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Re: Twitching Muscles! [HAPP-L]



Consistency in location does not eliminate randomness -- it simply 
means that the location is consistent, but the leakage etc. of the 
membranes involved is random. In addition, in cardiovascular 
physiology there is such a thing as a "normal abnormality". In other 
words, what is normal for you (i.e. the twitching) is abnormal for 
the general population. Therefore, the twitching may be a "normal" 
membrane leak etc. for you, but an "abnormal" one for the population 
as a whole. I also doubt it has to do with membrane protein turnover 
rates. etc., but that is a SWAG (scientific wild-_ _ _ guess).

Bob

>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
>>  639 38'th Street
>>  Rock Island, IL.  61201-2296
>>  Internet: bitallitsch@augustana.edu
>>  Office telephone: (309)794-3441
>  > FAX: (309)794-7722 (please mark to my attention)
>>
>>  World Wide Web information about Dr. Tallitsch, the courses he
>>  teaches, and Augustana College is available at:
>>  http://www.augustana.edu/users/bitallitsch
>>
>>  **********************************************************
>>
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>--
>Alice Mills, Ph. D.
>Assoc. Prof., Dept. of Biology
>125 Strobel Biology Annex
>Middle Tennessee St. U.
>Murfreesboro, TN  37132
>(615) 898-5021
>(615) 898-5093 (fax)
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-- 
**********************************************************
Robert B. Tallitsch, Ph.D.
Professor of Biology
Augustana College
639 38'th Street
Rock Island, IL.  61201-2296
Internet: bitallitsch@augustana.edu
Office telephone: (309)794-3441
FAX: (309)794-7722 (please mark to my attention)

World Wide Web information about Bob Tallitsch, the courses he
teaches, and Augustana College is available at: 
http://www.augustana.edu/users/bitallitsch

**********************************************************