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Re: Twitching Muscles! [HAPP-L]



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
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Internet: bitallitsch@augustana.edu
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