Forced convection (airflow) significantly enhances the intensity of heat transfer. Radiation occurs in the form of long-wave infrared radiation. About 20% of the heat transfer of the human body in neutral temperature conditions is due to the evaporation of water from the skin and mucous membranes of the respiratory tract.
The influence of clothing - from the point of view of physiology, it is a form of thermal resistance or insulation. The effectiveness of clothes is due to the smallest volumes of air in the structure of the fabric or in the pile, where external flows do not penetrate. In this case, heat is transferred only by conduction, and air is a poor conductor of heat.
Body temperature and heat balance. If it is necessary to maintain a constant body temperature, a stable equilibrium must be achieved between heat production and heat transfer. By lowering the temperature of the medium, the constancy of body temperature can be maintained only if regulatory mechanisms provide enhanced thermogenesis in proportion to heat loss. The highest heat production provided by these mechanisms in humans corresponds to 3-5 major exchanges. This indicator characterizes the lower limit of the range of thermoregulation (0-5 ° C in the external environment for adults, 23 ° C for newborns). In case of going beyond this border, hypothermia and cold death develop.
When T о of the medium rises, the temperature equilibrium is maintained due to a decrease in metabolism, due to additional heat transfer mechanisms. The upper limit of the thermoregulation range is determined by the mechanisms of intense sweat secretion, which increases by 60% at 100% skin moisture and can reach 4 l / h.
With an increase in T about the environment, the vessels of the skin expand, the total amount of circulating blood increases due to its exit from the depot, due to the flow of water from the tissues. This contributes to an increase in heat transfer. But the main thing is evaporation. The average heat production per day during vigorous activity is about 2500-2800 kcal. To maintain T about the body at a constant level under these conditions, it is necessary to evaporate 4.5 liters of water. With heavy muscle work - up to 12 liters. in a day. Evaporation of water depends on the relative humidity in the room and is not possible at 100% humidity. Therefore, high humidity at high temperature is poorly tolerated. In this case, the sweat does not evaporate, but flows off the skin. This perspiration does not contribute to heat loss. Poorly tolerated and airtight clothes (leather, rubber), as it prevents evaporation. In completely dry air a person does not overheat in 2-3 hours at T 55 o C.
Human body temperature. The heat generated in the body is given to the surrounding space by the surface of the body. Therefore, T about the surface is less than T about the core of the body, and T about the distal part of the limbs is less than proximal. In this regard, the spatial distribution of body temperature has a complex three-dimensional shape. For example, when a lightly dressed adult is in a room with an air temperature of 20 ° C, the temperature in the deep muscles of his thigh is 35 °, in the calf muscle - 33 °, on the foot - 27 °, in rectum -37 ° C.
Oscillations of T about the body with changes in external temperature are more pronounced near the surface of the body and in the ends of the limbs. There is a “homoyothermal core” and a “poikilothermal membrane”.
The internal temperature of the body itself is not constant in either spatial or temporal terms. The differences are 0.2-1.2 about C. Even in the brain, T about the center and cortex differs by 1 about. As a rule, the highest T o is observed in the rectum (and not in the liver, as was previously thought!). In this regard, it is impossible to express T about the body with a single number. For practice, it is enough to find a certain site, T about in which can be considered representative for the entire inner layer. Clinical measurements require an easily accessible area with insignificant spatial temperature variations. In this sense, rectal temperature is preferred. A special rectal thermometer is introduced in this case at 10-15 cm. Normally, it is 37 about C.
Oral temperature (sublingual) is also used in the clinic. Usually it is 0.2-0.5 about less than rectal.
Axillary temperature (more commonly used in Russia) is equal to 36.5-36.6 about. It can serve as an indicator of the internal temperature of the body, because when the arm is firmly pressed to the chest, the temperature gradient is shifted so that the border of the core of the body reaches the axilla. However, one must wait a rather long time (10 min) until enough heat accumulates in these areas. If the surface tissues were initially cold in conditions of low ambient temperature and vasoconstriction occurred in them, then about half an hour should pass to establish the appropriate balance in these tissues.
Periodic fluctuations in internal temperature. During the day, the minimum temperature in a person is observed in the early hours, and the maximum - in the afternoon. The amplitude of the oscillations is 1 ° C. The daily (circadian) rhythm is based on the energy mechanism (biological clock), which is usually synchronized with the rotation of the earth. In conditions of travel associated with the intersection of terrestrial meridians, it takes 1-2 weeks for the temperature regime to come in line with the conditions of the new local time. Others are superimposed on circadian rhythms (menses in women, etc.).
The temperature during exercise can increase by 2 ° C or more, depending on the intensity of the load. At the same time, the average skin temperature is reduced, as due to the work of the muscles sweat is released, which cools the skin. Rectal temperature during work can reach 41 o (for marathon runners).
Skin blood vessels can respond directly to T changes - the so-called cold expansion, which is due to local heat sensitivity of the musculature of the vessels. Cold vasodilation is usually observed in the form of the following reaction. When a person falls into extreme cold, at first he has a maximum narrowing of the vessels, which manifests itself in pallor and a feeling of cold in open areas. However, after some time, blood suddenly rushes into the vessels of the cooled parts of the body, which is accompanied by redness and warming of the skin. If exposure to cold continues, events periodically recur.
