Download The Nervous System When you caught the ruler with your fingers

The Nervous System
When you caught the ruler with your fingers, what caused the muscles
in your fingers to move? What makes your heart beat day and night
every day of your life? How can you tell when something is burning?
Your ability to perform these actions, and sense changes in your
environment is all thanks to your nervous system.
cerebrum
cerebellum
brain stem
The brain is the center of the nervous system and coordinates all of
the body’s activities. It is the most complex organ in the human body.
The brain is made up of approximately 100 billion nerve cells
(neurons). The three major parts of the brain are the cerebrum,
cerebellum, and brain stem. Surrounding and protecting the brain
are membranes, a fluid layer, and the skull.
How do messages from your brain reach all
parts of your body? How do messages from all
parts of your body reach your brain? Nerve
cells, called neurons, transport impulses from
your body to your brain and from your brain to
all parts of your body. The messages are
carried through electrical and chemical signals.
Neurons are made up of three main parts, the
cell body, axons, and dendrites. Axons and
dendrites branch out to messages to be sent
and received to all parts of the body.
The spinal cord is the long bundle of nerves that runs down the
middle of your back. It serves as the main pathway for messages
between the brain and the body. In men the spinal cord is about 45
centimeters long. In women it is about 43 centimeters long. Your
backbone protects the spinal cord from damage.
The organs of the nervous system - brain, neurons, and spinal cord all work together to control and coordinate all the activities of the
body. Information is transferred throughout your body by electrical
and chemical impulses. Your nervous system helps your body act and
react to this information.