Cardiology Quiz #14: Myocardial and Pacemaker Action Potentials

1. A 55-year-old man with a history of heart failure is being evaluated for potential arrhythmia. A cardiologist explains the phases of the myocardial action potential to the medical students observing the case. Which phase of the myocardial action potential is chiefly responsible for the plateau phase, maintaining the depolarized state and prolonging the action potential duration? 

Question 1 of 5

2. A 70-year-old woman with a history of atrial fibrillation is considered for pacemaker implantation. The electrophysiologist describes the unique action potential of pacemaker cells in the SA node to the patient. Which of the following best characterizes the pacemaker action potential?

Question 2 of 5

3. During a pharmacology lecture, a professor explains the effect of Class IV antiarrhythmic drugs on the heart. These drugs primarily act by inhibiting which phase of the myocardial action potential? 

Question 3 of 5

4. A 32-year-old man presents to the emergency department after experiencing palpitations. His EKG reveals premature ventricular contractions. Which phase of the ventricular myocyte action potential is responsible for initiating the rapid depolarization that leads to the contraction of the ventricular muscle? 

Question 4 of 5

5. A medical student is studying the differences between pacemaker and myocardial action potentials. She notes that one significant difference lies in the mechanism of automaticity. Which feature of pacemaker cells allows them to spontaneously depolarize and generate an action potential without external stimuli? 

Question 5 of 5


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