One of the first things we become aware of as children is our bodies. Usually, once we become aware of our bodies, we begin to ask questions about how they work, why they are the way they are, and what happens to them as they grow. Kids are often given answers to these questions, but they're not always true. And even what we think is true when we're kids may change over time, as scientists learn more about human anatomy and how it really works.
In the meantime, we're left believing myths about the human body - things "everyone knows" are true but have no basis in fact. How these myths came to be is more interesting and, in some cases, stranger than the fiction. These are the dumb things we believe about our bodies, why we think them, and the truth.
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Myth: You Shouldn't Wake A Sleepwalker
Someone getting out of bed and walking around while not fully conscious can be a little scary. But sleepwalking is much more common that people think: Up to 15% of the United States population sleepwalks.
According to Dr. Mark Mahowald, a sleep specialist at Stanford University, the legend that one should never wake a sleepwalking person originated from an ancient belief that a person’s soul left the body during sleep. Waking them would doom that person to wander soullessly forever.
Sleepwalking is a mixture of wakefulness and non-REM sleep. The best thing to do is guide a sleepwalker back to bed. It can be difficult to wake them in that state, but it is not harmful.
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Myth: You Can Sweat Out Toxins
Sweat is our body's air conditioning system: When we get hot, we sweat water onto our skin that can evaporate and cool us off. Sweat is about 99% water with a small amount of salt, proteins, carbohydrates and urea.
What our sweat does not contain is toxins.
Our skin is not an excretory organ. Toxins such as mercury and alcohol are processed and eliminated by our liver and kidneys. Increased activity like exercise can help the body rid itself of toxins by increasing the circulation of lymph fluid and blood, which are filtered by the lymph nodes and kidneys - but it's not our sweat that's eliminating the toxins.
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Myth: You Have Only Five Senses
Many people are taught at an early age that the human body has five senses. Indeed our sense of touch, sight, hearing, smell, and taste are all very important, but we actually have many important senses in addition to those.
Our sense of balance is maintained through our inner-ear and helps us stay steady as we move. Proprioception is how we sense where our limbs are in space and how we can control them without looking at them. Our sense of hunger tells us when we need to refuel our bodies. Our inner carbon dioxide detectors tell us how much oxygen we need to take in at any given time and how much carbon dioxide we must expel.
All of our senses, both major and lesser-known, work together so that we can function.
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Myth: Adults Can't Grow New Brain Cells
If you were worried that we couldn't grow new brain cells as adults, your fears can be put to rest. A 2019 article in Nature Medicine confirmed that it is possible for adults to form new neurons in the part of the brain responsible for learning, memory, and mood regulation - a process called neurogenesis.
The question is still hotly debated in the scientific community and, as we develop new technologies that can locate cells in the living brain and measure the cells’ individual activity, we will be sure to learn more.
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Myth: You Need To Drink Eight Glasses Of Water A Day
The origin of the old "you must drink eight cups of water a day" myth is up for debate, but it may stem from a 1945 Food and Nutrition Board recommendation that said people need about 2.5 liters of water a day, or roughly eight cups.
What people often fail to remember from that report, and from other papers with recommendations on water consumption, is that the water can come from food and other beverages. The water in our coffee and the moisture in our fruits and vegetables counts as water hydrating our bodies.
As for when we work out or when we are overheated, our bodies have a mechanism to tell us when we need more water and when we've had enough: our thirst.
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Myth: Fingernails And Hair Keep Growing After We Die
The old trope of fingernails and hair continuing to grow on the bodies of the deceased long after they are buried is the stuff of nightmares. It's the sort of eerie tale that one hears as a child and then passes on to the next generation.
But any sort of after-death growth is merely an illusion. Fingernails and hair are not growing; instead, the skin around them retracts as it becomes dehydrated, making them appear longer.
In order for fingernails or hair to grow in the human body, new cells must be produced. For that to happen, the body has to burn glucose, which requires the burning of oxygen. This process does not occur in the deceased.