Thermoregulation and Why Humans Sweat

Internal body temperature is controlled and regulated through a process called thermoregulation. The body constantly tries keeps its core temperature around 98.6 degrees, although it can waver within a narrow range between 91.76 and 100.72 degrees safely. Thermoregulation is part of a constant process the body goes through to stay in balance, called homeostasis. To maintain such a specific temperature range a part of the brain called the hypothalamus uses thermoreceptors (cells that sense temperature) throughout the body to determine what the body needs to do in order to heat up or cool off based on the environment it is in. The main reason why humans sweat is to cool off the body during times of high heat. The body also uses other processes like dilating or constricting blood vessels, shivering, and behavioral adaptations to control its internal temperature.[1]

How Sweating Cools the Body

When the environmental temperature exceeds a person’s internal body temperature various processes begin to induce sweating in order to keep that person’s core body temperature stable and cooler than their environment. Sweating is actually the only automatic way the body has to cool itself off when exposed to hot temperatures, which makes it very important for human survival. The body begins to sweat when a person’s brain senses that the body’s core temperature is beginning to rise, at which time it activates sympathetic cholinergic fibers, a part of the sympathetic nervous system that is responsible for activating sweat glands. Specifically, the body uses eccrine sweat glands, which are located all over the body, to regulate temperature. There is another type of sweat gland, called apocrine sweat glands, but they are not thought to be important in the process of thermoregulation. Once sweat glands are activated vasodilation occurs (expanding of the blood vessels) and sweat glands begin taking liquid from inside a person’s body and pumping it onto the surface of the skin. When the sweat is on the surface of the skin is evaporated as water vapor it transfers heat from the body to the surrounding environment. This essentially cools the human body as sweat transfers heat energy as it moves away from the body. When the body is cool enough the brain sends signals to sweat glands to stop producing sweat and the process is halted.[1]

Some people have a condition, called hyperhidrosis, that causes them to sweat too much. Luckily, hyperhidrosis is not particularly dangerous, although it is quite uncomfortable and can have a significant detrimental impact on a person’s quality of life. Hyperhidrosis is probably the most common sweating disorder, but there are other sweating conditions that cause people to sweat too little, have stinky sweat, or even have colored sweat.[1]

In addition to sweating because of high of surrounding temperatures, the body also produces sweat because of other factors that influence body temperature, like exercise and fever. Exercise, in and of itself, increases the body’s internal temperature and so the body responds by sweating to cool itself down.[1] In the instance of a fever, the body is trying raise its internal temperature in order to kill off intruders that are causing illness. Often sweating is a symptom of fever and it may also be a way the body uses to resolve a normal temperature once a fever is over, although the mechanism is not well understood.[3]

It is clear that sweating is an important process for regulating homeostasis in the human body. The brain and body work within a delicate balance to ensure that a person’s temperature is never too high nor too low and sweating is an essential part of its ability to do so.

Sources
  1. Tansey, E. A., & Johnson, C. D. (2015). Recent advances in thermoregulation. American Physiological Society. Retrieved February 26, 2019, from https://doi.org/10.1152/advan.00126.2014.
  2. Pariser, D. M. (2014). Hyperhidrosis (4th ed., Vol. 32). Philadelphia, PA: Elsevier.
  3. Del Bene, V. E. (1990). Temperature. Clinical Methods: The History, Physical, and Laboratory Examinations. Retrieved February 26, 2019, from https://www.ncbi.nlm.nih.gov/books/NBK331/.