Question

1. One of the feedback mechanisms for high H+ (low pH) levels in the blood is to increase respiratory rate. Explain why this helps to return blood pH to a neutral level (6pts).

2. List a general description of the 3 lines of defense and provide an example cell or organ from each (6 pts).

3. Explain counter current flow and its importance to aquatic species. Explain the difference in gas exchange for a tadpole versus adult bullfrog.

4. What are the four symptoms/signs associated with inflammation and how is each created by the inflammatory response? (4 points)

5. The cardiac output of each ventricle is the same. Why is this? What would happen if the right ventricle pumped more blood than the left? (6pts)

6. What is the relative speed (slower, faster, the same) of a second response compared to the first response to a non-specific (innate) versus a specific (adaptive) pathogen? Explain (4 points)

7. Considering what you know about blood filtration and reabsorption, explain why too little dietary protein can cause swelling of the tissues (edema) (6 pts).

8. What is the least common formed element?

Answer 1

1. The second line of defense against acid load is respiratory compensation. When there is a fall in pH of plasma (acidosis), the respiratory rate is stimulated resulting in hyperventilation. This would eliminate more CO2, thus lowering the H2CO3 level.

The hemoglobin serves to transport the CO2 formed in the tissues, with minimum change in pH. Side by side, it serves to generate bicarbonate or alkali reserve by the activity of the carbonic anhydrase system. The reverse occurs in the lungs during oxygenation and elimination of CO2. When the blood reaches the lungs, the bicarbonates re-enters the erythrocytes by reversal of chloride shift. It combines with H+ liberated on oxygenation of Hb to form carbonic acid which dissociates into CO2 and H2O. CO2 is thus eliminated by the lungs.

HHb + O2 HbO2 + H+

HCO3- + H+ H2CO3

H2CO3 H2O + CO2

Hence excess elimination of acidic CO2 by hyperventilation mechanism helps to return blood pH to a neutral level.