Thermoregulation is ... Thermoregulation and metabolism

Thermoregulation is a mechanism that allows living organisms to maintain the constancy of the internal environment. Most of the processes in the human body depend on temperature: metabolism, synthesis of proteins and hormones, digestion, cognitive functions. In addition, overheating or hypothermia can lead to serious illnesses and even death.

Temperature range

For normal life of a person, thermoregulation is extremely important. The body temperature of healthy people is in a narrow range from 36.0 to 37.0 Celsius. A sharp decrease or increase in these values usually leads to death.

In the heat, a person sweats intensely. Loss of fluid in this way leads to dehydration, sometimes quite serious. Together with sweat, the body is left with vitamins and minerals. Due to dehydration, blood becomes thicker, metabolism is disrupted. Normal loss of water during sweating - up to three percent of the total body weight. If this value exceeds the six percent barrier, cognitive functions suffer. Twenty percent is enough for a fatal outcome. In addition, there is another danger. During prolonged exposure to the sun, the body accumulates more heat than it releases into the environment, and according to the law of thermodynamic equilibrium, the human body gradually heats up to air temperature, that is, up to 39-41 degrees Celsius. This entails heat stroke and loss of consciousness. The cardiovascular system also works on wear and tear: the pulse becomes more frequent, the pressure rises, the blood hardly passes through the vessels.

Subcooling is no less dangerous for humans. In the cold, the vessels of the body contract, which causes tissue ischemia. And if the effect of cold temperature is prolonged, then the death of skin or muscle areas is possible. Low temperatures also affect the metabolism, which takes place several times faster, because the body needs energy for heating.

Core and shell

Conditionally, the whole human body can be divided into two levels: the core and the shell. The core (mostly internal organs) has a constant temperature of about thirty-seven degrees. This is achieved by a balance between heat production and heat transfer. The shell is a barrier between the environment and a 2.5 cm thick core. Thermoregulation is the ability of the shell to maintain a constant core temperature.

The skin of a healthy person in different areas can be heated from 24 to 36.6 degrees. The coldest are the tips of the fingers, and the warmest place is the armpit. Fluctuations in body temperature during the day reach one degree: the lowest - early in the morning, and high - at six in the evening.

Heat generation and heat transfer

What is thermoregulation and how is it maintained in the human body? This question is not as easy to answer as it seems at first glance. In our body, heat is continuously generated, which is for the most part spent on heating the external environment. This process is called heat exchange. It is regulated by the help of the nervous system, the results of it depend on the metabolism, the activity of the heart, the contraction of muscles, etc.

Normally, heat production equals heat transfer, that is, isotherm is observed. The reasons for thermoregulation are simple - it helps to maintain the inviolable temperature of the nucleus and ensure a certain independence of the body from external conditions. For an hour in a person it generates enough heat to boil a liter of water. And if it were not for the heat output, then within three days after birth we would all literally have cooked from the inside. Therefore, processes that help people get rid of excess heat, are extremely important.

Hardening

Thermoregulation and hardening go hand in hand. The organism adapts itself to the effect of ever lower or higher temperatures, new mechanisms are created for keeping the core temperature constant.

At home, there are several common methods of hardening. For example, wiping with cool water. The first time water should be 30 degrees, then 28, 26 and so, until it reaches 15 degrees Celsius. When the body gets used to the cold, you can go to dousing or showering with rubbing. Air and sunbathing are also recognized as effective. Initially, the duration of the sessions should not exceed 15 minutes, but with time you can bring the time to 60. However, it should be remembered that prolonged insolation can lead to problems with the skin and cancer.

Thermoreceptors

The skin in the thermoregulation of the body plays a key role. As the largest organ of the human body, it performs many functions, including contains thermoreceptors (cold and heat). It is known that the cold is about ten times larger, so we are much more sensitive to low temperatures. The largest accumulation of receptors is on the face, neck, and least of all - at the fingertips. However, the sensitivity of them has an inverse proportion to the number. Despite the fact that the thermal receptors are larger, they are almost twice as sensitive as the cold ones.

Kinds of thermoregulation

Thermoregulation is a whole conglomerate of processes aimed at maintaining a constant body temperature through heat exchange. The mechanism of operation of this system can be described using the principle of "feedback". That is, the ambient temperature first changes, the receptors of the skin react and the signal is transmitted to the brain. And from there comes the regulation of heat production and its recoil.

