The brain consists of billions of neurons, or nerve cells, that communicate via chemical messages. This is a schematic drawing of a neuron. Towards the left of the diagram is the cell body, where neurotransmitters are made. Extending outward from the cell body are dendrites, which receive information from other neurons. When the cell body is sufficiently stimulated, an electric pulse called an action potential is generated and subsequently travels down the axon to the terminal region of the cell. Fast transmission of this electrical message is aided by an insulator material covering the axon called myelin. Once the impulse reaches the nerve terminal, neurotransmitters, such as dopamine are released into the synapse or gap between neurons. These chemicals can then attach to receptors located on the dendrites of neighboring neurons, thus transmitting information from one cell to the next within the brain and other parts of the body. Some axons can travel a long distance, extending all the way from your brain to your toes!
As a result of scientific research, we know that addiction is a disease that affects both brain and behavior.