#1
Which ion plays a crucial role in initiating the contraction of cardiac muscle cells?
Sodium (Na+)
Potassium (K+)
Calcium (Ca2+)
Chloride (Cl-)
#2
What is the role of the sinoatrial (SA) node in the cardiac conduction system?
It conducts electrical impulses to the atrioventricular (AV) node.
It initiates the electrical impulses for the heart's contraction.
It regulates blood flow between the atria and ventricles.
It controls the heart's relaxation phase.
#3
What is the term for the volume of blood ejected by each ventricle during one contraction?
Stroke volume
Cardiac output
End-diastolic volume
Ejection fraction
#4
Which structure is responsible for conducting the electrical impulses from the atria to the ventricles in the heart?
Sinoatrial (SA) node
Atrioventricular (AV) node
Bundle of His
Purkinje fibers
#5
During the cardiac cycle, which phase corresponds to the simultaneous contraction of both atria?
Atrial systole
Isovolumic contraction
Ventricular ejection
Isovolumic relaxation
#6
What is the primary energy source for cardiac muscle contraction?
Glucose
Fatty acids
Amino acids
Lactic acid
#7
Which neurotransmitter is released at the neuromuscular junction of the cardiac muscle?
Acetylcholine
Dopamine
Epinephrine
Norepinephrine
#8
Which of the following factors can increase myocardial oxygen demand?
Decreased heart rate
Decreased afterload
Increased preload
Increased stroke volume
#9
During which phase of the cardiac action potential does calcium influx lead to muscle contraction?
Depolarization
Plateau
Repolarization
Resting phase
#10
Which of the following is responsible for the long refractory period in cardiac muscle cells?
Sodium (Na+)
Potassium (K+)
Calcium (Ca2+)
Chloride (Cl-)
#11
What is the role of the Frank-Starling mechanism in the heart?
Regulation of heart rate
Control of afterload
Adjustment of preload
Maintenance of heart rhythm
#12
What is the primary function of troponin in cardiac muscle contraction?
Binds to calcium and initiates muscle contraction.
Regulates the myosin-actin interaction.
Transmits electrical impulses between cardiac cells.
Stores energy for muscle contraction.
#13
What is the term for the relaxation phase of the cardiac cycle when the heart chambers refill with blood?
Systole
Diastole
Ejection phase
Isovolumic contraction
#14
Which of the following hormones increases heart rate and force of contraction?
Insulin
Thyroxine
Aldosterone
Epinephrine
#15
What is the primary function of the atrioventricular (AV) node in the cardiac conduction system?
To delay the transmission of electrical impulses.
To contract the ventricles.
To initiate the heartbeat.
To regulate blood flow in the atria.
#16
Which of the following factors can increase the contractility of cardiac muscle?
Parasympathetic stimulation
Hypoxia
Positive inotropic drugs
Acidosis
#17
Which of the following factors is known to decrease heart rate?
Sympathetic stimulation
Increased potassium levels
Parasympathetic stimulation
Elevated calcium levels
#18
What is the term for the volume of blood in the ventricle at the end of diastole, just before contraction?
End-systolic volume
Stroke volume
End-diastolic volume
Preload
#19
What is the primary factor determining the duration of the action potential in cardiac muscle cells?
Sodium (Na+) influx
Potassium (K+) efflux
Calcium (Ca2+) influx
Chloride (Cl-) influx