Cardiac Cycle Flashcards
What are the basic 3 events in the cardiac cycle
LV contraction
LV relaxation
LV filling
What parts of the cardiac cycle are in left ventricle contraction
Isovolumetric contraction
Maximal elejection
What parts of the cardiac cycle are in left ventricle relaxation
Start of relaxation and reduced ejection
Isovolumetric relaxation
Rapid LV filling and LV suction
Slow LV filling (diastasis)
Atrial booster
What is ventricular contraction
Systole
What happens at systole
Wave of depolarisation arrives
Opens the L-calcium tubule
Ca2+ arrive at contractile proteins
LVp rises > LAp
MV closes
LVp rises (isovolumetric contraction) > Aop
AoV opens and ejection starts
In systole is the L ventricle or atria have more pressure
Left ventricle pressure
In isovolumetric contraction does the L ventricle or atria have more pressure
Left ventricle pressure
What valve opens in systole to start ejection
Aortic valve
What is diastole
Ventricular relaxation
Describe diastole
LVp peaks then decreases
Influence of phosphorylated phospholambdam cytosolic calcium is taken up into the SR
Phase of reduced ejection
Ao flow is maintained by aortic distensibility
LVp < AoP
Ao. valve closes
Isovolumetric relaxation the MV opens
In diastole is the left ventricle pressure more than the aortic pressure
Less than
Describe ventricular filling
LVp < LAp
MV opens
Rapid filling starts
Ventricular suction contributes
Diastasis (seperation) LVp = LAp filling temporarily stops
Filling is renewed when A contraction raises LAp creating pressure gradient
In ventricular filling is the left ventricle or atria have more pressure
Atria
What does ventricular suction contribute to
Ventricular filling
What is physiologic systole
Isovolumetric contraction
Maximal ejection
What is cardiologic systole
From M1 to A2
Only part of isovolumetric contraction - includes maximal and reduced ejection phases
What is physiologic diastole
Reduced ejection
Isovolumetric relaxation
Filling phases
What is cardiologic diastole
A2 to M11 interval - filling phases included
Define preload
Load present before LV contraction has started
Define afterload
Load after the ventricle starts to contract
Define starlings Law
Within physiologic limits, the larger the volume off the heart, the greater energy of its contraction and the amount of chemical change at each contraction
In starlings law what is LV filling pressure
Left atrium pressure - left ventricle diastolic pressure
In the cardiac sarcomere at 80% of the optimal length, what % of the maximal force is produced
10%
What is the maximal length of the cardiac sarcomere
2.2 um
When the sarcomere lengthens to 85% of Lmax what is effected
Physiologic LV volume
What is the relationship of the sarcomere
Length-dependent activation
All or none
Define contractility (inotropic state)
State of the heart which enables it to increase its contraction velocity, to achieve higher pressure, when contractility is increased independent of load
Define elasticity
Myocardial ability to recover its normal shape after removal of systolic stress
Define compliance
Relationship between the change in stress and resultant strain (dP/dV)
Define diastolic distensibility
Pressure required to fill the ventricle to the same diastolic volume
Define myocardial work
Pressure-volume loop reflects contractility in the end-systolic pressure volume relationship, while compliance is reflected at the end diastolic pressure volume relastionship
When is compliance reflected
End diastolic pressure volume relationship
When is contractility reflected
End-systolic pressure volume relationship
What type of contraction does the heart perform
Isometric conditions found during isovolumetric contraction (isotonic are impossible)
What does sympathetic stimulation do
Increases HR (positive chronotropic)
Increases force of contraction (positively inotropic)
Increases CO
What does parasympathetic stimulation do
Decreases HR (negatively chronotropic)
Decreases force of contraction (negatively inotropic)
Increases CO
What is sympathetic stimulation controlled by
Adrenaline and noradrenaline + type 1 beta adrenoreceptors
Increased adenylyl cyclase = increase cAMP
What does increased sympathetic stimulation do
Increases HR (up to 180-250bmp)
Increases force of contraction
Large increase in CO (by up to 200%)
What does decreased sympathetic stimulation do
Decreases HR and force of contraction
Decreases CO (by up to 30%)
What is parasympathetic stimulation controlled by
Acetylcholine
M2 receptors - inhibit adenyl cyclase = reduced cAMP
What does increased parasympathetic stimulation lead to
Decreased HR (temporary pause or as low as 30-40bpm)
Decreased force of contraction
Decreased CO (by up to 50%)
What does decreased parasympathetic stimulation do
Increased HR
What is the pressure in the right atrium
0-4mmHg
What is the pressure in the right ventricle during systole
25mmHg
What is the pressure in the right ventricle during diastole
4mmHg
What is the pressure in the pulmonary artery during systole
25mmHg
What is the pressure in the pulmonary artery during diastole
10mmHg
What is the pressure in the left atrium
8-10mmHg
What is the pressure in the left ventricle during systole
120mmHg
What is the pressure in the right ventricle during diastole
10mmHg
What is the pressure in the aorta during systole
120mmHg
What is the pressure in the aorta during diastole
80mmHg
Describe the filling phase
Ventricles fill with blood during diastole and atrial systole
Describe outflow phase
Ventricles continue to contract, pushing blood into the aorta and pulmonary trunk (systole)
Describe isovolumetric relaxation
Ventricles relax, ready to re-fill with blood in the next filling phase
Describe what happens in the filling phase
Ventricle pressure is higher than the atria causing the atrioventricular valves (mitral/tricuspid) valves to close
How long does isovolumetric contraction last
50ms - while pressure builds up
At the beginning of diastole what valves are open
Atrioventricular valves an
What happens during diastole
Tricuspid and mitral valves are open
Contraction of atrium moves blood into the ventricle
(Can move straight through)
Tricuspid/mitral valve prevents blood from flowing back
Describe diastole
Ventricles filled with blood
Atrioventricular valves close
Semilunar valves open
Contraction of ventricles