Stimulation increases heart rate through which receptor?

Stimulation increases heart rate through which receptor?

• A. Alpha One Adrenergic Receptors
• B. Beta One Adrenergic Receptors
• C. Beta Two Adrenergic Receptors
• D. Muscarinic Receptors

Answer: (B)

When the heart rate increases due to sympathetic stimulation, the key receptor involved is the beta-1 adrenergic receptor in the heart. Activation of beta-1 receptors by catecholamines (epinephrine or norepinephrine) couples to Gs proteins, which boosts cAMP levels. This enhances the funny current (If) and calcium channel activity in the SA node, speeding up diastolic depolarization and atrial-ventricular conduction, so the heart beats faster. Beta-2 receptors exist too, but their direct impact on heart rate is not as strong as beta-1 in the heart. Alpha-1 receptors mainly control vascular tone and blood pressure, with indirect effects on heart rate through reflexes rather than a direct chronotropic action. Muscarinic receptors, in contrast, mediate parasympathetic effects that slow the heart rate.

When the heart rate increases due to sympathetic stimulation, the key receptor involved is the beta-1 adrenergic receptor in the heart. Activation of beta-1 receptors by catecholamines (epinephrine or norepinephrine) couples to Gs proteins, which boosts cAMP levels. This enhances the funny current (If) and calcium channel activity in the SA node, speeding up diastolic depolarization and atrial-ventricular conduction, so the heart beats faster. Beta-2 receptors exist too, but their direct impact on heart rate is not as strong as beta-1 in the heart. Alpha-1 receptors mainly control vascular tone and blood pressure, with indirect effects on heart rate through reflexes rather than a direct chronotropic action. Muscarinic receptors, in contrast, mediate parasympathetic effects that slow the heart rate.