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Nervous System

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Nervous System
The Nervous System

The nervous system is the most complex part of the body, as they govern our thoughts, feelings, and bodily functions. It is an important factor in science because it can lead to new discoveries for cures or diseases. The studies of the nervous system helped lower death rates from heart disease, stroke, accidents, etc. The nervous system is a network of neurons (nerve cells) that that sends information to the brain to be analyzed. Neurons live both in and outside the central nervous system. Understanding how the neurons work is vital to understanding the nervous system. Neurons The neuron has two important structures called the dendrite and axon, also called nerve fibers. The dendrites are like tentacles that sprout from the cell and the axon is one long extension of the cell. The dendrites receive signals from other neurons, while the axon sends impulses to other neurons. Axons can extend to more than a meter long. Average sized neurons have hundreds of dendrites; therefore it can receive thousands of signals simultaneously from other neurons. The neuron sends impulses by connection the axon to the dendrites of another nerve cell. The synapse is a gap between the axon and the adjacent neuron, which is where data is transmitted from one neuron to another. The neuron is negatively charged and it bathes in fluids that contain positively charged potassium and sodium ions. The membrane of the neuron holds negatively charged protein molecules. The neuron has pores called ion channels to allow sodium ions to pass into the membrane, but prevent the protein molecules from escaping (potassium ions can freely pass through the membrane since the ion channels mostly restrict sodium ions). When a neuron is stimulated (not at rest), the pores open and the sodium ions rush in because of its attraction to the negatively charged protein molecules, which makes the cell positively charged. As a result, potential energy is released and the neurons send electrical



Bibliography: 1. Clayman, Charles; The Brain and Nervous System; © 1991 Dorling Kindersley, Ltd., and American Medical Association; published by Reader 's Digest Association, Pleasantville, New York. 2. Nathan, Peter; The Nervous System; © 1969 by Peter Nathan; published by Penguin Books, England. 3. The Human Brain: Controlling the Body; © 1998 Knowledge Adventure, Inc. ; http://www.letsfindout.com/subjects/body/rfibrain.html 4. The Nervous System; © 1992, 94, 97, 98, MJ Farabee; http://gened.emc.maricopa.edu/bio/bio181/biobk/biobooknerv.html 5. The Spinal Cord: Sensation and Movement; © 1998 Knowledge Adventure, Inc.; http://www.letsfindout.com/subjects/body/rfispinl.html Word Count: 1989

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    Published in 2011 by Britannica Educational Publishing (a trademark of Encyclopædia Britannica, Inc.) in association with Rosen Educational Services, LLC 29 East 21st Street, New York, NY 10010. Copyright © 2011 Encyclopædia Britannica, Inc. Britannica, Encyclopædia Britannica, and the Thistle logo are registered trademarks of Encyclopædia Britannica, Inc. All rights reserved. Rosen Educational Services materials copyright © 2011 Rosen Educational Services, LLC. All rights reserved. Distributed exclusively by Rosen Educational Services. For a listing of additional Britannica Educational Publishing titles, call toll free (800) 237-9932. First Edition Britannica Educational Publishing Michael I. Levy: Executive Editor J.E. Luebering: Senior Manager Marilyn L. Barton: Senior Coordinator, Production Control Steven Bosco: Director, Editorial Technologies Lisa S. Braucher: Senior Producer and Data Editor Yvette Charboneau: Senior Copy Editor Kathy Nakamura: Manager, Media Acquisition Kara Rogers: Senior Editor, Biomedical Sciences Rosen Educational Services Alexandra Hanson-Harding: Senior Editor Nelson Sá: Art Director Cindy Reiman: Photography Manager Matthew Cauli: Designer, Cover Design Introduction by Don Rauf Library of Congress Cataloging-in-Publication Data The brain and the nervous system / edited by Kara Rogers. p. cm. — (The human body) “In association with Britannica Educational Publishing, Rosen Educational services.” Includes bibliographical references and index. ISBN 978-1-61530-256-7 (eBook) 1. Nervous system—Popular works. 2. Brain—Popular works. I. Rogers, Kara. QP355.2.B725 2011 612.8—dc22 2010004639 On the cover: The human brain makes up only 2 percent of peoples’ total body weight. © www.istockphoto.com / Sebastian Kaulitzki Introduction: This image shows a longitudinal section of the human torso showing the autonomic nervous system. 3DClinic/Getty Images On pages 19, 50, 85, 112, 142, 167, 201, 233, 266, 268, 271, 275: © www.istockphoto.com /…

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