1. CARDIAC CYCLE SYSTOLE AND DIASTOLE PHASES : A.RAPID FILLING
B.DIASTASIS
C.ISOVOLUMETRIC CONTRACTION
D.RAPID EJECTION
E.ISOVOLUMIC RELAXATION 1

2. Cardiac Cycle Systole Muscle is Contracting
A contracting “sphere” generates Pressure
Pressure causes a change in Volume
This is measured by CONTRACTILITY
This is affected by
Function of Muscle
Initial Volume (PRELOAD)
Initial Pressure (AFTERLOAD) 2

3. FIGURE 9-16: Cardiac cycle
FIGURE 9-16: Cardiac cycle. This graph depicts various events that occur concurrently during the cardiac cycle. Follow each horizontal strip across to see the changes that take place in the electrocardiogram; aortic, ventricular, and atrial pressures; ventricular volume; and heart sounds throughout the cycle. Late diastole, one full systole and diastole (one full cardiac cycle), and another systole are shown for the left side of the heart. Follow each vertical strip downward to see what happens simultaneously with each of these factors during each phase of the cardiac cycle. See the text (pp. 255 and 257) for a detailed explanation of the circled numbers. The sketches of the heart illustrate the flow of O2-poor (dark blue) and O2-rich (bright red) blood in and out of the ventricles during the cardiac cycle.
Fig. 9-16, p. 256 3

4. Cardiac Cycle Diastole Muscle is Relaxing
Veins return blood to the heart
As the heart fills with blood, the absolute volume and pressure change
This relationship is measured by COMPLIANCE
This is affected by
Connective Tissue
Venous Pressure
Venous Resistance 4

5. Cardiac Cycle
Both systole and diastole can be divided into early and late phase 5

6. Cardiac Cycle Early Systole
The Pressure in the Ventricle is the same as in the great veins
The Ventricle contracts
The AV valves close
Since the Aortic and Pulmonic valves were already closed, the heart is a closed ball
As the heart contracts, the pressure in the ball rises at a fixed volume. 6

7. Cardiac Cycle Late Systole
The Pressure in the Ventricles is the same as in the great arteries
The A/P valves open
Further contraction of the ventricles causes blood flow at a relatively constant pressure
(this is because the aorta is compliant as well and increase in volume causes only a small increase in pressure) 7

8. Cardiac Cycle Early Diastole The Ventricles begin to relax
As the Ventricular pressure falls below the great artery pressure, the A/P valves close
Since the AV valves were already closed, the heart is a closed ball
As the heart relaxes, the pressure in the ball falls at a fixed volume.
ISOMETRIC RELAXATION 8

9. Cardiac Cycle Late Diastole
When the pressure inside the heart falls below the pressure of the great veins AND the papillary muscles have relaxed, the AV valves open
The blood flows down its pressure gradient and the ventricles fill passively at a fixed pressure (because the ventricle has compliance)
ISTONIC RELAXATION 9

10. Cardiac Cycle End Diastole Early Systole Late Systole Early Diastole
Atrial Contraction
Early Systole
Isometric Contraction
Late Systole
Isotonic Contraction
Early Diastole
Isometric Relaxation
Late Diastole
Isotonic Relaxation 10

11. Cardiac Cycle End Diastole Is unique because the atria contract
This leads to an increase in pressure in three places:
The great veins
The atria
The ventricles 11

12. Pressure Volume Loop
Early
Systole

13. Pressure Volume Loop
Late Systole

14. Pressure Volume Loop
Early
Diastole

15. Pressure Volume Loop
Late
Diastole

16. Pressure Volume Loop
End
Diastole 16

17. RELATIONSHIP OF ECG TO CARDIAC CYCLE17

18. R T P P Q S PR ST TP interval
FIGURE 9-14: Electrocardiogram waveforms in lead II. PR ST
TP interval
Fig. 9-14, p. 254 18