[Neuroscience] Re: number of ion channels in a neuron, type and probability of open/closed

Bill via neur-sci%40net.bio.net (by connelly.bill from gmail.com)
Thu Oct 7 16:07:39 EST 2010


Wow, that is a lot more of a complicated question than I suspect you
know.

The best answer I can give you is to look up the Hodgkin and Huxley
equations. Theres are arbitrary functions that phenomenologically
explain the excitable behaviour of neurons. They do not work on a
single ion channel level, but model the total conductance of ions that
pass across a neurons membrane.

We could do a pretty rough back of an envelope calculation though.
Lets say a "typical" neuron has a resting input conductance of 10
nS... a twin pore K channel that mediates a lot the resiting membrane
conductance has a single channel conductance of about 30 pS and I
think, quite a high open probability at rest, of about 0.5... while
Ih, another important leak channel is about 500 fS and an open
probability of about 0.2 at resting membrane potentials... lets just
say the conductance is half and half of these two... so 50,000 Ih
channels and 350 Twin Pore channels... this is just at the perisomatic
region...

That's my attempt anyway. I've probably made some fundamental flaw in
my logic, which I'm sure someone will correct.

I think Greg Stuart has a paper where he estimates the density of Ih
expression in channels per um^2 from the soma out to the dendrite

On Oct 5, 7:15 am, "pennsylvaniaj... from gmail.com"
<pennsylvaniaj... from gmail.com> wrote:
> How many ion channels are in a typical neuron?  And of these, how many
> are K, Cl, Na and so on?
> Also, is there an equation that give the probability of how many are
> open and closed based on time?



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