Final answer:
Bronchoconstriction occurs when the smooth muscle of the airways contracts, not relaxes. It results in narrowed airways and is controlled by the parasympathetic nervous system, while the sympathetic nervous system causes relaxation and bronchodilation.
Step-by-step explanation:
The statement that bronchoconstriction results from relaxation of smooth muscle in the walls of airways is False. Bronchoconstriction is the decrease in the size of the bronchiole due to the contraction of the muscular wall. Conversely, bronchodilation is an increase in the size of the bronchiole that occurs when the smooth muscle of the airways relaxes.
The nervous innervation of the bronchial tree is a key factor in the mechanisms of bronchoconstriction and bronchodilation. The parasympathetic nervous system induces bronchoconstriction, whereas the sympathetic nervous system triggers bronchodilation. Such control ensures the regulation of airflow into the lungs, necessary for the body's respiratory demand.
During an asthma attack, for example, the bronchioles swell and the muscles around them contract, leading to narrowed airways and difficulty breathing. This reaction is an example of bronchoconstriction, which illustrates its role in respiratory health disorders.