Blood Vessels and Blood Flow 4

Question 1

What regulates structure and resistance in small arteries/arterioles?

Answer 1

Smooth muscle

Question 2

What acts as a reservoir for blood volume?

Answer 2

The veins

Question 3

What akes the largest cross-sectional area in the CVS?

Answer 3

The capillaries

Question 4

What is Darcys Law?

Answer 4

Pressure Difference = Flow x Resistance
P=QxR

Q = Cardiac output
R = Peripheral vascular resistance
P = Mean blood pressure

Question 5

`Why does pressure fall across the CVS?

Answer 5

Viscous pressure losses and resistance

Question 6

What are the 3 variables of resistance?

Answer 6

• Fluid viscosity
• Length of tube (fixed)
• radius of tube (variable)

Question 7

Which equation shows importance of vessel radius for resistance?

Answer 7

Poisuille’s

Question 8

How much would halving the radius decrease blood flow?

Answer 8

16 times

Question 9

What are the two types of blood flow?

Answer 9

Laminar and turbulent

Question 10

Where does blood flow the quickest?

Answer 10

In the middle of the vessel, slowest at the sides

Question 11

What is the Shear Rate?

Answer 11

The difference in velocity between the highest in the middle of the lumen and the lowest that adheres to the lumen walls

Question 12

What does shear stress do?

Answer 12

Disturbs endothelial function

Question 13

What does low shear stress cause?

Answer 13

Endothelial proliferation and therefore vasoconstriction, coagulation, platelet aggregation and atheroma formation

Question 14

What is the pulse pressure?

Answer 14

The difference between diastoic and systolic blood pressure

Question 15

How do you calculate mean blood pressure?

Answer 15

Diastolic + a third of pulse pressure

Question 16

What is the Windkessel effect?

Answer 16

Aortic elasticity keeping blood pressure a lot higher than in the pulmonary artery

Question 17

What is pressure inside a vessel called?

Answer 17

Transmural pressure

Question 18

How does an aneurysm form?

Answer 18

Weakened blood vessel walls over a prolonged period of time as a result of the law of laplace.

Question 19

Why dont we faint when were standing?

Answer 19

Standing activates the sympathetic nervous system which stiffens and contracts the veins, especially in the legs. This increases total peripheral resistance and paired with slightly higher heart rate and cardiac contractile strength allows blood pressure to be maintained

Question 20

What is a skeletal pump?

Answer 20

The contraction of the muscles squeezes blood back through the veins and to the heart

Question 21

What is the respiratory pump?

Answer 21

During inspiration, our chest expands and intrathoracic pressure decreases allowing blood to come back into the right atrium and increase venous return

Question 22

What do incompetent valves cause when standing?

Answer 22

Varicose veins and oedema of the feet