Tuesday, October 23, 2007

10 Things You Didn't Know About You




1. Your Skin Has Four Colors

All skin, without coloring, would appear creamy white. Near-surface blood vessels add a blush of red. A yellow pigment also tints the canvas. Lastly, sepia-toned melanin, created in response to ultraviolet rays, appears black in large amounts. These four hues mix in different proportions to create the skin colors of all the peoples of Earth.



2. The World Laughs with You

Just as watching someone yawn can induce the behavior in yourself, recent evidence suggests that laughter is a social cue for mimicry. Hearing a laugh actually stimulates the brain region associated with facial movements. Mimicry plays an important role in social interaction. Cues like sneezing, laughing, crying and yawning may be ways of creating strong social bonds within a group.



3. Big Brains Cause Cramped Mouths

Evolution isn't perfect. If it were, we might have wings instead of wisdom teeth. Sometimes useless features stick around in a species simply because they're not doing much harm. But wisdom teeth weren't always a cash crop for oral surgeons. Long ago, they served as a useful third set of meat-mashing molars. But as our brains grew our jawbone structure changed, leaving us with expensively overcrowded mouths.



4. Cell Hairs Move Mucus

Most cells in our bodies sport hair-like organelles called cilia that help out with a variety of functions, from digestion to hearing. In the nose, cilia help to drain mucus from the nasal cavity down to the throat. Cold weather slows down the draining process, causing a mucus backup that can leave you with snotty sleeves. Swollen nasal membranes or condensation can also cause a stuffed schnozzle.



5. Puberty Reshapes Brain Structure, Makes for Missed Curfews

We know that hormone-fueled changes in the body are necessary to encourage growth and ready the body for reproduction. But why is adolescence so emotionally unpleasant? Hormones like testosterone actually influence the development of neurons in the brain, and the changes made to brain structure have many behavioral consequences. Expect emotional awkwardness, apathy and poor decision-making skills as regions in the frontal cortex mature.



6. Thousands of Eggs Unused by Ovaries

When a woman reaches her late 40s or early 50s, the monthly menstrual cycle that controls her hormone levels and readies ova for insemination ceases. Her ovaries have been producing less and less estrogen, inciting physical and emotional changes across her body. Her underdeveloped egg follicles begin to fail to release ova as regularly as before. The average adolescent girl has 34,000 underdeveloped egg follicles, although only 350 or so mature during her life (at the rate of about one per month). The unused egg follicles then deteriorate. With no potential pregnancy on the horizon, the brain can stop managing the release of ova.



7. Much of a Meal is Food For Thought

Though it makes up only 2 percent of our total body weight, the brain demands 20 percent of the body's oxygen and calories. To keep our noggin well-stocked with resources, three major cerebral arteries are constantly pumping in oxygen. A blockage or break in one of them starves brain cells of the energy they require to function, impairing the functions controlled by that region. This is a stroke.



8. Bones Break (Down) to Balance Minerals

In addition to supporting the bag of organs and muscles that is our body, bones help regulate our calcium levels. Bones contain both phosphorus and calcium, the latter of which is needed by muscles and nerves. If the element is in short supply, certain hormones will cause bones to break downeupping calcium levels in the bodyeuntil the appropriate extracellular concentration is reached.



9. Body Position Affects Your Memory

Can't remember your anniversary, hubby? Try getting down on one knee. Memories are highly embodied in our senses. A scent or sound may evoke a distant episode from one's childhood. The connections can be obvious (a bicycle bell makes you remember your old paper route) or inscrutable. A recent study helps decipher some of this embodiment. An article in the January 2007 issue of Cognition reports that episodes from your past are remembered faster and better while in a body position similar to the pose struck during the event.



10. Your Stomach Secretes Corrosive Acid

There's one dangerous liquid no airport security can confiscate from you: It's in your gut. Your stomach cells secrete hydrochloric acid, a corrosive compound used to treat metals in the industrial world. It can pickle steel, but mucous lining the stomach wall keeps this poisonous liquid safely in the digestive system, breaking down lunch.

Emotions Run Amok in Sleep-Deprived Brains

Charles Q. Choi
Special to LiveScience
LiveScience.com Mon Oct 22, 12:20 PM ET

Without sleep, the emotional centers of our brains dramatically overreact to bad experiences, research now reveals.

"When we're sleep deprived, it's really as if the brain is reverting to more primitive behavior, regressing in terms of the control humans normally have over their emotions," researcher Matthew Walker, a neuroscientist at the University of California, Berkeley, told LiveScience.

Anyone who has ever gone without a good night's sleep is aware that doing so can make a person emotionally irrational. While past studies have revealed that sleep loss can impair the immune system and brain processes such as learning and memory, there has been surprisingly little research into why sleep deprivation affects emotions, Walker said.

Walker and his colleagues had 26 healthy volunteers either get normal sleep or get sleep deprived, making them stay awake for roughly 35 hours. On the following day, the researchers scanned brain activity in volunteers using functional magnetic resonance imaging (fMRI) while they viewed 100 images. These started off as emotionally neutral, such as photos of spoons or baskets, but they became increasingly negative in tone over time—for instance, pictures of attacking sharks or vipers.

"While we predicted that the emotional centers of the brain would overreact after sleep deprivation, we didn't predict they'd overreact as much as they did," Walker said. "They became more than 60 percent more reactive to negative emotional stimuli. That's a whopping increase—the emotional parts of the brain just seem to run amok."

The researchers pinpointed this hyperactive response to a shutdown of the prefrontal lobe, a brain region that normally keeps emotions under control. This structure is relatively new in human evolution, "and so it may not yet have adapted ways to cope with certain biological extremes," Walker speculated. "Human beings are one of the few species that really deprive themselves of sleep. It's a real oddity in nature."

In modern life, people often deprive themselves of sleep "almost on a daily basis," Walker said. "Alarm bells should be ringing about that behavior—no pun intended."

Future research can focus on which components of sleep help restore emotional stability—"whether it's dreaming REM sleep or slow-wave, non-dreaming forms of sleep," Walker said.

Many psychiatric disorders, "particularly ones involving emotions, seem to be linked with abnormal sleep," he added. "Traditionally people mostly thought the psychiatric disorders were contributing to the sleep abnormalities, but of course it could be the other way around. If we can find out which parts of sleep are most key to emotional stability, we already have a good range of drugs that can push and pull at these kinds of sleep and maybe help treat certain kinds of psychiatric conditions."