Answer: During the repolarization phase of a contractile myocardial action potential, the cell is highly permeable to sodium, potassium and calcium.
Step-by-step explanation:
Apart from the fact that contractile cells conduct impulses, it also helps in contractions which are needed for pumping of blood. It should also be noted that the myocardial conducting cells serves as the heart's conduction system. They also have a lower resting membrane potential.
Of the options given, the answer is the last option i.e. during the repolarization phase of a contractile myocardial action potential, the cell is highly permeable to sodium, potassium and calcium. This is wrong.
Repolarization occurs due to a rise in the permeability of potassium and during repolarization, the calcium channels close.