Chapter 44

Which of the following describes a respiratory medium? In the liver the rate of diffusion is high. b. In the brain \(\mathrm{CO}_{2}\) moves from the neurons to the blood. c. In the big toe \(\mathrm{O}_{2}\) moves from blood to tissues. d. Epithelial cells form thin surfaces in the lungs. e. A running brook provides \(\mathrm{O}_{2}\) to fish.

Which of the following describes a respiratory surface? a. a surface consisting of multiple layers of epithelial cells b. the exoskeleton of an insect c. the nasal passages of a mammal d. a thin surface consisting of a single layer of epithelial cells e. the outer membrane of a mitochondrion.

At the end of a basketball game, the opposing teams line up and file past each other and shake hands. This efficient exposure of the teams to each other is analogous to: a. countercurrent exchange of gases in fish gills and bird lungs. b. diffusion of \(\mathrm{O}_{2}\) from blood to cells in shark tissues. c. diffusion of \(\mathrm{CO}_{2}\) from cells to blood in crabs. d. utilization of \(\mathrm{O}_{2}\) in cells in insects. e. excretion of \(\mathrm{CO}_{2}\) from mammalian cells.

Tracheal systems are characterized by: a. closed circulatory tubes that move gases. b. spiracles that move gases between cells and body fluids. c. body movements that compress and expand air sacs to pump air. d. positive pressure breathing, which swallows air into the body. e. negative pressure breathing, which lowers air pressure at the respiratory surfaces.

The structures at which one third of \(\mathrm{O}_{2}\) in the atmosphere moves into the blood of humans are: a. alveoli. b. bronchi. c. bronchioles. d. tracheae. e. pharynges.

A speed skater is finishing his last lap. At this time: a. the diaphragm and rib muscles contract when he exhales. b. positive pressure brings air into his lungs. c. his lungs undergo an elastic recoil when he inhales. d. his tidal volume is at vital capacity. e. his residual volume momentarily reaches zero.

A teenager is frightened when she is about to step onto the stage but then remembers to breathe deeply and slowly as she faces the audience. What is occurring here? Interneurons in the medulla cause the rib muscles to relax, followed later by stimulation and contraction of the intercostal muscles. b. Signals from the pons override the initial brain stem stimuli. c. The limbic system stabilized her emotional state, so there is no change in the mechanical movement of air. d. The brain signals the aortic bodies in the carotid arteries to adjust the breathing rate. \mathrm{e. } ~ I n i t i a l ~ l o w ~ C O ~ \(_{2}\) blood levels causing high pH are followed by increased \(\mathrm{CO}_{2}\) levels that lower \(\mathrm{pH}\).

Oxygen enters the blood in the lungs because relative to alveolar air: a. the \(\mathrm{CO}_{2}\) concentration in the blood is high. b. \(\quad\) the \(\mathrm{CO}_{2}\) concentration in the blood is low. c. the \(\mathrm{O}_{2}\) concentration in the blood is high. d. the \(\mathrm{O}_{2}\) concentration in the blood is low. e. the process is independent of gas concentrations in the blood.

The hemoglobin \(\mathrm{O}_{2}\) dissociation curve: a. reflects about \(50 \%\) saturation of hemoglobin in the alveoli. b. shifts to the left when \(\mathrm{pH}\) rises. c. demonstrates that hemoglobin holds less \(\mathrm{O}_{2}\) when the \(\mathrm{pH}\) is higher. d. proves lack of dependence on \(\mathrm{CO}_{2}\) levels. e. explains how hemoglobin can bind \(\mathrm{O}_{2}\) at high \(\mathrm{pH}\) in the lungs and release it at lower \(\mathrm{pH}\) in the tissues.

The majority of \(\mathrm{CO}_{2}\) in the blood: a. is in the form of carbonic acid and bicarbonate ions b. dissociates to add \(\mathrm{H}^{+}\) to the blood to raise its \(\mathrm{pH}\) to 7.4 c. has a lower \(\mathrm{P}_{\mathrm{CO}_{2}}\), than the \(\mathrm{P}_{\mathrm{CO}_{2}}\) in the alveolar air. d. increases in the lung capillaries, which have a higher \(\mathrm{pH}\) than the tissue capillaries.