{"id":13297,"date":"2026-06-24T06:34:53","date_gmt":"2026-06-24T06:34:53","guid":{"rendered":"https:\/\/natharatmouchrika.net\/home\/?p=13297"},"modified":"2026-06-24T06:34:53","modified_gmt":"2026-06-24T06:34:53","slug":"effects-of-high-temperatures-on-the-organism","status":"publish","type":"post","link":"https:\/\/natharatmouchrika.net\/home\/?p=13297","title":{"rendered":"Effects of high temperatures on the organism"},"content":{"rendered":"

\"\"<\/p>\n

Introduction<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h2>\n

Man, as a warm-blooded (homoiothermal<\/b>) animal, is characterized by the fact that he is able to maintain\u00a0a constant temperature of the core<\/b>, i.e. deep-seated organs, almost independent of changes in the surrounding environment, using thermoregulatory mechanism. An organism as an open system is in constant interaction with its environment. Constant temperature maintenance is possible only if\u00a0heat production is in balance with heat output.<\/b><\/p>\n

From the point of view of thermodynamics, the human organism is\u00a0an open thermodynamic system<\/b>. Such systems exchange substances, energy and information with the environment. Under normal conditions, the organism obtains a substantial part of its energy from food in the form of chemical energy. A small part of the energy from the surrounding environment consists of chemical, light, mechanical and\u00a0thermal energy<\/b>, causing irritation of the relevant receptors and subsequently and adequate perception.<\/p>\n

Heat in the body is produced mainly as a\u00a0by-product of other forms of energy<\/b>, only exceptionally is it produced purposefully (cold shivering as a mechanism of\u00a0thermoregulation<\/a>). In order to prevent this heat from accumulating in the organism and thereby increasing its temperature, the organism is able to regulate its discharge to the environment to a certain extent. High temperatures prevent the body from cooling down and cause\u00a0heating<\/b>.<\/p>\n

The system is able to\u00a0regulate its temperature within a certain range<\/b>, but if it is exceeded and temperature regulation is no longer possible, the temperature of the core (deep-seated organs) rises. This leads to overheating and collapse of the organism.\u00a0Self-regulation of temperature is a feedback loop of the organism<\/b>. Its principle is that the control center constantly compares the required temperature with the actual temperature of the core and controls the intake and output of heat based of their difference.<\/p>\n

The center of temperature regulation is the Centrem regulace teploty je\u00a0hypothalamus<\/a><\/b>. Central thermoreceptors are located in the anterior hypothalamus. Two-thirds of them react to heat, a third to cold. The thermoregulatory center located in the posterior hypothalamus itself is not sensitive to temperature, but it \u201ccalculates\u201c information coming from peripheral thermoreceptors, which are located mainly in the skin, and sends out control signals. There are ten times more cold receptors (Krause corpuscles<\/i>) than heat receptors (Ruffiini corpuscles<\/i>). (see Thermoregulation)<\/p>\n

The constant human body temperature is set at\u00a037\u00b0C<\/b>.<\/p>\n

Mechanism of heat exchange and effects of climatic conditions on the organism<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h2>\n

Heat exchange takes place until an equilibrium state is reached.<\/p>\n

The heat received (given out) by a body depends on the mass of the body (\ufffd<\/span>\"{\\displaystyle<\/span>), to increase (decrease) body temperature\u00a0(\ufffd\u2212\ufffd0)<\/span>\"{\\displaystyle<\/span>,\u00a0(\ufffd0\u2212\ufffd)<\/span>\"{\\displaystyle<\/span>\u00a0and on the type of fabric\u00a0\ufffd<\/span>\"{\\displaystyle<\/span>\u00a0(specific heat capacity).<\/p>\n

Calorimetric equation:<\/b><\/p>\n

\n
Heat received:\u00a0\ufffd1=\ufffd\u22c5\ufffd\u22c5(\ufffd\u2212\ufffd0)<\/span>\"{\\displaystyle<\/span><\/dd>\n
Heat transferred:\u00a0\ufffd2=\ufffd\u22c5\ufffd\u22c5(\ufffd0\u2212\ufffd)<\/span>\"{\\displaystyle<\/span><\/dd>\n<\/dl>\n

