Current flow in neurons (was Re: Auditory Impulse Travel and Distance)

Brad Jones bjones at uhunix1.uhcc.hawaii.edu
Tue Jun 25 08:57:28 EST 1991


In article <pluto.677811956 at koko> pluto at koko.ucsd.edu (Mark Plutowski) writes:
....[deleted section]...
>Even in wires, since current occurs by movement of charge associated
>with massive particles, (for example, as carried by electrons,) it will
>be very fast, and, may be taken to be close to the speed of light in
>vacuum, but will not equal it due to the mass on the charge carrying
>particles.

I suspect you are right.  In fact, it wouldn't surprise me if the speed
of electrical conduction in an ion containing solution depended on the
concentration of the ions, etc. and was even slower than that in a
wire.  Still, it must be better than .8 of the speed of light even
under the worst circumstances.  Any physicists out there with a real
number?

>My question is, is the electrical conduction speed in neurons fast
>enough that assuming it to be close to the speed of light causes
>negligible error in the analysis? 

This reminds me of a joke Jeff Wine used to tell in his introductory
Physiological Psychology classes at Stanford:  Physicists try to get
their results correct to the 8th decimal place, biologists try to get
their decimal point in the right place, and psychologists try to get
the sign right. ;-)

The more serious answer is that the time increment in physiological
models of neuronal activity is so much longer than the time scale of
electrical conduction that it is assumed to be instantaneous.  As far
as physiological measurements are concerned, I don't think the sweep
speed on my oscilloscope is fast enough to even come close...

--
--------
    Brad Jones -- bjones at uhunix.uhcc.hawaii.edu - bjones at uhunix.bitnet
    Bekesy Laboratory of Neurobiology, Pacific Biomedical Research Center
    University of Hawaii, Honolulu, HI  96822



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