Control of Cardiac Output Flashcards
what is afterload
the pressure in the wall of the LV during ejection
what is preload
the amount the ventricles are stretched during diastole
what is the total peripheral resistance
resistance to blood flow
which blood vessels offer the greatest resistance to blood flow
arterioles
what happens to arterial and venous pressure if total peripheral pressure decreases
arterial pressure decreases but venous pressure increases
what happens to arterial and venous pressure if total peripheral pressure increases
arterial pressure increases but venous pressure decreases
what happens to arterial and venous pressure if cardiac output increases
arterial pressure increases but venous pressure decreases
what happens to arterial and venous pressure if cardiac output decreases
arterial pressure falls but venous pressure rises
true or false; narrowing the arterioles increases blood flow
false.
true or false constricting arterioles increases arteriole pressure but decreases venous pressure
true
true or false; constricting arterioles increases resistance
true
what happens to the arterioles and precapillary sphincters if tissues need more blood
they will dilate
what happens to the heart rate if the peripheral resistance falls
pumps more so that the arterial pressure doesn’t fall and venous pressure doesn’t rise
what are the 2 mechanisms of how the heart changes to control arterial and venous pressure
intrinsic and extrinsic
what is the intrinsic mechanism of heart response
where the heart response if due to factors within the heart
what is the extrinsic mechanism of the heart response
where the heart responds to factors outside of the CVS e.g. the ANS
what is cardiac output equal to
stroke volume x heart rate
what is the stroke volume
end diastolic volume - end systolic volume
what is the end diastolic volume of a normal heart
120ml
what is the LV pressure of a normal heart at the end diastolic volume
10 mmHg
what is the normal stroke volume
70 ml
what does the Frank-Starling Law state
as the heart fills more, it contracts harder and so the stroke volume increases
what must happen to the venous pressure to allow the heart to fill more
it increases
what happens to contraction there is too much overlap of filaments in a sarcomere
the cell cant contract well
what happens when the filaments in a sarcomere are stretched
the cell can contract better
what happens to calcium sensitivity as cardiac muscle fibres are stretched
it increases
is the frank starling mechanism an intrinsic or extrinsic control mechanism
intrinsic
what is the mechanism by which increasing the filling of the heart increases stroke volume
Frank-Starling mechanism
what does it mean by saying the pulmonary and systemic circulations operate in series
same volume of blood pumped to the body must also be pumped to the lungs
what is contractility
the force of contraction for a given fibre length
was do extrinsic mechanisms do
increases contractility without increasing fibre length
what happens to aortic pressure when peripheral resistance is increased
it increases
what happens to the filling of the heart when peripheral resistance is increased
it decreases as venous pressure is reduced
what is cardiac output
how much the ventricles empty
what does cardiac output depend on
how hard the heart contract and how hard it is to eject blood
what increases contractility
sympathetic drive (extrinsic mechanisms)
what happens to the total peripheral pressure when metabolism increases
decreases to supply more blood. this causes an increase in venous pressure and decrease in arteriole pressure so the heart responds by pumping more
what happens to the TPR when eating
decreases as there is vasodilation. this decreases arteriole pressure and increases venous pressure so heart rate increases
what happens to venous pressure when you stand
it decreases so cardiac output decreases causing arteriole pressure to decrease
true or false; pressure changes in the veins and arteries when standing up can be corrected by intrinsic mechanisms
false. baroreceptor reflex and the ANS increase heart rate and TPR. if this doesn’t work you get postural hypotension
