Beta-1 adrenergic receptors are described as located in the heart and producing which effects?

• A. Located in the heart; stimulates the heart, dilates bronchioles, dilates blood vessels in skeletal muscle/brain/heart; glycogenolysis
• B. Causes bronchoconstriction and slows heart rate
• C. Inhibits glycogen breakdown
• D. Mediates vasodilation in all tissues

Answer: (A)

Beta-1 adrenergic receptors are mainly in the heart and drive the heart’s activity. When they’re activated, they produce positive chronotropic and inotropic effects: the heart rate increases, the force of contraction strengthens, and conduction through the AV node speeds up. They also promote renin release from the kidney, which can raise blood pressure. So the key point is that beta-1 receptors primarily cause the heart to work harder and faster, with a secondary effect on blood pressure via renin. The other actions listed—bronchodilation and wide vascular dilation in skeletal muscle/brain/heart—are mainly mediated by beta-2 receptors, not beta-1.