question about activated channels
k.p.collins at worldnet.att.net
Wed Jun 11 02:33:45 EST 2003
"KP_PC" <k.p.collins at worldnet.att.net> wrote in message
news:yQvFa.955$3o3.61016 at bgtnsc05-news.ops.worldnet.att.net...
| "r norman" <rsnorman_ at _comcast.net> wrote in message
| news:jmrcevgi57v18ll782virvflh8gm4amek4 at 4ax.com...
| | On Tue, 10 Jun 2003 23:29:01 GMT, "KP_PC"
| | <k.p.collins at worldnet.att.net> wrote:
| | >"David Capelle" <dcapelle at gmx.de> wrote in message
| | >news:754d51cf.0306100507.42c984d5 at posting.google.com...
| | >| hi,
| | >|
| | >| i have got a question about so
| | >| called activated membrane
| | >| channels. having read in "from
| | >| neuron to brain" that membrane
| | >| channels can be activated by
| | >| extracellular application of ACh
| | >| I was wondering what exactly this
| | >| means. i suppose it refers to the
| | >| fact that activated channels are
| | >| constantly switching between an
| | >| open and a closed state whereas
| | >| unactivated channels are most
| | >| likely to be closed at any time.
| | >| however in the mentioned book it
| | >| is stated (in box 1 in chapter 2)
| | >| that if all channels were activated
| | >| there would not be any noise in
| | >| the overall membrane current to
| | >| be expected. therefore it is argued
| | >| the formula relating variance, mean
| | >| current and the current through
| | >| an individual channel ought to be
| | >| c=Var/I(1-p) rather than c=Var/I;
| | >| where c is the individualcurrent, I
| | >| the mean current and p the fraction
| | >| of activated channels. i would
| | >| appreciate if anyone could explain
| | >| this to me as it does not make
| | >| sense at the moment (possibly
| | >| becos i am not getting the
| | >| meaning of "activated"). besides
| | >| i fear the book which is supposedly
| | >| so brilliantly elucidating just does
| | >| not suit the level of medical
| | >| undegraduates like me .........
| | >|
| | >| thanks a heap in advance,
| | >| david
| | >
| | >The view I'll discuss is not [yet] accepted
| | >by others, so do not 'quote' it as if it is.
| | >
| | >It requires a =lot= of discussion, but in my
| | >view, the "noise" to which the Author refers
| | >probably occurs as a function of detector-
| | >response characteristics, rather than any-
| | >thing in the Biology.
| | >
| | >It's a problem through all of Science where
| | >'detector' probes are employed.
| | >
| | >The detectors have their response character-
| | >istics, and experimenters attribute their
| | >data as 'capturing everything' that's going
| | >on within the experimental set-up.
| | >
| | >But this's =never= the case.
| | >
| | >In the view I hold, although an ion gate
| | >can be "open" or "closed", it can also be
| | >"in-between" - that is, the gates' func-
| | >tionality is not 'instantaneous', but the
| | >detectors' responses give the illusion
| | >that they are 'instantaneous'.
| | >
| | >The difference is important because it's
| | >important to see the overall Continuity,
| | >which is in the "in-between" stuff.
| | >
| | >Which leads me to 'lean' toward the
| | >formulation that the book 'denies'.
| | >
| | >ken [K. P. Collins]
| | >
| | Sorry, Ken, the patch clamp data
| | on this is quite unambiguous. The
| | current detection in the patch clamp
| | is exquisitely sensitive, but is not
| | at the quantal level nor even at the
| | level of single ions. The currents
| | measured are very small, but
| | "macro"scopic with really little
| | possibility of being instrumental
| | or conceptual artifacts.
| | Nothing is literally "instantaneous",
| | but the time course of opening and
| | closing of the channel is so rapid as
| | to be, for all practical purposes,
| | instantaneous. That is, it is much
| | shorter than the duration of opening
| | of the channel. As far as can be told,
| | all the experimental evidence
| | indicates that gates should be
| | considered either "open" or "closed"
| | with no in-between. When you put into
| | effect the spatial averaging that occurs
| | by summing over the number of
| channels found within a space constant
| | and the temporal averaging that occurs
| | by summing over a time constant
| | (using just ballpark figures that are
| | physiologically reasonable) then you
| | do get "continuously" graded signals.
| Hi Ron.
| I'm Sorry, too, because I've got to
| stand on what I've posted.
| All 'voltage clamp' studies are done
| in-vitro, which 'just' eliminates the
| substrate for the extremely-important
| 3-D energydynamics that I've
| "Of course", if one uses a leaky-pail,
| the pail will leak :-]
| K. P. C[o]llins
Please read this 'addendum' through
before converging on your reaction.
Let's see. What else can I add that will
be of use to folks in comprehending
the position I've been discussing.
The thing to which I initially reacted
was "the noise".
I'd already Verified that, in the stuff I
discussed in my previous post [=not=
quoted above], there could not be any
"noise" within ion-gating dynamics.
