How does extracellular fluid differ from cellular fluid?

1a. What is an action potential?
1b. What is meant by saying that an action potential is an "all or none" event?
2. What do a motor neurons stimulate?
3. What kinds of chemicals are released into chemical synapses?
4. What is the "resting membrane potential"?
5. What are the two most important ions controlling the resting potential of neurons?
6. How does extracellular fluid differ from cellular fluid?
7. What is meant by "threshold" stimulus of an action potential?
8a. What is meant by "myelination"?
8b. How does myelination affect conduction velocity of a neuron?
9. How does the width of an axon affect conduction velocity?