The set of physiological mechanisms that regulate body temperature is called the physiological thermoregulation system.

Heat formation in the body. Heat in the body is formed as a result of the oxidation of nutrients during the breakdown of proteins, fats and carbohydrates. The energy that was previously hidden in them is released, consumed and ultimately given back to the body in the form of heat.
The place where heat production mainly occurs is the muscles. This process occurs even when a person is completely at rest. Minor muscle movements already contribute to greater heat formation, and when walking, its amount increases by 60-80%. During muscle work, heat generation increases 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 generates, otherwise the 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 carried out by a number of adaptive mechanisms, which we will now consider.
Regulation of heat generation and heat transfer. Body temperature remains constant due to the fact that both the formation and release of heat are regulated in the body.
Heat is consumed by the body in different ways. The main way of heat transfer is heat loss by conduction, i.e. heating of the surrounding air and radiation; in addition, heat is consumed with exhaled air, for the evaporation of sweat, etc.
Consequently, the human body temperature remains constant due to the fact that, on the one hand, the intensity of oxidative processes, i.e., heat formation, 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 as a change in metabolic rate under the influence of environment. There is a certain relationship between air temperature and metabolism in the body. Thus, as the air temperature decreases, the formation of heat in the body increases.
Most of the heat is generated in the muscles. In the cold, muscles tremble. When the ambient temperature drops, the skin receptors that perceive temperature stimulation are irritated: an excitation arises 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 during the cold season or in a cold room are reflex acts that contribute to increased metabolism and, consequently, increased heat production. Increased metabolism occurs under the influence of cold, even when there is no muscle movement.
A significant amount of heat is also generated in the abdominal organs - in the liver and kidneys. This can be observed by measuring the temperature of the blood flowing to and from the liver. It turns out that the temperature of the outflowing blood is higher than the temperature of the inflowing blood. Consequently, the blood became warmer as it flowed through the liver.
As air temperature rises, heat generation in the body decreases.
Physical thermoregulation. When the ambient temperature increases or decreases, not only a change in oxidative processes occurs, i.e., heat generation, but also heat transfer, and when the temperature decreases, the heat transfer decreases, and when it increases, it increases.
Heat is given off by the body mainly through conduction and radiation, and only some part through other ways. Thus, heat transfer by conduction is 31% of the total heat generated in the body, by radiation - 44%, with the evaporation of water by the skin, 10% is lost, with the evaporation of water by the lungs - 12%, 3% of the heat is spent on heating the inhaled air and excreted urine and feces .
Through conduction, the body loses heat by heating the surrounding air and objects with which it comes into contact. Another way of heat transfer is heat radiation. This happens
heating objects located at some distance from the body.
How does the change in heat transfer occur? The expansion and contraction of skin blood vessels plays a major role in heat transfer. Everyone knows that in cold, frosty air, a person’s skin turns pale, and when the air is heated and hot, it turns red.
The change in skin color is due to the fact that under the influence of cold, blood vessels, primarily arterioles, narrow. As a result, blood flow to the surface of the body decreases, and consequently, heat transfer by conduction and radiation decreases.
Under the influence of heat, the blood vessels of the skin dilate, blood flows abundantly to the surface of the body, which enhances the conduction and radiation of heat. In this way, heat is released into the environment only when the air temperature is lower than body temperature. The smaller the difference between skin temperature and air temperature, the less heat is released into the environment. In this case, sweating plays a significant role. When 1 g of sweat evaporates, 0.58 kcal is lost. Since sweating and evaporation occurs continuously at any temperature, the number of calories that a person loses depends on the intensity of sweating. At average temperature, a person loses about 800 ml of sweat per day. Losing this amount of sweat consumes 450-500 kcal. As the temperature rises, sweat production increases and sometimes reaches several liters.
The greatest amount of sweat is produced in cases where the air temperature is equal to or higher than body temperature. Under these conditions, heat transfer by radiation is impossible, 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 released only by evaporation. At the same time, a person produces up to 4.5 liters of sweat during the day, which provides 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 particularly hard work a person loses up to 9 liters of sweat per day and thus gives up up to 5000 kcal through evaporation.
Sweating largely depends on the saturation of air with water vapor. Under equal temperature conditions, greater evaporation of sweat, and therefore greater heat loss, is ensured under conditions of low water vapor content in the air. Therefore, heat is easily tolerated in places where the air is drier.
The evaporation of sweat is prevented by impermeable clothing (rubber, anti-spirit suit, etc.). A person wearing such clothes sweats even in the cold, since a constant layer of air is created around him, which is not renewed due to the lack of ventilation. This layer of air is saturated with vapor, which prevents further evaporation of sweat. Therefore, long-term stay in these suits is impossible, as it causes an increase in body temperature.
In hot countries, hot workshops, and during long hikes, a person loses large number sweat. Thirst appears, but water does not quench it; on the contrary, the more water a person drinks, the more he sweats and the stronger his thirst becomes.
At the same time as sweat, 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, to drinking water add 0.5% table salt. This slightly salted water is given in hot shops, during long hikes, etc. It quenches thirst and improves well-being.
Breathing plays some role in heat transfer. Heat is spent on the evaporation of water by the lungs and partly on warming the inhaled air. In the cold, a reflex slowing of breathing occurs, and at high temperatures, breathing becomes more frequent, 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 importance of fans, fanning, etc. Clothing creates a stationary layer of air and thereby impedes heat transfer.
Subcutaneous fat prevents heat transfer. The thicker the layer of fat, the worse it is performed. Therefore, people with a thick layer of fat in the subcutaneous tissue tolerate cold more easily than thin people.
The human body temperature is constant. It is measured in the armpit or 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 liver temperature is 38-38.5°C. The human body temperature fluctuates throughout the day. It is lowest at 3-4 hours
nights, then gradually increases, reaching its highest point at 16:00, and begins to decrease again. Temperature fluctuations occur within 0.5°C of the average value.
Body temperature can rise sharply during muscular work and reach 38-39°C or even 40°C. After the work stops, it quickly falls and reaches a normal value.
The constancy of body temperature is maintained by the two mechanisms already described: chemical and physical thermoregulation. However, the capabilities of the human body are limited, and under some conditions these mechanisms are insufficient. Then the constancy of temperature is disrupted and either an increase or decrease is observed. An increase in temperature above normal is called fever. Fever can occur because heat production increases without changes in heat transfer, or, conversely, heat generation remains unchanged, and heat transfer decreases.
A decrease in temperature to 32-33°C, as well as an increase above 42-43°C, leads to death.
Thermoregulation centers. The thermoregulation center, called the thermal 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 increased, then the thermoregulation center is excited, and changes occur in the body’s activity that contribute to its decrease. When the blood temperature decreases, the heat generation center reacts in such a way that the intensity of the processes that contribute to the increase in temperature increases.
Another method of excitation is reflex effects. When exposed to temperature fluctuations on human skin, excitation occurs in the receptors, which enters the thermal center. From there, the impulses go 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 production and heat transfer is transmitted through the sympathetic nervous system.
The cerebral cortex plays an extremely important role in thermoregulation. Under normal conditions, the process of heat generation and heat transfer is under its influence.
The thermocomfortable temperature for a person in air is usually +19°C, in water - +34°C. At such 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.
Cold snaps in nature are usually very sharp. In order to safely endure climatic “surprises”, a person must harden himself.
As you know, there are three levels of the body’s response to stimuli of different strengths: training, activation and stress. Extreme cold means stress, including mental stress. If you are afraid of hypothermia in advance, freeze and bundle up long before going out into the cold, then you urgently need to harden not only your body, but also your nerves. The survival experiment showed that people die, as a rule, not from the cold, but from the fear of it.
The mood for hardening sets a person a strategic task: to make friends with the cold for life. “The Boundary of Pleasure” allows you to solve a tactical problem: dose cold or heat. If the strategy encourages hardening, then the tactics control 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 attitude toward hardening and interest in it is the most important principle. You shouldn’t waste time on 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, the desire to preserve it and not give it away. Training teaches the body to clearly react to cold, to quickly and actively respond to low environmental temperatures with increased heat production and reduced heat transfer. Thus, despite the cold, the normal body temperature is maintained. In an unhardened person, the mechanisms of thermoregulation work weaker, body temperature decreases, which leads to a weakening of the immune defense and increased activity of pathogenic microorganisms. As a result of this, colds, flu, etc., which not only disable the working condition, but also accumulate harmful effects, which inevitably undermines the overall potential of the body and reduces its vitality.

