cardiac output and venous return Flashcards
value, Cardiac output of the heart
5 L/m
4,9 l/m in women
5.6 L/m in men
but varies throughout life
cardiac output (def)
quantity of blood that goes out of the heart to systemic circulation
Venous return (def)
amount of blood that returns from the systemic veins to the heart
Factors that change the cardiac output
Basal metabolism
Physical exercise
Age
Body size
what is controlled by venous return
the cardiac output
frank sterlings law
more distended- more filling - more blood goes out
if venous return increases what happens to the sinus node and therefore to the heart rate ?
It distends the sinus node and increases the heart rate.
HEART ONLY BECOMES A LIMITING FACTOR F VR> PUMPING CAPACITY
PLATEAU VALUES FOR NORMAL, HYPEREFFECTIVE AND EXTREME HEART
NORMAL: 13L/M
HYPEREFFECTIVE: 25 L/m
EXTREME: 30-40 L/m
PRELOAD: mitral valve, volume, pressure
mitral valve opens due to the diff of pressures
blood enters the ventricle and reaches 140 ml of blood
th increase of volume is high but the pressure increases mildly
isovolumetric concentration phase: aortic and mitral valve, contraction and pressure
aortic and mitral valves are closed
although contraction starts the volume is the same
the pressure increases dramatically and rapidly
VENTRICULAR EJECTION: pressure, volume, stroke volume
Lv pressure opens the aortic valve
volume starts to decrease and pressures continuous to increase
lv pressure no longer increases until it falls to the pressure of the aorta and then it closes
the stroke volume is 70ml
ISOVOLUMETRIC RELAXATION (AFTERLOAD )
when the aortic valve closes the ventricle relaxes and pressure decreases
volume is constant as no blood enters
IF PRELOAD INCREASES: VR, telediasuolic volume, stroke volume
- VR increases
- Telediastolic volume increases
- stroke volume increases
IF CONTRACTILITY INCREASES: pressure, blood ejection, stroke volume, telesistolic volume will?
increased pressure
increased blood ejection
higher stroke volume
low telesistolic volume
IF AFTERLOAD INCREASES: aortic valve, stroke volume will?
aortic valve opens at higher pressures and closes earlier
stroke volume is lower
