What substance allows for rapid action potential

“This transient switch in membrane potential is the action potential. The cycle of depolarization and repolarization is extremely rapid, taking only about 2 milliseconds (0.002 seconds) and thus allows neurons to fire action potentials in rapid bursts, a common feature in neuronal communication.”

Alright, i'm gonna try to explain this as good as possible. the law of conservation is like a collection overtime. it never changes though. no matter how you change the constituent parts.