heat generation

Human life processes are accompanied by continuous heat generation in the body and heat release to the environment.

Human body is a self-regulating system, the physiological mechanism of which, in order to maintain a constant body temperature, is aimed at ensuring that the amount of heat generated corresponds to heat production) the amount of heat given off to the external environment ( heat transfer) . Under normal conditions heat production equal to heat transfer.

Heat generation in the human body occurs as a result of continuously occurring exothermic reactions. These reactions occur in all organs and tissues, but not with equal intensity. In tissues and organs that perform active work (muscle tissue, liver, kidneys), more heat is released than in less active ones ( connective tissue, bones, cartilage).

Heat loss from organs depends to a large extent on their location: superficially located organs, for example, skin, skeletal muscles, give off more heat and cool more strongly than internal organs, which are more protected from cooling.

Heat production and heat transfer are caused by the activity of the central nervous system, which regulates metabolism, blood circulation, sweating and the activity of skeletal muscles.

Heat in the human body is produced as a result of energy transformations in living cells. Heat generation is related to:

With the continuously occurring biochemical synthesis of proteins and other organic compounds;

With osmotic work (ion transport);

With the mechanical work of muscles (cardiac muscle, smooth muscles various organs, skeletal muscles).

In the human body, which is in a state of relative physical rest, 50% of the heat is generated in the abdominal organs (mainly in the liver); 20% - in skeletal muscles and the central nervous system; 10% - during the work of the respiratory and circulatory organs. Part of the energy generated in the body during physical work is spent on external work. The main part goes into thermal Q T.P . .

Core body temperature(core) is constant due to regulation of the intensity of heat production and heat transfer depending on temperature external environment. A person's body temperature is usually judged based on its measurement in the armpit. Here, the temperature in a healthy person is 36.5–36.9 o C. The temperature in the rectum is often measured, where it is higher than in the armpit, and in a healthy person is on average 37.2–37.5 o C.

Body temperature does not remain constant, but fluctuates during the day within the range of 0.5–0.7 o C. Rest and sleep lower the temperature, muscle activity increases it. The maximum body temperature is observed at 16–18 o’clock, the minimum – at 3–4 o’clock in the morning. For workers who work long night shifts, temperature fluctuations may be the opposite of those indicated above.

Skin temperature of a person, when exposed to external conditions, changes over a relatively wide range.

Condition of comfort is the thermal balance of the human body and the environment. Factors influencing the state of thermal equilibrium of the body are:

Ambient temperature (walls and surfaces, surrounding objects);

Temperature, speed, air humidity;

The nature of the clothing;

The amount of human heat production.

Heat production value depends on the age, gender of the person, his diet, muscle activity etc.

