To assist with your understanding for Wednesday's test, here is a video, shown in class, that summarizes the changes:
Notice that the resting potential is negative (-70mv) while the action potential is positive (+40mv).
Notice that the change in potential is generated by the motion of positively-charged sodium (Na+) and potassium (K+) ions across the axon membrane.
Before the nerve fires, sodium is in high concentration OUTSIDE the axon membrane, while potassium is in high concentration WITHIN the membrane. In the video, the sodium channel is shown in green while the potassium channel is shown in blue. There are also 'leak' channels shown in purple.
The graph shown in the video is commonly used in college-level courses to convey a great deal of information about the various stages of the action potential (resting potential, depolarization, repolarization, hyperpolarization, etc.) and uses significant vocabulary and concepts not found in your text. You will not be responsible for knowing the graph, but as it may help you to understand the concepts behind the video, I enclose a version of that graph here: