Which receptor subtype mediates the heart's rate increase during sympathetic stimulation?

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Prepare for the Ivy Tech Anatomy and Physiology II (APHY 102) Heart Test with multiple-choice questions, detailed explanations, and study resources. Enhance your understanding and excel in your exam!

Multiple Choice

Which receptor subtype mediates the heart's rate increase during sympathetic stimulation?

Explanation:
Sympathetic stimulation speeds the heart mainly through beta-1 adrenergic receptors on the sinoatrial node. When norepinephrine binds these receptors, it activates Gs proteins, increases cAMP, and enhances the funny current and calcium handling. This accelerates pacemaker depolarization and boosts heart rate (and contractility). Alpha-1 receptors drive vascular smooth muscle constriction, not heart rate. Beta-2 receptors exist in some tissues but are not the primary drivers of heart rate. Muscarinic receptors mediate parasympathetic effects that slow the heart. So the beta-1 adrenergic receptor is the receptor subtype responsible for the heart rate increase during sympathetic stimulation.

Sympathetic stimulation speeds the heart mainly through beta-1 adrenergic receptors on the sinoatrial node. When norepinephrine binds these receptors, it activates Gs proteins, increases cAMP, and enhances the funny current and calcium handling. This accelerates pacemaker depolarization and boosts heart rate (and contractility). Alpha-1 receptors drive vascular smooth muscle constriction, not heart rate. Beta-2 receptors exist in some tissues but are not the primary drivers of heart rate. Muscarinic receptors mediate parasympathetic effects that slow the heart. So the beta-1 adrenergic receptor is the receptor subtype responsible for the heart rate increase during sympathetic stimulation.

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