Basic (standard) exchange(OO) of the human body is the amount of energy consumed by the human body at complete muscular rest, before eating at an external temperature corresponding to the minimum activity of the thermoregulatory mechanism. Basic metabolism depends on the functional state of a person, gender, age, weight and is calculated in calories per unit of weight or unit of body surface.

For an adult, the average value of OO is 1 kcal/kg/hour. Hence, for an adult man weighing 70 kg, the amount of energy consumption OO is about 1700 kcal/day, for women - about 1500 kcal/day.

The process of heat transfer by the human body (heat transfer) is carried out:

Radiation (radiation) – 43 - 50%;

Convection (movement) – 25 - 30%;

Evaporation from the surface of the skin and lungs – 23 - 29%;

Heating food – 1 - 2%;

Heating of air in the lungs – 1 – 1.5%;

Heat loss with emissions - less than 1%.;

Conduction (conduction) is a very insignificant value, because The thermal conductivity coefficient of still air is very small.

Heat conduction conduction carried out from the surface of the human body to solid objects or environmental materials in contact with it.

Heat transfer in this case occurs according to Fourier’s law:

Where Q COND – heat transfer passing through a wall with an area S over time τ, W;

S– surface area of ​​contact between a person and an object, m2;

t 1 – temperature of the inner wall (clothing package), o C;

t 2 - temperature of the outer (cold) side, o C;

λ – thermal conductivity coefficient of a clothing package, W/m∙ o C;

δ – thickness of the clothing package, m.

From the presented equation it is clear that heat transfer by conduction increases with a decrease in the temperature of the object with which a person comes into contact, with an increase in the contact area and a decrease in the thickness of the clothing package.

Heat Transfer convection carried out from the surface of a person’s body or clothing to the air moving around him. To calculate heat transfer by convection, you can use Newton's law:

Q CONV = α CONV. S (t OD – t V),

Where α CONV – heat transfer coefficient by convection, W/(m∙ o C), depends on the shape of the body and the speed of air movement;

S – body surface area, m2;

t OD – body surface temperature (clothing);

t B – air temperature, o C.

Heat loss by convection from the surface of clothing covering the body is expressed by the formula

,

Where S –

– the ratio of the surface area of ​​the body covered by clothing to the surface area of ​​the exposed parts of the body;

α CONV – heat transfer coefficient by convection, W/(m∙ o C);

t OD –

t B – air temperature, o C.

Heat transfer by radiation is the transfer of heat in the form of radiant energy from the surface of the human body to surrounding surfaces that have a lower temperature, or into the surrounding space. The amount of heat given off by radiation depends on the temperature of the surface of the body (clothing), the temperature of the walls and surfaces surrounding the body.

Radiation human body characterized by a wavelength from 5 to 40 microns, and human skin absorbs infrared rays as a completely black body.

Under operating conditions of clothing, there is practically a small difference in temperature between the body and clothing. In this case, the equation for determining the amount of heat transferred by radiation is presented in the form

Q RAD = α RAD · S RAD (t 1 – t 2),

Where α RAD– emissivity coefficient (heat transfer by radiation), W/(m 2 ∙ o C);

S RAD – surface area of ​​the human body involved in radiation heat exchange, m 2 ;

t 1 - surface temperature of the human body (clothing);

t 2 – surface temperature of surrounding bodies, o C.

Emissivity α RAD depends on the temperature of the surface of the human body (clothing) and the temperature of surrounding objects. Not the entire surface of the human body participates in radiation heat exchange, because some parts of the body are mutually irradiated and do not take part in heat exchange. Radiation heat exchange involves 74-75% of the human body area in a sitting position and 77-85% in a standing position.

The surface area of ​​a person's body depends on his height and weight and can be determined from the graph presented in Figure 1.1.

Fig.1.1. Dependence of body surface area on height and body weight

person

In Figure 1.2. The dependence of the surface area of ​​the human body involved in radiation heat exchange on height and mass is shown.

Fig.1.2. Dependence of the surface area of ​​the human body involved

in radiation heat transfer, from height and mass

Heat loss from the body surface dressed man are determined by the equation

Where S – surface area of ​​the body of an undressed person, m 2 ;

S OD - body surface area covered with clothing, m2;

S O - open body surface area, m2;

t OD - clothing surface temperature, °C;

t SR – average radiation temperature, o C.

Heat transfer by evaporation carried out by evaporation of diffusion moisture and sweat. Diffusion moisture(imperceptible perspiration) is lost from the surface of human skin and the upper respiratory tract under conditions of thermal comfort and cooling in a state of relative physical rest. In comfortable conditions (dry cooling), the amount of steam released from 1 m2 of the surface of the human body is 23 g/hour, and from the entire surface - 40-42 g/hour. In this case, 1/3 comes from heat loss by evaporation from the upper respiratory tract and 2/3 from the surface of the skin.

Heat loss by evaporation from the upper respiratory tract determined by the equation

Q EXP.BREATH = 14.9 · 10 -6 · Q T.P. · (1880 – R A),

Where Q T.P. – human heat production W ,

R A – partial pressure of vapor in ambient air, Pa.

Moisture evaporation rate from the body surface depends on:

Differences in partial vapor pressures in the boundary layer near the skin and in the surrounding air,

Air speed;

Air and vapor permeability of clothing;

Surface area moistened by sweat.

Moisturized body surface area can be calculated using the formula

,

Where R US.K – saturated vapor pressure at skin temperature above wet areas of the skin.

Heat loss by evaporation of diffusion moisture from the skin surface can be determined by the equation

Q ISP.D = 3.06 10 -3 S(256t K – 3360 – R A),

Where R A - partial pressure of vapor in the ambient air;

t K – skin temperature, o C.

