Fahrenheit 98.6

When you're well, your body temperature stays very close to 37o C. (98.6o F.), whether you're playing basketball in an overheated gym or sleeping in the stands at an ice hockey game in a snowstorm. Your body temperature is controlled by an area of the brain called the hypothalamus. It's about the size of the tip of your thumb and weighs a little more than a penny.

The hypothalamus is much like the thermostat attached to a furnace. Just as a thermostat senses temperature and turns the furnace on or off, the hypothalamus regulates the body's energy use and keeps temperature very near the norm. The hypothalamus can sense the temperature of the blood. If the blood becomes too cool, the hypothalamus causes the pituitary, a gland at the base of the brain, to release a hormone called TSH. (Hormones are chemicals made in one organ that travel through the blood and affect other organs.)

TSH travels through the blood and reaches the thyroid gland in the neck. There, it stimulates the thyroid to make another hormone, thyroxine. Thyroxine travels to all the cells of the body through the blood stream. It makes the cells burn food faster, generating more heat. If the blood is too warm, the reverse occurs. TSH production decreases, thyroxine levels decrease, and body cells release energy more slowly.

About the Author

Faith Brynie, Ph D

Faith BrynieFaith Brynie holds a B.A. in Biology from West Virginia University and an M.A. and Ph.D in science curriculum and instruction from the University of Colorado. She writes books and articles on science and health topics for children, teens, and non-scientist adults. Some of her books have won awards, including two 'Best Book of the Year' citations from the American Association for the Advancement of Science.