Glucagon can increase heart rate even when a patient is on beta-blockers.

Glucagon can increase heart rate even when a patient is on beta-blockers.

• A. It can increase heart rate even when beta-blockers are used
• B. It cannot affect heart rate in the presence of beta-blockers
• C. It reduces heart rate
• D. It has no effect on heart rate

Answer: (D)

Glucagon raises heart rate by activating glucagon receptors in the heart, which stimulates adenylate cyclase via a Gs protein to increase intracellular cAMP. This boost in cAMP enhances pacemaker activity and calcium handling in cardiac cells, producing a positive chronotropic effect. Because this pathway operates independently of beta-adrenergic receptors, beta-blockers cannot fully blunt it, so heart rate can increase even when a patient is on beta-blockers. This is why glucagon is used to treat bradycardia or hypotension due to beta-blocker overdose. Side effects can include hyperglycemia and nausea.

Glucagon raises heart rate by activating glucagon receptors in the heart, which stimulates adenylate cyclase via a Gs protein to increase intracellular cAMP. This boost in cAMP enhances pacemaker activity and calcium handling in cardiac cells, producing a positive chronotropic effect. Because this pathway operates independently of beta-adrenergic receptors, beta-blockers cannot fully blunt it, so heart rate can increase even when a patient is on beta-blockers. This is why glucagon is used to treat bradycardia or hypotension due to beta-blocker overdose. Side effects can include hyperglycemia and nausea.