Untitled Quiz

Study Notes

Electrocardiogram (ECG) records heart-generated voltage from the body surface, representing each heartbeat.
P wave indicates atrial depolarization, leading to atrial contraction.
QRS complex results from ventricular depolarization, occurring approximately 0.16 seconds after P wave onset, initiating ventricular contraction.
T wave reflects ventricular repolarization.

Approximately 80% of ventricular filling occurs during diastole before atrial contraction.
Atrial contraction contributes the remaining 20% to the ventricles' filling, enhancing pumping effectiveness by 20%.
Atria dysfunction may lead to significant symptoms like shortness of breath during exercise but usually remain asymptomatic at rest.

At the start of diastole, A-V (atrioventricular) valves are closed; atria fill with blood during systole.
Isovolumic relaxation occurs as ventricles relax, leading to decreased pressure.
A-V valves open when ventricular pressure falls below atrial pressure, allowing blood flow into the ventricles.
Rapid ventricular filling occurs in the first third of diastole, providing most volume, followed by continuous filling.
Atrial contraction, termed “atrial kick,” happens in the last third of diastole, contributing 20% of ventricular filling.

Systole begins with ventricular contraction, closing A-V valves and increasing ventricular pressure.
Isovolumic contraction occurs when no blood is ejected, and fetal volume remains constant while pressure builds.
Aortic and pulmonary valves open when left ventricular pressure exceeds 80 mm Hg and right ventricular pressure surpasses 8 mm Hg, allowing blood ejection.
70% of the total blood ejected from the ventricles occurs during the rapid ejection phase, while 30% happens in the slow ejection phase.

End-diastolic volume, the volume in each ventricle at the end of diastole, ranges from 110 to 120 milliliters.
Stroke volume, the amount of blood ejected per beat, is approximately 70 milliliters.
End-systolic volume, remaining blood post-ejection, measures around 40 to 50 milliliters.
Ejection fraction is calculated by the formula: Ejection Fraction = Stroke Volume / End-Diastolic Volume, typically around 60%.
Stroke volume may be increased by elevating end-diastolic volume and reducing end-systolic volume.