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Why do we sweat?

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Human bodies usually sweat during exercise, when it’s hot outside, when we’re sick, and when we’re nervous. Eating spicy foods can make bodies sweat, too. What’s going on inside our brains, bodies, and our skin, the largest organ in our bodies, to make us sweat? A lot.

This TED-Ed lesson by John Murnan, directed by Dogzilla Studio, shares the biological processes behind perspiration—and why it’s important for our health—with why we sweat when we exercise:

“A process called cellular respiration consumes glucose and oxygen to form ATP, the energy currency of the cell. Much of this process takes place in structures called mitochondria. The more you move, the harder mitochondria work to supply your body with energy.”

releasing heat

“All this work comes at a cost, though: As the cells break down the ATP, they release heat. The heat stimulates temperature sensors throughout your body. Those receptors detect the excess heat being produced by your muscle cells and communicate that information to the hypothalamus, which regulates body temperature.

“The hypothalamus responds by sending signals out through the sympathetic nervous system to the sweat glands in your skin. These are distributed all over the body with especially high concentrations on the palms of your hands, the soles of your feet, and on your head.”

sweat

“When a sweat gland first receives the signal, the fluid surrounding the cells in its coiled base contains high amounts of sodium and chloride. The cells pump these ions into a hollow tube that runs through the sweat gland. Then, because it’s saltier inside the tube than outside, water moves into the tube by osmosis.

“As what’s called the primary secretion builds up in the bottom of the tube, water pressure pushes it up into the long straight part of the duct. Before it seeps onto the skin, cells lining the tube will reclaim as much salt as possible so the process can continue.”

running and sweating

“The water in sweat absorbs your body’s heat energy and then evaporates off of you when it reaches the surface, which in turn lowers your temperature.

“This process, known as evaporative cooling, was an important adaptation for our ancestors. This cooling effect isn’t only helpful during exercise…”

adrenaline
Watch these related videos about sweat next:
An up close look at fingerprints and sweat glands
• What is wet bulb temperature?
What causes body odor?
Summertime Science: Sunburn, Sweat, and Wrinkly Fingers

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