1. The ionic current primarily responsible for conduction of the cardiac action potential through cells in the atrioventricular node is the:

A. transient outward current.

B. sodium current.
C. delayed rectifier potassium current.
D. L-type calcium current.
E. T-type calcium current.

2. The ionic current primarily responsible for normal diastolic depolarization or automaticity in the His-Purkinje fiber system is the:

A. transient outward current.
B. sodium current.

C. delayed rectifier potassium current.

D. L-type calcium current.
E. hyperpolarization activated cation current .

3. The ionic current which when activated is primarily responsible for controlling the rate of repolarization during phase 3 of the ventricular action potential is the:
A. transient outward current.
B. sodium current.
C. delayed rectifier potassium current.
D. L-type calcium current.
E. hyperpolarization activated cation current.
4. Gap junctions that permit the spread of electrical current between cardiac myocytes may close in response to which pathological conditions?

A. Intracellular alkalosis and low cytoplasmic calcium
B. Intracellular acidosis and high cytoplasmic calcium
C. Intracellular alkalosis and high cytoplasmic calcium
D. Intracellular acidosis and low cytoplasmic calcium

E. Neutral intracellular pH and low cytoplasmic calcium

5. A common mechanism by which acute myocardial ischemia can cause significant disturbances in ventricular conduction is:
A. local tissue hyperkalemia.
B. local tissue hypokalemia.
C. inactivation of the L-type calcium current.
D. activation of sympathetic reflexes.
6. Ectopic pacemaker automaticity is commonly enhanced by:
A. hypokalemia.
B. hypercalcemia.
C. hyponatremia.
D. vagal stimulation.
E. muscarinic agonists.
7. The cellular mechanism(s) by which sympathetic stimulation increases heart rate include:
A. stimulation of muscarinic receptors.
B. inhibition of adenylate cyclase.
C. stimulation of L-type calcium current.
D. inhibition of nonselective cation current.
E. decreased rate of phase 4 depolarization .
8. Enhanced vagal tone will produce which effect on the cardiac electrocardiogram?
A. Decreased RR interval
B. Decreased PR interval
C. Increased QRS interval
D. Increased QT interval
E. Increased PR interval
9. In a patient suffering from atrial fibrillation or atrial flutter, a decrease in vagal tone would be expected to:
A. increase the RR interval.
B. decrease the PR interval.
C. increase ventricular rate.
D. increase the QRS duration.
E. shorten the QT interval.
10. In the cardiac electrocardiogram, the interval which primarily reflects the conduction time through the AV node is the:
A. PR interval.
B. QRS duration.
C. QT interval.
D. ST segment.
E. HV interval.
11. In the cardiac electrocardiogram, the interval which primarily reflects the time it takes for ventricular depolarization is the:
A. PR interval.
B. QRS duration.
C. QT interval.
D. ST segment.
E. HV interval.
12. In the cardiac electrocardiogram, the interval which primarily reflects the time it takes for ventricular repolarization is the:
A. PR interval.
B. QRS duration.
C. QT interval.
D. ST segment.
E. HV interval.
13. A cardiac arrhythmia in which an electrocardiogram reveals no discernable P waves, a wavy baseline, irregular time intervals between R waves (irregularly irregular), relatively normal QRS and QT intervals is most likely:
A. ventricular fibrillation.
B. ventricular tachycardia.
C. atrial flutter.
D. atrial fibrillation.
E. ventricular bigeminy.
14. A cardiac abnormality that can produce a multifocal ventricular tachycardia (e.g. Torsade de Pointes) in patients having a long QT interval is:
A. delayed after depolarizations.
B. enhanced normal automaticity.
C. early after depolarizations.
D. abberant conduction.
E. bi-directional conduction block.
15. A variable that does not favor the development of reentrant excitation:
A. multiple parallel conduction pathways.
B. unidirectional conduction block.
C. dispersion of refractoriness.
D. conduction time shorter than the effective refractive period.
E. slow conduction time.
16. A form of cardiac arrhythmia in which the PR interval is longer than normal, but where each P wave is followed by a QRS complex and T wave:
A. 1st degree AV block .
B. 2nd degree AV block.
C. 3rd degree AV block .
D. sick sinus snydrome.
E. atrial bradycardia.
17. Sympathetic stimulation can increase ventricular stroke volume and cardiac output because it produces a:
A. stronger sodium current.
B. weaker potassium current.
C. inhibition of the Na/K pump.
D. stimulation of calcium current.
E. reduction in intracellular sodium.