Which process describes narrowing of airways?

• A. Bronchoconstriction
• B. Epinephrine
• C. Histamine
• D. Sepsis

Answer: (A)

Narrowing of the airways happens when the smooth muscle around the bronchi contracts, a process known as bronchoconstriction. When the bronchial smooth muscle tightens, the airway radius decreases, which greatly raises airway resistance because airflow is highly sensitive to radius changes. This makes breathing more difficult and is a hallmark in conditions like asthma or allergic reactions. While histamine can trigger this constriction, the actual narrowing is the result of the smooth muscle tightening. In contrast, epinephrine would relax the smooth muscle and widen the airways (bronchodilation), and sepsis is a systemic infection that does not describe this airway-tightening process.