Which statement correctly pairs a receptor with its typical effect?

Which statement correctly pairs a receptor with its typical effect?

• A. Beta One Receptors Increase Heart Rate
• B. Alpha One Receptors Increase Heart Rate
• C. Beta Two Receptors Decrease Heart Rate
• D. Beta One Receptors Increase Heart Rate

Answer: (D)

In the heart, beta-1 receptors are the primary drivers of heart rate and contractility. When these receptors are activated, they raise cAMP in cardiac cells, which speeds up the pacemaker activity of the SA node and enhances conduction through the AV node, leading to a higher heart rate and stronger contractions. Alpha-1 receptors mainly cause vasoconstriction of vascular smooth muscle, which raises blood pressure and can trigger a reflex decrease in heart rate rather than a direct increase. Beta-2 receptors primarily cause relaxation of smooth muscle, such as bronchodilation and some vasodilation, and are not the main mediators of heart rate. So, Beta-1 receptors increasing heart rate is the correct and most direct pairing.

In the heart, beta-1 receptors are the primary drivers of heart rate and contractility. When these receptors are activated, they raise cAMP in cardiac cells, which speeds up the pacemaker activity of the SA node and enhances conduction through the AV node, leading to a higher heart rate and stronger contractions. Alpha-1 receptors mainly cause vasoconstriction of vascular smooth muscle, which raises blood pressure and can trigger a reflex decrease in heart rate rather than a direct increase. Beta-2 receptors primarily cause relaxation of smooth muscle, such as bronchodilation and some vasodilation, and are not the main mediators of heart rate. So, Beta-1 receptors increasing heart rate is the correct and most direct pairing.