An electrophysiology quesiton
k p Collins
kpaulc at [----------]earthlink.net
Tue Feb 10 16:33:51 EST 2004
"dielectric" is =just= a redundant name for "resistance".
K. P. Collins
"k p Collins" <kpaulc@[----------]earthlink.net> wrote in message
news:g4cWb.19824$jH6.702 at newsread1.news.atl.earthlink.net...
> I comment with respect to "capacitance",
> "Christian Wilms" <usenet at out-of-phase.de> wrote in message
> news:1g8xwye.12xgfy85v29dsN%usenet at out-of-phase.de...
> > Xiaoshen Li <xli6 at gmu.edu> wrote:
> > > I am always confused EPSC and EPSP.
> > > In voltage clamp condition, are we
> > > measuring EPSCs?
> > Yes, under voltage clamp you measure you
> > are measuring EPSCs. It tends to be confusing
> > at first, but after a while one gets acustomed to it.
> > When you voltage clamp a cell that means you
> > are injecting a current in order to keep the cell
> > at a constant voltage. What you measure is that
> > injected current.
> > When you current clamp a cell you are injecting
> > a constant current into that cell and what you
> > measure is the resulting voltage of the cell (the
> > cell potential). The name current clamp is a bit
> > misleading, as it implies that you are keeping
> > the current through the cell membrane constant,
> > which you are not.
> > The connection between postsynaptic currents
> > (PSC) and postsynaptic potentials (PSP) isn't
> > as trivial as it might seem at first. Ohm's law
> > is only one of the factors, that play a role here.
> > More important is that the membrane functions
> > as a capacitance _and_ a resistor. Because
> > of this capacitance PSP are always longer than
> > the PSC which causes them.
> > Hoping that I did add too much to your confusion, Chris
> "Capacitance" is =just= the current that is allowed
> by "resistance", so Ohm's Law is, in fact, all that's
> It's 'just' that "resistance" is dynamic.
> This isn't a 'trivial' matter.
> Nervous systems do their version of setting an
> analog computer's "zero-points" by, literally,
> dynamically setting "resistance".
> For those who have AoK, this is what "biological
> mass" [Ap5] is, and why "biological mass" embodies
> "behavioral inertia".
> Tuning "resistance", determines conductance, which
> determines activation.
> There's no 'magic' in any of this.
> See my earlier post, here in b.n, with respect to
> the "Binding Problem".
> Protein synthesis establishes "biological mass", and
> this "biological mass" is dynamically-tuned ['addressed']
> in accord with the activation that comes from the
> environment. This tuning includes dynamic 3-D
> conformational and conductance variations that occur
> within neural glia.
> The conformations of proteins are activated by the
> =net= ionic conductances.
> But, modify "resistance", and, of course, "capacitance"
> is modified in a rigorously-coupled way.
> Cheers, Chris, ken [K. P. Collins]
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