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Flaws of the musculoskeletal system

  1. Feb 20, 2006 #1
    What are the flaws of the musculoskeletal system?
     
  2. jcsd
  3. Feb 20, 2006 #2

    DocToxyn

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    I'm assuming you mean the typical endoskeletal system of animals and how muscles interplay with it? Perhaps its best to make a comparison to the exoskeletal system of insects. The external skeleton allows much better protection of the softer tissues and organs and affords much better leverage to be achieved. This allows insects to carry very heavy loads, much heavier than themselves, something we cannot do.

    The exoskeleton does have some disadvantages such as the requirement for shedding to permit growth and the accompanying periods of vulnerability and I also think that there are limits that cap the ultimate size one can achieve with an exoskeletal system before the weight of tissues inside the structure cannot support itself. The endoskeletal system obviously isn't limited by this as much, thus animals using this strategy can attain much larger sizes.
     
  4. Feb 20, 2006 #3
    Perhaps you mean the human musculoskeletal system?

    We've got particularly bad lower backs, due to how we evolved to become bipedal. I can really be more specific than that, but it accounts for why so many suffer from lower back pain.

    There's also the problem with women's hips. Infants have to have small brains and underformed skulls to fit through the birth canal, which is why they're so helpless when they're born. But the hip is wide enough that it's fragile, which is why broken hips due to falls is a problem with elderly women.
     
  5. Feb 22, 2006 #4
    Cheers for the responses. Yes I meant the human musculoskeletal system. Maybe also the muscle is normally acting at a disadvantage? But the advantage of that is a small change in contractile force gives a large change in movement...
     
  6. Feb 22, 2006 #5
    Can you put your question into some context? Because without this you can have a free for all: muscles cannot function without blood supply, there is an unbalanced number of opposable digits (1 against 4), the skull position is off-balance, we lack rotational joints, the rate of muscular growth can exceed tendon strenghtening, we only have two arms, all sorts of things that may or may not be considered flaws, depending on context and purpose.
     
  7. Feb 22, 2006 #6
    The question is exactly the way I put it: maybe they want a general argument...
     
  8. Feb 22, 2006 #7
    They? This is a school assignment? What subject?
     
  9. Feb 22, 2006 #8
    No - it's a past uni question - anatomy...
     
  10. Mar 4, 2006 #9

    somasimple

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    Hi,

    Just a ridiculous assumption. Our back is a perfect machine but our static life our misery.
     
  11. Mar 8, 2006 #10
    This isn't a correct statement since pain in the lower back is attributed to the fact humans used to walk on all fours, but when they became bipedal the spinal column did not advance as much as it should have. If it had the lower portion of the spinal column would much thicker and stronger than it is right now.

    ~Kitty
     
  12. Mar 8, 2006 #11
    TRCSF's statement is accurate.

    ~Kitty
     
  13. Mar 9, 2006 #12

    somasimple

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    vey,
    we are walking since 5 miliions years.
     
  14. May 1, 2006 #13
    anymore? I cant think of many ideas
     
  15. May 2, 2006 #14

    Curious3141

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    I've always thought the MS system had a fundamental flaw - the inability to maintain a passive tone in fast skeletal muscle fibers.

    For that to happen, the muscle has to remain contracted without the expenditure of significant amounts of energy. This actually happens consistenty post mortem and randomly in life with a rigor state configuration of the myosin on the actin. The myosin remains locked onto the actin and needs an ATP molecule (energy carrier) to detach and resume crossbridge cycling. If ATP is not forthcoming the myosin and actin remain in a locked state and the muscle remains at a fixed length. This is the explanation of rigor mortis, and the state remains until proteolysis dissolves away the bonds.

    In life, myosin and actin never get into a perma-lock state like that. This is why when carrying a heavy load, or even pushing against a wall, the endless cycling of myosin and actin end up costing energy (ATP and glycogen) and causing the build-up of lactic acid, leading to fatigue and pain.

    I find this more than a little inefficient. Cycling during the increasing phase of force generation is unavoidable, but I should be able to consciously lock my muscle into a pseudo-rigor state in order to maintain a contracted tone without energy expenditure or fatigue. This will, for example, help me to keep carrying a heavy dumbbell for hours on end - the relevant parts of my forearm and arm just become like a rigid mannequin.

    There are dangers of course. Once the muscle is locked into a passive tonic state, a sudden increase in the load can tear the muscle apart physically. I doubt stretch reflexes are going to be fast enough to prevent that since ATP influx has to unlock all the acto-myosin crossbridges to get the muscle into active mode once more to allow correction. It will be too late to prevent muscle damage.

    But I've often thought that were I to play God and build a perfect human, I would incorporate some mechanism to allow fast skeletal muscle to maintain a high state of tone for nil or negligible energy expenditure for hours on end. I don't think it's unfeasible.
     
    Last edited: May 2, 2006
  16. May 6, 2006 #15

    Moonbear

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    Actually, you're both correct on this. Other than back pain caused by injuries while lifting improperly, a sedentary lifestyle is a risk factor for back pain. Weak muscles put people at higher risk of back injuries and/or pain.

    http://adam.about.com/reports/000054_3.htm

    http://neurology.health-cares.net/lower-back-pain.php

    http://familydoctor.org/117.xml

    http://www.doctorndtv.com/lifestyle/exerdetailtopics.asp?id=24

    We've evolved fairly well to be bipedal, but we haven't evolved to sit or stand still for long periods of time. It's the strain of that inactivity that contributes to much of the back pain people experience. The adaptations to the spine that make it possible for us to stand erect also make us vulnerable to lower back pain and injuries given our current lifestyel.

    http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_073_08.html

    http://www.sciencemag.org/cgi/content/summary/311/5764/1071

    Note that they use the word "apparent." That this vulnerability exists doesn't mean it is an abnormality or flaw of any sort, it means our activities have changed from those which originally influenced the evolution of the structure of our backs.
     
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