![]() ![]() To maintain a normal T c, the hypothalamus works by a variety of autonomic mechanisms, such as changing basal metabolism, muscle tone, thyroid activity, or adrenal response. For instance, the conductive transfer of water is 100 times that of air, so heat can be lost from the body very quickly when it is immersed in cold water. The body loses about 2% of its heat through air conduction, although different mediums transfer heat by conduction at different rates. Conduction is the loss of molecular kinetic energy and occurs when heat is transferred between two objects that are in contact with one another, such as heat loss that occurs from sleeping on cold ground. The body loses 10% to 15% of its heat through convection. This mechanism of heat loss is similar to sitting in front of a fan. Convection is heat loss by the physical movement of a fluid or gas from one location to another. During intense exercise, the body loses 85% of its heat through sweating. Evaporation is the basic mechanism of heat loss in high ambient temperatures. Water vaporization needs energy and consumes heat, therefore accelerating heat loss. Evaporation is an endothermic process that converts liquid into gas and is the second major source of heat loss, accounting for about 20%. This normal process usually occurs in air temperatures below 20 ☌. Radiation is the most important mechanism of heat loss, accounting for approximately 65% of loss. Radiation is the electromagnetic energy radiated by the body in the form of electromagnetic waves (mainly infrared rays) and is similar to the process of heat leaving a woodstove. ![]() Heat loss rate is determined by the level of heat transferred from inner tissues to the skin and from the skin to the surrounding environment by four mechanisms: radiation, evaporation, convection, and conduction. Skin is the largest structure of the human body and is responsible for about 90% of heat loss. Body heat production is mainly the effect of a transformation of chemical energy in foods into heat by cellular oxidative metabolism. This statement is important because proper body function depends on a stable T c. Humans are warm-blooded animals therefore, our bodies are able to adjust their metabolic rate to maintain equal heat production and loss. The T c is a balance between heat generated by the body and heat lost to the environment. In the present review, we discuss the current insights into proper body temperature measurements as well as related challenges and complications. Thus, the temperature that best describes a human thermal status is the T c. Temperatures of the peripheral parts of the body are cooler than the core, depending on the environment and thermoregulatory vasoconstriction. In addition, daily variations can be as much as 0.25–0.5 ☌, with the lowest body temperature occurring usually at about 4 a.m. The menstrual cycle is also one of the main causes of temperature variations. Among healthy persons, the average daily temperature can differ by 0.5 ☌. The T c of the human body is maintained within a narrow range, close to 37 ± 0.5 ☌ at rest. The core thermal compartment is very well perfused and relatively homogeneous. It is also believed that mean body temperature characterizes the overall thermal status, but its use is impractical for everyday use. ![]() There is increasing evidence that body temperature is controlled by independent thermoeffector loops composed of specific afferent and efferent branches collectively producing a balance point of core temperature (T c). Currently, the traditional model of an individual set point in the hypothalamus is being questioned. Central thermoregulatory management is based on afferent thermal signals coming from the core and peripheral thermoreceptors, which are integrated by the central nervous system, especially the hypothalamus. Thermoregulation is the element of homeostasis that maintains a stable internal temperature, regardless of the environmental conditions.
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