Help me with my homework? (muscle stuff)

Discussion in 'Road Cycling' started by Raptor, Oct 28, 2003.

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  1. Raptor

    Raptor Guest

    I'm studying for personal trainer certification. It's very interesting so far. I feel like I'll be
    ready for med school after this. These are questions prompted by my natural curiosity and my
    reading, but I doubt are part of any test.

    (Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    different as Type I and Type II?

    What's a typical motor unit firing rate? How many action potentials can a sarcomere handle per unit
    time? (Depending, I suppose, on what "handle" means, and if there's a "typical" to be found.)

    --
    --
    Lynn Wallace http://www.xmission.com/~lawall "I'm not proud. We really haven't done everything we
    could to protect our customers. Our products just aren't engineered for security." --Microsoft VP in
    charge of Windows OS Development, Brian Valentine.
     
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  2. J999w

    J999w Guest

    >What's a typical motor unit firing rate? How many action potentials can a sarcomere handle per
    >unit time?

    A single muscle twitch lasts for 25-50 msec; the action potential lasts < 5 msec.

    http://human.physiol.arizona.edu/SCHED/CV/Burt/Burt3/Burt.L3.pdf

    Google to the rescue.

    >I feel like I'll be ready for med school after this.

    Riiiiiiiight.

    :^]

    Keep going and good luck !

    John Wilke RN Milwaukee
     
  3. On Wed, 29 Oct 2003 00:01:35 -0700, Raptor wrote:
    > (Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    > different as Type I and Type II?

    Standard explanation: historical reasons.
     
  4. Wayne

    Wayne Guest

    > (Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    > different as Type I and Type II?

    I believe historically at first only 2 types were identified, and then it was realized that there
    were actually 2 different types of Type II fibers once people actually started being able to detect
    differences in the myosin heavy chains (MHC) or the consequence of these differences. Now it is
    known that there are 3 types of Type II MHC (a, x, and b) expressed in mammals, although humans only
    express a and x, but not the fastest b isoform. But because historically, using histochemical
    staining for ATPase activity (which is determined by the MHC) established the nomenclature for human
    fibre types, you still see the 3 human fibre types given as Type I, Type IIA, and Type IIB (although
    expressing Type IIx MHC). Given that some muscle fibres also express combinations of either Type
    I/IIa or Type IIa/IIx MHC you end up with more of continuum of muscle fibre contractile
    characteristics rather than 2 or 3 distinct fibre types. You can also have differences in the
    mysosin light chains and calcium handling proteins that may affect contractile properties, and then
    you have differences in the amount of glycolytic or oxidative enzymes that will affect energy
    production and the fatigue resistance of fibre.

    > What's a typical motor unit firing rate? How many action potentials can a sarcomere handle per
    > unit time? (Depending, I suppose, on what "handle" means, and if there's a "typical" to be found.)

    Typical average motor unit firing rates for whole muscle are pretty low, I believe around 15-25 Hz.
    A fast motor unit reaches tetani around 60 Hz, anything higher would be overkill. But you could
    drive the muscle fibres at higher frequencies using electrical stimulation. I believe you have to go
    pretty high (like > 150Hz) to start getting electrical fatigue, which i guess would define the
    maximal rate the fibre could "handle".
     
  5. Raptor

    Raptor Guest

    Wayne wrote:
    >>(Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    >>different as Type I and Type II?
    >
    snip

    > (although expressing Type IIx MHC). Given that some muscle fibres also express combinations of
    > either Type I/IIa or Type IIa/IIx MHC you end up with more of continuum of muscle fibre
    > contractile characteristics rather than 2 or 3 distinct fibre types.

    That's the impression I've been getting in my reading: more of a continuum.

