The Cardiac Cycle Flashcards
What happens in diastole
Heart relaxes and fills
What happens in systole
Heart contracts and ejects
What are the AV valves
Mitral on L side
Tricuspid on R side
What are the semilunar valve
Aortic
Pulmonary
What are the 4 stages of the cardiac cycle
Filling Phase
Isovolumetric contraction
Outflow phase
Isovolumetric relaxation
What happens in the filling phase
Atria fill with blood
Ventricles relax
AV valve opens when Pa > P ventricle
Blood flows into ventricle by gravity
At end of diastole atria contract filling the remainder of the ventricle
Increases Pressure in v so that is greater than A
AV valve closes
What causes the 1st HS
AV closes
Start of systole
What happens in isovolumetric contraction
As contraction begins both sets of valves are closed
Start of systole massively increases the pressure within the ventricles
Ready to eject blood into the aorta and pulmonary trunk
Atria repolaries and relaxes in this time and blood begins to flow n again
What happens in the outflow phase
When pressure in ventricle is greater than pressure in aorta the SL valves open
High pressure blood forces into arteries
At end of systole ventricles begin to relax
What happens in isovolumetric relaxation
Ventricles begin to relax
When pressure in ventricle less than aorta SL valve closes
Also some back flow of blood = closure of valve
What causes 2nd heart sound
SL valve closes
End of systole
What is the EDV
Volume in ventricle at end of diastole
Will decrease as HR increases as reduced filling time
What is ESV
Volume in ventricle at end of systole
What is stroke volume
EDV - ESV
Volume of blood pumped per contraction
70ml
Can increase up to 100ml during exercise
What is ejection fraction
SV / EDV
Should be 2/3
