What is the role of sodium in skeletal muscle contraction?
A. Sodium flows into a muscle cell to initiate and propagate the action potential.
B. Sodium flows out of a muscle cell to initiate and propagate the action potential.
C. Sodium binds to receptors on the sarcoplasmic reticulum triggering release of calcium.
D. Sodium binds to myosin and acts as a cofactor for the myosin ATPase.
E. None of the above; Sodium has no role in skeletal muscle contraction.