The above image shows a PET scan of a human brain. A PET scan is a recently created technological tool that allows scientists to see activity in the brain. The red and yellow spots are the most active parts of the brain.
But if one part of the brain is more active than another, what does that mean? Are there different parts of the brain? Do they have different jobs? The brain controls all body functions, including ones you cannot control, like digestion, and ones you can control, like texting on a cellphone. But how does it control every function when it sits in your skull on top of your body?
Does the brain send messages to other parts of your body? What does a "message" in your body look like?
Additionally, what would it mean if there were few active parts in the above brain scan? Would a person's brain be functioning properly? What kind of diseases can cause brain damage?
Consider these questions about the brain as you read about the system that controls all other body systems, the nervous system.
Jens Langner. commons.wikimedia.org/wiki/File:PET-image.jpg. Public Domain.