Amount of sweating person is determined by:

The level of physical activity of a person ;

Meteorological conditions;

The degree of compliance of clothing with operating conditions.

Maximum possible heat loss by evaporation of sweat Quse.p. can be determined by the equation

Q ISP.P = 17.3. (E F – e) . (0.5 + √v),

Where E F – maximum possible water vapor pressure at human skin temperature, mm Hg;

e– water vapor pressure in the air ( absolute humidity), mmHg, are determined from tabular data depending on temperature and relative humidity.

The difference (Eph – e) called physiological deficiency of saturation and is determined depending on the speed of air movement and the possible amount of sweat evaporation R from the surface of the human body.

Comfortable thermal sensations can be observed only at certain ratios of heat transfer by evaporation and heat transfer by heat flow (Q CONV + Q RAD + Q COND). Comfortable level of evaporative heat transfer Q ISP.P.K, W, determined from the equation

.

Heat transfer during breathing constitutes a small proportion of total heat loss and increases with increasing energy consumption and decreasing air temperature.

Heat loss for heating inhaled air Q BREATH.N, W can be determined from the equation

Q BREATH.H = 0.0012. Q E.T. (34 – t V),

Where t V – ambient air temperature, o C;

34 – average temperature of exhaled air, o C.

According to A.I. Beketov, the temperature of exhaled air is recommended to be taken depending on the temperature of inhaled air (Table 1.1.).

About the author of books and articles: doctor, leading acupuncturist of Belarus, candidate of medical sciences, Molostov Valery Dmitrievich, published 23 books in Moscow and Minsk (on neurology, acupuncture, massage, manual therapy and on the aging of society as an organism), home phone: Minsk, (8---107 -375-17) 240–70–75, E-mail: [email protected]. My page on the Internet: www.molostov-valery.ru, where books are posted (previously published in Moscow and Minsk) with a detailed justification for the real existence of the idea described here.

Which organ of the human body produces heat?

Every person knows well that our body temperature is 36.6 degrees Celsius. But for a long time medicine has not resolved 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 produced by only one organ - the skin. And heat is produced by acupuncture points into which acupuncturists love to insert needles. A very unexpected discovery for the entire world of 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 engaged in such research.

Figure 1.

This article is dedicated to acupuncture points, about which I can tell you a lot of interesting things, since I am a professional acupuncturist by profession. See Figure 1. There are 3,478 acupuncture points 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 acupuncture points in animals are located anatomically exactly where they are in humans. It can be assumed that all warm-blooded animals on Earth have some common ancestor, for example, some kind of marine ichthyosaur. 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. Warm-blooded.

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 generated in the body of the animal itself and the person. 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). The five senses also produce electricity: vision, hearing, touch, smell, and taste. They also work like microscopic power plants, but they transform light, sound and chemical energies into electrical potentials of a specific wavelength. How does the eye generate electricity? Light hits the retina of the eye, where it is transformed into a continuous stream electrical impulses, entering through the optic nerve into the visual centers of the cerebral cortex. The same transformers (not generators) electrical energy There are other sense organs: 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 produced by the heart, brain and five senses? It turns out that there is a very strange pattern: only 5% of the electrical energy they produce is absorbed by all electricity generators. The remaining 95% of the electrical energy from these organs travels through the intercellular space to the skin and acupuncture points. Static electricity covers the entire surface of the skin. On the surface of the skin, electricity “spreads”, just as the waters of the ocean spread over the surface of the Earth. Next, acupuncture points absorb static currents, which cover the skin with a “thin layer”, burning them in their “furnaces” " See Figure 4. The “burning of electrons” produces heat for the human body in the amount of 36.6 degrees Celsius.

Figure 4. Electrons are absorbed by an acupuncture point.

Figure 5. Acupuncture.

This is the mechanism for producing heat by the body of our body and the body of an animal. True, the question remains unanswered: why does a person have a normal body temperature, which is exactly plus 36.6º Celsius? Medical science cannot answer the question “Why does inserting needles into acupuncture points have a healing effect on a person?” See Figure 5. This problem has not yet been studied either. 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 natural death of an absolutely healthy, but very old person. It turns out that in old people, the production of electrical energy in the brain and heart first decreases and then 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) stop generating electricity.

Figure 6. Old man.

Then breathing and heartbeat immediately stop, and death occurs. It is for this reason that absolutely healthy, but very old people, over 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 in the brain - and the person will live forever. After all, as long as the heartbeat and breathing continue, the body will live. A healthy brain, liver, kidneys, stomach, intestines and other organs can function for a millennium.

August 10th, 2017

Just the other day, while lying around with a fever, I wondered not only the question, but also, for example, why during an illness a person feels either hot or cold.

Having delved into this issue, I learned a lot of new things for myself...

Chemical reactions throughout the body produce heat when food is broken down. Blood carries this heat and nourishes the cells of the body along the way, taking away decay products and waste products, which are cleansed in the kidneys and liver

All chemical reactions in the body (even depression) produce heat. The blood heats up due to the release of this heat, and this results in heating the entire body to a temperature of 36.6. But when a person is sick, the intensity of chemical reactions in the body increases, as the body fights infection (harmful bacteria) and the temperature rises.

Energy processes occur in every cell of the body, that is, there is no separate heater organ in the body. Processes that release heat also occur in blood cells.
Blood heats up as it circulates through the organs and tissues of the human body. And the human body heats up due to the exothermic reactions continuously occurring in them. These reactions occur in all organs and tissues, but not with equal intensity.

In tissues and organs that perform active work - muscle tissue, liver, kidneys - a greater amount of heat is released than in less active ones - connective tissue, bones, cartilage.

