Which of these statements concerning cardiac muscle is correct?
a. Cardiac muscle has more sarcoplasmic reticulum than skeletal muscle.
b. Cardiac muscle has a prolonged period of slow repolarization called the plateau phase.
c. Cardiac muscle has a shorter refractory period than skeletal muscle.
d. Depolarization of cardiac muscle occurs when K+ and Na+ diffuse into the cell.
e. all of these are correct
Answer: B