Did you know that no one else in the world smells like you? Or that your feet produce nearly a gallon of sweat each week? Or that more than 500 species of bacteria call your body home? The human body is a fascinating piece of machinery – but it also has its share of interesting quirks. Here are 20 odd body facts explained.
You’ve just dug into that delicious bowl of ice cream when it strikes — a sharp, stabbing pain in the middle of your skull. Thirty seconds later, it’s gone. You’ve just been hit with brain freeze.
Brain freeze occurs when something really cold touches the soft palate on the roof of your mouth, causing the blood vessels there to suddenly constrict. As warm blood starts to flow through them again, the vessels dilate, causing receptors to send a pain signal to your brain. The message is sent through the nerve that is responsible for feeling in your face, so your brain thinks the pain is coming from your forehead — which is what causes that brief but intense headache sensation.
Déjà vu is a strange feeling of familiarity during a new experience — like you’ve been there, done that or met someone before, even though you haven’t.
There are a lot of different theories about what causes déjà vu. It’s a difficult sensation to study because it occurs randomly, without warning, and usually only lasts 10 to 30 seconds. But one plausible explanation involves the parts of our brain that process long-term memory. These brain areas also deal with familiarity — knowing whether certain objects, events and people are new or not. An occasional delay in connection between recognition and memory could explain the déjà vu feeling of familiarity without having an actual memory to base it on.
Even if you don’t recognize the term, you’re probably familiar with the action: you’ve just nodded off to sleep when, suddenly, your leg jerks you awake, startled, your heart pumping.
Believe it or not, these hypnic jerks are part of the natural sleeping process. As you start dozing off, your muscles begin to relax. Sometimes, the brain interprets that relaxation as a sign that you’re falling (which may be one of the reasons that people often dream they’re falling right before they get that body twitch). The jerking movement is your arms and legs trying to regain their balance.
Sneezing may not be a prophetic sign from the gods, like they thought in ancient Greece, but this reflex is anything but ordinary. Sneezes are powerful — the velocity of a sneeze is around 100 miles per hour, and the saliva that sprays from your sneeze can travel up to 5 feet. (Eww, is right!)
Sneezing is your body’s equivalent of a leaf blower — its way of keeping your nose clean — and is usually triggered when dust, dirt or some other particle has irritated the mucous membranes in your nose and throat.
It’s physically impossible to sneeze with your eyes open, or while you’re sleeping. And while sneezing does change the flow of blood in your body and the rhythm of your heartbeat, your heart doesn’t stop functioning when you sneeze, as urban legend has it.
If you’ve ever gotten a charley horse before, you know how painful these muscle spasms can be — it feels like your muscle has tied itself into a tight knot, one that you can’t unclench.
The most common causes of these spasms are dehydration or an electrolyte imbalance. Sodium, potassium, magnesium and calcium are all minerals that help your muscles move. If one or more of those minerals is lower or higher than it should be, or if you’re dehydrated, the processes that help your muscles contract normally can cramp up.
Thank your sympathetic nervous system for that rosy red hue that hits your cheeks whenever you trip in public or say something silly on a first date. When you’re embarrassed, adrenaline in your body automatically speeds up your breathing and heart rate and sends more blood than usual to your face, causing your skin to blush.
There is an upside to blushing. A series of recent studies found that blushing actually helps strengthen social bonds and increases empathy from others, meaning people may judge your embarrassing behavior less harshly if they see your skin turn crimson.
People who experience phantom limb sensations feel a temperature change or a tingling or itching coming from a body part that they either had amputated or were born without.
Unlike phantom sensation, which is usually painless, phantom pain is a shooting, throbbing or stabbing pain that comes from an area of the body where an amputation has taken place.
Doctors are still searching for the exact cause of phantom pain — damaged nerve endings, scar tissue or the physical memory of the pain of the injury may play a role.
But many experts point to the spinal cord and the brain as the probable source of the pain. After an amputation, the brain and spinal cord stop receiving messages from the missing limb, which sends a signal to the brain that something is wrong. The end result is a pain sensation.
Have you ever caught a case of the yawns: you see your coworker yawn and next thing you find yourself yawning too? Yawning is an involuntary action that humans do starting in the womb (there’s research that shows that fetuses as young as 11 weeks old yawn). But studies suggest that contagious yawning is a learned behavior that we don’t pick up until the age of 4. So far, scientists aren’t sure exactly why one person yawns after someone else does.
Each of your feet has more than 250,000 sweat glands that produce more than a pint of sweat each day — that’s nearly a gallon of sweat every week!
When we sweat, we automatically attract bacteria on our skin, which eats the sweat and produces smelly waste. But don’t blame the bacteria for the odor — blame your socks and shoes. Because our feet are usually covered, the smell can’t escape our feet as easily it does our hands or other areas that sweat equally or more, making the feet one of the smelliest parts of the human body.
