Thought of more..

Basically, it goes like this.

Your nerve cells have tiny spaces between them called synapses (singular is synapse) The stimulus goes from one nerve cell, the nerve cell transfers the signal to a neurochemical (like Dopamine, for instance), and then dumps the neurochemical into the "Synaptic Cleft", so that another nerve cell can pick up the signal and send it onward. After the receiving Neuron sees what the neurochemical is, it drops it back into the synapse so the sending neuron can pick it back up (called "re-uptake"). Cocaine keeps it from being "re-uptaken" for a while, so it stays in the synapse for longer. Amphetamines work by keeping the dopamine from being re-uptaken at all, so you get more "speedy".

Okay, really done now. hehe