Norepinephrine and Epinephrine Open ____ Channels Inducing a Faster Diastolic

Question

Norepinephrine and epinephrine open ____ channels inducing a faster diastolic depolarization. A)voltage-gated Ca²⁺ B)fast Ca²⁺ C)HCN D)fast Na⁺

Accepted Answer

HCN channels, also known as hyperpolarization-activated cyclic nucleotide-gated channels, are responsible for the pacemaker potentials in the heart. Norepinephrine and epinephrine, by activating beta-adrenergic receptors, lead to an increase in cyclic AMP, which directly opens HCN channels. This results in a faster diastolic depolarization, contributing to an increased heart rate.