Reducing the extracellular Na+ concentration from a normal value of 150 mM to 75 mM would have what effect on the action potential?

Question

reduce the maximum voltage of the action potential
prevent action potentials from occurring
prevent repolarization of the action potential
prevent the after-hyperpolarization of the action potential

Answer 1

Reducing the extracellular Na+ concentration from a normal value of 150 mM to 75 mM would prevent action potentials from occurring. This is because the reduction in extracellular Na+ would impair the ability of Na+ channels to open, thus preventing the depolarization phase of the action potential.