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The Nervous System

The Nervous System. Taylor Price, Cora Hersh, David Alpert, Jillian Palladino. What is a motor neuron?. A motor neuron passes from the central nervous system to the muscles and glands, and sends nerve impulses to stimulate muscle movement. (1).

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The Nervous System

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  1. The Nervous System Taylor Price, Cora Hersh, David Alpert, Jillian Palladino

  2. What is a motor neuron? A motor neuron passes from the central nervous system to the muscles and glands, and sends nerve impulses to stimulate muscle movement. (1)

  3. (7)Dendrites: where neuron receives information from adjacent neurons (2)Axon: long, thin "conducting zone" of electrical impulse (2)Myelin Sheath: enhances rate of action potential transmission by insulating with layers of lipids (Schwann's Cells) (2)Node of ranvier: gaps in myelin sheath, covered in voltage-sensitive sodium channels.  Helps to send electrical signal (2)Axon terminals: "output zone", sends chemical messages to other cells (2)Trigger zone: between the cell body and the axon. contains voltage-sensitive gated sodium channels. Begins electrical impulse (2)

  4. Neurons at RestWhen a neuron is at rest, it is not transmitting a signal. (3)  The inside of the neuron is negative and the outside has a positive charge. (3)Ions are unable to balance out the charge because gated ions channels only allow certain ions to pass through (3)only K+ can pass through, but Na+ has difficulty. (3)

  5. How do K+ and Na+ cross the plasma membrane? • Along with selective ion channels, an energized pump moves Na+ out of the neuron and K+ into the neuron at a 3 (out):2 (in) ratio

  6. What is Action Potential? • Abrupt, brief reversal in the resting membrane potential of a neuron and other excitable cells • Occurs when a neuron transmits information down an axon • Caused by the exchange of ions in the neuron across the plasma membrane.  • small stimuli do not provoke action potentials  • Created by a depolarizing current (reversal of charge) • This stimulus causes the Na+ channel to open and Na+ ions enter the neuron because there are more sodium ions outside than inside the negatively charged neuron. • When Na+ enters, the inside and outside of the cell switch charges • The K+ channels do not open as quickly, but when they do K+ leaves the neuron, reversing the depolarization   (whole slide from source 2) 

  7. http://www.youtube.com/watch?v=m79HiApDJ2I

  8. How does the Myelin Sheath help Action Potential? • The myelin sheath strengthens the action potential signal by insulating the axon (5).  • Lipids in the cell membranes of the Schwann's cells inhibit electricity, but at the nodes of Ranvier, ions can move in and out of the neuron and continue the action potential (5) • This causes the reversals of polarity to move in jumps from node to node, which is much faster than without the myelin sheath (5)

  9. Multiple Sclerosis • multiple sclerosis, also known as MS, is a central nervous system disease (4) • autoimmune: the body's immune system attacks the myelin sheath of neurons (4) • without the myelin sheath, nerve impulses cannot be transmitted efficiently from node to node, so signals weaken and slow (5) • symptoms range from vision impairment to trouble walking to paralysis (4) • there is currently no cure for MS, but there are certain medications, like Copaxone and Ampyra, that can help alleviate the symptoms (4)

  10. The effect of MS on the myelin sheath (6)

  11. Works Cited (1) "Neuron." Merriam-Webster. Merriam-Webster, Incorporated, n.d. Web. 3 Nov. 2010.               <http://www2.merriam-webster.com/cgi-bin/mwmednlm?             book=Medical&va=motor%20neuron >. (2) Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity of Life. 9th               ed. Pacific Grove, CA: Brooks/Cole, 2001. (3) Chudler, Eric H. "Lights, Camera, Action Potential ." Neuroscience For Kids. Eric H Chudler,                  2010. Web. 4              Nov. 2010. <http://faculty.washington.edu/ chudler/ap.html>.             (4) "NINDS Multiple Sclerosis Information Page." National Institute of Neurological Disorders and                 Stroke. N.p.,                 n.d. Web. 4 Nov. 2010.                         <http://www.ninds.nih.gov/disorders/multiple_sclerosis/multiple_sclerosis.htm>.

  12. Works Cited cont. (5)"Myelin Sheath." Psychology 402: Biological Psychology. Athabasca                         University, 2010. Web. 4 Nov. 2010. <http://psych.athabascau.ca/html/Psych402/             Biotutorials/2/myelin.shtml?sso=true>. (6) Riverside Health System. "Multiple Sclerosis." Riverside. N.p., 2010. Web. 4 Nov. 2010.         <http://www.riversideonline.com/health_reference/Nervous-System/DS00188.cfm>. (7) U.S. National Institutes of Health. "Neurons." The Internet Encyclopedia of Science. Ed. David         Darling. N.p., n.d. Web. 4 Nov. 2010. <http://www.daviddarling.info/encyclopedia/N/                          neuron.html>.

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