1: Introduction
Introduce the topic of your talk. Indicate that you will explain how the brain basically works and how drugs such as cocaine, opiates and marijuana interact with the brain's normal activities. Tell students that you will introduce the concept of "reward" which is the property that is characteristic of many addictive drugs. Describe the brain as a functional unit; it is made up of billions of nerve cells (neurons) that communicate with each other using electrical and chemical signals.

2: Brain regions and neuronal pathways
Certain parts of the brain govern specific functions. Point to sensory, motor, association and visual cortex to highlight specific functions. Point to the hippocampus to highlight the region that is critical for memory, for example. Indicate that nerve cells or neurons travel from one area to another via pathways to send and integrate information. Show, for example, the reward pathway. Start at the ventral tegmental area (VTA) (in blue), follow the neuronal path to the nucleus accumbens (purple), and then on to the frontal cortex. Explain that this pathway gets activated when a person receives positive reinforcement for certain behaviors ("reward"). Indicate that you will explain how this happens when a person takes an addictive drug.

3: Neuronal structure
Remind the student that pathways are made up of neurons. Describe the anatomy of a neuron (soma, dendrites, and axon are marked with text). State that this neuron is real - as viewed through a microscope. Explain the normal direction of impulse flow. Dendrites and soma receive chemical information from neighboring neuronal axons. The chemical information is converted to electrical currents which travel toward and converge on the soma. A major impulse is produced (the action potential) and travels down the axon toward the terminal. Point to the terminal.

4: The synapse and synaptic neurotransmission
Describe the synapse and the process of chemical neurotransmission. Indicate how vesicles containing a neurotransmitter, such as dopamine (the stars), move toward the presynaptic membrane as an electrical impulse arrives at the terminal. Describe the process of dopamine release (show how the vesicles fuse with the presynaptic membrane). Once inside the synaptic cleft, the dopamine can bind to specific proteins called dopamine receptors (in blue) on the membrane of a neighboring neuron. Introduce the idea that occupation of receptors by neurotransmitters causes various actions in the cell; activation or inhibition of enzymes, entry or exit of certain ions. State that you will describe how this happens in a few moments.

5: Dopamine neurotransmission
Using the close-up of a synapse, continue using dopamine for your example of synaptic function. Explain that it is synthesized in the nerve terminal and packaged in vesicles. Reiterate the steps in neurotransmission. Show how the vesicle fuses with the membrane and releases dopamine. The dopamine molecules can then bind to a dopamine receptor (in blue). After the dopamine binds, it comes off the receptor and is removed from the synaptic cleft by uptake pumps (also proteins) (in red) that reside on the terminal. This process is important so that not too much dopamine is left in the synaptic cleft at any one time. Also point out that there is a neighboring neuron, which releases another compound called a neuromodulator. In this case it is an "endorphin" (blue flying saucers). Endorphins bind to opiate receptors (in green) which reside on the post-synaptic cell or in some cases on the terminals of other neurons (this is not shown so it must be pointed out). The endorphins are destroyed by enzymes rather than removed by uptake pumps.

6: Dopamine and the production of cyclic AMP
Using the close-up view, explain what happens when dopamine binds to its receptor. When dopamine binds to its receptor, another protein called a G-protein (in pink) moves up close to the dopamine receptor. The G-protein signals an enzyme to produce cyclic adenosine monophosphate (cAMP) molecules (in green) inside the cell. [Sometimes the signal can decrease production of cAMP, depending on the kind of dopamine receptor and G-protein present.] Point to the dopamine receptor-G-protein/adenylate cyclase complex, and show how cAMP is generated when dopamine binds to its receptor. Indicate that cAMP (point to the cyclic-looking structures) controls many important functions in the cell including the ability of the cell to generate electrical impulses.

7: Summary of neuronal transmission
Use the example of two neurons making contact to summarize neuronal transmission. Point to the cell on the top and indicate that electrical impulses flow in the direction toward the terminal. Remind the students what happens when impulses reach the terminal; neurotransmitters are released, they bind to their receptors, and new impulses are generated in the cell on the bottom. Explain that this is how information travels from neuron to neuron.