40. Circulatory System

How does myoglobin aid diving mammals such as the Weddell seal?

Which of the following would increase the release of oxygen from red blood cells?

When you hold your breath, which of the following blood gas changes leads initially to the urge to breathe again?

What causes CO₂ in the blood to decrease?

When you exhale, __________.

In the alveoli and lung capillaries, carbon dioxide and oxygen are exchanged by means of __________.

Which structure in a human is most similar in function to the gill lamellae of a fish?

What happens when the CO₂ level from cellular respiration increases in the blood?

What is the major reason that land-dwelling mammals evolved lungs rather than gills as a primary respiratory organ?

What is the correct order of structures through which air passes as it is inhaled by a typical mammal?

Which of the following components of the mammalian gas exchange system has a surface covered by a thin film of fluid without cilia?

Countercurrent flow in the gills of a fish __________.

Which respiratory organ is most often found only in fully aquatic animals?

Gas exchange in the gills of a bony fish is maximized by which of the following?

For a body surface to be a respiratory surface, it must __________.

Complete the following concept map to review some of the concepts of gas exchange. a. b. c. d. e. f. g.

When you hold your breath, which of the following first leads to the urge to breathe? a. falling CO2 b. falling O2 c. falling pH of the blood d. rising pH of the blood

Countercurrent gas exchange in the gills of a fish a. maintains a gradient that enhances diffusion. b. enables the fish to obtain oxygen without swimming. c. means that blood and water flow at different rates. d. allows O2 to diffuse against its partial pressure gradient

When you inhale, the diaphragm a. relaxes and moves upward. b. relaxes and moves downward. c. contracts and moves upward. d. contracts and moves downward.

What is the primary feedback used by the brain to control breathing? a. heart rate b. partial pressure of O2 c. blood pH, which indicates O2 level d. blood pH, which indicates CO2 level

What are two advantages of breathing air, compared with obtaining dissolved oxygen from water? What is a comparative disadvantage of breathing air?

Carbon monoxide (CO) is a colorless, odorless gas found in furnace and automobile engine exhaust and cigarette smoke. CO binds to hemoglobin 210 times more tightly than does O2. CO also binds with an electron transport protein and disrupts cellular respiration. Explain why CO is such a deadly gas.

Partial pressure reflects the relative amount of gas in a mixture and is measured in millimeters of mercury (mm Hg). Llamas are native to the Andes Mountains in South America. The partial pressure of O2 (abbreviated PO2) in the atmosphere where llamas live is about half of the PO2 at sea level. As a result, the PO2 in the lungs of llamas is about 50 mm Hg, whereas that in human lungs at sea level is about 100 mm Hg. A dissociation curve for hemoglobin shows the percentage of saturation (the amount of O2 bound to hemoglobin) at increasing values of PO2 As you see in the graph below, the dissociation curves for llama and human hemoglobin differ. Compare these two curves and explain how the hemoglobin of llamas is an adaptation to living where the air is 'thin.'

Mountain climbers often spend weeks adjusting to the lower partial pressure of oxygen at high altitudes before and during their ascent of high peaks. During that time, their bodies begin to produce more red blood cells. Some runners and cyclists prepare for competition by training at high altitudes or by sleeping in a tent in which PO2 is kept artificially low. Explain why this training strategy may improve an athlete's performance.

One of the many mutant opponents that the movie monster Godzilla contends with is Mothra, a giant mothlike creature with a wingspan of 7–8 m. Science fiction creatures like these can be critiqued on the grounds of biomechanical and physiological principles. Focusing on the principles of gas exchange that you learned about in this chapter, what problems would Mothra face? Why do you think truly giant insects are improbable?

SCIENTIFIC THINKING E-cigarettes pose a dilemma for public health officials. Because e-cigarettes produce fewer toxic chemicals than regular cigarettes, they may be a safer alternative for people who want to quit smoking but still crave nicotine. On the other hand, e-cigarettes may encourage nicotine addiction among teenagers. Evaluate the scientific evidence. Are e-cigarettes an effective aid for quitting cigarettes? What evidence supports the assertion that e-cigarettes are especially harmful to adolescents?