Which term describes the narrowing of the airways caused by tightening of airway smooth muscle?

Which term describes the narrowing of the airways caused by tightening of airway smooth muscle?

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

Answer: (D)

Narrowing of the airways caused by tightening of airway smooth muscle is called bronchoconstriction. When the smooth muscle surrounding the bronchi contracts, the airway radius decreases. Because the resistance to airflow increases dramatically as radius shrinks (even a small decrease makes a big difference), breathing becomes harder. This tightening is the direct mechanism behind wheezing and shortness of breath seen in conditions like asthma. Bronchodilation would be the opposite—relaxation of that smooth muscle and widening of the airways. Inflammation contributes to obstruction by causing swelling and mucus, but the term described here specifically refers to the muscle tightening that narrows the passages. Chemoreceptors are sensors that detect chemical changes to help regulate breathing, not the process of airway narrowing.

Narrowing of the airways caused by tightening of airway smooth muscle is called bronchoconstriction. When the smooth muscle surrounding the bronchi contracts, the airway radius decreases. Because the resistance to airflow increases dramatically as radius shrinks (even a small decrease makes a big difference), breathing becomes harder. This tightening is the direct mechanism behind wheezing and shortness of breath seen in conditions like asthma.

Bronchodilation would be the opposite—relaxation of that smooth muscle and widening of the airways. Inflammation contributes to obstruction by causing swelling and mucus, but the term described here specifically refers to the muscle tightening that narrows the passages. Chemoreceptors are sensors that detect chemical changes to help regulate breathing, not the process of airway narrowing.