Within nervous systems Information-
content is literally 'contained' within
the ionic conductances [the 3-D
energydynamics], so, if the ionic
conductances were subject to "noise",
to the degree of such, the information-
content would degrade in a way that's
analogous to 'snow' on a weak-signal-
broadcast-driven TV screen.
In the TV instance, the weakness of the
signal results in the 'dropping' of inform-
ation-content in a way that's correlated
to the signal-strength =and= the char-
acteristics of the components comp-
rising the TV receiver's circuitry.
Due to the weakness of the signal, the
circuitry 'sporadically' fails to attain
threshold values, and each 'time' it does
so, a little 'patch' of non-information-
containing 'snow' is shot from the
'electron' guns [color TV] to the phos-
phors on the inside of the screen.
I'm =not= saying, here, that nervous
systems 'are TVs'. Of course they're not.
But in in-vitro experimental preparations,
analogous dynamics occur =be-cause=
the 'pail is leaky', and the ionic conduct-
ances are free to flow in ways that they
are not free to flow in-vivo.
This leaves a 'weak-signal' condition be-
cause of the artificially-biased ion-conduct-
I'm not saying anything about the specific
=number= of gates that are 'open' or 'closed'
I'm saying that be-cause the in-vivo ionic
conductances are biased =only= with
respect to the activation that occurs
within the neural Topology, the result is
'noisless'-gate-functioning - not the 'noisy'
stuff that's recorded in-vitro.
The in-vitro-recorded 'noise' is analogous
to the weak-broadcast-signal TV display -
a sporadic sub-specification error-condition.
In the view I hold, the gating dynamics are,
themselves determined by the ionic cond-
uctances ["of course"], "passive spread"
is exquisitely-refined, and is functional way-
beyond 'summing-to-threshold' [including
'addressing' of the DNA, and generalized
cell function] via 3-D energydynamics, all
of which would degrade if the continuity of
the ionic conductances were not maintained
to high-degree - the degree necessary to
drive all of the molecular-'level' 3-D energy-
dynamics [protein-folding, as I've discussed
in former posts, etc.]].
The 3-D energydynamics literally 'address'
and 'schedule' modifications to 3-D cellular
structure over all 'terms' pf system function.
In this view, the gating is as a rigorously-
orchestrated 'symphony' comprised of the
ionic conductances [3-D energydynamics]
which are the information-content - there's
nothing 'statistical' in their 'orchestrated'
co-operation - the gates that're 'open'
closed, or 'waiting' are 'all' continuously
'tuned' to the 'symphony' - out of this, arises
the 3-D energydynamics [3-D ionic conduc-
tances] that are the information-content.
The ionic conductances embody a 'complex'
[I 'hate' that word] wave-form that literally
embodies the information-content, and
simultaneously 'addresses' the neural and
glial structure at all of it's 'levels' [microscopic
[molecular] to global-system].
The various microscopic trophic modifica-
tions that occur in a way that's Rigorously-
coupled to the neural activation that actually
occurs within a nervous system [within a
brain] are literally constructions within the
'circuitry' which 'tunes' itself in accord with
the 3-D energydynamics that occur within
the system. They are =not= the information-
content. They are the circuitry that's 'tuned'
in accord with the 3-D energydynamics that
occur within the circuitry. The information-
content is in the 3-D energydynamics.
In =this= way, nervous systems literally
Grasp the external experiential 3-D energy-
dynamics. turn them inside-out, upside-down,
and backward [as is discussed in AoK,
"Short Paper" and Ap3], in order to simul-
taneously align internal directionalities
with respect to avoidance of noxious stimu-
lation and with respect to optimizing such
avoidance via TD E/I-minimization, which
is what enables Consciousness in which
a 3-D energydynamics transformation of
the external 3-D energydynamics literally
exists within Consciousness.
So it's Crucial that the continuity of the 3-D
energydynamics be maintained.
To the degree that it is not, the system's
functionality degrades, and 'randomness'
[TD E/I(up)] augments - like an assembly
line that is delivering the wrong parts to its
work-stations - what can the workers do
with the parts that don't fit-together? How
can the assembly line produce it's 'normal'
The analogous thing happens within nervous
systems when the continuity of the ionic cond-
uctances 'breaks-down', to the degree that it
[Which is strikes me, as I write this, as
being very-close to what happens in
Alzheier's, except in Alzheimer's it's
'incomplete parts'. Perhaps its the sort
of 'weak-signal' condition, because of
break-down of ionic-conductance
continuity, that underpins the disease(?).]
It's Funny. I saw a cloud in the moon-lit sky
tonoght. It looked 'exactly' like the 'friendly
dragon' in "The Never-Ending Story."
Seems appropriate :-]
Anyway, there's a lot in these posts.
Somebody please say something.
[I'm Sorry, what's here should be more. My
sleep schedule is otu of whack because I'm
switching shifts at my Dishwashing Job.
Honorable Employment, but I'm having to
try to get subsidized housing - so my 'world's
To See what's here, just zoom-in on ionic-
conductance directionalities with respect to
cellular structure. You'll see the information-
content in that highly-dynamic directionality
as it 'addresses' cellular structure.
K. P. Collins
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