For sodium to accumulate rapidly inside a neuron cell membrane,

For sodium to accumulate rapidly inside a neuron cell membrane,
  a. a stimulus above the threshold must open sodium gates in an accelerating manner.
  b. the wave of repolarization must occur to reestablish a resting potential.
  c. there must be a dramatic increase in the negative charge of the cytoplasm.
  d. a voltage surge must cause the sodium gates to close.
  e. the potassium gates must open first.

Question 2

Which of the following is the first response a neuron makes to a stimulus?
  a. Sodium ions enter the cell.
  b. Sodium ions leave the cell.
  c. Potassium ions enter the cell.
  d. Potassium ions leave the cell.
  e. Calcium ions leave the cell.