1.1 CVS Flashcards
Why is diffusion not viable in large organisms? How is this overcome?
Cells are too far away from an oxygen source. Large organisms have a gas exchange system and a circulatory system
What is diffusion?
Movement of particles from a high concentration to a low concentration
Where does diffusion between the blood and the tissues take place in humans?
The capillaries
Name a feature of the capillaries that allows efficient gas exchange
Very thin wall- therefore short diffusion pathway
How do molecules move from the capillaries to the tissues?
Through pores
Directly though the membrane (O2, CO2)
How does surface area affect diffusion?
The larger the surface area, the more efficient the diffusion. There is more area for diffusion to occur.
What can cause diffusion resistance?
The nature of the molecule
The nature of the barrier
The diffusion path length
How does the concentration gradient affect diffusion?
The greater the concentration gradient, the greater the rate of diffusion.
What is another name for the ‘rate of blood flow’?
Perfusion rate
What is the total blood flow at rest?
5 L per min
Name 3 areas of the body that must have a constant perfusion rate
Brain
Kidneys
Heart
Name the mechanism that controls the perfusion rate to different areas of the body
Resistance
Where in the body is there a temporary store of blood?
The veins- walls distend and collapse to act as a reservoir