All the processes of thermoregulation can be divided into two types:

- physical;

- chemical.

Physical thermoregulation, in turn, is divided into evaporation, radiation, thermal conductivity and convection. Among the chemical processes , a contractile and non-reduced thermogenesis is distinguished.

Physical thermoregulation

Physical thermoregulation is a combination of processes that ensure the removal of heat from the body. For this, nature provides for several ways:

- Conduction;

- convection;

- radiation;

- evaporation.

In addition, the body can regulate the intensity of blood circulation and the degree of expansion of the vessels of the skin, which also affects the loss of heat. Another mechanism for the release of heat is sweating. It is most effective in case of a hot climate or an artificial increase in the temperature of the environment.

In a state of rest, at a comfortable temperature of 20 degrees Celsius, a person by radiation loses about sixty percent of the heat, evaporates only twenty, and the rest is due to conduction and convection. In an hour, we lose about one hundred kilocalories or four hundred and nineteen joules.

Evaporation and Radiation

Evaporation is the release of energy into the environment by loss of moisture through the skin or mucous membranes. Otherwise this process is called sweating. Being in a comfortable temperature (about twenty degrees Celsius), a person loses about 36 grams of fluid every hour. With increasing temperature or intensive work, this figure sometimes increases to two liters per hour.

If the air is dry, then the heat is tolerated by the person relatively well, since there is an opportunity for evaporation of sweat. However, in a humid climate, even thirty degrees of heat can be fatal.

Radiation is the path of heat release by means of electromagnetic radiation. A person emits heat from the moment when the temperature of the environment falls below the temperature of the body, that is, almost always. To prevent heat loss during cold running times, the minimum number of open skin areas should be left. Clothing can suspend radiation and reduce the amount of heat produced, but it can not completely stop it.

Even the position of the body is involved in thermoregulation. When an animal or person is cold, he tries to group (curdle) so that as little as possible of the surface of the body is in contact with the external environment. And vice versa, if it's warm, then people and animals try to open up to increase the area of the skin for radiation.

Conduction and convection

Conduction is manifested when a person comes into contact with other bodies. It depends on the contact time, the area of the object and the thermal conductivity of the material.

In order not to get frostbite or not to fall ill, you must adhere to the elementary rules:

- Do not sit on cold stones;

- In winter, do not miss metal objects with bare hands;

- In nature, do not sit on bare ground, but always put something (sleeping bag, rug, clothes);

- Do not walk in wet clothes in winter.

Convection is a dynamic way of losing heat, which is carried out by moving particles of water or air, for example, such streams create a wind or a fan. If it is simple, the body, releasing heat, heats the air next to the skin. He becomes lighter than the cold, and rises higher, and his place is taken by a new portion. When we are in the wind or move fast, the air around us also moves faster, therefore, the heat does not stay near the skin for long.

Chemical thermoregulation

Thermoregulation and metabolism are closely related concepts. The chemical method is just based on a change in the intensity of the process of oxidation and vibration of muscles. Energy for heating the body is obtained by hydrolysis of ATP (adenosine triphosphate). It is necessary for the transformation of complex compounds into simpler ones. Heat, which is then released, dissipates in the surrounding space. This is a non-reduced thermogenesis.

Depending on the temperature of the environment, the metabolism can be accelerated or slowed down to maintain the constancy of the nucleus. The most comfortable person feels at 18-20 degrees Celsius. But this is for the air. Water is more conducive to heat, so the temperature should be higher. Most of the heat is produced by the muscles during the aerobic glycolysis. Therefore, when we are cold, the body begins to tremble to increase heat production. This condition is called contractive thermogenesis.

Thermoregulation control

Thermoregulation of the brain goes the same way as the rest of the body, with the difference that it is here that the center that manages the entire process is located. In the hypothalamus is located the center of thermoregulation, which coordinates the speed of metabolic processes, muscle contraction, and the tone of the vessels of the skin.

The sensory nerve cells of this part of the brain can distinguish between the vibrations to hundredths and thousandths of a degree. They analyze the incoming information and, on the basis of feedback, regulate the internal temperature, setting it depending on external circumstances.

Subordinate to the hypothalamus are the thyroid gland and adrenal glands. The first affects the metabolic rate, and the second affects the vascular tone and oxidative processes in the muscles. Using neurotransmitters and hormones, the hypothalamus adjusts the state of the body in accordance with the circumstances.