Thus, the liver, located deep inside the body and producing greater heat production, has a higher and constant temperature in humans (37.8-38 ° C) compared to the skin, the temperature of which is much lower (in areas covered with clothing 29.5-33. 9 °C) and largely depends on the environment. So the liver can rightfully be considered the hottest organ.

Blood circulating in the tissues is heated in active tissues (thereby cooling them) and cooled in the skin (at the same time warming it). This is heat transfer.
A person is heated by the chemical reaction of glucose oxidation by air oxygen in the cells of the body. And blood only transfers heat more or less evenly throughout the body. And the body temperature is maintained constant due to heat transfer: heat is lost with warm exhaled air, through the surface of the entire body - into the air, with the evaporation of sweat.

A special thermoregulation system ensures that there is a balance of heat gain and heat loss.

If the body temperature is below 36-37 degrees, then vital processes will begin to slow down, if above 40, then the protein will begin to coagulate (did you see what happens with meat poured over with boiling water?). The hypothalamus is responsible for thermoregulation (this is in the brain); it is like a thermostat.
The source of heat in the body is all tissues. Blood flowing through tissue heats up. The liver and skeletal muscles give off more heat to the blood than other organs. An increase in ambient temperature causes a reflex decrease in metabolism, so heat generation in the body decreases. A decrease in ambient temperature causes a reflex increase in metabolism and increased heat generation. Heat generation is also enhanced by muscle activity. Involuntary muscle contraction (shivering) is the main form of increased heat production.

Heat transfer occurs in several ways:

1. By conducting it, the air and surrounding objects in contact with heat are heated.


2. By radiation - a heated body emits heat (in the form of infrared rays).


3. By evaporation - water and sweat evaporate from the surface of the skin.

Regulation of body temperature constancy is carried out by neurohumoral means.

Fluctuations in ambient temperature are perceived by special receptors - thermoreceptors. There are a lot of them in the skin, oral mucosa, and upper respiratory tract. Skin thermoreceptors are very sensitive to fluctuations in ambient temperature; Nerve impulses arise in them, which enter the spinal cord along afferent (centripetal) nerve fibers. Along the pathways, the nerve impulse reaches the thalamus, hypothalamus and cerebral cortex.

The thermoregulation center is located in the hypothalamus. Neurons of the hypothalamus are excited under the influence of nerve impulses received from thermoreceptors. From the center of thermoregulation, nerve impulses along efferent (centrifugal) nerve fibers will go to the muscles, blood vessels (constricting or dilating skin vessels), and to the sweat glands.

Humoral regulation (hormonal)

1. Hormones of the thyroid gland, adrenal glands and pancreas enhance oxidative processes, i.e. increases metabolism and body temperature.


2. The pituitary gland inhibits the secretion of thyroid hormones, i.e. reduces metabolism and body temperature.

Each person's body temperature fluctuates slightly throughout the day, remaining in the range of 35.5 to 37.0 °C for a healthy person. Following the circadian rhythm, the lowest body temperature is observed in the morning, around 6 o'clock, and the maximum value is reached in the evening.

Like many other biorhythms, temperature follows the daily cycle of the Sun, not our activity level. People who work at night and sleep during the day exhibit the same temperature cycle as others.

A temperature level below 35 °C indicates the presence of a serious illness (usually the result of radiation exposure). Victims of hypothermia go into stupor if their body temperature drops to 32.2°C, most lose consciousness at 29.5°C and die below 26.5°C. The record for survival in hypothermia is 14.2 °C, and in experimental studies - 8.8 °C.

Temperature is affected by gender and age. In girls, body temperature stabilizes at 13-14 years of age, and in boys - at approximately 18 years of age. The average body temperature of men is approximately 0.5–0.7 °C lower than that of women.

Many diseases of the endocrine system and brain tumors affecting the hypothalamus region cause pronounced and often persistent disturbances in thermoregulation. For example, a thyrotoxic crisis (accompanied by a sharp release of the hormones T3 and T4 into the blood) leads to a sharp rise in body temperature, often exceeding a critical level and causing the death of the patient.

Organisms have a special response to the entry of foreign substances into the internal environment - fever. Fever is a condition of the body in which the thermoregulatory center stimulates an increase in body temperature. This is achieved by rebuilding the “set point” mechanism to a higher than normal regulation temperature.

So, what temperature is considered normal? It is widely accepted that the temperature of the human body is exactly 36.6 degrees. A slight deviation in one direction or the other is allowed.

Based on the person’s condition, surrounding climatic conditions and time of day, as well as other parameters, body temperature can be from 35.5 to 37.4 degrees. It is worth noting that the average temperature of women is higher, in contrast to men - by 0.5 degrees.

In the armpit the body temperature should be 36.3-36.9, in the mouth - 36.8-37.3, in the rectum 37.3-37.7, and this is a normal temperature.
An interesting point is that the average body temperature may differ depending on nationality. For example, for the Japanese the average is 36 degrees, and for the Australians it is 37.

Throughout the day, a person's body temperature can fluctuate by about one degree. The lowest body temperature occurs in the morning, and the highest in the evening.
In females, body temperature may fluctuate depending on the menstrual cycle. There are people for whom a temperature of 38 is normal and is not a symptom of the development of the disease.

Each organ in the human body also has its own temperature.
To correctly measure the temperature in the armpit, you need to follow these recommendations:

1. Make sure that the armpit is dry.


2. Take a thermometer, wipe it with a dry cloth, you can bring it down to 35.


3. Place it in the armpit so that the tip filled with mercury is in close contact with the body.


4. Keep for at least 10 minutes.


5. You can evaluate the result.

How to correctly measure the temperature in the mouth:

• Before measuring the temperature in your mouth, you need to spend about five minutes at rest.


