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Problems with myelin theory

Stephen Black sblack at UBISHOPS.CA
Thu Feb 12 20:53:27 EST 1998

nOn Thu, 12 Feb 1998, Jeremy Leipzig wrote:

> Several neuroscience textbooks cite the ability of myelin to increase
> the capacitance of the neural membrane as one of its principal means of
> increasing the velocity of propagation of neural impulses.  Increasing
> the capacitance of the membrane (by effectively making it thicker) means
> less charge is needed to create the same potential difference across
> that membrane.

Actually, I think you've got that backwards. Capacitance is _inversely_ 
related to axon diameter. So myelinization _reduces_ capacitance. Kandel 
(1995, p. 156) discusses this point. My own intuitive feeeling for what 
this does is cause less charge to be soaked up at each point along the 
membrane, so it can pass it along the membrane more quickly. 

Kandel, E. et al (1995). Essentials of neural science and behavior. Appleton
  & Lange.

Stephen Black, Ph.D.                      tel: (819) 822-9600 ext 2470
Department of Psychology                  fax: (819) 822-9661
Bishop's University                    e-mail: sblack at ubishops.ca
Lennoxville, QC           
J1M 1Z7                      
Canada     Department web page at http://www.ubishops.ca/ccc/div/soc/psy

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