#1
Which structure in the heart initiates the heartbeat?
Sinoatrial node
ExplanationSinoatrial node is the pacemaker of the heart, initiating the heartbeat.
#2
What is the function of the atrioventricular (AV) node?
To conduct electrical signals from the atria to the ventricles
ExplanationAV node conducts electrical signals from atria to ventricles.
#3
Which ion plays a crucial role in the initiation of cardiac muscle contraction?
Calcium
ExplanationCalcium is crucial for initiating heart muscle contraction.
#4
Which chamber of the heart has the thickest muscular wall?
Left ventricle
ExplanationLeft ventricle has the thickest muscular wall.
#5
Which phase of the cardiac cycle is characterized by the closure of the atrioventricular valves?
Isovolumetric contraction
ExplanationClosure of AV valves occurs in isovolumetric contraction.
#6
During which phase of the cardiac cycle do the ventricles fill with blood?
Ventricular filling
ExplanationVentricular filling phase involves filling of ventricles with blood.
#7
Which of the following is NOT a component of the cardiac conduction system?
Interventricular septum
ExplanationInterventricular septum is not part of the cardiac conduction system.
#8
What is the role of the Purkinje fibers in the heart?
To conduct electrical signals to the myocardium
ExplanationPurkinje fibers conduct signals to the heart muscle.
#9
What is the term for the volume of blood pumped out by each ventricle in one minute?
Cardiac output
ExplanationCardiac output is the volume pumped by ventricles in a minute.
#10
What is the main function of the atrioventricular bundle (Bundle of His) in the heart?
To conduct electrical signals from the atria to the ventricles
ExplanationBundle of His conducts signals from atria to ventricles.
#11
What is the term for the period of relaxation of the heart chambers during the cardiac cycle?
Diastole
ExplanationDiastole is the relaxation period of heart chambers.
#12
Which of the following factors can increase heart rate?
Sympathetic stimulation
ExplanationHeart rate increases with sympathetic stimulation.
#13
During which phase of the cardiac cycle does ventricular contraction occur?
Ventricular ejection
ExplanationVentricular ejection phase involves ventricular contraction.
#14
Which of the following is responsible for the long refractory period in cardiac muscle cells?
Slow efflux of potassium ions
ExplanationLong refractory period due to slow potassium ion efflux.
#15
Which of the following is a characteristic of the plateau phase in cardiac muscle action potentials?
Slow influx of calcium ions
ExplanationPlateau phase characterized by slow calcium ion influx.
#16
What is the term for the volume of blood remaining in each ventricle after contraction?
End-systolic volume
ExplanationEnd-systolic volume is blood left in ventricles post-contraction.
#17
What is the term for the volume of blood pumped out by each ventricle in relation to the volume of blood it received?
Ejection fraction
ExplanationEjection fraction is the ratio of pumped blood to received blood.
#18
Which of the following is responsible for the rapid depolarization phase in cardiac muscle cells?
Influx of sodium ions
ExplanationRapid depolarization due to influx of sodium ions.