Radiation<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

Radiation<\/b>\u00a0is the transfer of heat from one body to another with a different temperature by\u00a0infrared electromagnetic radiation<\/a><\/b>, without the two objects touching. The amount of heat thus transferred according to the\u00a0Stefan-Boltzmann law<\/b>\u00a0corresponds to the function of the fourth power of the temperature of the radiating body. The environment affects the human body through the same mechanism, which means that the total radiated energy is proportional to the difference of the fourth powers of the surface temperature of the body and the temperature of objects in the environment. The temperature of the air through which the thermal radiation, a person can feel cold in a room with cold walls, even if the air in the room is relatively warm. A person in a cold environment loses heat by conduction into the air that surrounds him and by radiation to cold objects in his vicinity. On the contrary, an individual in an environment warmer than his body’s body temperature receives heat through the same mechanisms and his temperature rises. On a cold, sunny day, the sun’s thermal radiation is reflected off bright objects and thus contributes to warming.\u00a060%<\/b>\u00a0of total heat loss.<\/p>\n

Conduction<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

Conduction is the transfer of heat through contact between two bodies of different temperatures. It involves the\u00a0transfer of thermal energy<\/b>\u00a0from a place (body) with a higher temperature to a place (body) with a lower temperature. Molecules are in motion and the energy of their motion is proportional to temperature. Molecules of warmer body collide with molecules of a colder body and thereby transfer part of their thermal energy to them. The amount of heat transferred is proportional to the temperature difference of the two touching objects (thermal gradient). Heat can also be transferred by conduction to the surrounding air. In the human body, the most important heat transfer mechanism is\u00a0blood circulation<\/b>. On the other hand, the thermal insulator in the body is\u00a0fat tissue<\/a><\/b>\u00a0(it has 3x less thermal conductivity than blood). By driving, one loses about\u00a015%<\/b>\u00a0heat energy. Air that does not flow intensively is a thermal insulator. If the body is surrounded by water or moist, intensively flowing air, then heat loss through conduction will be decisive.<\/p>\n

Convection<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

Convection (flow) is the movement of air or water molecules in the direction away from the point of contact based on the temperature gradient in the environment. Convection is closely related to heat conduction. Increases heat output by conduction by maintaining a large temperature gradient. The heat must first be transferred by conduction to the substance, through which it is then removed to the surroundings.<\/p>\n

The amount of heat that is per time\u00a0\ufffd<\/span>\"{\\displaystyle<\/span>\u00a0carried away by flow from the surface of the body about the area\u00a0\ufffd<\/span>\"{\\displaystyle<\/span>\u00a0to surroundings with a lower temperature o\u00a0\u0394\ufffd<\/span>\"{\\displaystyle<\/span>, can be expressed by the relation\u00a0\ufffd=\ufffd\u22c5\ufffd\u22c5\u0394\ufffd\u22c5\ufffd<\/span>\"{\\displaystyle<\/span>.<\/p>\n

\u03b1 is the coefficient of heat transfer through the interface, which is determined experimentally using\u00a0alphameters<\/b>. An object that is in contact with air of a different temperature changes its specific gravity because it affects its temperature. As warm air rises and cold air descends, new air comes into contact with the object. Convection increases strongly if the object moves in the environment or if the environment flows around the object (a person swimming in water or a fan in a room). Wind cools because it replaces the warm and humid air from the immediate surroundings of the body with cooler and drier air. The effects of flow and heat conduction are evident under extreme climatic conditions. The organism tolerates frost better at low relative air humidity and when there is no wind than at temperatures above the freezing point with intense currents and high air humidity<\/p>\n

