Vandenberg_Lec6_2009

Vandenberg_Lec6_2009 - Today: Action Potential Propagation...

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1 Action Potential Propagation 10/12/09 Today: • Action potential propagation • Myelination • Threshold • Refractory period Action Potential Conduction along Unmyelinated Axon What Controls the Speed of an Action Potential (or how can you make a faster axon)? • Make a bigger diameter axon so it conducts current better • Insulate the axon with myelin
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2 Glial cells wrap axons with myelin Schwann cells (PNS) wrap single segments of axons Oligodendrocytes (CNS) wrap multiple segments of axons Myelinated Axons Where are ion channels located in myelinated axons?
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3 Channels are localized: Na at Node of Ranvier K at Juxtaparanode Schwann cells & oligodendrocytes wrap axons To form myelin sheath Saltatory AP Conduction along Myelinated Axon AP animation Alterations in Myelination Cause AP Conduction Deficits • Human demyelinating diseases: – Multiple sclerosis – Guillain-Barré syndrome • Even small changes in myelin-axon adhesion decrease AP conduction: – Caspr/NPC1 mutant mice or contactin mutant mice
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4 A complex of Caspr,Contactin & NF155 link myelin to paranode Caspr mutant is lacking myelin-axon contact Na channels K channels Caspr/NCP Figure 2 . Phenotype of NCP1 Mutant Mice (A) Appearance of NCP1 mutant mice. Wild-type (on left) and NCP1
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This document was uploaded on 10/21/2009.

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Vandenberg_Lec6_2009 - Today: Action Potential Propagation...

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