Beta blockers exert their action primarily in which cardiac cells?

Beta blockers exert their action primarily in which cardiac cells?

• A. Ventricular myocytes
• B. Nodal cells
• C. Purkinje fibers
• D. Atrial myocytes

Answer: (B)

Beta blockers mainly affect cells that control heart rate and rhythm. In the heart, the nodal tissue—specifically the sinoatrial (SA) node and the atrioventricular (AV) node—depends on beta-adrenergic signaling to increase automaticity and to speed conduction. Activation of beta-1 receptors in these nodal cells raises cAMP, which boosts the funny current and calcium currents, making the pacemaker potential rise more quickly and speeding AV conduction. Blocking these receptors slows these processes, lowering heart rate and slowing conduction through the AV node. While beta receptors are present on other cardiac cells like atrial and ventricular myocytes and Purkinje fibers, the most clinically prominent effect of beta blockade relates to nodal cells, because these cells set the heart rate and the primary route of conduction. By dampening nodal activity, beta blockers exert their characteristic rate- and rhythm-suppressing actions.

Beta blockers mainly affect cells that control heart rate and rhythm. In the heart, the nodal tissue—specifically the sinoatrial (SA) node and the atrioventricular (AV) node—depends on beta-adrenergic signaling to increase automaticity and to speed conduction. Activation of beta-1 receptors in these nodal cells raises cAMP, which boosts the funny current and calcium currents, making the pacemaker potential rise more quickly and speeding AV conduction. Blocking these receptors slows these processes, lowering heart rate and slowing conduction through the AV node.

While beta receptors are present on other cardiac cells like atrial and ventricular myocytes and Purkinje fibers, the most clinically prominent effect of beta blockade relates to nodal cells, because these cells set the heart rate and the primary route of conduction. By dampening nodal activity, beta blockers exert their characteristic rate- and rhythm-suppressing actions.