What is the primary effect of parasympathetic stimulation on bronchial smooth muscle?

Parasympathetic stimulation primarily induces bronchoconstriction in the bronchial smooth muscle. The parasympathetic nervous system, when activated, releases acetylcholine, which binds to muscarinic receptors located on the bronchial smooth muscle. This binding causes the muscle to contract, leading to narrowing of the airways. This process is important for the regulation of airflow during physiological states, such as resting conditions or certain reflexes, where it helps manage bronchial secretions and maintains optimal airway resistance.

In contrast, other choices either describe effects that are more associated with sympathetic activity, such as bronchodilation, or effects that do not directly involve bronchial smooth muscle contraction or relaxation, like mucus production. Understanding the actions of the autonomic nervous system on the respiratory system is crucial for recognizing how various therapies might affect airway management in conditions such as asthma or COPD.