With thermoregulation, the human body maintains an ambient body temperature of 37 degrees Celsius. Metabolism, as well as muscles and oxygen transport, depend on this temperature. Thermoregulatory disorders present themselves, for example, in heat stroke.
What is thermoregulation?
With thermoregulation, the human body maintains a body temperature of 37 degrees Celsius, independent of the environment. Thanks to thermoregulation, the human body temperature is relatively independent of outside temperatures. This means that humans belong to the group of creatures with the same body temperature. A distinction must be made between these and other warm-blooded creatures, whose body temperature changes significantly with the outside temperatures. In humans, thermoregulation corresponds to maintaining a constant core body temperature of about 37 degrees Celsius. Metabolism, as well as oxygen transport and muscle activity, depend on a constant temperature that corresponds to their optimal operating temperature. To maintain the temperature, a permanent exchange takes place between the human body and its environment. Convection, conduction, radiation and evaporation make up this exchange. Through these mechanisms, the organism can autonomously either decrease or increase its temperature. The hypothalamus is considered the center of thermoregulation, from which all of the above processes are initiated. Ambient and internal temperatures are permanently determined by so-called thermocells in the skin and mucosa and transmitted to the hypothalamus.
Function and task
Thermoregulation forms the prerequisite for various processes in the human organism. Temperature increases, for example, increase the elastic properties of all muscles and tendons. Metabolic reactions in the human organism are equally dependent on temperature. An increase in temperature increases the kinetic energy of the particles involved and thus makes a reaction more likely. Since proteins in the human organism denautrate at temperatures above forty degrees, the ideal metabolic temperature is 37 degrees Celsius. Enzyme reactions, as well as the fluidity properties of cell membranes and diffusion or osmosis behaviors in the organism are all influenced by the kinetics of particles, which in turn is determined by temperature. Temperatures also play a role in oxygen transport through the bloodstream. Hemoglobin provides the blood with the binding ability to oxygen particles. The binding affinity decreases with falling temperatures, so oxygen transport can only occur at relatively warm temperatures. Without oxygen transport, tissue loss and ultimately death would occur. Thus, thermoregulation is imperative for human life. Body heat results from the energy conversion of muscles and in metabolism. In the muscles, chemical energy becomes kinetic energy, which gives rise to heat. The transport and distribution of this heat takes place through convection, which has the blood as its medium. Heat loss is prevented by the subcutaneous adipose tissue, as with an insulating layer. If the body temperature nevertheless drops due to extremely low outside temperatures, this loss is reported to the hypothalamus by the thermocells. The brain then stimulates the pituitary gland, which releases thyrotropin releasing hormone, thus increasing sympathetic tone. The heart rate increases due to the hormone, the metabolism is stimulated and the muscles provide more energy. In this way, body temperature can be maintained despite the cold. If, on the other hand, the body becomes too warm due to persistently high ambient temperatures, the hypothalamus lowers the sympathetic tone. As a result, peripheral vasodilation occurs and blood flow improves, providing some surface area for heat exchange. Heat loss takes place through convection. In addition, sweat secretion is stimulated because sweat glands are sympathetically innervated. Evaporative cooling occurs via evaporation, which cools the organism.
Diseases and ailments
Various medications, as well as deficiency symptoms such as iron deficiency, cause disturbances in thermoregulation. These disturbances usually correspond to inappropriate sweating in cold ambient temperatures or shivering despite a warm temperature.Such phenomena can also occur in the context of nervous system diseases such as polyneuropathies. Pure sensory disturbances, in which only the sensation of warmth and cold is disturbed, are to be distinguished from this. This sensation is subject to individual components anyway. Real perception disorders in connection with temperatures often occur in the context of central nervous system injuries, which in turn can have various causes. Disturbed temperature perception need not be immediately related to disturbed thermoregulation. Actual thermoregulatory disorders usually have their cause in the hypothalamus or the sympathetic nervous system. If there is a lesion in either part of the brain, then this can cause misregulation of metabolism, as well as muscle, which in turn affects the maintenance of body temperature. Thermoregulation can fail just as quickly in phenomena such as heat stroke. There are different forms of heat stroke. In the severe variants of the phenomenon, heat damage to the cells and sometimes even to the organs sets in. The balance of thermoregulation is upset. Heat stroke, for example, is caused by increased heat production, as can occur when exercising beyond all limits. The lack of heat release can also result in heat stroke. If a core temperature of more than 40 degrees Celsius is reached as part of this, the enzyme systems take damage. The cells’ energy stores empty and membrane permeability and sodium flux increase. Thermoregulatory mechanisms completely cease and the temperature continues to rise, resulting in necrosis and multiorgan failure.