• If you have dentures in your mouth, remove them.


• If the thermometer is ordinary, wipe it dry and place it under the tongue on either side.


• Close your mouth and wait 4 minutes.

And what is fever - a feeling of excess heat, usually associated with an increase in human body temperature. It can also be caused by functional changes in the nervous system, hyperemia and increased metabolism in tissues. It is one of the symptoms of fever.
As a rule, fever is an increase normal temperature body by 1° or more degrees Celsius, associated with chills and sweating (at temperatures above 40° - delirium). Exceeding body temperature by more than 5.5°C can cause permanent brain damage. There is a hypothesis that such an increase in body temperature suppresses the reproduction of pathogenic microorganisms and, together with an increase in the intensity of biochemical processes, increases the body's resistance.

Depending on the reasons causing the temperature increase, the hypothalamus can work both to increase it and to decrease it. At strong increase body temperature, the metabolism in the body is disrupted, as the activity of enzymes is disrupted.
Generally treated with antipyretics (such as acetylsalicylic acid, dipirone, paracetamol), cold compresses and bed rest.

In addition to the fever, there is also chills, but this is a different reaction. Chills are a sensation of cold caused by spasm of the superficial (skin) blood vessels, accompanied by muscle tremors (mainly masticatory muscles, then the muscles of the shoulder girdle, back and limbs) and spasm of the skin muscles (“goose bumps”).

Chills often occur during hypothermia, as well as at the onset of fever due to infections, injuries and other diseases. During chills, the body's transfer of heat to the external environment decreases, and its production increases (due to muscle contractions), which leads to an increase in body temperature, after which the chills usually end.

Chills also occur at the height of a fever if the body temperature fluctuates sharply. But most often as a result of the acute development of a febrile reaction during infectious, autoimmune, allergic processes or in response to parenteral (not through the stomach, for example, intravenously and intramuscularly) introduction into the body of foreign proteins, mucopolysaccharide complexes and other pyrogenic substances during the treatment of the patient (for example , during blood transfusion, administration of pyrogenal).

Unlike chills, chills, which can be observed, for example, with neuroses, are only a subjective sensation. In a healthy person, chills occur when exposed to cold as a normal protective reaction of the body. In easily excitable people, chills may also appear during severe excitement or fear.

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In accordance with the laws of thermodynamics, metabolic and energy processes are associated with the production of heat. In some animals (and humans), body temperature remains at a constant level, which significantly exceeds the temperature of the environment due to intensive heat production controlled by special regulatory mechanisms. This - homeothermic (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 environment and undergoes the same fluctuations ( poikilothermic, cold-blooded animals).

Heat production and body temperature. All chemical reactions in the body depend on temperature. In poikilotherms, the intensity of energy processes increases in proportion to the external temperature in accordance with Van Hoff's rule. In homeothermic animals, this rule is masked by another effect (regulatory thermogenesis) and appears only when thermoregulation is blocked (anesthesia, damage to the nervous system). Even after blockade of the regulatory component, significant quantitative differences remain between metabolic processes in cold-blooded and warm-blooded animals: at the same body temperature, the intensity of energy exchange per unit of body mass 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 the processes of tissue destruction - 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 function of body weight (m): M = km 0.75. The coefficient k is approximately the same for both a mouse and an elephant. This law of the dependence of metabolism on body weight reflects the tendency to establish a correspondence between heat production and the intensity of heat transfer into the environment. The greater the ratio between the surface and volume of the body, the greater the heat loss per unit mass, and this ratio decreases with increasing body size. In addition, in small animals the insulating layer of the body is thinner. If you arrange some animals in order of decreasing intensity of metabolic processes, you get the following: mouse, rabbit, dog, human, elephant.

Thermoregulatory thermogenesis. When additional heat is needed to maintain body temperature, it can be generated in the following ways:

1. Voluntary activity of the muscular system.

2. Involuntary tonic or rhythmic (tremor) activity. These two pathways are called contractile thermogenesis.

3. Acceleration of metabolic processes not associated with muscle contraction (not contraction)

body thermogenesis).

In an adult, shivering is the most significant involuntary manifestation of thermogenesis mechanisms. In a newborn baby, it is not contractile thermogenesis (the combustion of brown fat in the “metabolic cauldron”) that is of greater importance. Accumulations of brown fat with a large number of mitochondria are located between the shoulder blades, in the armpit. As the body cools, its temperature increases and blood flow increases. By increasing thermogenesis, body temperature is maintained at a constant level.

Environmental factors and thermal comfort. The effect of environmental temperatures on the body depends on at least four physical factors: air temperature, humidity, radiation temperature and air speed (wind). These factors determine whether a person feels "thermal comfort" or feels hot or cold. The condition of comfort is that the body does not need the functioning of thermoregulatory mechanisms: it does not require either trembling or sweating, and blood flow in the peripheral areas maintains average speed. This is the so-called thermoneutral zone.

These four factors are to some extent interchangeable.

The comfort temperature value for a lightly dressed (shirt, shorts, long cotton trousers) sitting person is 25-26 o C with a humidity of 50% and equal air and wall temperatures. For a naked person = 28 o C. Under conditions of thermal comfort, the average skin temperature = 34 o C. As physical work is performed, the comfort temperature drops. For light office work it is 22 o C.

Discomfort increases with the average temperature and humidity of the skin (the part of the body surface covered with sweat).

Heat dissipation.

1. Internal heat flow. Less than half of all heat generated inside the body spreads to the surface by conduction through tissue. Most of it goes by convection into the bloodstream. Blood has a high heat capacity. The blood flow of the extremities is organized according to the principle of a rotary-countercurrent mechanism, which facilitates heat exchange between the vessels.

