In Cardiac Muscle, the Fast Depolarization Phase of the Action

Multiple Choice

In cardiac muscle, the fast depolarization phase of the action potential is the result of

A) increased membrane permeability to sodium ions.
B) increased membrane permeability to chloride ions.
C) decreased membrane permeability to calcium ions.
D) decreased membrane permeability to sodium ions.
E) increased membrane permeability to potassium ions.