Which term describes the widening of the air passages in the lungs, often in response to medications that relax airway smooth muscle?

• A. Bronchoconstriction
• B. Chemoreceptors
• C. Bronchodilation
• D. Inflammation

Answer: (C)

Bronchodilation is the widening of the air passages in the lungs, which happens when the smooth muscle surrounding the bronchioles relaxes. This relaxation increases the airway radius, lowers resistance, and allows more air to flow during breathing. Medications that relax airway smooth muscle—like bronchodilators used for asthma or COPD—trigger this effect by promoting smooth muscle relaxation, often through signaling pathways that raise cyclic AMP in the cells.

This is different from bronchoconstriction, which narrows the airways by contracting the smooth muscle. Inflammation can contribute to narrowing through swelling and mucus, but it doesn’t describe the widening process itself. Chemoreceptors are sensors that help regulate breathing, not the physical change in airway diameter.

So the widening of the airways in response to these relaxing medications is bronchodilation.