Discuss the electrical nature of the nerve impulse. Use a diagram to show the the concentration of sodium, chlorine, and calcium ions on both sides of the plasma membrane. Define polarized cell membrane. Indicate that a stimulus changes the permeability of the membrane to these ions. This "action potential" now causes the iside of the membrane to become positive and the outside negative. The cell is now depolarized. Show how depolarization and repolarization will occur along the cell membrane until it reaches the end terminals and causes the secretion of neurotransmitters across the synapse. This is the cell electrical transmission.