General purpose of this lecture is to present on Nervous System and Drug Addiction. Here briefly describe on Nervous system; Synapses and neurohormones and Drug addiction. Here also focus on Nerve Impulse: Stimulation of neuron, opens channels so that sodium (Na+) goes in, depolarizing the membrane. The adjacent section of membrane allows Na+ to go in, depolarizing it. This wave of depolarization continues at a rapid rate down the neuron, resulting in a nerve impulse traveling to the brain in milliseconds.