Circulation Questions  

1. What is the basic difference between an open and closed circulatory system? What sorts of animals would you find each in? What are the main functional differences between open and closed systems?

2. What is special about the AV node and transmission through it? What would happen to the efficiency of heart contraction if you "short circuited" it (ran an action potential directly from the atria to the Bundle of His)?

3. How do cardiac muscle cells differ from the other types of muscle cells in terms of the nature of their control, the stimulus for contraction in each, and their morphology (both overall cellular morphology and detailed aspects of membrane structure)? How about cellular constituents?

4. Diagram the path a blood cell would take through the circulatory system in a fish, the possible paths in a frog, and a mammal (how might this differ if this was instead a fetal mammal and what specific structures are involved in this?). What are the possible numbers of capillary beds that would/could be crossed in each case? What variations on heart structure are associated with these different possible pathways?

5. Related to this, what is the advantage of a "double circulation" such as we see in a mammal, bird, or crocodile as compared with the single circuit characteristic of a fish?

6. Where does lymph come from? What sorts of things might you imagine could alter the production and accumulation of lymph in tissues? What other fluid would lymph be most similar to do you think?

7. Arteries, veins and capillaries are built very differently. Associate these structural differences with differences in their function (think like an engineer here!).

8. Tough Question: A bluefin tuna has an extensive rete system to help prevent loss of heat from deep swimming muscles. What is the nature of this system and how does it work? Given that this rete is produced with relatively large arterioles and venules, why is heat transferred, but not oxygen or carbon dioxide to any appreciable degree as far as we know. Answer with reference to general properties of structures involved in diffusion across membranes.

9. Blood clots rapidly when injury to the vascular system takes place, but not before. What is the mechanism of this rapid response? Unnecessary clotting can be dangerous. Based on this, draw parallels between the conversion of fibrinogen to fibrin when needed and enzyme action in the digestive system.