It is believed that cold vasodilation is a protective mechanism that prevents frostbite, especially in people adapted to the cold. At the same time, this mechanism can accelerate the lethal outcome of general hypothermia in those who are forced to swim in cold water for a long time.
When the role of the environment is played by water, since it has a higher thermal conductivity and heat capacity than air, more heat is removed from the body by convection. If the water is in motion, then the heat is removed so quickly that at an ambient temperature of + 10 ° C even strong physical work does not allow maintaining thermal equilibrium, and hypothermia occurs. If the body is completely at rest, then to achieve thermal comfort T about water should be 35-36 about. The lower limit of the thermoneutral zone depends on the thickness of the adipose tissue.
Thermoregulation Mechanisms. Thermoregulatory reactions are reflexes carried out by the central nervous system. They occur in response to thermoreceptor irritations in the periphery and in the central nervous system itself. There are two types of thermoreceptors - some perceive heat (thermal receptors), others - cold (cold receptors). Both react with the appearance of a flash of pulses in response to adequate stimulation (a corresponding change in the temperature of the medium), and the rate of change of temperature and the magnitude of the stimulus (the difference between the initial and new temperatures in the tissues) matter.
Temperature receptors in the central nervous system are located in the preoptic zone of the anterior part of the hypothalamus, in the reticular formation of the midbrain and in the spinal cord. The presence of such receptors is proved by the appearance of a shiver in the dog when the denervated limb is cooled. Local cooling of different parts of the brain causes flashes of impulses.
Thermoregulation centers are located in the hypothalamus. Its destruction makes the animal poikilothermic. Removal of other parts of the brain does not significantly affect the processes of heat generation and heat transfer. There are cores for heat transfer and heat production. It has been shown that the processes of physical thermoregulation are mainly regulated by the anterior hypothalamus, and chemical - by the caudal nuclei. Both centers are in complex reciprocal relationships.
The executive mechanisms of the functional system for maintaining a constant body temperature (FST) are all those organs that can provide two mutually balanced normal processes of heat production and heat transfer, as well as special adaptive behavior.
The endocrine system is also involved in temperature regulation. So, thyroxine increases the metabolic rate, enhancing heat production. Adrenaline narrows blood vessels while maintaining core temperature.
Ontogenesis of thermoregulation. In non-breeding animals, newborns are not capable of thermoregulation and are actually poikilothermic (ground squirrels, hamsters, etc.). In other animals and in humans, all temoregulatory reactions (enhanced thermogenesis, vasomotorism, sweat, behavior) can be included immediately after birth to some extent. This applies even to premature babies weighing about 1000 g. It is widely believed that in newborns the immature hypothalamus is responsible for thermoregulation. However, the newborn provides its needs through non-contractile thermogenesis. Heat production in children rises by 200% without trembling.
The small size of the newborn is a disadvantage in terms of thermoregulation. The ratio between the surface and body volume in them is 3 times more than an adult, the fat layer is small. Therefore, per unit mass of heat in children generated 4-5 times more. The upper boundary of the thermoneutral zone of newborns is 32-34 °, the lower boundary is 23 ° C. Within this limited range, the newborn is able to maintain a constant temperature.
Thermal adaptation. The most important feature that occurs during thermal adaptation is a change in the intensity of sweat secretion, which can increase 3 times and reach 4 l / hour for short periods. During adaptation to high temperatures, the electrolyte content in sweat is significantly reduced in order to avoid salt loss.
One of the main adaptive changes is an increase in thirst at a given level of water loss as thermal adaptation develops. This is necessary to maintain water balance.
In addition, the threshold temperatures of the corresponding vasomotor reactions and perspiration change in different directions depending on whether acute, chronic, moderate or severe thermal effects. So, 4-6 days after a daily 2-hour heat stress with maximum sweat (sauna), the reaction of sweat and vasodilation occurs at internal temperatures, by 0.5 about lower than before. The biological significance of the threshold shift is that due to adaptation, the body temperature decreases with a given heat load, so that the body is protected from a critical increase in heart rate and blood flow - reactions that can lead to thermal fainting.
In contrast, in individuals living for a long time in the tropics (chronic moderate heat shift), the internal temperature at rest is greater, and the reactions of sweat secretion and vasodilation begin at a body temperature of 0.5 ° higher than in a temperate climate. This type of thermal adaptation is called adaptive endurance.
Hyperthermia. Hyperthermia occurs when the temperature in the armpit rises above 37 ° C. The limiting body temperature for survival is + 42 ° C (very short 43 °). Moreover, all thermoregulatory processes are extremely stressful. Under conditions of prolonged heat stress at temperatures above 40-41 ° C, severe brain damage occurs - “heat or sunstroke”. Thermal syncope with relatively mild overheating in people with impaired cardiovascular function is more dependent on circulatory failure than on thermoregulation mechanisms.
