What is happening during the plateau phase of cardiacdepolarization?
A) Sodium ions block voltage-gated calcium ion channels.
B) Acetylcholine is hyperpolarizing the SA node
C) Nothing - all ion gates and valves are closed.
D) voltage-gated potassium ion channels open to allowpotassium ions to diffuse out.
E) Calcium ions enter the cystol of cardiac myofibers fromsarcoplasmic reticulum and through voltage-gated slowchannels.