During Contraction of Heart Muscle Cells

Multiple Choice

During contraction of heart muscle cells .

A) the action potential is initiated by voltage- gated slow calcium channels
B) the action potential is prevented from spreading from cell to cell by gap junctions
C) some calcium enters the cell from the extracellular space and triggers the release of larger amounts of calcium from intracellular stores
D) calcium is prevented from entering cardiac fibers that have been stimulated