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Old 02-21-2013
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Default cAMP dependent Protein Kinase A in Myocytes

Hi everyone,
I needed some help with a roadblock.
It regards the role of cAMP dependent Protein Kinase A. In smooth muscles, it supposedly phosphorylates and inhibits Myosin Light Chain Kinase, thereby restricting muscle contraction.
However, the B1 receptor in cardiac muscles is a Gs coupled receptor, meaning it will increase the concentration of cAMP. What's the mechanism for increased chronotropy and inotropy due to activation of the B1 receptor when cAMP concentration is increased?
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Old 02-21-2013
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Default cAMP

increased cAMP increases phase 4 slope (fNa channels) + increase Ca influx in sa node that increase rate of depolarization and shortens PR interval in AV node (phase 0)
in ventricles increase Ca influx causes more Ca release from sarcoplasm (Ca induced Ca release) + phosphorylates phospholamban that pumps more Ca into sarcoplasm than outside the myocyte leading to increased force of contraction

by the way increased HR through staircase effect increases inotropism too
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Last edited by MedicalExaminer; 02-21-2013 at 05:27 AM.
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