Fever. Heat develops as a result of increased heat production through tremors and maximum narrowing of blood vessels in the peripheral parts of the body, i.e. the body behaves like at a low temperature of the environment. During the recovery period, the opposite process takes place - with the help of sweat secretion and vasodilation, the body temperature drops in the same way as when a person has fever. In this case, a person can correctly respond to true changes in external temperature. The mechanism of the appearance of a febrile reaction is associated with the release of leukocyte and bacterial pyrogens to the central thermoregulation apparatus.
Cold adaptation. Fur, fat layer, brown fat - all these are types of mechanisms of adaptation to cold in different animals. For adults, these mechanisms are not characteristic, therefore, one can often hear the opinion that adults are not capable of any physiological adaptation to the cold, they should only rely on behavioral adaptation (clothes and warm homes). It is said that man is a "tropical creature" that can survive in the Arctic only because of its civilization.
However, it is shown that in cases of prolonged exposure to cold, people develop tolerance (endurance) to cold. The threshold for the development of tremors and changes in metabolic thermoregulatory reactions shifts toward lower temperatures. In this case, even moderate hypothermia may occur. Such tolerance is observed among the natives of Australia, who can spend the whole night almost naked without trembling at an ambient temperature of about 0 ° C, as well as Japanese divers who are in the water for several hours at about 10 ° C. The same applies to ours " walruses. "
It was shown that the threshold of shivering can be shifted toward lower temperatures in just a few days, during which the subjects were subjected to repeated cold stress. With prolonged exposure (Eskimos, residents of Patagonia), the intensity of the main metabolism increases by 25-50% - this is a metabolic adaptation.
Local adaptation. If the hands of a warmly dressed person are regularly cooled, then the pain in the hands is reduced. This is due to the fact that the cold expansion of blood vessels occurs at a higher room temperature.
Hypothermia. Hypothermia occurs when T armpit falls below 35 °. This happens faster when immersed in cold water. In this case, a condition similar to anesthesia is observed - the disappearance of sensitivity, the weakening of reflex reactions, a decrease in central nervous system excitability, metabolic rate, respiratory depression and heart rate, and a drop in blood pressure. This is the basis for the use of artificial hypothermia, which reduces the brain's need for oxygen, and longer bleeding is tolerated during operations on the heart and large vessels. Now there are cases of heart failure with hypothermia for 40-60 minutes (Vereshchagin). Hypothermia is stopped by rapid warming of the body. Artificial hypothermia is carried out when the thermoregulation mechanisms are turned off.
In old age, hypothermia develops due to the overshoot of temperature reactions - in the norm, Т о of the body reaches 35 о (a phenomenon opposite to fever).
A decrease in body temperature to 26-28 ° C causes death from cardiac fibrillation.
About the author of books and articles: Doctor, Leading Acupuncturist in Belarus, Candidate of Medical Sciences, Valery Dmitrievich Molostov, published 23 books in Moscow and Minsk (on neurology, acupuncture, massage, manual therapy and aging of a society as an organism), home phone: Minsk, (8 --- 107 -375-17) 240–70–75, E-mail: [email protected] My page on the Internet is www.molostov-valery.ru, where books (previously published in Moscow and Minsk) with detailed justification for the real existence of the idea described here are available.
In which organ of the human body is heat generated?
Everyone knows well that our body temperature is 36.6 degrees Celsius. But for a long time medicine did not solve the question of which organ produces heat in animals, including humans. Finally, Russian physiologists have found the answer to this question. (For example, read the research of Dr. Molostov). It turns out that heat is generated only by one organ - the skin. And acupuncture points generate heat at which acupuncturists are so fond of injecting needles. A very unexpected discovery for all of world science was research on the physiological role of acupuncture points. Not a single scientist in the world in other countries (even in the USA, Germany and France) has been engaged in such studies.
Picture 1.
This article is devoted to acupuncture points, which I can tell you a lot of interesting, as I am a professional acupuncturist by profession. See figure 1. 3478 acupuncture points were found on human skin. By the way, the number of acupuncture points in a cat, cow, elephant, ram, dog, chicken, elephant, bison is exactly the same - 3478 acupuncture points. And the animals have acupuncture points in anatomical terms exactly where they are in humans. It can be assumed that all the warm-blooded animals of the Earth have a single ancestor, for example, some marine ichthyosaurus. It is interesting to note that all “warm-blooded” animals have acupuncture points, and all cold-blooded animals (worms, frogs, fish, snakes) do not have acupuncture points on the surface of their skin. See figure 2 and 3.
Figure 2. Warmbloods.
Figure 3. Cold-blooded.
What is the mechanism of heat generation (production) in warm-blooded animals? It turns out that the energy “substance” for generating heat inside acupuncture points is the electricity that is produced in the body of the animal and man. Physiology claims that many animal and human organs play the role of small power plants. The largest generators of electricity are the heart (produces 60% of the electricity) and the brain (generates 30% of the electricity). Five sensory organs also produce electricity - this is sight, hearing, touch, smell, taste. They also work like microscopic power plants, but they transform light, sound and chemical types of energy into electrical potentials of a certain wavelength. How does the eye generate electricity? Light enters the retina of the eye, where it is transformed into a continuous stream of electrical impulses that enter through the optic nerve to the visual centers of the cerebral cortex. Other sensory organs are the same transformers (not generators) of electric energy: ears, tactile glomeruli of the skin, olfactory bulbs in the nasal mucosa, taste nerve networks in the mucous membrane of the tongue.
