Hi, and thanks for the question
I really like this definition of the nervous system from "A look
inside the human body" at
http://users.tpg.com.au/users/amcgann/body/nervous.html
"The Nervous System is the most complex of all the body systems. At
the centre of the nervous system is the brain. The brain sends and
receives messages through a network of nerves. This network can be
explained as similar to a road network"
- The spinal cord is a thick bundle of nerves which runs down the
centre of the spine. This is like a freeway.
- Along the spinal cord smaller bunches of nerves branch out. These
are like highways.
- From these bundles, smaller bundles of nerves branch out again.
These are like main roads.
- Finally, individual nerves branch out to every part of the body.
These are like normal roads.
"This network of nerves allows the brain to communicate with every
part of the body. Nerves transmit information as electrical impulses
from one area of the body to another. Some nerves carry information to
the brain. This allows us to see, hear, smell, taste and touch. Other
nerves carry information from the brain to the muscles to control our
body's movement.
The site above also has some impressive graphics showing how neurons
(nerve cells) communicate with each other to send messages up and down
these "roads"
..o0o..
For a more detailed overview you'll find all the info you need at the
Online Biology Book page about the Nervous System here:
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html#Nervous%20Systems
or, for a definition of the key words, see here:
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html
There is a fine diagram of how the nervous system is spread through the body here:
Virtual Anatomy Textbook
http://www.acm.uiuc.edu/sigbio/project/nervous/
willie-ga
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