From hiccups to brain freeze, you’re intimately familiar with many strange things your body does. The reason why these things happen, however, is a bit more elusive. Here, we shed light on 11 bodily processes you know well, but might not fully understand.
1. CHARLEY HORSES ARE MUSCLE SPASMS.
Muscle cramps are common while exercising, but they can also strike when you least expect it (like in the middle of the night). Charley horses, which can occur in almost any muscle but are most common in the legs, are actually muscle spasms. They occur when your muscles suddenly tighten and don’t release for several minutes. These spasms can happen for any number of reasons, including poor circulation, overexertion, insufficient stretching, dehydration, or potassium deficiency.
2. ITCHINESS COMES FROM YOUR BRAIN.
It’s long been believed that humans experience itchiness so that we can keep harmful irritants—like insects—at bay (when we scratch an itch, it makes that pesky pest leave our skin). But this explanation still doesn’t answer the question of how your body gets itchy. Recent research shows that when your skin comes into contact with an external irritant, it sets off a complex chain of reactions that stretch from itch receptors in your skin to your spinal cord to your brain. Nerve cells far from the irritation site release specialized molecules that tell your brain it’s time to scratch. Scratching relieves itchiness, scientists believe, because it creates a mild pain—which researchers now know is a distinct sensation from itchiness—that replaces the itch.
3. YOUR MIND ISN’T PLAYING TRICKS ON YOU WHEN YOU “SEE STARS.”
Those bright flashes and squiggly lines you see when you rub your eyes, sneeze, or stand up too fast aren’t figments of your imagination: There really are sparks of light inside your eyeballs. All cells within the human body let off light. These light emissions, called biophotons, are always present within the eye, but your brain is usually able to ignore them. However, when you apply pressure to your eyes, more biophotons are created than your brain is able to process, and as a result, you can see the light. These visible flashes are called phosphenes.
4. BRAIN FREEZE IS A RAPID-ONSET HEADACHE.
That sharp, stabbing pain in your forehead you feel when you take too big a sip of your milkshake is called sphenopalatine ganglioneuralgia, and it’s caused when two blood vessels that bring blood to your brain (the internal carotid artery and anterior cerebral artery) expand. When something cold hits the roof of your mouth, blood is directed to that area in order to warm it back up. That sudden rush of blood causes your blood vessels to dilate (or expand), which in turn triggers pain receptors that tell your brain something is amiss.
5. YOUR TASTE IS OFF AFTER YOU BRUSH YOUR TEETH.
There’s a good reason why orange juice (and many other things) taste terrible after you brush your teeth: Chemicals in your toothpaste mess with your taste buds. The two chemicals that cause your toothpaste to get foamy, sodium lauryl ether sulfate (SLES) and sodium lauryl sulfate (SLS), suppress the receptors on your taste buds that perceive sweetness. At the same time, SLES and SLS break down the phospholipids on the tongue that usually inhibit bitterness. In plain terms, these chemicals diminish your ability to taste sweet things while simultaneously heightening your ability to taste bitter things, a combo that wreaks havoc on your breakfast.
6. CHEWING GUM REALLY DOES HELP YOUR EARS ON AIRPLANES.
Stocking up on chewing gum before a flight has become just as routine a part of flying as the TSA line or returning your seat to its upright position. But, it turns out, chewing really does help equalize the pressure in your ears (and therefore help ease that uncomfortable or painful blocked feeling).
The reason your ears “pop” on airplanes is because air is less dense at higher altitudes. As you travel higher into the air, the air pressure outside your ears drops while the air pressure inside your ears remains the same. This causes the air in your inner ear to press against your eardrum (in an attempt to escape the inner ear and equalize the pressure). One way to help equalize the pressure is to open the Eustachian tube, a small cavity in the middle ear that connects the ears to the nose and throat. You can do this by swallowing, yawning, or—you guessed it—chewing.
7. YOU CAN BRUSH YOUR TEETH TOO HARD.
Logic may indicate that the more rigorous you are with your brushing, the better job you’re doing. However, brushing too hard or with a hard-bristled brush can actually do more harm than good. Overzealous brushing—as well as consuming acidic foods like wine, citrus, or iced tea—can cause your teeth’s enamel to wear down. This exposes the sensitive layers of your teeth and can make eating hot, cold, or sugary foods painful.
8. GOOSE BUMPS ARE POINTLESS.
Many, many generations ago, when humans were much hairier, goose bumps served a useful function: They helped our ancestors’ hair stand on end in order to make them appear larger in threatening situations (the same way a cat bristles its fur when it’s scared). Today, we no longer need to stave off predators in this way—and without all the extra hair, our goose bumps are much more visible—but the response remains, which explains why goose bumps show up not only when you’re cold, but also when you’re afraid.
9. YAWNING DOESN’T WAKE US UP; IT COOLS US DOWN.
For a long time, scientists couldn’t figure out why we yawn. But new research shows that the commonly held belief that yawns help wake us up by raising oxygen levels in the bloodstream is only a myth. Instead, yawning helps us regulate the temperature of our brains. Stretching our mouths wide to yawn increases the rate of blood flow to the skull, and the cool air we breathe in changes the temperature of that blood flow, therein bringing cooler air to the brain. We yawn when we’re sleepy, therefore, because the body is warmest when we are falling asleep and first waking up. Our body temperatures drop as we fall asleep, and yawning helps quicken the process.
10. A HICCUP IS A SPASM OF YOUR DIAPHRAGM.
The diaphragm is the dome-shaped muscle that separates the chest from the abdomen and works in conjunction with the lungs to help us breathe. When you take a breath in, the diaphragm contracts, flattening and pulling downward as it does so in order to make more room in the chest cavity for the influx of oxygen. When there’s a disturbance in the nerve passageways leading from the brain to the diaphragm—which can happen by swallowing too much air, eating too quickly, or experiencing anxiety—the diaphragm spasms. You experience these spasms as hiccups.
11. BLUSHING IS CAUSED BY AN ADRENALINE RUSH.
Blushing is part of our bodies’ fight-or-flight response. When triggered by an emotion such as embarrassment or nervousness, adrenaline is released into the body. This speeds up your heart rate and dilates your blood vessels to improve blood flow. When the veins in your face dilate, they create that signature rosy glow. While it’s long been known how blushing occurs, for a long time, scientists were stumped by the reason why we blush. A 2013 study indicates that blushing is an evolutionary trait. A team of Dutch psychologists found that we are more likely to forgive people who blush when admitting their transgressions, and people who blush are rated as more likable and trustworthy.