Cardiac Cycle Flashcards
What are the 3 basic events in the cardiac cycle
LV Contraction
LV Relaxation
LV Filling
What is systole
Ventricular contraction
What happens during systole
Wave of depolarisation arrives,pressure rises in the ventricle which causes the mitral valve to close and so the aortic valve opens and ejection of blood begins
What is diastole
Ventricular relaxation
What happens during diastole
The ventricular pressure decreases, the ventricle goes through a phase of reduced ejection but the aortic flow is maintained due to distension, eventually the aortic valve will close and isovolumic relaxation will occur before the mitral valve opens agin to begin refilling
How does ventricular filling occur
The ventricles fill due to the mitral valve opening caused by increased pressure which exceeds that of the ventricles and so rapid filling starts.
When does ventricular filling stop
Ventricular filling stops when diastasis is reached, this is when the pressure in the atria and ventricles is equal, this is only a temporary stop
How is ventricular filling restored after diastasis
Filling is renewed when a contraction used as a booster raises the atria pressure again and so the pressure gradient been present again
Apart from the pressure gradient what else can cause rapid ventricular filling
Ventricular suction
What is preload
Preload is the load present before left ventricular contraction has started
What is after load
After load is the load after the ventricle starts to contract
What is starlings law of the heart
Within physiologic limits the larger the volume of the heart the greater the energy of its contraction and the amount of chemical change at each contraction
What is LV filling pressure
LV pressure is the difference between the Left Atrial pressure and the left ventricular diastolic pressure
Explain the force-length interaction and starlings law
The force which is produced by the skeletal muscle declines when the sarcomere is less than optimal length so in the cardiac sarcomere at 80% of the optimal length only 10% of the maximal force is produced
Explain all or none in the cardiac sarcomere
The cardiac sarcomere must function near the upper limit of their maximal length- 2.2um
The left ventricular volume changes are affected when the sarcomere lengthens from 85% to the full LMAX
