#1
Which structure in the heart initiates the heartbeat?
Atrioventricular node
Purkinje fibers
Sinoatrial node
Bundle of His
#2
What is the function of the atrioventricular (AV) node?
To conduct electrical signals from the atria to the ventricles
To initiate the heartbeat
To contract the ventricles
To conduct electrical signals from the ventricles to the atria
#3
Which ion plays a crucial role in the initiation of cardiac muscle contraction?
Sodium
Potassium
Calcium
Chloride
#4
Which chamber of the heart has the thickest muscular wall?
Right atrium
Left atrium
Right ventricle
Left ventricle
#5
Which phase of the cardiac cycle is characterized by the closure of the atrioventricular valves?
Isovolumetric relaxation
Ventricular filling
Ventricular ejection
Isovolumetric contraction
#6
During which phase of the cardiac cycle do the ventricles fill with blood?
Isovolumetric relaxation
Ventricular filling
Ventricular ejection
Isovolumetric contraction
#7
Which of the following is NOT a component of the cardiac conduction system?
Sinoatrial node
Atrioventricular node
Purkinje fibers
Interventricular septum
#8
What is the role of the Purkinje fibers in the heart?
To initiate the heartbeat
To conduct electrical signals to the myocardium
To regulate blood pressure
To contract the atria
#9
What is the term for the volume of blood pumped out by each ventricle in one minute?
Stroke volume
End-diastolic volume
Cardiac output
Ejection fraction
#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
To initiate the heartbeat
To contract the ventricles
To conduct electrical signals from the ventricles to the atria
#11
What is the term for the period of relaxation of the heart chambers during the cardiac cycle?
Systole
Diastole
Repolarization
Depolarization
#12
Which of the following factors can increase heart rate?
Parasympathetic stimulation
Hypothermia
Sympathetic stimulation
Increased potassium levels
#13
During which phase of the cardiac cycle does ventricular contraction occur?
Isovolumetric relaxation
Ventricular filling
Ventricular ejection
Isovolumetric contraction
#14
Which of the following is responsible for the long refractory period in cardiac muscle cells?
Rapid influx of potassium ions
Slow influx of calcium ions
Rapid influx of sodium ions
Slow efflux of potassium ions
#15
Which of the following is a characteristic of the plateau phase in cardiac muscle action potentials?
Rapid influx of sodium ions
Rapid efflux of potassium ions
Slow influx of calcium ions
Slow influx of sodium ions
#16
What is the term for the volume of blood remaining in each ventricle after contraction?
End-systolic volume
Stroke volume
End-diastolic volume
Ejection fraction
#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
Stroke volume
Cardiac output
End-systolic volume
#18
Which of the following is responsible for the rapid depolarization phase in cardiac muscle cells?
Influx of sodium ions
Efflux of potassium ions
Influx of calcium ions
Efflux of chloride ions