Beta blockers are effective in treating certain cardiac arrhythmias

Beta blockers are effective in treating certain cardiac arrhythmias because they _____ the excitatory effects of ______ on the heart.
A)   increase; acetylcholine
B)   decrease; acetylcholine
C)   increase; catecholamines (epinephrine and norepinephrine)
D)   decrease; catecholamines (epinephrine and norepinephrine)
E)   increase; beta interferons


An antiarrhythmic drug that prolongs the effective refractory period of the cardiac action potential:
A)   will speed up repolarization of cardiac muscle cells.
B)   will generally increase heart rate.
C)   will decrease the time interval between cardiac action potentials.
D)   all of the above
E)   none of the above

Depending on the dose and route of administration, lidocaine (Xylocaine) and similar drugs can be used as local anesthetics or cardiac antiarrhythmic drugs because they affect the excitability of _____ ion channels.
A)   sodium
B)   potassium
C)   chloride
D)   calcium
E)   magnesium