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Old 05-30-2013
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Question the role of cAMP/cGMP on muscle contraction!

Hello everyone!
Iím having a terrible time with the secondary messengers and their effects on muscle contraction, specifically their role in contractions in the different types (smooth, skeletal, cardiac).
1. Could someone please explain the roles and onward cascades of cAMP and cGMP in smooth and cardiac muscles?
From what Iíve been able to collect
a) cAMP cardiac muscle contraction and smooth muscle (vasculature muscle) contraction right?
b) cGMP smooth muscle (vascular musculature) contraction?
IS THIS A CORRECT CONCLUSION??
2. As far as I understand, neither of these messengers play any role in skeletal muscle contraction right?
IS THIS CORRECT?
3. cAMP activates protein Kinase A which in turn
a) Ca+2 in cardiac muscles (thereby increasing contraction) HOW DOES THIS HAPPEN?
b) Phosphorylates Myosin Light Chain Kinase, thereby inactivating it
c) Phosphorylates CREB (if this has any significance, please do tell)
Is this all in order?
4. Gq activates Phospholipase C which forms IP3 and DAG. IP3 goes to the ER and stimulates Ca+2 release, which activates Protein Kinase C. DAG directly activates protein Kinase C.
WHATíS THE ROLE OF PROTEIN KINASE C??
5. The Ca+2 released from the SR also binds to Calmodulin, increasing NO which then activates Guanyl Cyclase releasing cGMP.
cGMP is supposed to do two things
a) Activates a Ca+2 pump which pumps Ca+2 out
b) Activates Protein Kinase G which phosphorylates Phosphatase (activating it) which then removes phosphate from Myosin Light Chain, thereby inactivating it and causing smooth muscle relaxation.

Please help out, I've been trying but just haven't been able to get my head around all these doubts. I'd really appreciate some clarity here.
Thank you
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Old 06-02-2013
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Could someone please answer this? I've googled till I got calluses, and still haven't been able to get any real clarity on this.
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Molecular-Biology-, Musculoskeletal-, Physiology-

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