membrane lenght constant of rat hippocampal pyramidal cells?

Richard Norman rnorman at
Mon Feb 18 14:24:08 EST 2002

Certainly you know that the space constant varies with the dendrite
diameter (more specifically, with the square root of diameter).  It is
actually a lot more complicated than that -- one effect of synaptic
activation is to reduce membrane resistance (the "short circuiting
effect") which produces very local but perhaps very intense transient
reductions in both the time constant and the space constant.

5 mm does seem like a rather large value and a 50:1 ratio (corresponding
to a 2500:1 ratio in diameter) does seem rather extreme.  Still, there
is no one answer to your question.

"Edmund Müller" <edmund.mueller at> wrote in message
news:jims6uc4bgqtgvnqvagu98a9ifje7jpf2o at
> Hi NG,
> My textbooks give a rough estimate like "0.1 to 5 mm in different sort of
> cells."
> Could anyone tell me more precisley?
> Thanks Edmund

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