What is the fate of the electrons that the heart, brain and five senses produce? It turns out that there is a very strange pattern: only 5% of the electricity produced by them is absorbed by all electricity generators. The remaining 95% of the electrical energy from these organs through the intercellular space goes to the skin and to the acupuncture points. Static electricity covers the entire surface of the skin. On the surface of the skin, electricity “spreads” like the waters of the ocean spread over the surface of the Earth. Further, the acupuncture points absorb static currents that cover the skin with a “thin layer”, burning them in their “furnaces ". See figure 4. When "burning electrons" heat is generated for the human body in the amount of 36.6 degrees Celsius.
Figure 4. Electrons are absorbed by an acupuncture point.
Figure 5. Acupuncture.
Here is such a mechanism of heat production by the body of our body and the animal’s body. True, while the question remains unanswered, why does a person have a normal body temperature, which is exactly equal to plus 36.6 ° Celsius? Medical science cannot answer the question “Why does the introduction of needles into acupuncture points have a therapeutic effect on a person?” See figure 5. This problem has not yet been studied. Let's hope that in the next decade, scientists will find the answer to these questions. By the way, stopping the activity of electricity generators in the human body is the only cause of the natural death of an absolutely healthy, but very old person. It turns out that in old people it first decreases, and then the production of electric energy in the brain and heart stops. See figure 6. The death of the old organism occurs at the moment when the “power plants” in the heart (Ashof-Tavarovsky node) and in the brain (reticuloendothelial formation) cease to generate electricity.
Figure 6. The old man.
Then breathing and a heartbeat instantly stops, death comes. It is for this reason that absolutely healthy, but very old people, whose age is more than 100 years old, die. Knowing this information, you can easily extend the life of old people: you need to insert small electric generators in the heart and brain - and a person will live forever. After all, while the heartbeat and breathing continue, the body will live until then. A healthy brain, liver, kidney, stomach, intestines, and other organs can function for the millennium.
The set of physiological mechanisms that regulate body temperature is called the physiological system of thermoregulation.
The formation of heat in the body. Heat in the body is formed as a result of the oxidation of nutrients in the decay of proteins, fats and carbohydrates. The energy that was previously in them in a latent state is released, consumed, and ultimately given up by the body in the form of heat.
The place where heat is produced mainly is the muscles. This process goes even when a person is completely at rest. Minor muscle movements already contribute to a greater formation of heat, and when walking, its amount rises by 60-80%. During muscular work, heat generation increases by 4-5 times. In addition to skeletal muscles, heat generation occurs in the stomach, intestines, liver, kidneys and other organs.
The formation of heat in the body is accompanied by its release. The body loses as much heat as it forms, otherwise a person would die within a few hours.
These complex processes of regulation of the formation and release of heat by the body are called thermoregulation and are accomplished by a number of adaptive mechanisms, which we will consider now.
Regulation of heat generation and heat transfer. Body temperature remains constant due to the fact that both the formation and the release of heat are regulated in the body.
Heat is consumed by the body in various ways. The main way of heat transfer is the loss of heat by conduction, i.e., heating of the surrounding air and radiation; In addition, heat is expended with exhaled air, on the evaporation of sweat, etc.
Consequently, the temperature of the human body remains constant due to the fact that, on the one hand, the intensity of oxidative processes, i.e., the formation of heat, is regulated, and on the other, the intensity and volume of heat transfer. These two methods of regulation are called chemical and physical thermoregulation.
Chemical thermoregulation is understood to mean a change in metabolic rate under the influence of the environment. There is a certain relationship between air temperature and metabolism in the body. So, with a decrease in air temperature, the formation of heat in the body increases.
Most of the heat is generated in the muscles. Muscle trembles in the cold. With a decrease in ambient temperature, skin receptors that perceive temperature irritations are irritated: excitation occurs in them, which goes to the central nervous system and from there to the muscles, causing them to contract. Thus, the trembling and chills that we experience in the cold season or in a cold room are reflex acts that increase metabolism and, consequently, increase heat production. Increased metabolism occurs under the influence of cold, even when there is no muscle movement.
A significant amount of heat is generated in the abdominal organs - in the liver and kidneys. This can be seen by measuring the temperature of the blood flowing to the liver and flowing from it. It turns out that the temperature of the flowing blood is higher than the temperature of the flowing blood. Consequently, the blood warmed up while flowing through the liver.
With increasing air temperature, heat generation in the body decreases.
Physical thermoregulation. With an increase or decrease in the ambient temperature, not only changes in the oxidation processes occur, i.e., heat generation, but also heat transfer, moreover, with a decrease in temperature, the heat transfer decreases, and with an increase it increases.
Heat is given off by the body mainly through conduction and radiation, and only a certain part - in other ways. So, heat transfer through conducting accounts for 31% of all heat generated in the body, by radiation - 44%, when water evaporates by the skin, 10% is lost, when water evaporates by the lungs - 12%, 3% of heat is used to heat inhaled air and excreted urine and feces .
