11 terms

USI Summer Session Chapter 18 A&P - The Heart part 5

Cardiac cycle
all events associated with blood flow through the heart during one complete heartbeat
contraction of the heart
relaxation of the heart
Ventricular filling
takes place in mid-to-late diastole

•AV valves are open
•80% of blood passively flows into ventricles
•Atrial systole occurs, delivering the remaining 20%
End diastolic volume
Volume of blood in each ventricle at the end of ventricular diastole
Ventricular systole
Atria relax and ventricles begin to contract

•Rising ventricular pressure results in closing of AV valves
•Isovolumetric contraction phase (all valves are closed)
•In ejection phase, ventricular pressure exceeds pressure in the large arteries, forcing the SL valves open
End systolic volume (ESV)
volume of blood remaining in each ventricle
Isovolumetric relaxation
occurs in early diastole

•Ventricles relax
•Backflow of blood in aorta and pulmonary trunk closes SL valves and causes dicrotic notch (brief rise in aortic pressure)
Cardiac Output (CO)
Volume of blood pumped by each ventricle in one minute

heart rate (HR) x stroke volume (SV)
Heart Rate
Number of beats per minute
stroke volume
volume of blood pumped out by a ventricle with each beat