    >>What's a typical motor unit firing rate? How many action potentials can a sarcomere handle per
    >>unit time? (Depending, I suppose, on what "handle" means, and if there's a "typical" to be found.)
    >
    >
    > Typical average motor unit firing rates for whole muscle are pretty low, I believe around 15-25
    > Hz. A fast motor unit reaches tetani around 60 Hz, anything higher would be overkill. But you
    > could drive the muscle fibres at higher frequencies using electrical stimulation. I believe you
    > have to go pretty high (like > 150Hz) to start getting electrical fatigue, which i guess would
    > define the maximal rate the fibre could "handle".

    How does this square with my (or anyone's) ability to spin pedals at
    >150 RPM? Or stirring up egg whites or whatever? The muscles are
    contributing to cyclic motion faster than the frequencies you state.

    --
    --
    Lynn Wallace http://www.xmission.com/~lawall "I'm not proud. We really haven't done everything we
    could to protect our customers. Our products just aren't engineered for security." --Microsoft VP in
    charge of Windows OS Development, Brian Valentine.
     
  6. Raptor wrote:

    > Wayne wrote:
    > >>(Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    > >>different as Type I and Type II?
    > >
    > snip
    >
    > > (although expressing Type IIx MHC). Given that some muscle fibres also express combinations of
    > > either Type I/IIa or Type IIa/IIx MHC you end up with more of continuum of muscle fibre
    > > contractile characteristics rather than 2 or 3 distinct fibre types.
    >
    > That's the impression I've been getting in my reading: more of a continuum.
    >
    > >>What's a typical motor unit firing rate? How many action potentials can a sarcomere handle per
    > >>unit time? (Depending, I suppose, on what "handle" means, and if there's a "typical" to be
    > >>found.)
    > >
    > >
    > > Typical average motor unit firing rates for whole muscle are pretty low, I believe around 15-25
    > > Hz. A fast motor unit reaches tetani around 60 Hz, anything higher would be overkill. But you
    > > could drive the muscle fibres at higher frequencies using electrical stimulation. I believe you
    > > have to go pretty high (like > 150Hz) to start getting electrical fatigue, which i guess would
    > > define the maximal rate the fibre could "handle".
    >
    > How does this square with my (or anyone's) ability to spin pedals at
    > >150 RPM? Or stirring up egg whites or whatever? The muscles are
    > contributing to cyclic motion faster than the frequencies you state.

    150 Hz is cycles/SECOND, not minute!

    Steve

    >
    >
    > --
    > --
    > Lynn Wallace http://www.xmission.com/~lawall "I'm not proud. We really haven't done everything we
    > could to protect our customers. Our products just aren't engineered for security." --Microsoft VP
    > in charge of Windows OS Development, Brian Valentine.

    --
    Mark & Steven Bornfeld DDS Brooklyn, NY 718-258-5001 http://www.dentaltwins.com
     
  7. Andy Coggan

    Andy Coggan Guest

    "Raptor" <[email protected]> wrote in message news:[email protected]...
    > Wayne wrote:

    > > Typical average motor unit firing rates for whole muscle are pretty low, I believe around 15-25
    > > Hz. A fast motor unit reaches tetani around 60 Hz, anything higher would be overkill. But you
    > > could drive the muscle fibres at higher frequencies using electrical stimulation. I believe you
    > > have to go pretty high (like > 150Hz) to start getting electrical fatigue, which i guess would
    > > define the maximal rate the fibre could "handle".
    >
    > How does this square with my (or anyone's) ability to spin pedals at
    > >150 RPM? Or stirring up egg whites or whatever? The muscles are
    > contributing to cyclic motion faster than the frequencies you state.

    Hz = cycles/s

    RPM = rev/min

    I'll let you work out the conversion factor for yourself. ;-)

    Andy Coggan
     
  8. Tom Kunich

    Tom Kunich Guest

    Raptor <[email protected]> wrote in message news:<[email protected]>...
    > I'm studying for personal trainer certification. It's very interesting so far. I feel like I'll be
    > ready for med school after this. These are questions prompted by my natural curiosity and my
    > reading, but I doubt are part of any test.
    >
    > (Nomenclature:) Why do we have just two muscle types, if Type IIA and Type IIB are seemingly as
    > different as Type I and Type II?

