The Wikipedia article on the action potential is just beautiful – clearly written and wonderfully illustrated.
The action potential is the electrical impulse that travels along nerve cells, facilitating communication throughout the brain and peripheral nervous system.
The action potential was researched by Alan Hodgkin and Andrew Huxley, who managed to generate equations which explained the process. Unsurprisingly, they won the Nobel prize for their efforts.
Link to Wikipedia article on the action potential.
Mind Hacks 
And as I found out last week, if your body doesn’t have enough sodium or potassium in it, it gets very flaky. Especially the heart…