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skeletal muscle physiology

Discussion in 'Step I' started by obiwan, Jun 6, 2008.

  1. obiwan

    obiwan Junior Member
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    in FA it says that skeletal muscle has calcium induced calcium release. is this incorrect? i always thought cardiac muscle involved calcium induced calcium release from sarcoplasmic reticulum
     
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  3. agranulocytosis

    Physician 10+ Year Member

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    I believe you are 1/2 right. I thought that cardiac muscle and skeletal muscle had the same mechanism, but the nodes involve influx of Ca++ which result in direct depolarization. It's my understanding that skeletal and cardiac muscle involve Ca++-induced Ca++ release from the sarcoplasmic reticulum. That's the basis for dantrolene working as a skeletal muscle relaxant (via inhibition of ryanodine receptors on the SR). Now I don't understand how dantrolene doesn't affect myocytes...
     
  4. opb

    opb
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    Skeletal muscle contraction is actually not a calcium-induced-calcium release mechanism. The ryanodine receptors in skeletal muscle cells are associated with voltage-sensitive receptors (dihydropyridine receptors) in the T-tubules. Depolarization of the T-tubles causes a conformational change in the DHP receptors which opens the ryanodine receptors. Then calcium is released.

    Cardiac cells use the calcium-induced-calcium release method. The influx of Ca2+ opens the ryanodine receptors which cause release of Ca2+ from the SR. That's why extracellular calcium is required for cardiac myocyte contraction but not for skeletal muscle contraction.
     
  5. agranulocytosis

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    Thanks for the clarification, you guys are correct. Although I don't see where in FA it says this, obiwan. p347 in musculoskeletal physio lays it out just like opb says.
     
  6. obiwan

    obiwan Junior Member
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    Thanks for clarifying. i guess i misread the page.
     

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