    Because under an optical microscope you can sort Type's I and II visually. IIA and IIB
    look the same.
     
  9. H Squared

    H Squared Guest

    Raptor wrote:
    >
    > Ewoud Dronkert wrote:
    > > Does this help with your homework then? http://www.15times.com/gallery/0012/01_the%20endx328.jpg
    > >
    > > (cplotm).
    >
    > Not really, sorry. Just leads to more questions, though of a different type. Like, where's the
    > front view,

    you can look at that and want to see a front view?!

    baffled, heather
     
  10. H Squared

    H Squared Guest

    h squared wrote:
    >
    > Raptor wrote:
    > >
    > > Ewoud Dronkert wrote:
    > > > Does this help with your homework then?
    > > > http://www.15times.com/gallery/0012/01_the%20endx328.jpg
    > > >
    > > > (cplotm).
    > >
    > > Not really, sorry. Just leads to more questions, though of a different type. Like, where's the
    > > front view,
    >
    > you can look at that and want to see a front view?!
    >
    > baffled, heather

    goddam, i would make a terrible ambassador or public relations person. i *cannot* write what i
    mean to say.

    i just meant that it can't get any better than that.

    heather
     
  11. "h squared" wrote:
    >> you can look at that and want to see a front view?!
    >
    > i just meant that it can't get any better than that.

    I know. I mean, I know you did :)
     
  12. Raptor

    Raptor Guest

    Andy Coggan wrote:
    > "Raptor" <[email protected]> wrote in message news:[email protected]...
    >
    >>Wayne wrote:
    >
    >
    >>>Typical average motor unit firing rates for whole muscle are pretty low, I believe around 15-25
    >>>Hz. A fast motor unit reaches tetani around 60 Hz, anything higher would be overkill. But you
    >>>could drive the muscle fibres at higher frequencies using electrical stimulation. I believe you
    >>>have to go pretty high (like > 150Hz) to start getting electrical fatigue, which i guess would
    >>>define the maximal rate the fibre could "handle".
    >>
    >>How does this square with my (or anyone's) ability to spin pedals at
    >> >150 RPM? Or stirring up egg whites or whatever? The muscles are
    >>contributing to cyclic motion faster than the frequencies you state.
    >
    >
    > Hz = cycles/s
    >
    > RPM = rev/min
    >
    > I'll let you work out the conversion factor for yourself. ;-)
    >
    > Andy Coggan

    Uh... I knew that.

    Now where's that damn calculator.

    --
    --
    Lynn Wallace http://www.xmission.com/~lawall "I'm not proud. We really haven't done everything we
    could to protect our customers. Our products just aren't engineered for security." --Microsoft VP in
    charge of Windows OS Development, Brian Valentine.
     
  13. Raptor

    Raptor Guest

    h squared wrote:
    >
    > Raptor wrote:
    >
    >>Ewoud Dronkert wrote:
    >>
    >>>Does this help with your homework then? http://www.15times.com/gallery/0012/01_the%20endx328.jpg
    >>>
    >>>(cplotm).
    >>
    >>Not really, sorry. Just leads to more questions, though of a different type. Like, where's the
    >>front view,
    >
    >
    > you can look at that and want to see a front view?!
    >
    > baffled, heather

    Front view, top view, bottom view, upside down, rightside up. Feel, smell, taste, hear... Oh,
    mmm, YEAH!

    We now return to our regularly-scheduled newsgroup.

    --
    --
    Lynn Wallace http://www.xmission.com/~lawall "I'm not proud. We really haven't done everything we
    could to protect our customers. Our products just aren't engineered for security." --Microsoft VP in
    charge of Windows OS Development, Brian Valentine.
     
  14. Nick Burns

    Nick Burns Guest

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