In Cardiac Muscle, the Fast Depolarization Phase of the Action

Question

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

Accepted Answer

In cardiac muscle, the fast depolarization phase of the action potential is the result of increased membrane permeability to sodium ions. This allows sodium ions to rush into the cell, leading to depolarization of the membrane and initiation of the action potential.