Thinking Scientifically

1. HIV colonizes lymph nodes before it appears in the bloodstream. Why is the presence of HIV in lymph nodes dangerous?

2. Chemotherapy used to treat cancer often severely damages bone marrow. Which biochemical mentioned in the chapter might help patients receiving chemotherapy to recover their bone marrow function?

3. Athletes tend to be slim and strong, have low blood pressure, do not smoke, and alleviate stress through exercise. How might these characteristics complicate a study to assess the effects of exercise on the circulatory system?

4. Explain why women who have had cancerous breasts and the associated lymph nodes removed can develop swollen arms.

5. It usually takes 13 seconds for prothrombin to be converted to thrombin and thrombin to trigger the formation of fibrin. When a person’s diet lacks vitamin K, however, these chemical reactions take 30 seconds or longer. Which circulatory system function does this impair? Which symptoms might a dietary deficiency of vitamin K cause?

Additional Questions

1. Some members of a Scandinavian family have inherited a condition that causes them to overproduce erythropoietin (EPO). One young man from this family has won several Olympic medals for skiing. How might the extra EPO account for his athletic prowess? When some athletes learned of this skier’s biological abnormality, they attempted to obtain EPO as a drug (normally used to help surgical patients rebuild blood supplies). Why would athletes want to take EPO? What might a side effect of EPO abuse be?

2. Cigarette smoke contains thousands of chemicals, including nicotine and carbon monoxide. Nicotine constricts blood vessels. Carbon monoxide prevents oxygen from binding to hemoglobin. How would these two components of smoke affect the circulatory system?