Cardiovascular System: Regulation of Contractility
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Questions and Answers

What is the primary mechanism by which stimulation of beta-adrenergic receptors increases calcium inside cardiac myocytes?

  • Activation of Na+-Ca++ exchanger
  • Phosphorylation of L-type Ca++ channel in the sarcolemma (correct)
  • Phosphorylation of L-type Na+ channel in the sarcolemma
  • Inhibition of calcium release from the sarcoplasmic reticulum

Which of the following drugs increases Ca++ entry in cardiac myocytes by inhibiting Na+-K+ ATPase in the sarcolemma?

  • Catecholamines
  • Digitalis (correct)
  • Glucagon
  • Caffeine

What is the effect of xanthines like caffeine on c-AMP concentration in cardiac myocytes?

  • Has no effect on c-AMP concentration
  • Increases c-AMP concentration (correct)
  • Causes c-AMP breakdown
  • Decreases c-AMP concentration

Which negative inotropic mechanism is primarily due to insufficient blood supply to cardiac muscle?

<p>Hypoxia (D)</p> Signup and view all the answers

How do glucagon hormones affect c-AMP levels in cardiac myocytes?

<p>Increase c-AMP levels (A)</p> Signup and view all the answers

Which process occurs when Protein Kinase A phosphorylates Ry-calcium release channels on the sarcoplasmic reticulum in cardiac myocytes?

<p>Increased release of Ca++ from SR (D)</p> Signup and view all the answers

Which drug inhibits the breakdown of c-AMP, leading to increased c-AMP concentration inside cardiac myocytes?

<p>Caffeine (C)</p> Signup and view all the answers

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