By holding the body loses heat by heating the surrounding air and objects in contact with it. Another way of heat transfer is heat radiation. When this happens
heating objects located at a distance from the body.
How does the change in heat transfer occur? An important role in heat transfer is played by the expansion and narrowing of the vessels of the skin. Everyone knows that in cold, frosty air, a person’s skin turns pale, and when the air is warm, it becomes red-hot.
The change in skin color is due to the fact that under the influence of cold blood vessels, primarily arterioles, narrow. As a result, the blood flow to the surface of the body decreases, and therefore, the heat transfer through conduction and radiation also decreases.
Under the influence of heat, the vessels of the skin expand, the blood flows abundantly to the surface of the body, which helps to increase the conductivity and radiation of heat. In this way, heat is released to the environment only when the air temperature is below body temperature. The smaller the difference between skin temperature and air temperature, the less heat is given to the environment. In this case, sweating plays a significant role. With the evaporation of 1 g of sweat, 0.58 kcal is lost. Since sweating and evaporation occur continuously at any temperature, the number of calories that a person loses in this case depends on the intensity of sweating. At an average temperature per day, a person loses about 800 ml of sweat. With the loss of this amount of sweat, 450-500 kcal is consumed. With an increase in temperature, sweat secretion increases and sometimes reaches several liters.
Most sweat is released when the air temperature is equal to or higher than body temperature. Under these conditions, heat transfer by conducting radiation is not possible, and therefore it is consumed mainly through sweating.
In hot countries or hot rooms where the air temperature is 37 ° C or slightly higher, heat is only given off by evaporation. In this case, up to 4.5 liters of sweat are released in a person during the day, which ensures a return of 2400-2800 kcal.
A large amount of sweat is lost during physical work, and this happens at any temperature. It is estimated that during especially hard work a person loses up to 9 liters of sweat per day and, thus, gives up to 5000 kcal by evaporation.
Sweating is largely dependent on air saturation with water vapor. Under equal temperature conditions, greater evaporation of sweat, and hence greater heat loss, is ensured under conditions of low water vapor content in the air. Therefore, the heat is easily tolerated in places where the air is drier.
Sweat is impeded by impervious clothing (rubber, anti-dusting suit, etc.). A person in such clothes sweats even in the cold, as a constant layer of air is created around him, which is not updated due to lack of ventilation. This layer of air is saturated with vapors, which prevents further evaporation of sweat. Therefore, a long stay in these costumes is impossible, as it causes an increase in body temperature.
In hot countries, hot shops, during long trips, a person loses a lot of sweat. Thirst appears, but water does not quench it; on the contrary, the more water a person drinks, the more he sweats and the more thirst becomes.
At the same time, then salts are lost, so there is a need to replenish not only the loss of water, but also the loss of salts. To this end, 0.5% of sodium chloride is added to drinking water. Such slightly salted water is given in hot shops, during long trips, etc. It quenches thirst and improves well-being.
Some role in heat transfer is played by respiration. Heat is consumed by the evaporation of water by the lungs and partly by the warming of the inhaled air. In the cold, a reflex slowdown of breathing occurs, and at high temperature, breathing quickens, so-called thermal shortness of breath occurs.
For better heat transfer, air circulation is of great importance. When the air is in motion, a constant layer of heated and vapor-saturated air is not created near the body. This is the meaning of fans, fanning, etc. Clothing, on the other hand, creates a fixed layer of air and thereby hinders heat transfer.
Heat is prevented by subcutaneous fat. The thicker the layer of fat, the worse it is carried out. Therefore, people with a thick fat layer in the subcutaneous tissue tolerate cold more easily than thin ones.
The human body temperature is constant. It is measured in the armpit or in the rectum (in infants). The average temperature in the armpit ranges from 36.5-36.9 ° C, in the rectum - slightly higher (37.2-37.5 C). The temperature of the internal organs is higher than the average body temperature, for example, the temperature of the liver is 38-38.5 ° C. The human body temperature fluctuates during the day. It is lowest at 3-4 hours
nights, then gradually increases, reaching the highest point at 16 hours, and begins to decline again. Temperature fluctuations occur within 0.5 ° C of the average value.
Body temperature can increase sharply with muscle work and reach 38-39 ° C or even up to 40 ° C. Upon termination of the work, it quickly falls and reaches a normal value.
The constancy of body temperature is supported by the two mechanisms already described: chemical and physical thermoregulation. However, the capabilities of the human body are limited, and under certain conditions, these mechanisms are insufficient. Then the constancy of temperature is violated and either its increase or decrease is observed. An increase in temperature above normal is called fever. Fever can occur because heat generation increases in the absence of changes in heat transfer, or, conversely, heat generation remains unchanged, and heat transfer decreases.
Lowering the temperature to 32-33 ° C, as well as increasing it above 42-43 ° C, leads to death.
Centers of thermoregulation. The thermoregulation center, called the heat center, is located in the diencephalon. Its activity is determined by two factors: blood temperature and reflex effects. If the temperature of the blood washing the diencephalon is elevated, the center of thermoregulation is excited, and changes occur in the body's activity that contribute to its decrease. With a decrease in blood temperature, the heat-generating center reacts so that the intensity of the processes contributing to an increase in temperature increases.
