The following are the main steps in the generation of an action potential: 1. sodium channels are closed 2. more voltage-regulated potassium channels open and potassium moves out of the cell, initiating repolarization 3. sodium channels return to their resting properties 4. a graded depolarization brings depolarization to threshold 5. a temporary hyperpolarization occurs 6. sodium channels open 7. sodium ions enter the cell and further depolarization occurs The proper sequence of these events is