Final answer:
Extrinsic controls include epinephrine, while intrinsic controls include carbon dioxide, which triggers the release of nitric oxide (NO) for smooth muscle relaxation.
Step-by-step explanation:
The relaxation of bronchiolar smooth muscle is controlled by both extrinsic and intrinsic factors. Extrinsic controls refer to factors that come from outside the body, while intrinsic controls are factors within the body.
Extrinsic controls that cause the relaxation of bronchiolar smooth muscle include epinephrine, which is released in response to certain stimuli. Epinephrine activates beta-2 adrenergic receptors on the smooth muscle, leading to its relaxation and bronchodilation.
Intrinsic controls that cause the relaxation of bronchiolar smooth muscle include carbon dioxide. When carbon dioxide levels increase, it triggers the release of nitric oxide (NO), which acts as a powerful vasodilator, relaxing the smooth muscle and promoting bronchodilation.