10. Peripheral Circulation Flashcards
What is compliance?
The ability to distend and increase in relative volume due to pressure increase.
What is capacitance?
Measure of relative volume increase per unit increase in pressure.
What is pressure a measure of?
Mechanical energy gradient in blood that drives its flow round different parts of the system.
Why does arterial pressure need to be high?
To push the cardiac output of each beat through high resistance arterioles.
What is the Windkessel effect?
The aortic compliance and elastic arteries means that the pulsatile nature is dampened. So there isn’t such rapid pressure rises.
What factors affect systolic and diastolic pressure?
Cardiac output, arterial compliance/stretchiness of elastic arteries, compliance in elastic arteries, total peripheral resistance.
How can pulse pressure be calculated?
It’s the difference between systolic and diastolic pressure: SBP - DBP = 40mmHg as an average healthy pressure.
How can average pressure be calculated?
Diastolic blood pressure + 1/3 systolic blood pressure. Only a third of systolic pressure as the diastole predominates time wise.
What is the vasomotor to be mostly controlled by?
Autonomic sympathetic nervous system.
Why do arterioles have high vasomotor tone at rest?
Only need low blood flow at rest so there is no need to employ large functional reserves.
What does reduced arterial vasomotor tone lead to?
Increased vasodilatation.
What does vasodilatation do?
Decreases resistance to flow.
How can vasomotor tone be reduced?
By local vasodilator factors. They relax vascular smooth muscle. Can be due to metabolic activity, usually acute.
Also affected by hormones, myogenic factors, and endothelial factors.
How is resistance linked to vessel diameter?
They are inversely proportional.
