What determines the airway diameter in the normal lung?
a. Balance between sympathetic and para-sympathetic tone
b. In large part, the amount of patient effort
c. Activity level of the submucosal glands
d. Amount of dopamine present in the air-way walls
ANS: A
Both sympathetic and parasympathetic postganglionic efferents innervate the smooth muscle and glands of the airways. They influence the diameter of the airway by causing more or less tension in the smooth muscles that wrap the airway and influence glandular secretion. The combined ef-fects of the parasympathetic and sympathetic nervous activity, which generally oppose each oth-er's action, result in a balanced control of airway diameter.
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