Another way of arousal is reflex effects. Under the influence of temperature fluctuations on the human skin, excitation occurs in the receptors, which enters the heat center. From there, the impulses go already to the organs associated with heat generation (muscles, liver, etc.) and with heat transfer, and cause a change in their activity. Excitation from the centers of thermoregulation to the organs of heat generation and heat transfer is transmitted through the sympathetic nervous system.
An exceptionally large role in thermoregulation is played by the cerebral cortex. Under normal conditions, the process of heat generation and heat transfer is under its influence.
Thermocomfort temperature for a person in the air is usually + 19 ° С, in water - + 34 ° С. At these temperatures, the thermoregulation system does not turn on.
To maintain a constant body temperature of 36.6 ° C, a person needs to spend 200 kcal per day.
A decrease in body temperature even by 0.1 ° leads to a decrease in immunity.
Cooling in nature, as a rule, are very sharp. To tolerate climatic "surprises" painlessly, a person must be tempered.
As you know, there are three levels of the body's reaction to stimuli of different strengths: training, activation, and stress. Great cold is stress, including mental. If you are afraid of hypothermia in advance, freeze and wrap yourself long before going to the cold, then you need to urgently temper not only the body, but also the nerves. The survival experiment showed that people die, as a rule, not from the cold, but from fear of it.
The tempering attitude sets a strategic task for a person: to make friends with the cold for life. “Border of pleasure” allows you to solve a tactical problem: to dose the cold or heat. If the strategy induces hardening, then the tactic controls the load during hardening. Moreover, it does this in accordance with the individual physiological characteristics of the body and, of course, taking into account specific climatic conditions.
The need for a psychological mood for hardening, interest in it is the most important principle. You can not spare time for it.
The essence of hardening is the training of thermoregulation processes, which include heat production and heat transfer. Cooling stimulates, on the one hand, an increase in heat production in the body, and on the other hand, the desire to preserve it, not to give it out. Training teaches the body to clearly respond to cold, quickly and actively respond to low ambient temperatures with increased heat production and reduced heat transfer. Thus, despite the cold, normal body temperature is maintained. In a non-hardened person, the thermoregulation mechanisms are weaker, body temperature decreases, which leads to weakened immune defenses and increased activity of pathogenic microorganisms. As a result of this - colds, flu, etc., which not only bring out of working condition, but also accumulate harmful effects, which inevitably undermines the overall potential of the body and reduces its vitality.
Heat value
Heat sources
Heat production and heat supply
Heat use
New heat supply technologies
Heat value
Heat is one of the sources of life on Earth. Thanks to fire, the emergence and development of human society became possible. From ancient times to this day, heat sources have served us faithfully. Despite the hitherto unprecedented level of technological development, a person, like many thousands of years ago, still needs heat. With a growing world population, the need for heat is increasing.
Heat is among the most important resources of the human environment. It is necessary for man to maintain his own life. Heat is also required for technologies without which a modern person does not imagine his existence.
Heat sources
The oldest heat source is the sun. Later at the disposal of man was fire. On its basis, man created a technology for producing heat from fossil fuels.
Relatively recently, nuclear technology began to be used to produce heat. However, the burning of fossil fuels is still the main way of generating heat.
Heat production and heat supply
Developing technology, a person learned to produce heat in large volumes and transfer it over fairly considerable distances. Heat for large cities is produced at large thermal power plants. On the other hand, there are still many consumers who are supplied with heat by small and medium-sized boiler houses. In rural areas, households are heated by domestic boilers and stoves.
Heat production technologies make a significant contribution to environmental pollution. Burning fuel, a person throws a large amount of harmful substances into the surrounding air.
Heat use
In general, a person produces much more heat than he uses for his own benefit. We simply dissipate a lot of heat in the surrounding air.
Heat is lost
due to imperfections in heat production technologies,
when transporting heat through heat pipes,
due to imperfection of heating systems,
due to housing imperfections,
due to imperfect ventilation of buildings,
when removing "excess" heat in various technological processes,
when burning industrial waste,
with vehicle exhaust gases on internal combustion engines.
To describe the state of affairs in the production and consumption of heat by a person, the word wasteful is well suited. An example, I would say, of notorious wastefulness is the burning of associated gas in oil fields.
New heat supply technologies
Human society spends a lot of effort and money to generate heat:
produces fuel deep underground;
transports fuel from deposits to enterprises and housing;
builds plants for heat;
builds heat networks for heat distribution.
Perhaps you should think: is everything reasonable here, is everything justified?
The so-called technical and economic advantages of modern heat supply systems are inherently momentary. They are associated with significant environmental pollution and non-rational use of resources.
There is heat that does not need to be generated. This is the heat of the sun. It must be used.
One of the ultimate goals of heat supply technology is the production and delivery of hot water. Have you ever used a summer shower? A container with a crane installed in an open place under the rays of the sun. A very simple and affordable way to supply warm (even hot) water. What prevents using it?
With the help of heat pumps, a person uses the heat of the Earth. For a heat pump, fuel is not needed; an extended heating main with its heat losses is not needed. The amount of electricity needed to operate the heat pump is relatively small.
