Flashcards in CVS 1.1 - intro Deck (20):
Where does gas exchange take place in the cvs?
What is used as a transporter in the cvs?
What is used to control the perfusion rate and how is this achieved?
- Arterioles and pre-capillary sphincters
- Add resistance to flow by decreasing the diameter of the lumen therefore making it harder to flow through
How do O2 and CO2 diffuse through the capillary wall?
Both are lipid soluble so move through by simple diffusion
How do molecules such as glucose or amino acids move through the capillary wall?
Both are hydrophilic so diffuse through specific pores by facilitated diffusion
What are the three factors that affect the rate of diffusion? Which is the most limiting?
- Area (not usually limiting)
- Resistance (not usually limiting)
- Concentration gradient (not usually limiting)
How does the area of a diffusion surface affect the rate?
- Smaller diffusion area = lower rate of diffusion
- Higher capillary density = higher rate of diffusion
Where are the most likely areas of high capillary density?
Areas that have high metabolic activity
What are the three factors that affect the resistance to diffusion?
- 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
How does the concentration gradient affect the rate of diffusion?
Higher concentration gradient = higher rate of diffusion
Where is the affect of a concentration gradient most significant?
Between the blood and the capillaries
Why do concentration gradients need to be maintained?
So that supply can meet demand otherwise the gradients will disappear
What is the typical cardiac output for a 70kg male? What can this increase to in order to maintain perfusion rates to vital organs?
- 5.0 lmin-1
- 24.5-25 lmin-1
What is the typical perfusion rate to the brain? Describe it
High and constant
What is the typical perfusion rate to the heart? Describe it
0.9 - 3.6 ml.min-1g-1
Rest - high when exercising
What is the typical perfusion rate to the kidneys? Describe it
What is the distribution of blood within the cardiovascular system?
- Veins = 67%
- Arteries and Arterioles = 11%
- Capillaries = 5%
- Heart and lungs = 17%
Why does the total flow of blood need to be able to change?
So that the blood can return to the heart at a different rate to which it leaves at
How can veins act as a variable reservoir of blood?
Have thin walls that can distend and recoil (capacitance)