The cardiac cycle Flashcards
1
Q
The processed of Ventricular filling
A
- This phase starts as pressure in the ventricle drops below that of the atrium.
- The mitral/bicuspid valve opens quietly and blood enters the ventricle.
- Ventricle fills about 80% of it’s capacity during this phase
2
Q
The processed of Atrial contraction
A
- The left atrium contracts to complete the filling of the ventricle. (the rise in inertial pressure is small for two reasons).
- Firstly the atrial muscle layer is thin
- Secondly there are no valves where the pulmonary veins enter the atrium. (nothing to prevent backflow into veins).
3
Q
The processed of Isovolumetric ventricular contraction (SYSTOLE)
A
- The ventricle begins to contract.
- Blood within it lifts backwards towards the atrium and mitral valve closes (First heart sound) (LUB)
- Ventricle pressure is still below that in the aorta therefore aortic valve remains closed .
- In this time the ventricle is isolated with both its inlet /outlet valves closed.
4
Q
The processed of Ventricular ejection
A
- (systole continues) Ventricular pressure exceeds aortic pressure, allowing aortic valve cups to open quietly.
- Blood leaves the ventricle
- As blood is being pushed/ejected into aorta faster then run-off into arteries the pressure in the ventricle and aorta continues to rise steeply.
- Later in this phase rate of ejection falls below rate of run-off meaning aortic and ventricular pressures level-off and then decrease.
5
Q
The processed of Isovolumetric ventricular relaxation
A
- The ventricle relaxes; as this occurs ventricular pressure drops rapidly.
- Flow reverses in the aorta and the aortic valve closes (Second heart sound) (DUB) as blood tries to re-enter the ventricle.
- Mitral/bicuspid valve is closed as ventricular pressure although falling still exceeds atrial pressure.
- for a brief period the ventricle is again isolated.( when this period is finished the heart re-enters the stage of ventricular filling.