The advantages of the most modern and advanced technology will be nullified if its fruits are used stupidly. Why produce heat away from consumers, transport it, then distribute it to homes, heating the Earth and the surrounding air along the road?
Distributed heat production should be developed as close as possible to places of consumption, or even combined with them. A method of producing heat called cogeneration has long been known. Cogeneration plants produce electricity, heat and cold. For the fruitful use of this technology, it is necessary to develop the human environment as a single system of resources and technologies.
It seems that to create new heating technologies
review existing technologies
try to get away from their shortcomings,
gather on a single basis for interaction and complement each other,
make full use of their merits.
This implies understanding.
Taking medications that cause an increase in body temperature.
Body temperature is most often measured with a medical mercury thermometer. In 1714, the Polish-German physicist Daniel Gabriel Fahrenheit produced a mercury thermometer, and in 1742 the Swedish scientist Andres Celsius proposed a scale for a mercury thermometer graduated from 34 to 42 ° C with divisions of 0.1 ° C.
Medical devices for measuring body temperature.
▪ The mercury thermometer is a glass flask with a capillary that contains mercury (2 grams). It is designed so that the mercury column when heating the tank shows a figure corresponding to body temperature.
▪ Ear infrared thermometer. The time for changing the temperature with an ear infrared thermometer is one to four seconds.
▪ Digital thermometer. The measurement of body temperature is approximately one to three seconds. Such a thermometer is the safest.
▪ Electrothermometer. Using an electrothermometer, you can measure the temperature in the body cavities: esophagus, stomach, intestines, etc.
▪ The radio capsule is equipped with a sensor that transmits signals.
▪ Thermal imaging and thermography make it possible to determine the increase in the intensity of thermal radiation that occurs when there is a change in blood circulation and metabolic processes in individual organs and tissues during their pathology.
Body temperature is measured 2 times a day: in the morning on an empty stomach (from 6 hours to 7 hours) and in the evening before the last meal (from 17 hours to 18 hours) for 10 minutes.
Body temperature measurement every 3 hours - called the temperature profile.
The thermometer readings are entered in the temperature sheet, where the dots indicate the morning and evening temperature. According to the marks, a temperature curve is drawn over several days.
Physiological Thermoregulation System (from the Greek. "thermo" - heat, "regulation" - control) - This is a set of physiological mechanisms that regulate body temperature.
Thermoregulation can be carried out in two ways:
Ø due to changes in the rate of heat production (heat generation)
Ø due to changes in the rate of heat transfer (heat transfer)
The processes of heat generation and release are carried out under the control of the nervous system and endocrine glands.
The formation of heat in the body.
The exchange of thermal energy between the body and the environment is called heat transfer.
For the flow of vital processes in the body requires energy. It is formed as a result of the breakdown of chemicals (mainly carbohydrates and fats) that we consume with food. The energy that was previously hidden in them is released, consumed, and, ultimately, given up by the body in the form of heat. Most of the heat is generated in the muscles.
On the periphery (skin, internal organs) they have cold and thermal receptors that perceive the temperature fluctuations of the external environment. So, when the ambient temperature decreases, skin receptors are irritated, and excitement occurs in them, which goes to the central nervous system and from there to the muscles, causing them to contract. Thus, the trembling and chills that we experience in the cold season or in a cold room are reflex acts that enhance metabolic rate and, consequently, increase heat production. This process occurs even when a person is completely at rest, the temperature of muscle tissue at rest and at work can fluctuate within 7 ° C. During muscle work, heat generation increases by 4-5 times. The temperature of the internal organs: brain, heart, glands of internal secretion, stomach, intestines, liver, kidneys and other organs depends on the intensity of metabolic processes. The liver is the hottest organ in the body: the temperature in the liver tissue is 38-38.5 ° C. The temperature in the rectum is 37-37.7 ° C. However, it can fluctuate depending on the presence of feces in it, and its blood supply mucous membrane and other causes. The lowest skin temperature is observed on the hands and feet 24-28 ° C. A relatively uniform distribution of heat in the body is provided by blood. Passing through the brain, heart, liver, and other "warm" organs, the blood heats up, while cooling them. And, passing through the superficial muscles, skin and other "cold" organs, the blood cools, while warming them. However, the surface temperature of the body remains slightly lower than the temperature inside the body. The formation of heat in the body is accompanied by its release. The body loses as much heat as it forms in it, otherwise the person died within a few hours. If there were no heat transfer mechanisms, the temperature of an adult's body at rest would rise by 1.24 ° C every hour.
The constancy of body temperature is called isothermy. To maintain a constant body temperature of 36.6 ° C, a person needs to spend 200 kcal per day. A decrease in body temperature even by 0.1 ° leads to a decrease in immunity.
Chemical thermoregulation - the process of heat in the body , due to an increase in the intensity of metabolic processes in tissues, it is controlled by the posterior parts of the hypothalamus.
Physical thermoregulationcontrolled by the anterior hypothalamus, and are the center of heat transfer from the body to the environment through convection (heat conduction), radiation (heat radiation) and water evaporation.
