Sacramento temperatures hit 116 degrees in early September—an all-time record.
Salt Lake City—4,000 feet above sea level—hit 105 degrees.
Downtown Denver hit 98 degrees.
In all, weather experts estimated 54 million people were subjected to a severe “heat dome” that stressed electrical power grids and made cold beverages look extra enticing.
How does the body stay cool when subjected to such heat?
It’s worth pondering—and it’s a pretty remarkable, automatic part of our anatomy. The process is called thermoregulation.
We don’t have much wiggle room when it comes to our core temperatures. If our internal baseline temperature falls below 95° we are “hypothermic.” If we go above 107.6°, our bodies face brain damage or death.
The sweet spot is 98° to 100°.
And our hypothalamus is key. It’s a section of the brain that controls thermoregulation. The hypothalamus links the nervous system to the endocrine system (which controls all hormones) via the pituitary gland. The hypothalamus is part of the limbic system (controlling emotions, behavior, long-term memory, and olfaction).
All vertebrate brains contain a hypothalamus. In us humans, it’s about the size of an almond.
When our internal temperature increases, sensors in our central nervous system send messages to the hypothalamus, which passes the alert along to various organs and systems in our bodies.
The most obvious response is sweat. Perspiration. Sweat cools skin as it evaporates. Cooler skin helps lower your internal temperature. Where does the sweat come from? Good question. The middle layer of the skin (or dermis) stores most of the body’s water. It’s the sweat glands’ job to bring that water—along with the body’s salt—to the surface of the skin as sweat.
Next is vasodilatation. The blood vessels under your skin expand. This allows blood flow to increase to your skin where it’s cooler—away from your warm inner body.
If our bodies get too hot, the risks include heatstroke, when the evaporation process fails and/or is overwhelmed. Essentially, the body sweats so much that it depletes itself of fluids and those precious salts. Warning signs include a body temp above 103°; red, hot, and dry skin; a rapid heartbeat; and a throbbing headache.
External aides also help. You might lay down on a leather couch (we hope it’s indoors and not out in the sun) and immediately sense that it’s relatively cool. Your temperature is being conducted away by the cool surface. Same with swimming in a cool pool or standing under a ceiling fan—that’s convection.
Prevention, as you would likely assume, is wise. Hydrate!
The Mayo Clinic says the average healthy adult needs 15.5 cups of fluids per day (that’s 3.7 liters) and women need 11.5 cups (2.7 liters).
Your hypothalamus—your whole body—will appreciate the help.