Flashcards in CVS - Control Of Cardiac Output Deck (19):
What is afterload?
The load that the heart must eject blood against (roughly equivalent to aortic pressure)
What is preload?
Amount the ventricles are stretched in diastole - related to end diastolic volume
What is total peripheral resistance?
Aka systemic vascular resistance, this is the resistance to blood flow offered by all the systemic vasculature.
Why does contraction of the arterioles cause pressure on the arterial side to rise, while pressure on the venous side falls?
Constriction causes the artery to narrow. This means that less blood can get through, so pressure rises on the arterial side (before the blockage) and falls on the venous side (after the blockage).
What happens to arterial and venous pressure if total peripheral resistance FALLS and cardiac output is UNCHANGED?
Arterial pressure will fall and venous pressure will increase.
What happens to arterial and venous pressure if total peripheral resistance INCREASES and cardiac output is UNCHANGED?
Atrial pressure increases, venous pressure falls
What happens to arterial and venous pressure if total peripheral resistance is UNCHANGED and cardiac output INCREASES?
Arterial pressure will increase and venous pressure will fall
What happens to arterial and venous pressure if total peripheral resistance is UNCHANGED and cardiac output DECREASES?
Arterial pressure will fall and venous pressure will rise
What is the result of arterioles and pre-capillary sphincters dilating?
Peripheral resistance falls
Stroke volume x heart rate = ?
End diastolic volume - end systolic volume = ?
How can stroke volume be increased?
Increase end diastolic volume or decrease end systolic volume.
What is the Ventricular Compliance Curve used to illustrate?
Shows the relationship between venous pressure and heart filling.
- in state of decreased compliance, LV pressure increases while LV volume does not increase much
- in state of increased compliance, LV volume increases a lot but pressure does not increase
What is the Frank-Starling Law of the Heart?
The idea that the more the heart fills, the harder it contracts, which increases the stroke volume. The sarcomeres can be stretched to the optimum length, allowing better contraction
Is increased stroke volume with increased filling of the heart an intrinsic or extrinsic control mechanism?
True or false - Starling's law of the heart ensures that both sides of the heart are balanced?
True - they must both maintain the same output.
What is contractility?
The force of contraction for a given fibre length
Give some examples of extrinsic factors which can increase contractility
Sympathetic stimulation and circulating adrenaline