Once you pass puberty and stop growing, it seems like you’ve settled into the body you’ll have for the rest of your life. But the cells inside of your body are constantly dying and being replaced, a biological process called “cell turnover.” The average lifespan of all the cells in your body is 7 years — so in some ways, it’s like you’re a new person every 7 years! But there are exceptions to that rule: bone marrow stem cells divide and produce 2.5 million red blood cells every second, but your brain cells only replicate every 100 years (scientists used to think your brain cells didn’t replicate at all but now know it just takes a very long time).
Ever stopped to wonder what saliva is, and what it’s doing in your mouth? Saliva is made up mostly of water, with a sprinkle of electrolytes, mucus, antibacterial compounds and enzymes. It’s produced by the salivary glands inside your cheeks, on the bottom of your mouth and under your jaw. Those glands are on the job 24/7, creating 2 to 4 pints of saliva each day.
Not only does saliva help us chew and break down food, but it also helps keep the inside of our mouths healthy — without saliva, your teeth would start to decay, your tooth enamel would erode and your mouth would become a popular destination for fungus and bacteria.
Hiccups seem to start out of nowhere — but once they do, they’re hard to stop. The culprit? Involuntary contractions of the diaphragm. The contractions also cause your vocal chords to close suddenly, resulting in that “hic!” sound.
You can get the hiccups from a large meal, alcohol, carbonated beverages, or sudden excitement or stress. Thankfully, most cases only last a couple of minutes. But in 1922, Charles Osborne fell down, damaging the part of his brain that inhibits the hiccup response. He began hiccupping, and didn’t stop for approximately 68 years — the longest bout of hiccups ever recorded, according to the Guinness Book of World Records.
If you’ve ever gone to a loud concert and come home with your ears ringing, you’ve had one of the symptoms of inner ear damage — tinnitus. Tinnitus is the perception of ringing, buzzing, roaring, clicking, whistling or hissing when the sound isn’t actually there.
Your ears contain tiny hairs that move based on the different pressures of the sound waves that travel through them. That movement triggers your auditory nerve to send a signal to your brain, which interprets the signal as a sound. When those hairs get damaged, they can send broken or random signals to your brain, which the brain interprets as a ringing sound.
If you’re ticklish, just seeing someone’s fingers wagging playfully towards you may be enough to send you into a fit of the giggles. But turning your own fingers toward ticklish spots like your armpits or the heel of your foot won’t even make you chuckle.
It’s physically impossible to tickle yourself because your fingers can’t outsmart your own brain. The cerebellum (the part of the brain that monitors movements), can tell the difference between an expected and an unexpected sensation. So your brain anticipates what your hands are doing and tells your body to ignore the tickle.
What keeps your body snuggled safely in bed while your dream self is flying through the air, being chased by bad guys or sitting naked in a classroom? Every time you enter the REM phase of sleep, your brain flips a biochemical switch that puts your body on lockdown, blocking the brain’s ability to order your muscles to move.
If the switch isn’t flipped, you might find yourself sleepwalking, sleep-eating, sleep-talking or acting out some other part of your dream while still asleep.
You probably know that certain parts of your body, like your fingerprint and your DNA, are uniquely you. But did you know that no one else in the world has your scent?
That’s right. Mammals have genetically-determined body odors, or odor types, which means that every person has a different one (unless you have an identical twin). While your diet has some influence in changing or masking your odor, research has shown that it can’t completely change it — your unique odor is here to stay.
We put a lot of effort into trying to avoid bacteria: we wash our hands after we sneeze, scour the bathtub and grimace when riding public transportation. But try as we might, they outnumber us — literally. There are 10 times more bacterial cells in and on your body than human cells. Scientists estimate that more than 500 different species of bacteria live in and on our bodies at any given time, from tiny eyelash mites to microscopic bacteria on the soles of the feet. The truth is, many of our bacterial tenants are helpful, not harmful, like those that live in the intestinal tract and help us digest our food or the ones that work with our immune system to protect against infections.
Goosebumps are caused by the stress hormone adrenaline, which is released when we’re cold or afraid. Adrenaline prompts the tiny muscles attached to our body hair to contract. As a result, our hair stands upright and our flesh appears bumpy.
Most animals shed tears to help keep their eyes lubricated — though the wily crocodile may never admit as much. But the consensus among experts is that humans are the only species that cries for emotional reasons.
Part of this may be to releases stress hormones, which make us feel better when we’re upset or can calm us down when we’re excited. Research also suggests that tears, whether happy or sad, play an important part in conveying our emotions to others and in evoking emotion from others. That connection leaves us feeling protected and supported, and helps to form closer, stronger relationships — a key survival mechanism.