What physiological effect occurs when Beta 2 receptors in the airways are stimulated?

The stimulation of Beta 2 receptors in the airways primarily leads to bronchodilation, which is the widening or relaxation of the bronchial passages. This physiological effect is crucial for improving airflow, making it easier for individuals with respiratory conditions, such as asthma or chronic obstructive pulmonary disease (COPD), to breathe.

When Beta 2 adrenergic agonists bind to these receptors in the smooth muscle lining of the airways, a series of intracellular events is triggered that ultimately results in the relaxation of these muscles. This effect decreases airway resistance and enhances airflow, providing immediate relief from bronchospasm.

The other provided choices, while they may involve different receptor systems or pathways, do not pertain to the direct action of Beta 2 receptor stimulation in the respiratory tract. For instance, vasoconstriction is typically associated with Alpha receptors, and increased heart rate relates to Beta 1 receptor stimulation in the heart rather than the lungs. Increased muscle contraction isn’t directly linked to Beta 2 receptor activity in the peripheral airways. Thus, bronchodilation is the most accurate and relevant physiological effect in this context.