Vagal activation of the AV node has what effect on conduction velocity and ERP?

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Multiple Choice

Vagal activation of the AV node has what effect on conduction velocity and ERP?

Explanation:
Vagal (parasympathetic) activation slows AV nodal conduction and lengthens its refractory period. Acetylcholine acting on M2 receptors in the AV node activates Gi, which lowers cAMP and reduces L-type calcium current responsible for the nodal upstroke. This slows the rate of depolarization, decreasing conduction velocity through the AV node. At the same time, I_K,ACh increases, hyperpolarizing the cells and prolonging repolarization, which raises the effective refractory period. So the AV node conducts more slowly and remains refractory longer, matching decreased conduction velocity with increased ERP.

Vagal (parasympathetic) activation slows AV nodal conduction and lengthens its refractory period. Acetylcholine acting on M2 receptors in the AV node activates Gi, which lowers cAMP and reduces L-type calcium current responsible for the nodal upstroke. This slows the rate of depolarization, decreasing conduction velocity through the AV node. At the same time, I_K,ACh increases, hyperpolarizing the cells and prolonging repolarization, which raises the effective refractory period. So the AV node conducts more slowly and remains refractory longer, matching decreased conduction velocity with increased ERP.

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