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

Which of the following promotes oxygen release from hemoglobin? a. a decrease in temperature b. an increase in O2 level c. a decrease in pH d. a decrease in carbonic anhydrase activity

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

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.

Explain how each parameter in Fick's law of diffusion is reflected in the structure of the mammalian lung.

Frog lungs have a smaller surface area for gas exchange than mammalian lungs. How do frogs compensate for this difference? a. Frog tissue absorbs more oxygen from the blood than mammalian tissue does. b. Frogs breathe more quickly than mammals. c. Frogs also obtain oxygen via diffusion across the skin. d. Frog lung tissue has a greater density of capillary beds than mammalian lung tissue.

Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a a. higher PO2. b. higher PCO2. c. greater bicarbonate concentration. d. lower pH.

Carp are fishes that thrive in stagnant-water habitats with low oxygen partial pressure. Compared with the hemoglobin of many other fish species, carp hemoglobin has an extremely high affinity for O2. Draw an oxygen–hemoglobin equilibrium curve showing separate lines for carp and a fish that lives in water with a higher oxygen partial pressure. Explain why they differ.

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?

During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of wastes. How do the cardiovascular systems of athletes respond to prolonged exercise? During athletic training, the oxygen–hemoglobin dissociation curve a. shifts to the right, unloading more oxygen to tissues. b. shifts to the right, unloading less oxygen to tissues. c. shifts to the left, unloading more oxygen to tissues. d. shifts to the left, unloading less oxygen to tissues.

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.

During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of wastes. How do the cardiovascular systems of athletes respond to prolonged exercise? When athletes exercise, what is the primary physiological variable responsible for their sustained increase in ventilation rate? a. decreased blood PO2 b. increased blood PCO2 c. increased blood pH d. increased body temperature

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?