Download Your Nervous System— Ready for Action!

Your Nervous System—Ready for Action!
Your Nervous System—
Ready for Action!
Ouch! Have you ever pricked your finger on a thorn? When this
happens, lots of messages dart through your body at once.
Some messages cause your arm to jerk back. Some tell your eyes to
look at your hand. Others let you know, “That hurt!”
Parts of the Nervous System
Your nervous system delivers messages
all around your body. It includes your
brain, spinal cord, and nerves.
BRAIN
Messages travel to and from your brain
along nerves. The bundle of nerves that
runs from your brain down your back is
called your spinal cord. Nerves lead from
your spinal cord to different parts of your
body. They form branching pathways
throughout your body.
But how do messages actually move along
these pathways? To find the answer, you
will need to look at the tiniest part of your
nervous system—the cell. Neurons are
special cells designed to deliver
information.
SPINAL
CORD
NERVES
Your brain, spinal cord, and nerves send messages
around your body.
NEURON
Neurons—Nerve Cells
Neurons are found throughout your
nervous system. There are billions of
them in your brain alone. Neurons have
three main parts: the cell body,
dendrites, and an axon.
The axon forms the long part of a
neuron. A single axon is too thin to be
seen, but when many are bundled
together, they form hair-like nerves.
Most axons are small, but axons in
nerves from your feet to your spinal cord
can be three feet long!
CELL
BODY
DENDRITES
Neurons have three main parts.
Discovery Education Science
© 2007 Discovery Communications, LLC
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Your Nervous System—Ready for Action!
The cell body is the control center of the neuron. Dendrites are like
tiny tentacles that receive messages that will travel through the
axon. Nerve messages always move in one direction—from dendrite
to axon.
Delivering Messages
Neurons work together to deliver messages. Axons of one neuron
meet up with dendrites of another neuron so messages can travel
from one cell to the next.
If neurons end at a muscle, they tell the muscle to move or stop
moving. When neurons deliver messages from your eyes or ears to
your brain, your brain receives information about the world around
you. When neurons send messages between organs and your brain,
your body can function properly.
When a thorn pricks your finger, messages travel along nerves from
your fingertips, up your spinal cord, and to your brain to let you
know it hurt. Your brain sends other messages along nerves to
muscles that move your arm, fingers, and eyes. Your brain might
even send messages to make you yell out loud!
Discovery Education Science
© 2007 Discovery Communications, LLC
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