Download 9/12 Lecture 9

The Cardiac Cycle
The Heart
Wiggers Diagram
Walk through of a
Cardiac Cycle
What is going on
electrically?
Marieb 18
Wiggers Diagram and Pressure Changes
Pressure
Changes
Left atria
Left ventricle
Aorta
Electrical Activity  Pressure Changes
Systole:
Contracting
(sis-tuh-lee)
Diastole:
Relaxing
(di-ass-tuh-lee)
1. Pressure in Atria Higher than in Ventricles
Ventricular Filling
Passive filling (80%)
Atrial systole (20%)
2. Pressure in Ventricles higher than Atria
Atrial Valves Close
End Diastolic Volume (EDV)
How much blood
enters the ventricle
during filling
Ventricular Systole
All Valves Closed
All valves closed
Isovolumetric
Contraction
Contracts from PMI
towards base
3. Ventricle pressure higher than Aorta
SL Valves Open
Ventricular Ejection Phase
Still in Systole!
Pressure rises in
aorta
Pressure continues
rise in ventricle
(briefly)
4. Pressure in Aorta higher than Ventricles
SL Closes
(AV Valves still
closed)
End Systolic Volume (ESV)
How much blood
leaves the ventricle
during ejection
Ventricular Diastole
All valves closed
Isovolumetric
relaxation
1. Pressure in Atria Higher than in Ventricles
AV Valves open
Blood begins to fill
ventricle
And so on…
Timing the Cardiac Cycle
Assuming 75 bpm
CC= 0.8sec
0.1sec
0.3sec
0.4sec