Which type of stimulation leads to bronchoconstriction and increased resistance?

• A. Sympathetic
• B. Parasympathetic
• C. Nervous
• D. Hormonal

Answer: (B)

Bronchoconstriction, which is the narrowing of the airways, primarily occurs due to parasympathetic stimulation. The parasympathetic nervous system is responsible for the 'rest and digest' responses in the body and plays a crucial role in regulating the dimensions of the airways. When the parasympathetic division is activated, it releases acetylcholine, which binds to muscarinic receptors in the bronchial smooth muscle. This stimulation causes the muscles to contract, leading to bronchoconstriction and an increase in airway resistance.

This mechanism is particularly important in situations such as allergic reactions or asthma, where airway constriction can significantly impact breathing. In contrast, sympathetic stimulation generally leads to bronchodilation, which helps to increase airflow and reduce resistance in the respiratory tract. Understanding these different pathways of airway management is key in fields such as respiratory therapy and emergency medicine.