Chapter 18: Administration of Gas Mixtures Test Bank
MULTIPLE CHOICE 1. Vascular smooth muscle is largely dependent on which of the following intracellular ions? a. Na+ b. K+ c. Ca2+ d. Mg2+ ANS: C
Current understanding suggests that vascular smooth muscle is largely dependent on intracellular calcium ion (Ca2+) concentration. Smooth muscle tissue comprises bundles of myofibrils, threadlike contractile fibers encased by the sarcoplasmic reticulum, a network of tubes or channels that store Ca2+. REF: p. 344 2. Which of the following substances prevents the release of Ca2+ from the sarcoplasmic
reticulum? a. Intracellular cGMP b. EDRF c. cGMP-dependent kinase d. Calmodulin ANS: C
In the body, the process of smooth muscle relaxation uses cyclic guanosine monophosphate (cGMP) to reduce Ca2+ levels. In smooth muscle cells cGMP activates cGMP-dependent kinase, preventing the release of Ca2+ from the sarcoplasmic reticulum, resulting in smooth muscle relaxation. In the early 1980s researchers reported a potent smooth muscle–relaxing agent, endothelium-derived relaxing factor (EDRF), now understood to be endogenous nitric oxide. REF: p. 344 3. What is the primary physiologic activity of inhaled nitric oxide? a. Bronchodilation b. Pulmonary vasodilation c. Systemic vasodilation d. Cerebral vasodilation ANS: B
The underlying principle of inhaled nitric oxide (iNO) is its selectivity as a pulmonary vasodilator. Inhaled NO will relax only pulmonary smooth muscle adjacent to functioning alveoli. Atelectatic or fluid-filled lung units will not participate in iNO uptake.
