#1
Which of the following is a positive chronotropic agent?
Epinephrine
ExplanationEpinephrine increases heart rate.
#2
In cardiac physiology, what is the term for the time interval between successive heartbeats?
R-R interval
ExplanationR-R interval is the term for the time interval between successive heartbeats.
#3
What is the normal range for resting heart rate in adults?
60-80 beats per minute
ExplanationThe normal range for resting heart rate in adults is 60-80 beats per minute.
#4
Which ion plays a crucial role in the depolarization phase of the cardiac action potential?
Sodium
ExplanationSodium plays a crucial role in the depolarization phase of the cardiac action potential.
#5
What is the primary function of a negative chronotropic agent?
Decrease heart rate
ExplanationNegative chronotropic agents decrease heart rate.
#6
Which ion plays a crucial role in cardiac pacemaker activity?
Calcium
ExplanationCalcium plays a crucial role in cardiac pacemaker activity.
#7
What is the primary site of action for digitalis glycosides in the heart?
SA node
ExplanationThe SA node is the primary site of action for digitalis glycosides in the heart.
#8
Which of the following drugs is commonly used to treat supraventricular arrhythmias by slowing AV nodal conduction?
Verapamil
ExplanationVerapamil is commonly used to treat supraventricular arrhythmias by slowing AV nodal conduction.
#9
Which of the following factors can influence cardiac chronotropy?
Thyroid hormones
ExplanationThyroid hormones can influence cardiac chronotropy.
#10
Which phase of the cardiac action potential is responsible for the pacemaker activity of the SA node?
Phase 4
ExplanationPhase 4 of the cardiac action potential is responsible for the pacemaker activity of the SA node.
#11
What effect does acetylcholine have on heart rate?
Decreases heart rate
ExplanationAcetylcholine decreases heart rate.
#12
Which neurotransmitter is released by sympathetic nerves to increase heart rate?
Norepinephrine
ExplanationNorepinephrine is released by sympathetic nerves to increase heart rate.
#13
What effect does sympathetic stimulation have on cardiac contractility?
Increases contractility
ExplanationSympathetic stimulation increases cardiac contractility.
#14
Which receptor subtype in the heart is primarily responsible for mediating the positive chronotropic effects of catecholamines?
Beta-1 receptors
ExplanationBeta-1 receptors are primarily responsible for mediating the positive chronotropic effects of catecholamines.
#15
What is the mechanism of action of beta-blockers in the context of cardiac chronotropy?
Inhibit sympathetic activity
ExplanationBeta-blockers inhibit sympathetic activity in the context of cardiac chronotropy.
#16
What is the primary mechanism of action of calcium channel blockers in affecting cardiac chronotropy?
Decrease calcium influx
ExplanationCalcium channel blockers decrease calcium influx in affecting cardiac chronotropy.