The thermoregulatory radiation is a mechanism of heat loss that is characterized by heat radiation. With radiation, thermal energy moves out of the body as an electromagnetic wave or infrared radiation. Overheating due to radiation is considered to be a therapeutic step in cancer.
What is radiation?
The human body temperature is kept constant by a wide variety of mechanisms. The temperature of around 37 degrees Celsius (slightly different from person to person) corresponds to the ideal working temperature of numerous enzymes.
To maintain this ideal value, the human organism is permanently in heat exchange with the environment. The entirety of these exchange processes and the associated body processes is known as the body's thermoregulation. The hypothalamus is the regulatory center. The four mechanisms of heat exchange are convection, conduction, evaporation and radiation.
Medicine distinguishes between mechanisms of external and internal heat transport. The internal heat transport takes place mainly via convection and conduction. No carrier medium is required for conduction, while convection works with a carrier medium. Radiation and evaporation are primarily attributed to external heat transport. While evaporation corresponds to evaporation, radiation is thermal radiation.
Function & task
With radiation, thermal energy is moved in the form of an electromagnetic wave as infrared radiation. In contrast to transport by convection, for example, radiation does not depend on matter, but works exclusively with non-material thermal radiation.
Without reflection, long-wave infrared rays penetrate the human body from outside. These long-wave rays can emanate from various sources in the surrounding area. The most important source of long-wave infrared radiation is, for example, the sun. Objects or people in the immediate vicinity can also emit long-wave infrared rays. Short-wave infrared rays do not enter the organism without being reflected, but are reflected at a height of up to 50 percent. This reflection takes place mainly through the skin pigment.
The Stefan-Boltzmann law specifies the thermal radiation output of an ideal black body as a function of body temperature. It goes back to the physicists Ludwig and Josef Stefan Boltzmann. Its law forms the basic framework for thermoregulatory radiation. The Stefan-Boltzmann law was more or less experimentally discovered in the 19th century. Boltzmann based his derivation on the laws of thermodynamics and Maxwell's electrodynamics. In deriving it, it assumes the spectral radiation density of black bodies and achieves an integration of the radiation density over all frequencies and in the half-space that the surface element irradiates.
The radiation law of radiation indicates which radiation power a black body of a certain area emits into the environment at the absolute temperature.
Heat is constantly generated in the human body, primarily through metabolic processes and muscle work. This heat is transported to the surface through internal heat transport processes such as conduction and convection. The heat radiates from the body surface as part of radiation according to Boltzmann's law, so that heat losses occur. These heat losses protect people from overheating.
On the other hand, the human body also absorbs heat from the environment via radiation. In order that the constant body temperature can be maintained, heat losses are initiated again if necessary.
In this way, thermoregulatory processes such as radiation, convection, evaporation and conduction protect the human body from overheating and hypothermia. Both states would disrupt or even paralyze the enzymatic work and thus dozen of body processes.
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Hyperthermia is an overheating of the body that goes against the heat regulation center. Unlike fever, hyperthermia is not caused by pyrogens. Hyperthermic special forms are malignant hyperthermias that occur as a result of drug effects or drug use.
Hyperthermia can also be brought about artificially via radiation and then corresponds to a therapeutic step, as shown, for example, in the context of cancer treatments. Chemotherapy is often successfully supported by artificial hyperthermia. Different types of artificial hyperthermia are distinguished. In addition to whole-body hyperthermia, there is, for example, deep hyperthermia or prostate hyperthermia. With whole-body hyperthermia, the whole body is overheated except for the head.
This targeted overheating takes place with the help of infrared heaters and brings the body temperature to values of up to 40.5 degrees Celsius. Deep hyperthermia only takes place on the affected tissue and heats the diseased part of the body to up to 44 degrees Celsius. Prostatic hyperthermia is usually produced by transurethral hyperthermia. In addition to the heat, the radiation of an electrical field from radio short waves is used.
Hyperthermia as a medical term is opposed to hypothermia. It describes hypothermia due to excessive heat loss through radiation, conduction, convection and evaporation. Hypothermia due to heat losses are mainly supported by low air temperatures. Cold water or wind also promote the loss of heat from a body. Therefore, hypothermia typically occurs as part of accidents in the water, in the mountains and in caves. Staying in generally cold surroundings can also cause hypothermia.
Medicine differentiates between mild, moderate and severe hypothermia. Severe hypothermia causes the body temperature to drop below 28 degrees Celsius and can be fatal. In addition to unconsciousness or cardiac arrest, this form of hypothermia is characterized by reduced brain activity, pulmonary edema and rigid pupils. Cardiac arrhythmias occur. Often there is also a respiratory arrest due to hypothermia.
