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Re: Twitching Muscles! [HAPP-L]



I'm probably going to embarrass myself, but......

Like others that have written, I'll get a twitch that happens several
times a day for a period of several days in the same location, before it
finally disappears for years or forever, like the eye twitch or a toe twitch.

Because of the temporary constancy of location, it would seem that
subsequent bouts are not random.

So the question for cell biologists - what are the characteristics of
membrane protein turnover - steady or sporadic?  If sporadic, then could
the repetition of twitching in the same location indicate the duration
of a turnover period?  Just seems like if there is a bout of remodeling,
then ion leaks to threshold would be more likely.

alice, who is not twitching at the moment.




"Robert B. Tallitsch, Ph.D." wrote:
> 
> The twitching happens due to the instability in ionic channels in
> cellular membranes. Leaks (as much as we would like it) are not
> constant -- they have variable rates -- as due the pumps that
> counteract the leaks. I am only guessing, but I would guess the
> twitching is due to a temporary change in the leak and/or pump rate,
> thereby causing the leak.
> 
> Bob
> 
> >>Twitching muscles are typically due to one of three physiological
> >>phenomena: (a) spontaneous release of Calcium from the SR, which
> >>initiates excitation-contraction coupling in a few isolated
> >>skeletal muscle cells; (b) spontaneous action potential in a motor
> >>neuron innervating a few skeletal muscle cells (i.e. very small
> >>motor unit); (c) spontaneous release of Ach from the motor neuron
> >>due to calcium leak, thereby initiating excitation-contraction
> >>coupling in a small motor unit.
> >>
> >>Bob
> >>--
> >
> >Bob,
> >
> >OK, and thank you, but...why? Why does it happen?
> >
> >For instance, I have an eye muscle that "twitches" involuntarily
> >from time to time...starts suddenly, stops suddenly...no special
> >event attached to it...except maybe it occurs more often when I'm
> >overly tired.
> >And, this student says she ahs a facial muscle that does the same
> >thing, usually when she is upset or stressed.
> >
> >So, why? Or how? What is the connection? Why does it happen to some
> >people, at some times, and to some muscles? I need to be able to
> >explain it it "lay" terms...for non-science majors. I understand the
> >"mechanics," I just don't have an answer for the "Why?" for her.
> >Anyone have any good methods for explaining this, or "get" what I'm
> >asking/getting at?
> >
> >Thanks!
> >
> >Leslie Carlson
> >Dept. Zoology/Genetics
> >Iowa State university
> >
> >
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> --
> **********************************************************
> Robert B. Tallitsch, Ph.D.
> Professor of Biology
> Augustana College
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-- 
Alice Mills, Ph. D.
Assoc. Prof., Dept. of Biology
125 Strobel Biology Annex
Middle Tennessee St. U.
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(615) 898-5021
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