Muscle Questions..

[potbelly]

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THere are three muscles we should know for DAT.
Cardiac, Smooth, Skeletal..


However among these three which muscles require Ca++ for contraction? I am pretty sure that skeletal muscles require Calcium but how about Cardiac and smooth?

Can anyone help?

THanks!!

 

[yuppers]

Pretty sure they all do. But smooth muscles uses the Ca differently because it does not have sacromeres.

 

[FutureInternist]

They all use Ca.
Skeletal muscle uses outside Ca to allow actin-myosin cross-bridge formation

Cardiac muscle uses outside Ca to come in & release the Ca in the sarcoplasmic reticulum, which then allows the cross-bridge formation (hence cardiac activity is slower than skeletal)

Smooth muscle uses outside Ca to allow formation of Ca-calmodulin complexes which activates MLCK, which then puts a P on myosin regulatory site --> cross bridge formation.

 

[potbelly]

Thank you all!🙂

 

[marcusnasland]

I think also most skeletal muscle store the Ca in the terminal cisternae of the sarcoplasmic reticulum, while cardiac and smooth get calcium from extracellular fluid.

Calcium in skeletal and cardiac binds to troponin which moves tropomyosin and reveals the G actin active sites to alow cross bridging

Calcium binds to calmodulin in smooth muscle which i think basically activates myosin by transferring phosphate from ATP... Myosin still needs another ATP to begin first power stroke, so twice as much ATP is needed to start the process. Smooth muscle still more fatigue resistant though because latch-bridge system holds tension longer.