Explain this one

Can anyone familiar with human physiology explain this one to me:  When I cut my hands (cooking or cleaning, or something), it's no big deal; when I get a cut on my feet (today my daughter's cleets took off most of one of my toenails), I start to black out.  Why in the world?  I'm generally squeamish about blood, but I can't understand why the drops from my hands or arms should be a non-event, while the bleeding toe has me sitting on the ground with an ice compress to the back of my neck.  Any guesses?

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  • http://ymarsakar.blogspot.com/ Ymarsakar

    A nerve could have been hit, that tends to have sympathetic vibrations up your spinal column.

    There must be more nerve endings in the damaged part than was in the skin of your hands that were cut. There’s the swelling problem with blunt force trauma to consider as well, compared to slash and dice cutting of the skin. Internal bleeding and swelling, along with blood pressure, can create secondary damage that can affect the rest of the body. Any injury, I believe, can cause the blood vessels to constrict or relax, depending upon some physiological factors I’m unaware of. If the blood vessels constrict, this limits your oxygen to your brain, therefore while it prevents bleed death, it can cause headaches as well, or even black out.

    Those are my guesses

  • erp

    My guess is that blood rushed to your head when you were bending down looking at your injury.

  • Patrick O’Hannigan

    Psychologically speaking, foot cuts make mobility seem (or become) problematic. With a cut hand, you don’t feel like locomotion, too, is impaired.

  • JJ

    Oddly enough, as a matter of pure physiology, your hands contain more nerve endings than any other part of your body.
    There are therefore more neural pathways to the brain emanating from your hands.

    But (and now you get into the psychological part rather than the pure physiological) your hands get into trouble all the time. Your neurons are accustomed, over the course of a lifetime, to getting emergency messages from your hands, because it is generally your hands that get into trouoble.

    Example: little kids stick their hands into fans and hot places all the time, it’s how they learn – but how many times have you ever heard of a little kid sticking his foot into a fire, or the fan? I suspect the answer is: never. Me either.

    So, unless it’s a real emergency, your brain learns to accept messages from your hands with a grain of salt: getting into some trouble in the course of exploration of the world around us is what hands are for. Command Center up behind your eyeballs expects this, considers it normative, and deals with it.

    But not with the feets! We keep them wrapped up and protected in shoes and socks from the time we’re born. We try to keep them temperate, they react a lot more to hot and cold than hands do even though hands have all the nerves, and they are a lot more reactive to scrapes and bruises than hands are, even though, as noted, hands have all the nerves.
    But we protect our feet. Hands – they’re out there.

    Our ancestors ran around largely barefoot, and built up pretty thick padding down there, though fossil evidence also indicates that a whole lot of them had broken things over the course of a lifetime – toes, metatarsals, heels, etc. But at the time that was feet were for, and they probably didn’t notice it as much as we do, now that we have been training our feet to be protected for the last couple thousand years.

    Our feet are nowehere as tough as our ancestors’ – but our hands remain out there, first to arrive at the scene of any accident!

  • Kevin

    Good theories all but I choose to blame the Democrats (hey I may as well utilize their game plan.)

  • http://ymarsakar.blogspot.com/ Ymarsakar

    I don’t think the hands have all the nerves, rather the fingertips have the nerves as seen with paper cuts. So it all depends on what part of the hand Book cut.

    The same applies to the foot. Injuries to the toe or the toe nail, is much more painful than a cut in your sole or the callused part of your foot. There is also more of a fear reaction, if you are immobile, because a lame creature is a dead creature on nature’s lands. You can fight with one arm or 4 fingers, but you can’t run with one leg.

    I’d suggset you not put your finger nail under a hammer and strike it, or put it in a door jamb and shut the door.