The truth is out there

F. Frank LeFever flefever at ix.netcom.com
Thu Nov 26 22:17:38 EST 1998


My comments are interdigitated below:


In <912075256.24982.0.nnrp-03.d4e44203 at news.demon.co.uk> "Andrew K
Fletcher" <andrew.k.fletcher at naturesway.demon.co.uk> writes: 
>
>Hi Frank, Hi Ken,
>
>The flow of water in plants and trees is relevant to this discussion,
it was
>my interest in this that led directly to my working with spinal cord
injury,
>ms and other neurological conditions.


I'd be surprised if the processes were the same (i.e. water transport
in trees,  CSF formation and transport and absorption).  What is your
thesis re relevance of CSF circulation to MS?  to spinal cord injury?



>"
>Frank, could you please summarise the content of 'this wonderful
process'
>referred to in your posting and its relationship with how water
reaches the
>leaves of trees.


No, sorry, I could not.  Anyway, I thought you had listed the basic
components of the processe(s) yet could not accept an explanation in
these terms.

re your summary from the textbook account:  what's the publication date
of that textbook?  If a later edition, was this section revised in the
light of work done between earlier and later editions?

I am no expert in this area, but it was clear to me from the
presentations by the panel of very very expert neuroscientists at this
NSF (National Science Foundation) satellite meeting (preceding the
Society for Neuroscience annual meeting) that there were still
questions to be answered regarding CSF sources, contents, circulation,
and absorption and/or other clearance mechanisms.

Much of what your summary says may be true, but much may be yet open to
correction.  My own interest was not in mechanisms of circulation per
se, but in the central focus of the conference, which was the extent to
which neuroactive substances in the CSF could enter the CSF and reach
targets via the CSF in sufficient amounts to be physiologically
significant, and the kinds of long-term neural integration which might
be subserved by this mechanism.

F. Frank LeFever, Ph.D.
New York Neuropsychology Group

>
>The flow of cerebrospinal fluid as described in Principles of Anatomy
and
>Physiology is as follows.
>
>The entire central nervous system contains  between 80 and 150 ml (3
to 5oz)
>of cerebrospinal fluid, colourless fluid of watery consistency.
Chemically
>it contains, proteins, glucose, urea and salts. It also contains some
>lymphocytes.
>
>With regard to its circulatory function, cerebrospinal fluid delivers
>nutritive substances filtered from the blood to the brain and spinal
cord
>and removes wastes and toxic substances produced by brain and spinal
cord
>cells.
>
>It then goes on to illustrate the path of the circulation of CSF.
>
>The flow of cerebrospinal fluid as described in Advanced Human
Biology: J.
>Simpkins, J.I.Williams, is as follows.
>
>Pressure compensation
>CSF is produced from and returns to the blood passively in response to
>pressure differences between the blood and CSF. The effects of
increases in
>blood pressure distending intercranial vessels can thus be reduced as
more
>CSF is produced.
>
>Page 125 The beating of the cilia cells sets up currents in the
>cerebrospinal fluid, thus helping the circulation of metabolites.
Astrocytes
>are connected to the bases of ependymal cells which may assist
exchange of
>metabolites between CSF and neurons in the central nervous system.
>
>Fig 14.43, page 285 shows a simple drawing which illustrates the
circulation
>of fluids by arrows from the choroid plexus down one side of the spine
and
>up another side, it also shows a flow over the the surface of the
brain,
>indicated by an arrow on both sides.
>
>I did read an article, which was a reprint of text from another
physiology
>book, which I can't find, that stated something along these lines.
>Circulation in the CSF occurs due to respiration, postural, and
circulatory
>influences.
>
>Ken Collins wrote:
>
>I've not studied it, but I expect the cerebrospinal fluid flows
through
>active
>dynamics... when it's produced, it goes into the ventricles, more is
>produced...
>what was produced earlier flows to "get out of the way" of what's just
been
>produced. I don't know where the "drain" is... expect it's a
distributed
>thing,
>too. ken Collins
>
>Original post.
>
>>>Could someone therefore sum up the accepted mechanism for
circulation
>>in the
>>>cerebrospinal fluid, so that we have an independent benchmark for
>>further
>>>discussions? Only then will we see if this road leads us to any
>>conclusions.
>>
>>
>>- - - - - -(snip) - - - - - - -
>>F. Frank LeFever, Ph.D. wrote.
>
>>I won't comment on his itemizing the forces by which water could be
>>lifted up into trees and then demanding to know how this happens.
>>(Incidentally, I found treatment of this wonderful process in
Murchie's
>>"The Seven Mysteries of Life" fascinating; too bad he got spooky on
the
>>last 2-3 mysteries...)
>
>>However, I too am interested in CSF, and attended a satellite
>>conference (sponsored by NSF, prior to the Society for Neuroscience
>>meeting early this month) on CSF as a communications system.  Among
>>other things, problems of its circulation were considered.
>>
>>F. Frank LeFever, Ph.D.
>>New York Neuropsychology Group
>
>
>




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