2. External heat flow. Heat is transferred outwards through conduction, convection, radiation and evaporation. Heat transfer by conduction is when a body comes into contact with a dense substrate. When body contact occurs with air - convection, radiation or evaporation. If the skin is warmer than the air, the adjacent layer heats up and moves upward, being replaced by colder air. Forced convection (blowing) significantly increases the intensity of heat transfer. The radiation occurs in the form of long-wave infrared radiation. About 20% of the heat transfer of the human body in neutral temperature conditions occurs due to the evaporation of water from the skin and mucous membranes of the respiratory tract.

The influence of clothing - from a physiological point of view, it is a form of thermal resistance or insulation. The effectiveness of clothing is determined by the smallest volumes of air in the structure of the fabric or in the pile, where external currents 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 balance must be achieved between heat production and heat transfer. When the environmental temperature decreases, a constant body temperature can be maintained only if regulatory mechanisms ensure an increase in thermogenesis in proportion to heat loss. The highest heat production provided by these mechanisms in humans corresponds to basal metabolic rates 3–5. This indicator characterizes the lower limit of the thermoregulation range (0-5 o C in the external environment for adults, 23 o C for newborns). If this limit is exceeded, hypothermia and cold death develop.

When T about the environment increases, temperature equilibrium is maintained due to a decrease in exchange, 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 humidity and can reach 4 l/hour.

With an increase in the temperature of the environment, the skin vessels dilate, the total amount of circulating blood increases due to its exit from the depot, due to the entry of water from the tissues. This promotes increased heat transfer. But the main thing is still evaporation. The average heat generation per day during vigorous activity is about 2500-2800 kcal. To maintain body temperature at a constant level under these conditions, it is necessary to evaporate 4.5 liters of water. For heavy muscular work - up to 12 liters. per day. Water evaporation depends on the relative humidity of the air in the room and is impossible at 100% humidity. Therefore, high humidity at high temperatures is poorly tolerated. In this case, sweat does not evaporate, but flows off the skin. This type of sweating does not contribute to the transfer of heat. Clothing that is impervious to air (leather, rubber) is also poorly tolerated, 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 transferred 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 the proximal one. 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 o C, in the deep muscles of his thigh the temperature is 35 o C, in the calf muscle - 33 o C, on the foot - 27 o C, in the rectum -37 o C.

Fluctuations in body temperature with changes in external temperature are more pronounced near the surface of the body and in the end parts of the limbs. There is a “homeothermic core” and a “poikilothermic shell”.

Core body temperature itself is not constant, either spatially or temporally. The differences are 0.2-1.2 o C. Even in the brain, the temperature of the center and cortex differs by 1 o C. As a rule, the highest T o is observed in the rectum (and not in the liver, as was previously believed!). In this regard, it is impossible to express the T about the body in one number. For practice, it is enough to find a certain area in which T o can be considered as representative of the entire internal layer. Clinical measurements require an easily accessible area with minor spatial temperature variations. In this sense, it is preferable to use rectal temperature. In this case, a special rectal thermometer is inserted at 10-15 cm. Normally, it is 37 o C.

Oral temperature (sublingual) is also used clinically. Usually it is 0.2-0.5 o less than rectal.

Axillary temperature (most often used in Russia) is 36.5-36.6 o. Can serve as an indicator of core body temperature because when the hand is pressed tightly against chest, the temperature gradient shifts so that the border of the body core reaches the armpit. However, you have to wait quite a long time (10 minutes) until enough heat accumulates in these areas. If the superficial tissues were initially cold in conditions of low ambient temperature and vasoconstriction occurred in them, then about half an hour should pass for the appropriate equilibrium to be established in these tissues.

Periodic fluctuations in core temperature. During the day, a person's minimum temperature is observed in the pre-dawn hours, and the maximum in the afternoon. The amplitude of the oscillations is 1 o C. The daily (circadian) rhythm is based on an energy mechanism (biological clock), which is usually synchronized with the rotation of the earth. In conditions of travel associated with crossing the earth's meridians, it takes 1-2 weeks for the temperature regime to come into line with the conditions of the new local time. Circadian rhythms are superimposed on others (menses in women, etc.).

Temperature in conditions physical activity may increase by 2 ° C or more depending on the intensity of the load. At the same time, the average skin temperature decreases, as sweat is released due to the work of the muscles, which cools the skin. Rectal temperature during work can reach 41 o (for marathon runners).

Skin blood vessels can respond directly to changes in T - so-called. cold expansion, which is due to the local thermosensitivity of the vascular muscles. Cold dilation of blood vessels is usually observed in the form of the following reaction. When a person is exposed to extreme cold, he first experiences maximum vasoconstriction, which manifests itself in pallor and a feeling of cold in exposed 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, the events repeat periodically.

Cold vasodilation is thought to be a protective mechanism to prevent frostbite, especially in cold-adapted individuals. However, this mechanism can precipitate the death of general hypothermia in those who are forced to swim in cold water for a long time.

When water plays the role of the environment, since it has greater thermal conductivity and heat capacity than air, more heat is removed from the body by convection. If water is in motion, then heat is removed so quickly that at an ambient temperature of +10 o C even strong physical work does not allow thermal equilibrium to be maintained, and hypothermia occurs. If the body is at complete rest, then to achieve temperature comfort, the temperature of the water should be 35-36 o. The lower limit of the thermoneutral zone depends on the thickness of the adipose tissue.