Convection - provides heat transfer to air or liquid adjacent to the body. Heat transfer is more intense, the greater the temperature difference between the surface of the body and the surrounding air.
Heat transfer increases with the movement of air, such as in wind. The intensity of heat transfer largely depends on the thermal conductivity of the environment. In water, heat transfer occurs faster than in air. Clothing reduces or even stops heat conduction.
Radiation -heat is released from the body by infrared radiation from the surface of the body. Due to this, the body loses the bulk of the heat. The intensity of heat conduction and heat radiation is largely determined by the temperature of the skin. Heat transfer is regulated by a reflex change in the lumen of the skin vessels. When the ambient temperature rises, the arterioles and capillaries expand, the skin becomes warm and red. This increases the processes of heat conduction and heat radiation. With a decrease in air temperature, the arterioles and capillaries of the skin narrow. The skin becomes pale, the amount of blood flowing through its blood vessels decreases. This leads to a decrease in its temperature, heat transfer decreases, and the body retains heat.
Water evaporation from the surface of the body (2/3 of moisture), and in the process of breathing (1/3 of moisture). Evaporation of water from the surface of the body occurs when sweat is released. Even with the complete absence of visible sweating through the skin, up to 0.5 l of water evaporates per day - invisible sweating. On average, a person loses about 0.8 liters of sweat per day, and with it 500 kcal of heat. In hot countries, in hot shops, a person loses a large amount of liquid with sweat. At t ° up to 50 ° C a person loses up to 12 liters of sweat per day. In this case, a feeling of thirst appears, which is not satisfied with the intake of water. This is due to the fact that then a large amount of mineral salts is lost. To this end, 0.5% of sodium chloride is added to drinking water. It quenches thirst and improves well-being.
Heat is prevented by subcutaneous fat. The thicker the layer of fat, the worse it is carried out. Therefore, people with a thick fat layer in the subcutaneous tissue tolerate cold more easily than thin ones. The evaporation of 1 liter of sweat in a person weighing 75 kg can lower body temperature by 10 ° C.
In a state of relative rest, an adult emits 15% of heat to the environment through heat conduction, about 66% through heat radiation and 19% due to the evaporation of water.
Fever (febris), or fever - the general reaction of the body to any irritation, characterized by an increase in body temperature above 37 ° C, due to a violation of heat regulation. With fever, heat generation prevails over heat transfer. One of the causes of fever is infection. Bacteria or their toxins, circulating in the blood, cause a violation of heat regulation.
Types of Fever
Depending on the degree of temperature increase, the following types of fevers are distinguished:
§ low-grade fever - 37-38 ° С:
a) small subfebrile condition - 37-37.5 ° C;
b) large subfebrile condition - 37.5-38 ° С;
§ moderate fever - 38-39 ° С;
§ high fever - 39-40 ° C;
§ excessively high fever - over 40 ° C;
§ hyperpyretic - 41-42 ° C, it is accompanied by severe nervous phenomena and is itself life-threatening.
Types of fever
According to the nature of fluctuations in body temperature during the day, the following types of fevers are distinguished:
persistent fever - long, high, usually not less than 39 °, temperature with daily fluctuations of not more than 1 °; characteristic of typhus, typhoid fever and lobar pneumonia (Fig. 1).
Fig. 1. Persistent fever
laxative (remitting) fever, high temperature, daily temperature fluctuations exceed 1-2 ° C, with the morning minimum above 37 ° C; characteristic of tuberculosis, purulent diseases, focal pneumonia, in stage III of typhoid fever (Fig. 2).
Fig. 2. Laxing fever
intermittent (intermittent) fever (febris intermittens) - the temperature rises to З9 ° С - 40 ° С and higher, followed by a rapid drop to normal or slightly below normal. Fluctuations are repeated every 1-2 or 3 days, observed with malaria (Fig. 3).
Fig. 3. Intermittent fever
wave-like (undulating) fever (febris undulans) - it is characterized by periodic increases in temperature, and then a decrease in the level to normal numbers. Such "waves" follow one after another for a long time; characteristic for brucellosis, lymphogranulomatosis (Fig. 4).
Fig. 4. Wave-like fever
relapse fever (febris recurrens) - the correct alternation of increase and decrease in temperature for several days. It is characteristic for relapsing fever (Fig. 5).
Fig. 5. Relapsing fever
wrong (atypical or irregular) fever (febris irregularis) irregular diurnal temperature fluctuations of various sizes and durations are often observed with rheumatism, endocarditis, sepsis, tuberculosis, with flu, diphtheria, dysentery, pleurisy (Fig. 6).
Fig. 6. Wrong fever
draining (hectic) fever (febris hectica) is characterized by large (2-4 ° C) diurnal temperature fluctuations, which alternate with its falling to normal and below. A rise in temperature is accompanied by chills, and a drop is accompanied by profuse sweating, typical of severe pulmonary tuberculosis, suppuration, and sepsis (Fig. 7).
reverse (perverted) fever (febris inversus) - morning temperature is higher than evening; sometimes observed with sepsis, tuberculosis, brucellosis (Fig. 7).
Fig. 7. a - hectic fever