The Cardiac Cycle Flashcards
Mechanical Events
Systole: contraction of heart; pumping out
Diastole: relaxation of heart; filling up
What comes after the Atrial systole and diastole?
Ventricular systole and diastole
What is the flow of blood?
How many phases are there of the Cardiac Cycle?
FIVE. 5
What is the first phase of the Cardiac Cycle?
Ventricular filling (mid-to-late diastole)
AV valves– MUST BE OPEN
SL valves– ARE CLOSED
Valves open and close based on changes in pressure
What percentage is filled before the AV valves start to close?
80%
End Diastolic Volume (EDV)
volume of blood in each ventricle at end of ventricular diastole
What is the second phase?
Isovolumetric Contraction
- Atria relax; ventricles begin to contract
- ventricular pressure closes AV valves
–> ALL VALVES ARE CLOSED!
What is the third phase?
Ventricular Ejection
- pressure in ventricle exceeds pressure in the large arteries–> SL valves are forced open
What is stroke volume?
EDV-ESV
What is the fourth phase?
Isovolumetric relaxation
- pressure is decreasing rapidly
- atria are relaxed and filling
End systolic volume (ESV)
Volume of blood remaining in each ventricle after systole
What is the fifth phase?
Back to step one
How long is each cardiac cycle?
0.8 seconds
How is it split up?
Atrial systole = 0.1 sec
Ventricular systole = 0.3 sec
Quiescent period = 0.4 sec
MOST RELAXED
