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

When you hold your breath, which of the following first leads to the urge to breathe?a. falling CO2b. falling O2c. falling pH of the bloodd. rising pH of the blood

Which of the following promotes oxygen release from hemoglobin?a. a decrease in temperatureb. an increase in O2 levelc. a decrease in pHd. 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 O2b. falling O2c. rising CO2c, falling CO2

Countercurrent gas exchange in the gills of a fisha. 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

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 aa. 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.