Evaporation<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

During heavy physical exertion, radiation<\/b>\u00a0and\u00a0conduction alone<\/b>\u00a0are not enough to protect the body from overheating. Under these conditions, heat output is increased by evaporation of water during\u00a0perspiration<\/a>.\u00a0By evaporating 1 g of water, the organism loses about 0.6 kcal of heat<\/b>. Fluid reaches the surface of the skin by\u00a0diffusion<\/a>\u00a0and secretion from\u00a0sweat glands<\/a>. Evaporation cools the skin to a temperature lower than the ambient temperature. At an ambient temperature higher than 36\u00b0C, heat removal is effective only through the evaporation of water. At an ambient temperature significantly higher than 37\u00b0C, the body gains heat from the environment by radiation and conduction. In this case, the balance between the intake and output of heat is maintained by profusion sweating, the effectiveness of which is inversely proportional to the humidity of the air. Once the humidity reaches a certain value, the body’s ability to cool itself by sweating becomes limited and the expelled sweat will not evaporate from the skin.\u00a0One liter of evaporated liquid takes more than 2428 KJ (580kcal) from the body<\/b>. This mechanism makes it possible to tolerate dry heat (e.g. desert) at temperatures well above body temperature (in the case of replacing fluid and salt losses caused by sweating). However, if the surrounding air is highly saturated with vapors (tropical jungle), evaporation is prevented and it is difficult to tolerate temperatures above 34\u00b0C. With higher air humidity, a person feels the heat more strongly. Evaporation occurs from the surface of a liquid at any temperature at which the liquid state exists. The rate of evaporation of any liquid will increase if the temperature of the liquid increases, if its surface area increases, and if the vapors formed above the liquid are removed (suction, blowing, wind).<\/p>\n

The relative share of each of the processes described above in removing heat from the organism depends on the\u00a0temperature of the environment<\/b>. At temperatures below 19\u00b0C, heat output is reduced due to minimal blood flow to the skin due to peripheral\u00a0vasoconstriction<\/a>. In the temperature range of 19\u201331\u00b0C, the blood circulation of the skin can ensure a balance between the produced and dissipated heat. At temperatures above 31\u00b0C, evaporation is added to radiation, flow and heat conduction.\u00a0Evaporation<\/b>\u00a0is the only possible cooling mechanism in cases where the ambient temperature is higher than the body temperature.<\/p>\n

The body reacts to a hot surrounding environment or increased production of metabolic heat by\u00a0vasodilation<\/a><\/b>\u00a0(widening of the subcutaneous vessels). In this way, the heat of the body’s core is transferred to the blood and transferred to the surface of the body if its temperature is lower than the internal temperature. As a result of the increase in skin temperature, the removal of heat from the body increases. If an increase in skin temperature cannot restore thermal balance, sweat glands are activated and evaporative cooling begins. If these mechanisms do not restore the body’s thermal balance,\u00a0hyperthermia<\/a><\/b>, an increase in the body’s core temperature and overheating of the organism, will occur. If the system’s ability to regulate its tempetrautre is exceeded, the energy of thermal oscillations approaches the energy of weak chemical bonds, resulting in overheating and collapse of the organism. The first symptoms are: weakness\u00a0headache<\/a>, loss of appetite,nausea<\/a>, shortness of breath, rapid pulse (up to 150\/min), shiny eyes, mental restlessness, apathy or, on the contrary, irritability. In heat shock, the body temperature rapidly rises above 41\u00b0C, sweating stops,\u00a0coma<\/a>\u00a0begins and death occurs.<\/p>\n

The ideal temperature<\/b>\u00a0of the external environment for a person undressed in resting conditions is 28\u00b0C, for a light worker 25\u00b0C, for longer endurance loads 15\u00b0C.<\/p>\n

