Which type of stimulation causes bronchodilation and reduced resistance?

• A. Sympathetic
• B. Parasympathetic
• C. Central
• D. Peripheral

Answer: (A)

The correct choice is sympathetic stimulation because it triggers the release of catecholamines, such as epinephrine, which bind to beta-2 adrenergic receptors found in the smooth muscle of the bronchi and bronchioles. When these receptors are activated, the smooth muscles relax, leading to bronchodilation, which increases the diameter of the airways. This process reduces the airflow resistance, making it easier for air to move in and out of the lungs.

In contrast, parasympathetic stimulation is associated with the release of acetylcholine, which causes bronchoconstriction, leading to narrower airways and increased resistance to airflow. Central and peripheral stimulation, while they may have various effects on the body, do not directly mediate the bronchodilation process in the same way that sympathetic stimulation does. Thus, sympathetic stimulation is the key mechanism responsible for achieving bronchodilation and reducing resistance in the respiratory system.