The Nervous System
What Is A Motor Neuron?
axon endings
At Rest
Inner
• Dynamic equilibrium (1)
Transport Proteins
Stimulus
• Threshold level (1)
• Trigger zone (1)
Action Potential
• Sodium gated channels open
• Depolarization
• Sodium gates close
• Potassium gates open
• Repolarization
• Sodium potassium pump restores gradient
• (1,2)
Travels down the axon like a crowd doing the wave
(3)
• Electric charge travels to the next
set of protein channels (the next
node), and triggers the gates to be
opened.
• The electric current moves down the
axon of the cell.
• The Myelin Sheath, made of
insulating fat, quickens the process.
• This jumping of electrical impulse
between each sheath is called
Saltatory Conduction (3).
Overview
(4).
(skip to :29 then 2:18)
MULTIPLE SCLEROSIS
•
•
•
•
•
Loss of control in speech, muscle control, and sight
Loss of the myelin sheaths in the axon, or demyelination
Lowers the rate of propagation
Functions take much longer, if they ever happen
(3).
References
(1). Star, Cecie, and Taggart, Ralph. Biology, The Unity and
Diversity of Life. Pacific Grove, CA, 2001
(2). Bohan, Matthew. "Action Potential" President and Fellows of
Harvard College and MCB-HHMI Outreach. 2005. Web. 3 Nov.
2010. <http://outreach.mcb.harvard.edu/animations/actionpoten
tial.swf>
(3). faculty.stcc.edu 2006 Springfield Techinical Community
College 2006
<http://faculty.stcc.edu/AandP/AP/AP1pages/nervssys/unit11/sa
ltator.htm>
(4). garlandscience. "Action Potentials." Video. YouTube. 2009.
Web. 5 Nov.
2010. <http://www.youtube.com/watch?v=ifD1YG07fB8&feature
=related>