Factors affecting thermal comfort<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h2>\n
    \n
  1. Air temperature.<\/li>\n
  2. Radiant temperature of surfaces in space.<\/li>\n
  3. Operative temperature \u2013 the temperature of a black enclosed space in which the organism would share the same amount of heat by convection and radiation as in the real environment.<\/li>\n
  4. Effective temperature \u2013 the room temperature at 50%, relative humidity that causes the same total heat loss from the skin as in the real environment.<\/li>\n
  5. Air humidity \u2013 i.e. mass amount of water vapor in 1 kg of dry air.<\/li>\n
  6. Air flow speed and its turbulent. The speed of air movement affects heat transfer by flow and evaporation of moisture from the skin.<\/li>\n
  7. The value of metabolism indicates the heat output of a person. It depends on the activity, the person (figure, age and physical condition) and the conditions in which the person is.<\/li>\n
  8. Clothing is an important factor affecting heat transfer from the body to the environment.<\/li>\n
  9. Body shape and subcutaneous fat. Heat production is proportional to body mass, but heat loss depends on body surface area.<\/li>\n
  10. Age and gender. Older people have narrower range of optimal temperatures, women often prefer a higher ambient temperature than men.<\/li>\n<\/ol>\n

    The effect of high temperatures on the organism<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h2>\n

    Effects on the human organism<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h3>\n
      \n
    1. Vasodilatation<\/i>\u00a0(expansion of skin vessels – increases the transfer of heat to the skin).<\/li>\n
    2. Sweating(takes place from 37\u00b0C; water losses in a warm environment can be up to 5 liters per hour, at the same time ion losses occur; excessive Na and Cl losses are prevented due to higher aldosterone production).<\/li>\n
    3. Limitation of heat production<\/i>.<\/li>\n
    4. More intense breathing.<\/i><\/li>\n
    5. Acceleration of blood circulation<\/i>.<\/li>\n
    6. Reduction of muscle tension. relaxing effects.<\/i><\/li>\n
    7. Increased capillary\u00a0permeability<\/a>.<\/i><\/li>\n<\/ol>\n

      Shock states of the organism associated with high temperature<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h3>\n

      Heat stroke<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

      Heat stroke (siriasis<\/i>) is shock state of the organism caused by the accumulation of heat in the body. It occurs when the organism is unable to remove a sufficient amount of heat from the body with the help of thermoregulation. The body’s temperature is raised above\u00a040,5\u00b0C by external infuences<\/b>[1]<\/a><\/sup>. Heat stroke is mainly caused by a failure of thermoregulation, namely a failure of sweat secretion, the onset of paradoxical \u201ccold\u201c tremors\u00a0delirium<\/a>, convulsions.\u00a0[2]<\/a><\/sup>. Heat stroke can cause severe brain damage, often quickly leading to death.<\/p>\n

      Burn<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

      Sunburn (insolation<\/i>) is mainly caused by direct sunlight falling on the head and neck area, where there is rapid rise in temperature in the thermoregulatory centers. It leads to malaise, impaired concentration, headache, dizziness, nausea, vomiting, stiff neck. It causes congestion of the meninges (up to\u00a0brain edema<\/a>\u00a0), it can be fatal.<\/p>\n

      Collapse from the heat<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h4>\n

      It is a special form of\u00a0orthostatic collapse<\/a>. Extreme vasodilatation during heat stress while standing quietly leads to a \u201cpooling\u201c of larger volumes of blood in the veins of the legs and abdomen, and thus to a drop in blood pressure and unconsciousness. It is relatively risk-free.\u00a0[2]<\/a><\/sup><\/p>\n

      Adaptation of the organism to heat<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h3>\n
        \n
      1. Sweat secretion doubles<\/b><\/li>\n
      2. The sweating threshold shifts to lower core temperatures<\/b>.<\/li>\n
      3. the concentration of ions in sweat decreases<\/li>\n
      4. The feeling of thirst increases.<\/b><\/li>\n<\/ol>\n

        Heat utilization<\/span>[<\/span>edit<\/a>\u00a0|\u00a0<\/span>edit source<\/a>]<\/span><\/span><\/h2>\n

        The effect of heat has therapeutic effects on the organism in certain cases. Thermotherapy is one of the basic physical treatments used especially in spa medicine, where its analgesic and spasmolytic effect is mainly used.<\/p>\n