Intellectual curiosity is one of humankind's most admirable traits. We're fascinated by what we don't fully understand. Were this not true, we'd have no ongoing preoccupation with black holes, or what really happened to Amelia Earhart, or why you can't eat just one Pringle.

We search for mysteries at the far reaches of outer space, yet there are a great many strange and unknown things going on within the finite space of our own brains. Small wonder, really, when there are as many neurons in our brains as there are stars in our galaxy: about 100 billion, give or take a few million. Though in each brain there are some 100 trillion connections made among all of those cells, not a single neuron physically touches another.

Just by virtue of the enormous numbers, the human brain is beyond our comprehension.

And that's not even the weird stuff. Check out these mind-boggling facts.

Your eyeballs are an extension of your brain.

If someone were to open up your skull and remove your brain (carefully, please), your eyeballs would come with it. That's because your eyes are hardwired to a lobe at the back of the head responsible for sight information. Bundles of optic nerve fibers connect the retina, where images are received, directly to the brain's occipital lobe. The other four senses send their signals through convoluted pathways and nerve networks, but vision has a straight line into the brain, like a keyboard connected to a computer.

Brain surgery can be conducted while a patient is awake.

Patients suffering from brain tumors or epileptic seizures may undergo surgery while awake. Rather than relying exclusively on brain-imaging technology, a neurosurgeon can speak to an awake patient to mark or "map" critical areas of the brain that control vision, language, and body movement, ensuring the procedure's accuracy and safe outcome. The patient is anesthetized during the portion of surgery when doctors make their way through the cranium to the exposed brain.

The brain knows everything but can't feel a thing.

The brain itself has no receptors for pain. It has no sensory nerve system of its own to detect temperature, pressure, or even tissue damage. In the awake-surgery mentioned above, a surgeon could poke the exposed matter with a needle and the patient would not feel any sensation in the brain. When cysts or tumors cause headaches, the pain results from pressure on nerve tissue and/or blood vessels surrounding the brain.

Brain freeze is a mystery.

Nobody's quite sure why a fast gulp of Slurpee can leave you feeling like a vice is crushing the inside of your head. We call it "brain freeze," but the sensation is actually felt around the temples and the mask of the face; remember, the brain itself has no pain receptors. The best guess among scientists is that a cold drink, when rapidly consumed, shocks the trigeminal nerve, which is responsible for sensation to the face and head. The brain's hypothalamus gets a message to create warmth and responds by dilating vessels around the nerve to heat the area with blood flow. But the sudden dilation causes pressure and a stunning wave of pain.

The brain is an oxygen hog.

"Although the brain constitutes only 2 percent of our body mass, it uses 20 percent of the oxygen," explains Istvan Molnar-Szakacs, Ph.D., of the Semel Institute's Tennenbaum Center for the Biology of Creativity at UCLA. In other words, the brain uses up a fifth of the oxygen we breathe. This leaves the brain highly susceptible to damage during anoxic episodes; after about four minutes without oxygen-rich blood, brain cells start to die.

You can't tickle yourself.

Well, you can try, but you won't laugh. The body's sensory nervous system is active all the time, allowing us to hear our own breathing or feel the weight of our body on our feet. Yet, these are background sensations; our sensory attention is reserved for signals from the external world such as a honking car or a kiss on the cheek. Neuroscientists believe that the cerebellum, a small area responsible for coordinating movement and motion, predicts our own sensory actions and differentiates them. Says Molnar-Szakacs, "The cerebellum warns your brain/body that the 'tickle' movement is coming, and so the sensory part of the brain essentially knows to ignore the sensation."

The brain is terribly smart, but it can be fooled.

In the image shown here, the squares marked A and B are the same exact shade of gray. Really. No fooling. The checkershadow illusion plays on the way the brain's visual system uses contrast to determine light levels. (A complete explanation of the illusion by its creator, professor Edward H. Adelson of M.I.T., is available here.)

One thing that's great about that last experiment is that it underscores the confidence, even the blind faith, we have in the brain. With just a few scant clues about how that gelatinous mass works, we're absolutely certain that it does. We can imagine challenges beyond the capacity of other organs and body parts: a load we know is too heavy for our arms, a meal our stomach won't tolerate, a pitch too high for our ears to detect. But a challenge to the brain's reliability and accuracy? Do you really mean to tell me those hundred billion neurons are not doing their job? Them's fightin' words.

Find More on MSN Health & Fitness:

Rich Maloof's award-winning writing has covered subjects ranging from soda pop to stem cells. He has written for MSN, CNN, MSNBC, Yahoo!, Women’s Health, and various other publications. He is the published author of 12 books to date, including several instructional titles for musicians. His latest title, This Will Kill You, is being released by St. Martin's Press in May. Rich is a regular contributor to Brain & Body.

Mother's Day Guide - Gift ideas, plan the best day & more
slideshow spotlight on msn health & fitness
  • Cholesterol-Busting Foods // (© foodanddrinkphotos/Masterfile)
  • So Long, Muffin Top // (© Lynda Churilla for MSN Health)
videos © Bing
msn health social headquartersLike MSN Health on FacebookPin it on PinterestFollow MSN Health on Twitter
Download Windows Internet Explorer 9 © MSN

MSN Health & Fitness does not provide medical or any other health care advice, diagnosis or treatment.



IMA Winner 2011