question related to Hodgkin-Huxley model

k p Collins kpaulc at [----------]earthlink.net
Tue Dec 23 03:04:55 EST 2003


"r norman" <rsn_ at _comcast.net> wrote in message
news:4bveuvkjbubflf7dqmmil11sp6dvrp4rst at 4ax.com...
> > [...]
> [...]

> I don't really know of any way to calculate the
> threshold, even knowing the Hodgkin-Huxley
> equations.  It is usually just found by trial and
> error in a simulation or an experiment.

Hi Dr. Norman, forgive me, please, if, as usual,
I've found your cogent discussion to be stimulating.

No reply expected. I just want to comment in the
hope that I'll be able to convey some stuff that's
worth conveying.

One can only describe hypothetical cases, saying
that, if all these factors are this way, the threshold
will be that way.

In vivo, all of the factors involved in calculating
a thresholding 'event' are tuned [and literally
calculated] dynamically.

If it were not this way, to the degree of that, the
system's information-processing dynamics become
increasingly less-generalized [unable to adapt].

And, =not= to 'criticize' but to only offer a perspective
on stimulus-response continuity:

It's my analysis that the ionic flow is always
continuous. Even though the direction of the ionic
flow changes at threshold, it's still continuous.

To see a crude example of what I mean, fill your
kitchen sink and take a collander [spaghetti strainer]
and alternatingly partially submerse and lift it up.

The flow of the water into and out of the collander
is continuous, even though its directionality changes.

Why this matters with respect to nervous system
function is that the ability of a nervous system to
calculate the g'zillions of things that it calculates in
real 'time' derives in the inherent continuity of the
ionic dynamics.

If there actually were 'discontinuities' in there, then,
to the degree of that, there'd also be 'slack' in there
that would make it impossible to converge upon any
precise 'state' of tune, globally - the nervous system
wouldn't be able to manifest "2 + 2 = 4".

Disease processes do impose 'discontinuities' within
the ionic flow, and the 'ill-focused' externally observable
correlates reflect the resulting 'slackness' - the resulting
asynchrony of the collective thresholding dynamics. The
dynamic calculation I referred to above is breaking
down because the overall ionic continuity has broken
down.

And all of this feeds right into the tuning of molecular
dynamics, which is why 'abnormal' molecular dynamics
are, in fact, observable in disease conditions.

That is, molecular 'abnormalities' are rigorously coupled
to, and directly reflect, the break down of global ionic-
conductance continuity.

[My long former discussions of "3-D energydynamics'
always-down-hill-ness pertain.]

Cheers,

ken [k. p. collins]









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