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
How is a positive inotropic effect put on the heart
The heart can during the cycle increase and decrease the pressure even if the volume is fixed. Increasing the diastolic heart volume leads to increased velocity and force of contraction in line with franks law
What is contractility
Contractility is the state of the heart which enables it to increase its contraction velocity to achieve higher pressure when the contractility is increased independent of load
What is elasticity
Elasticity is the myocardial ability to recover its normal shape after removal of systolic stress
What is compliance within the myocardium
Compliance is the relationship between the change in stress and the resultant strain
What is diastolic distensibility
Diastolic distensibility is the pressure required to fill the ventricle to the same diastolic volume
What does the pressure-volume loop reflect
The pressure-volume loop reflects contractility in the end-systolic pressure volume relationship, while compliance is reflected at the end diastolic pressure volume relationship
Where can isometric conditions be found
Isometric conditions can be found during isovolumic contraction
Why can’t isotonic contraction be seen in the heart
Isotonic contraction is totally impossible in the heart due to constantly changing load
