The mitochondrion as a flip-flop memory element in neurons

Rich Cooper richcooper1 at mindspring.com
Wed Dec 13 12:37:42 EST 2000


> > > Protons are positively charged. The arrival of positive charges at
> the
> > > negatively charged inner surface of a neuron membrane that is ready
> > > to 'fire' will trigger a nerve impulse. The triggering positive
> charge
> > > need only be very small; the main strength of a nerve impulse is
> > > contributed by the subsequent increase in permeability of the
> membrane
> > > to sodium ions, and the inrush of that ion into the neuron.
> >
> > Are you sure that a single proton generates enough charge transfer
> > to start the avalanche of ion exchange that produces the nerve
> impulse?
> > This question should be answerable by a simulation.  My own feeling
> > is that one proton is probably not adequate to start the avalanche.
>
> I think that many protons would arrive at the inside of the membrane of
> the neuron to trigger a nerve impulse. There might be millions of
> identical ATPase enzymes rotating in phase, advancing in big steps of
> 120 degrees, and each pumping uphill 4 protons at each big step. That
> is why I wrote of a 'minor flood' of protons being produced at each big
> step.

I remember reading (somewhere) that a single molecule is sometimes
transferred across a synapse when a nerve impulse crosses it.  The idea
of a single proton at a time is intrigueing because that's the kind of
efficiency nature has used in so many other implementations.  For every
impulse to be translated into four protons at a time sounds wasteful,
though nature can also be wasteful (e.g., lemmings).

If 120 degrees is a big step, what's a small step?


> > > Triggering of 'gamma' waves
> > >
> > > I have suggested that a mitochondrion close to a 'critical spot' on
> the
> > > inner surface of the membrane of a neuron might work sometimes with
> its
> > > ATPsynthase/ATPase enzymes rotating in phase as ATPase, fuelled by a
> > > store of ATP in the matrix of the mitochondrion, and triggering
> nerve
> > > impulses in the neuron at three times the frequency of rotation of
> the
> > > ATPase enzymes.
> > >
> > > I proposed that this might be the origin of the 'gamma' waves
> observed
> > > in certain groups of neurons. These waves have been tentatively
> > > identified by some authors as the neural correlate of 'awareness'
> > > or 'consciousness' of particular aspects of objects.
> >
> > Since there is no way to measure 'consciousness' or 'awareness', I
> find
> > any neural correlates to be extreme speculation, rather than any
> hypothesis
> > that can be scientifically built upon.

I reassert this statement.


> 'Consciousness' and 'awareness' are difficult to define. Every person
> might have their own definitions! Nonetheless several workers,
> including Francis Crick and Christof Koch, have tried to study
> consciousness experimentally. Crick and Koch studied awareness in the
> visual system.

I prefer to say that they study EEG responses to invoked signals using
light stimuli.  That avoids the word 'consciousness' which, as you point
out, can't be consistently defined in a way that many people agree to.
Is a flatworm conscious?  Is a paramecium conscious?  Are all people
conscious?  What about that famous book 'Consciousness and the
bipartite brain' (I didn't get the title right, but you probably remember
it better than I do, if you are conscious!).  His claim is that
consciousness
is only about two thousand years old, separated by the old literature
of the Illiad when people wrote songs from the third person, and the
Odyssey, when they wrote heroic tales of Ulysses' clever ruses.

-Rich









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