CVS 1.1 - intro

Question 1

Where does gas exchange take place in the cvs?

Answer 1

The capillaries

Question 2

What is used as a transporter in the cvs?

Answer 2

Blood

Question 3

What is used to control the perfusion rate and how is this achieved?

Answer 3

• Arterioles and pre-capillary sphincters

- Add resistance to flow by decreasing the diameter of the lumen therefore making it harder to flow through

Question 4

How do O2 and CO2 diffuse through the capillary wall?

Answer 4

Both are lipid soluble so move through by simple diffusion

Question 5

How do molecules such as glucose or amino acids move through the capillary wall?

Answer 5

Both are hydrophilic so diffuse through specific pores by facilitated diffusion

Question 6

What are the three factors that affect the rate of diffusion? Which is the most limiting?

Answer 6

• Area (not usually limiting)
• Resistance (not usually limiting)
• Concentration gradient (not usually limiting)

Question 7

How does the area of a diffusion surface affect the rate?

Answer 7

• Smaller diffusion area = lower rate of diffusion

- Higher capillary density = higher rate of diffusion

Question 8

Where are the most likely areas of high capillary density?

Answer 8

Areas that have high metabolic activity

Question 9

What are the three factors that affect the resistance to diffusion?

Answer 9

• Molecule type e.g. Lipophilic? Hydrophilic? Size?
• Barrier type e.g. Size of pore, number of pores for hydrophilic substances
• Path length e.g. Capillary density, increased path length = lower rate of diffusion

Question 10

How does the concentration gradient affect the rate of diffusion?

Answer 10

Higher concentration gradient = higher rate of diffusion

Question 11

Where is the affect of a concentration gradient most significant?

Answer 11

Between the blood and the capillaries

Question 12

Why do concentration gradients need to be maintained?

Answer 12

So that supply can meet demand otherwise the gradients will disappear

Question 13

What is the typical cardiac output for a 70kg male? What can this increase to in order to maintain perfusion rates to vital organs?

Answer 13

• 5.0 lmin-1

- 24.5-25 lmin-1

Question 14

What is the typical perfusion rate to the brain? Describe it

Answer 14

0.5 ml.min-1g-1

High and constant

Question 15

What is the typical perfusion rate to the heart? Describe it

Answer 15

0.9 - 3.6 ml.min-1g-1

Rest - high when exercising

Question 16

What is the typical perfusion rate to the kidneys? Describe it

Answer 16

3.5 ml.min-1g-1

High, constant

Question 17

What is the distribution of blood within the cardiovascular system?

Answer 17

• Veins = 67%
• Arteries and Arterioles = 11%
• Capillaries = 5%
• Heart and lungs = 17%

Question 18

Why does the total flow of blood need to be able to change?

Answer 18

So that the blood can return to the heart at a different rate to which it leaves at

Question 19

How can veins act as a variable reservoir of blood?

Answer 19

Have thin walls that can distend and recoil (capacitance)

Question 20

What is the distribution system of the cvs?

Answer 20

Blood vessels and blood