The Nervous System

The central nervous system is made up of the brain, spinal cord, and nerves.  The brain has three main parts, the brain stem or medulla, the cerebrum, and the cerebellum.  Each part has a special job to perform.

The medulla keeps your heartbeat and your breathing regular.

The cerebellum is in charge of balance and coordinating all of the muscles.  The medulla and cerebellum work all of the time, even when we don't know it.

The cerebrum controls thinking, moving and sensing.  It is in control when you read a book or play a game.

The spinal cord is a long piece of nerve tissue that runs from the brain through the backbone.  It connects the brain to the body's nerves.  Nerves are tiny fibers that are in the spinal cord and throughout the entire body.  Nerves pick up information and send it up the spinal cord to the brain.  Individual nerves are in charge of seeing, hearing, smelling feeling, or touching something.

Certain nerves in the spine and brain tell parts of the body to act really fast.  When the body must act very fast in order to avoid injury, the message from the sensory nerves doesn't go all the way to the brain before your body takes action.  The message travels from the sensory nerve to the spinal cord and is sent back to a muscle right away.  This quick action is called a reflex.  A reflex is an action we take even before the brain knows about it.

Directions: Answer the questions about the nervous system.