[Neuroscience] Re: number of ion channels in a neuron,
type and probability of open/closed
pennsylvaniajake from gmail.com
via neur-sci%40net.bio.net
(by pennsylvaniajake from gmail.com)
Sat Oct 9 12:11:29 EST 2010
On Oct 7, 5:07 pm, Bill <connelly.b... from gmail.com> wrote:
> 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?
I appreciate you trying to answer my question. I know it is a hard
one. I have seen so many equations including the H & H and K
equations. But I have never run across in 25 years any one taking
about the summation of all of the channels and types in a single
neuron.
Due to my education, engineer and mathematician, with the engineer
coming out in me, too wonder if any one has ever looked at "the total
picture" vs just one ion channel or 3 at the most (K,Na,Cl).
Thanks once again.
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