The cardiac cycle refers to the sequence of events that takes place from one heart beat to the next. A full understanding of the cardiac cycle requires thorough examination of atrial systole, atrial diastole, ventricular systole, ventricular diastole, atrial and ventricular volume changes during the cycle, electrical events (depolarization and repolarization) of atria and ventricular myocytes, heart sounds associated with turbulent blood flow caused by the closure of semilunar valves, as well as hydrostatic blood pressure changes within the atria, ventricles, and the aorta. Test you basic understanding of the cardiac cycle by taking this simple quiz.
(1) Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the P wave:
(2) Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the QRS complex wave:
(3) Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the T wave:
(4) When the heart rate increases, the duration of both systole and diastole of the cardiac cycle decreases. Which phase of the cardiac cycle decreases to a larger extent?
(5) During a typical cardiac cycle under resting conditions, approximately __________ of the volume of blood present in the ventricles just before ventricular contraction (referred to as end-diastolic volume), enters the ventricles as a result of passive venous return of blood flowing through the atria and into the ventricles.