The autonomic nervous system and hypothalamus are primarily responsible for maintaining a constant temperature of the human body. Body temperature depends on the intensity of bioenergetic processes. Therefore, for example, in children, it may normally be higher than in the elderly, since metabolism slows down with age. The body perceives the ambient temperature due to nerve endings in the skin and muscles – thermoreceptors (Tan & Knight, 2018). Thermoreceptors constantly transmit this information to the central nervous system, namely to the hypothalamus, in which the thermoregulation center is located. In turn, the thermoregulation center determines the metabolic rate, which adjusts the main metabolism to heat production or heat transfer.
The hypothalamus, a small area in the intermediate brain, is responsible for controlling the complex process of thermoregulation, namely, for determining when it is necessary to activate the mechanisms of cooling or warming (Kenneth, 2020). Here are the neurons responsible for regulating temperature. The hypothalamus has no clear boundaries, it can be considered as part of a network of neurons stretching from the midbrain through the hypothalamus to the deep parts of the forebrain. Extensive anatomical and functional connections of the hypothalamus provide a wide range of its activities.
For example, in the case of a sharp change in air temperature, adaptive mechanisms aimed at maintaining a constant body temperature come into effect, and they are “triggered” mainly by the hypothalamus, which has special thermosensitive devices. At high ambient temperatures, under the control of the hypothalamus, peripheral skin vessels dilate, sweating increases and metabolic metabolism in the body decreases (Tan & Knight, 2018). Due to this, heat transfer increases. At low temperatures, to reduce heat transfer, peripheral skin vessels, on the contrary, narrow, the heart rate increases, and muscle tremors occur – asynchronous muscle contractions that increase heat production, metabolism increases, which enhances the metabolic processes of heat generation (Schlader & Vargas, 2019). In other words, the hypothalamus acts as a very efficient thermostat.
When the ambient temperature changes, people are aware of this, because they become either cold or hot, and they begin to struggle with this, for example, by changing clothes, including a heater, a gas boiler, or an air conditioner. The hypothalamus works in approximately the same way, but it does it more subtly with the help of mechanisms built into the body. Destruction of the hypothalamus centers or disruption of nerve connections leads to loss of the ability to regulate body temperature. Some injuries and brain tumors can disrupt the normal functioning of the hypothalamus, provoking profuse sweating.
The temperature has a significant impact on the course of life processes in the human body and on its physiological activity. The processes of vital activity are limited by a narrow range of the temperature of the internal environment, in which the main enzymatic reactions can occur. High temperature causes intense sweating, which leads to dehydration of the body, and loss of mineral salts and water-soluble vitamins. The consequence of these processes is blood thickening, violation of salt metabolism, gastric secretion, and development of vitamin deficiency. The systematic effect of high temperature causes changes in the cardiovascular system: increased heart rate, changes in blood pressure, and weakening of the functional ability of the heart.
Low temperatures can be the cause of cooling and hypothermia in the body. When cooling in the body, heat transfer reflexively decreases, and heat production increases. A decrease in heat transfer occurs due to a spasm (narrowing) of blood vessels, and an increase in the thermal resistance of body tissues. Prolonged exposure to low temperatures leads to persistent vascular spasms, and disruption of tissue nutrition. Exposure to low temperatures is accompanied by an increase in blood pressure, inhalation volume, and a decrease in respiratory rate. Cooling the body changes carbohydrate metabolism. Large cooling is accompanied by a decrease in body temperature and inhibition of the functions of organs and body systems.
References
Kenneth, S. S. (2020). Anatomy & physiology: The unity of form and function. McGraw Hill.
Tan, C. L., & Knight, Z. A. (2018). Regulation of body temperature by the nervous system. Neuron, 98(1), 31-48.
Schlader, Z. J., & Vargas, N. T. (2019). Regulation of body temperature by autonomic and behavioral thermoeffectors. Exercise and sport sciences reviews, 47(2), 116-126. doi: 10.1249/JES.0000000000000180