Read an Excerpt
Jiggle your toes. Scratch your nose. Take a deep breath and yawn. Decide which is your favorite food. Try to remember the last time you ate it. Count the number of words in this sentence. Think about what you would like to do tomorrow. Then cup your hands around your head and feel the bones of your skull. Inside your skull is your brain. Your brain is the control center for everything you do.
Each second, millions of signals pass through your brain, carrying all kinds of messages. They bring news about what your body is doing and feeling. Your brain examines the messages, produces thoughts and memories, then plans what to do next. Signals go out from your brain to other parts of your body to enable you to read, run, laugh, breathe, say hello to a friend, or turn to the next page in this book. Try it!
Your brain, like the rest of your body, is made up of hundreds of billions of microscopic cells. Many of them are special messenger cells called neurons. Neurons carry signals back and forth from the brain to other parts of your body.
Billions upon billions of neurons are linked throughout your body in networks that make up the two main parts of your nervous system. The central nervous system, or CNS, consists of your brain and spinal cord. The network of nerves outside your brain is called the peripheral nervous system, or PNS.
Glial cells in the brain outnumber the neurons ten to one. Glial cells do not carry messages. They support the neurons by supplying nutrients and other chemicals, repairing the brain after an injury and attacking invading bacteria.
