Beta-1 receptor stimulation results in which cardiovascular changes?

Beta-1 receptor stimulation results in which cardiovascular changes?

• A. Decrease HR
• B. Vasodilation
• C. Bronchodilation
• D. Increase HR, contractility, and CO

Answer: (D)

Beta-1 receptors in the heart drive the sympathetic boost to cardiac performance. When they’re stimulated, they activate the Gs pathway, increasing cAMP, which enhances calcium entry during systole. That raises the strength of contraction (positive inotropy). It also speeds the heart’s pacing and conduction by increasing the rate of SA node firing (positive chronotropy) and AV nodal conduction (positive dromotropy). The net result is a higher stroke volume and a faster heart rate, leading to increased cardiac output. Vasodilation is not a primary beta-1 effect (beta-2 mediates vascular smooth muscle relaxation, and bronchodilation is also beta-2). So the best description of beta-1 stimulation is increased heart rate, contractility, and cardiac output.

Beta-1 receptors in the heart drive the sympathetic boost to cardiac performance. When they’re stimulated, they activate the Gs pathway, increasing cAMP, which enhances calcium entry during systole. That raises the strength of contraction (positive inotropy). It also speeds the heart’s pacing and conduction by increasing the rate of SA node firing (positive chronotropy) and AV nodal conduction (positive dromotropy). The net result is a higher stroke volume and a faster heart rate, leading to increased cardiac output. Vasodilation is not a primary beta-1 effect (beta-2 mediates vascular smooth muscle relaxation, and bronchodilation is also beta-2). So the best description of beta-1 stimulation is increased heart rate, contractility, and cardiac output.