What is one reason beta-blockers are effective in treating hypertension?

Beta-blockers are effective in treating hypertension primarily because they reduce cardiac output. They achieve this by blocking the beta-adrenergic receptors in the heart, which leads to a decrease in heart rate and force of contraction. When the heart beats less forcefully and at a slower rate, the total volume of blood pumped by the heart each minute (cardiac output) is lowered, leading to a reduction in blood pressure.

In addition to their effects on heart rate and contractility, beta-blockers also influence the renin-angiotensin-aldosterone system (RAAS). By blocking beta-1 receptors on the juxtaglomerular cells of the kidneys, beta-blockers reduce the secretion of renin, further contributing to the blood pressure-lowering effects.

In contrast to the correct answer, the other options represent effects that are not beneficial in the management of hypertension. An increase in heart rate, promotion of vasoconstriction, or enhancement of renin secretion would all contribute to an increase in blood pressure rather than a decrease, which is the goal of antihypertensive treatments.