Cardiac Cycle Flashcards
What are the phases of the Cardiac Cycle?
LV contraction:
- Isovolumic contraction ( b )
- Maximal ejection ( c )
LV relaxation:
- Start of relaxation and reduced ejection ( d )
- Isovolumic relaxation ( e )
- Rapid LV filling and LV suction ( f )
- Slow LV filling (diastasis) ( g )
- Atrial booster ( a ).
What happens in Ventricular Contraction: Systole?
Wave of depolarisation arrives,
Opens the L-calcium tubule, {ECG: Peak of R},
Ca2+ arrive at the contractile proteins,
LVp rises > LAp:
MV closes: M1 of the 1st HS,
LVp rises (isovolumic contraction) > Aop,
AoV opens and Ejection starts.
What happens in Ventricular Relaxation: Dystole?
LVp peaks then decreases.
Influence of phosphorylated phospholambdan, cytosolic calcium is taken up into the SR.
“phase of reduced ejection”.
Ao flow is maintained by aortic distensibility.
LVp < Ao p, Ao. valve closes, A2 of the 2nd HS.
“isovolumic relaxation”, then “MV opens”.
What happens in Ventricular Filling?
LVp < LAp, MV opens, Rapid (E) filling starts.
Ventricular suction (active diastolic relaxation), may also contribute to E filling (esp. ex. ?S3).
Diastasis (separation): LVp=LAp, filling temporarily stops.
Filling is renewed when A contraction (booster), raises LAp creating a pressure gradient.(path, S4)
What happens in Physiologic systole?
Isovolumic Contraction
Maximal Ejection
What happens in Cardiologic Systole?
From M1 to A2
Only part of isovolumic contraction (includes maximal and reduced ejection phases)
What happens in Physiologic Diastole?
Reduced ejection
Isovolumic Relaxation
Filling Phases
What happens in Cardiologic Diastole?
A2 to M1 interval (filling phases included)
What is preload?
The load present before LV contraction has started.
What is afterload?
The load after the ventricle starts to contract
What is Starlings law of the heart?
Starling 1918: 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.
LV filling pressure: is the difference between LAp and LV diastolic pressure.
The relationship reaches a plateau.
What is The Force-Length Interaction & Starling’s law?
The force produced by the skeletal muscle declines when the sarcomere is less than the optimal length (Actin’s projection from Z disc “1micrometre” X 2).
In the cardiac sarcomere, at 80% of the optimal length, only 10% of the maximal force is produced!
What is the ‘all or none’ law?
The cardiac sarcomere must function near the upper limit of their maximal length (LMAX) = 2.2 micro metre.
The physiologic LV volume changes are affected when the sarcomere lengthens from 85% of LMAX to LMAX!
Steep relationship: length-dependent activation.
What is Frank & isovolumic contraction?
The heart can, during the cycle, increase and decrease the pressure even if the volume is fixed.
Increasing diastolic heart volume, leads to increased velocity and force of contraction (Frank 1895).
This is the positive inotropic effect.
Ino: Fibre (Greek); tropus: move (Greek).
What is contractility?
The state of the heart which enables it to increase its contraction velocity, to achieve higher pressure, when contractility is increased (independent of load)
