Cardiac Electrophysiology I: Nodal Fibers, Pacemaker Potentials, and Automaticity

Practice: Epinephrine is a hormone (and drug) that binds to β1 adrenergic receptors on nodal fibers. Binding of epinephrine to β1 adrenergic receptors activates an intracellular signaling cascade that increases the conductance of funny channels. Which of the following phases of the nodal fiber action potential is likely to be directly affected by epinephrine?

Practice: Epinephrine is a hormone (and drug) that binds to β1 adrenergic receptors on nodal fibers. Binding of epinephrine to β1 adrenergic receptors activates an intracellular signaling cascade that increases the conductance of funny channels. Which of the following is the likely effect of epinephrine on heart rate?