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Human body takes the heat like soldier

Mother Nature equipped us well for days like these

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Physiologically speaking, the blistering warm front that's blitzkrieged Utah this week plunged our bodies into an intense form of internal biological warfare.

We literally are in the heat of a battle as our body chemistry struggles to regulate our core and surface temperatures, facing triple-digit thermal salvos from the sun.

"Just sitting quietly, our metabolic rate generates as much heat as a 60-watt light bulb," says Walt Woodbury, professor emeritus of physiology at the University of Utah, who taught 45 years in his field. "Physical activity can multiply that by a factor of about 10, so now we're radiating 500 watts, and when you exert outside in this kind of climate, you're really heating up a hundred times over."

"The body is in a constant battle to get rid of this heat in order to survive," Woodbury said.

Every day, our bodies are waking up to the heat wave and more or less hollering, "Fire in the hole!" while placing defense mechanisms on red alert.

Fortunately, the human body is able to marshal impressive forces to meet Mother Nature's heat-seeking missiles. Along with deploying normal internal defenses, we also can throw up a perimeter of precautionary practices to win the day.

Some of the biomechanical troops and their allies the body rallies to beat the heat:

General Headquarters. The big brain behind our biological operation, Woodbury said, is the hypothalamus, located under the cerebral cortex near the pituitary gland.

"This is our body's command center. It regulates virtually every bodily function from respiratory rate to blood pressure to temperature control. It's like a very complicated, very smart thermostat clicking the air-conditioning on or off in our houses, as needed. The hypothalamus must be in good working order for us to deal with a wide range of physical challenges, extreme heat being just one of them," Woodbury said.

Corporal Corpuscle and Scout Patrols. The bloodstream has a key transport mission in ridding the body of heat, Woodbury said.

"The bloodstream carries calories away from all parts of the body where heat is produced in order the maintain core temperature of 98.6 (degrees). Also, thermal receptors in the skin act like scouts, telegraphing information via nerve fibers to the hypothalamus.

"With a sudden rise in temperatures, the message to headquarters is: 'Hey, things are changing around here. We'd better scramble to handle it.' "

Colonel Coronary and Sergeant Skinner. The heart's ability to increase blood supply and the skin's ranking as the body's largest organ make them, working in tandem, primary heat-defeating weapons.

"When we're under extreme heat conditions, the heart becomes the heavy artillery, pumping more blood to the skin," Woodbury said. "There, the blood vessels dilate to help dissipate heat through the skin."

The skin gets rid of the heat three ways:

Evaporation, or sweating.


Convection, that is, utilizing air molecule movement over the skin. "Fanning oneself or air-conditioning, in other words," Woodbury said.

Admiral Drinkwater. The time-honored tactic of fluid replenishment remains an essential strategy against heat.

"As the skin uses evaporation to dispense heat, we must constantly replace those lost fluids," said Dr. George Delavan, division director for Community and Family Health Services for the Utah Department of Health.

"Drinking every hour is the best method to prevent dehydration. Water is a great drink, but any of the drinks that also replenish salt lost in perspiration are probably the best choice. Gatorade, for instance.

"Soft drinks don't hurt you, by themselves. But the caffeine content can be a problem, because excessive caffeine constricts blood vessels that are trying to discharge heat.

"Neither is alcohol helpful, because it increases excretion of body fluids through the urine, leading to more dehydration."

Major Shade. Seeking shelter from the bombardment of the sun's rays helps the body dissipate heat.

"An umbrella or shade tree keeps the sun off, while affording plenty of room for evaporating and radiating heat," Woodbury said.

Captain Hatless. Donning a hat, a routine maneuver by many people in the heat, can be harmful, unless done properly.

"Bad idea, basically," said Dr. Scott Linscott, professor of surgery at the U. and emergency medical practitioner. "Since the body tends to lose 45 percent of its heat through the head, a hat can inhibit its ability to cool its core temperature and invite heatstroke. The only way a hat works is if it's light-colored, deflecting the sun's rays, and, more importantly, if it has some mesh in the crown to allow heat to escape."

Private Skimpy. Less is more in the clothing department.

"Again, light, loose-fitting clothing is best, because tight, dark clothes restrict heat loss," Linscott said. "But the best idea is to wear as little clothes as possible, because the more exposed skin, the more evaporation.

"Basically, I suppose, it would be best to go around nude, if we could."

E-MAIL: gtwyman@desnews.com