CVS The peripheral circulation

Question 1

Define
Systolic arterial pressure
Diastolic arterial pressure
Pulse pressure

Answer 1

Systolic pressure is the maximum arterial pressure (120mmHg) Affected by how hard the heart pumps, total peripheral resistance and stretchiness of arteries

Diastolic pressure is the minimum arterial pressure (80mmHg) Affected by systolic pressure and total peripheral resistance

Pulse pressure is the difference between systolic and diastolic (40mmHg)

Question 2

Define total peripheral resistance

Answer 2

The same of the resistance of all the peripheral vasculature in the systemic circulation

Question 3

How do you calculate mean arterial pressure?

Answer 3

Diastolic pressure + 1/3 of pulse pressure

Question 4

How does the elasticity of arteries reduce arterial pressure fluctuation between systole and diastole?

Answer 4

Arteries have distensible walls that stretch during systole
More blood flows in than out so pressure does not rise as much
The arteries then recoil in diastole

Question 5

What is the pulse wave?

Answer 5

Contraction of the ventricles creates the pulse wave which propagates along arteries faster than blood
It can be felt in locations where arteries come close to the surface and can be pushed against a reasonably hard surface

Question 6

Define:
Central venous pressure
Venous return

Answer 6

Central venous pressure is the pressure in the great veins supplying the heart
Venous return is the rate of flow of blood back to the heart. It limits cardiac output

Question 7

How do vasodilator metabolites modify vasomotor activity?

Answer 7

Metabolically active tissues produce vasodilator metabolites e.g. H+, K+, adenosine, lactate
These cause relation of smooth muscle lowering resistance and increasing blood flow

Question 8

What is reactive hyperaemia?

Answer 8

If circulation is cut off to an organ or limb for a short period, then restored, a large amount of blood enters after a period of no blood flow.
The organ/limb continues metabolising and producing vasodilators during the period of no blood flow, and there is no blood to remove them. Therefore when circulation is restored the arterioles dilate maximally and the blood flow is very high.

Question 9

What is auto-regulation?

Answer 9

At most levels of metabolic activity most organs automatically take the blood flow they need as long as the pressure in the arteries supplying them is kept within a certain range

Question 10

How do you calculate cardiac output?

Answer 10

Stroke volume x heart rate