What is the effect of stimulating a Beta1 receptor?

Stimulating a Beta1 receptor primarily affects the cardiovascular system, specifically leading to an increase in heart rate and the force of cardiac contractions. Beta1 receptors are predominantly located in the heart, and their stimulation activates the adenylate cyclase pathway, resulting in increased levels of cyclic AMP. This process enhances myocardial contractility and heart rate, making it critical in responses that require increased cardiac output, such as during stress or physical activity.

The other choices do not accurately reflect the primary action of Beta1 receptor stimulation. Decreased respiratory rate does not occur as a direct effect; rather, respiratory rate is more closely associated with other receptor types, including Beta2 receptors. Inhibition of inflammatory mediators and bronchial smooth muscle relaxation are linked more to the action of Beta2 receptors rather than Beta1 receptors. Therefore, the increase in heart rate stands as the correct response to the stimulation of Beta1 receptors.