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Date Submitted: 10/30/2015 07:52 AM
Handout of Cardiac Cycle
• Prepared by Dr. Magdi El Sersi
Atrial Systole
Both atria contract
1)
2)
3)
4)
5)
6)
7)
Atrial pressure: initially increases then it decreases again.
Ventricular pressure: initially increases slightly then it decreases
again (due to dilatation of the ventricle).
Ventricular volume: this increases slightly due to ventricular dilatation.
Valves: the A-V valves are open while the semilunar valves are
closed.
Aortic pressure: this decreases gradually due to continuous blood
flow from the aorta to the peripheral vessels.
Sounds: the 4th heart sound is recorded in this phase.
ECG: the P wave starts about 0.02 sec before this phase, while the
main part of the P wave, the P-R segment and the Q wave occur
during it.
Isovolumetric contraction phase
Early phase of ventricular systole in which the ventricles
contract but no ejection occurs.
1)
2)
3)
4)
5)
6)
Ventricular pressure & volume: the ventricles contract isometrically,
the left ventricular pressure rises sharply to 80 mmHg and the
ventricular volume remains unchanged .
valves: the A-V valves are closed because the ventricular pressure
exceeds the atrial pressure and the semilunar valves also remains
closed thus all valves are closed in this phase and the ventricles
become closed chamber .
sounds: the early component of the first heart sound is heard in this
phase due to the closure of the A-V valves.
Atrial pressure: on closure of the A-V valves, their cusps bulge into
the atria leading to a slight increase in the atrial pressure .
Aortic pressure: this decreases to a minimum of about 80 mmHg at
the end of this phase, which is called the diastolic blood pressure.
ECG: the Q wave starts about 0.02 sec before this phase, while the R
and S waves occurs during it.
Maximum ( Rapid) ejection phase
The semilunar valves open and blood is ejected into the great
arteries.
1)
2)
3)
4)
5)
6)
Ventricular...