What is the primary body system affected by selective beta agonists?

Selective beta agonists primarily target the respiratory system due to their mechanism of action on beta-adrenergic receptors found in the bronchial smooth muscle. When these receptors are stimulated, they cause relaxation of the smooth muscle, leading to bronchodilation. This response is particularly beneficial for conditions such as asthma and chronic obstructive pulmonary disease (COPD), as it helps to open the airways and improve airflow.

In the context of the question, understanding that selective beta agonists are often used in treating respiratory issues highlights their importance in managing obstructive airway diseases. This choice reflects their primary therapeutic application, focusing on alleviating respiratory distress. The action of these medications is less about impacting the circulatory, nervous, or digestive systems directly, which do not primarily utilize selective beta agonists for treatment in a similar capacity.