Mechanisms of thermoregulation. Thermoregulatory reactions are reflexes carried out by the central nervous system. They arise in response to stimulation of thermoreceptors in the periphery and in the central nervous system itself. There are two types of thermoreceptors - some perceive heat (heat receptors), others perceive cold (cold receptors). Both react with the appearance of a flash of impulses in response to adequate stimulation (a corresponding change in the temperature of the environment), and what matters is the rate of temperature change and the magnitude of the stimulus (the difference between the initial and new temperatures in the tissues).

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 proven by the appearance of tremors in the dog when the denervated limb is cooled. Local cooling of different parts of the brain causes bursts 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 regulated mainly by the anterior hypothalamus, and chemical thermoregulation 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 normally mutually balanced processes of heat production and heat transfer, as well as special adaptive behavior.

The endocrine system is also involved in temperature regulation. Thus, thyroxine increases the intensity of metabolism, increasing heat production. Adrenaline constricts blood vessels, maintaining core body temperature.

Ontogenesis of thermoregulation. In immature-bearing animals, newborns are not capable of thermoregulation and are actually poikilothermic (gophers, hamsters, etc.). In other animals and in humans, all themoregulatory reactions (increased thermogenesis, vasomotor activity, sweat, behavior) can be turned on immediately after birth to one degree or another. This applies even to premature babies weighing about 1000 g. It is widely believed that newborns have an immature hypothalamus, responsible for thermoregulation. However, the newborn meets its needs through non-contractile thermogenesis. Children's heat production increases by 200% without shivering.

The small size of the newborn is a disadvantage in terms of thermoregulation. The ratio between body surface and volume is 3 times that of an adult, and the fat layer is small. Therefore, per unit mass of heat, children produce 4-5 times more heat. The upper limit of the thermoneutral zone of newborns is 32-34 o, the lower limit is 23 o C. Within this limited range, a newborn is able to maintain a constant temperature.

Thermal adaptation. The most important feature that occurs during thermal adaptation is the change in the intensity of sweat secretion, which can increase 3 times and reach 4 l/h for short periods. During adaptation to high temperatures, the electrolyte content in sweat decreases significantly to avoid loss of salts.

One of the main adaptive changes is the increase in thirst for 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 responses and sweating change in different directions depending on whether the thermal exposure is acute, chronic, moderate, or severe. Thus, 4-6 days after a daily 2-hour heat stress with maximum sweat production (sauna), reactions of sweat secretion and vasodilation occur at internal temperatures 0.5 o lower than before. The biological significance of the threshold shift is that, due to adaptation, the body temperature at a given heat load decreases, so that the body is protected from a critical increase in heart rate and blood flow - reactions that can lead to heat syncope.

In contrast, in persons living long-term in the tropics (chronic mild heat shift), the core temperature at rest is higher, and the sweating and vasodilation reactions begin at a body temperature 0.5 ° C 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 to more than 37 o C. The maximum body temperature for survival is + 42 o C (very briefly 43 o). At the same time, all thermoregulatory processes are extremely tense. Under conditions of prolonged heat stress at temperatures above 40-41 o, severe brain damage occurs - “heat or sunstroke”. Heat syncope with relatively mild overheating in people with impaired cardiovascular system functions is more dependent on circulatory failure than on thermoregulation mechanisms.

Fever. Fever develops as a result of increased heat production through shivering and maximum vasoconstriction in the peripheral parts of the body, i.e. the body behaves as if it were at a low ambient temperature. During the recovery period there is opposite process- through sweating and vasodilation, body temperature drops in the same way as when a person has a fever. In this case, a person can correctly respond to true changes in external temperature. The mechanism of occurrence of a febrile reaction is associated with the release of leukocyte and bacterial pyrogens into central offices thermoregulation.

Cold adaptation. Fur, fat layer, brown fat are all types of cold adaptation mechanisms in different animals. These mechanisms are not characteristic of an adult, so you can often hear the opinion that adults are not capable of any physiological adaptation to cold; they should only rely on behavioral adaptation (clothing and warm homes). It is said that man is a “tropical creature” who can survive in the Arctic only due to his civilization.

However, it has been shown that in cases of prolonged exposure to cold, people develop tolerance (endurance) to the cold. The threshold for the development of tremors and changes in metabolic thermoregulatory reactions shifts towards lower temperatures. In this case, even moderate hypothermia may occur. Similar tolerance is observed among the aborigines of Australia, who can spend a whole night almost naked without shivering at an ambient temperature of about 0 o C, as well as among Japanese divers, who spend several hours in water of about 10 o C. The same applies to ours. walruses."

It was shown that the shivering threshold could be shifted toward lower temperatures over just a few days during which subjects were subjected to repeated cold stress. With prolonged exposure (Eskimos, residents of Patagonia), the intensity of the basal metabolism increases by 25-50% - this is a metabolic adaptation.

Local adaptation. If the hands of a warmly dressed person are regularly cooled, then painful sensations decrease in the hands. This is due to the fact that cold expansion of blood vessels occurs at a higher room temperature.

Hypothermia. Hypothermia occurs when the armpit temperature drops below 35°. This happens faster when immersed in cold water. In this case, a state similar to anesthesia is observed - the disappearance of sensitivity, a weakening of reflex reactions, a decrease in the excitability of the central nervous system, metabolic rate, slowing of breathing 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, making longer bleeding during operations on the heart and large vessels more tolerable. There are now known cases of heart shutdown during hypothermia for 40-60 minutes (Vereshchagin). Hypothermia is stopped by quickly warming the body. Artificial hypothermia is carried out when the thermoregulatory mechanisms are turned off.

In old age, hypothermia develops due to overregulation of temperature reactions - normally the body temperature reaches 35 o (a phenomenon opposite to fever).

A decrease in body temperature to 26-28 o causes death from cardiac fibrillation.