Thermoregulation is the process that allows the human body to maintain its core internal temperature. The state of having an even internal temperature is called homeostasis. All thermoregulation mechanisms are designed to return the body to homeostasis.
A healthy, safe temperature has a very narrow window – between 98°F (37°C) and 100°F (37.8°C). Within a few degrees of that range, you may experience signs related to body temperature changes. For example, if your body temperature falls just 3 degrees to 95°F (35°C), you might experience hypothermia. Hypothermia can cause cardiac arrest, stroke, or even death. At 107.6 °F (42 °C), you could suffer brain damage as a result of temperatures that are too high.
A section of your brain called the hypothalamus controls thermoregulation. It issues instructions to your muscles, organs, glands, and nervous system when it senses your core internal temperature is becoming too low or too high.
Many factors can affect your body’s temperature. Illness or infection is one of the most common causes for a fever. Exercise, digestion, and being outdoors in a hot climate can also increase your temperature. Cold climates can lower your temperature. Drug or alcohol use and metabolic conditions like diabetes can cause low temperatures, too.
When your temperature increases, your body activates a system to promote heat loss. This returns body temperature back to normal.
This process has three steps:
1) Sensors in your central nervous system (CNS) send messages to your hypothalamus, telling it your internal temperature is increasing.
2) Your hypothalamus, which controls thermoregulation, receives the message.
3) Your hypothalamus activates one of several mechanisms to decrease your temperature.
The same process occurs when your body senses your temperature is falling too low.
When your brain receives a temperature warning from your body, it sends signals to various organs and body systems, which try to slow or increase heat production.
If your body needs to cool down, these include:
- Sweating: Sweating is one of the first methods your body will use to control your temperature. Sweat cools your skin as it evaporates. This helps lower your internal temperature.
- Vasodilatation: Your CNS may instruct the capillaries under the surface of your skin to dilate, or open. Vasodilatation, or enlarged capillaries, increases blood flow at the skin surface. This lets your body release heat through radiation.
If your body needs to warm up, these include:
- Stopping sweating: Your nervous system can lower sweat production to help maintain the heat your body generates.
- Vasoconstriction: Your CNS may signal your capillaries to constrict, or become narrower. This decreases blood flow under the skin and reduces heat loss.
- Thermogenesis: Your body’s muscles, organs, and brain can produce heat when your internal temperature is sinking. This process is called thermogenesis. Muscles are especially effective at thermogenesis. They can produce large quantities of heat quickly. Shivering is one way muscles generate heat.
- Hormonal thermogenesis: Your body can activate the thyroid gland if you are getting too cold. This releases hormones that increase your metabolism. An increased metabolism increases the energy your body creates and the amount of heat your body is able to make.