From owner-biophysics@net.bio.net Thu Nov 26 22:00:00 1998 Path: biosci!news.stanford.edu!newsfeed.concentric.net!207.155.183.80.MISMATCH!global-news-master From: kkollins@pop3.concentric.net Newsgroups: bionet.biophysics,bionet.microbiology,bionet.neuroscience Subject: Re: The truth is out there Date: 26 Nov 1998 19:25:12 PST Organization: Concentric Internet Services Lines: 93 Message-ID: <365E1B1F.429B55CB@pop3.concentric.net> References: <721spg$cr7$1@nnrp1.dejanews.com> <36449D67.378533CC@pop3.concentric.net> <36449FE2.313F8F3@pop3.concentric.net> <36477CA4.D2FED10@pop3.concentric.net> <3647B373.953F0A70@pop3.concentric.net> <3649B0AF.E720E242@psci.net> <364AAB63.C5056FB9@pop3.concentric.net> <364B5C6D.75E14B08@indiana.edu> <72s9eb$2fe@apple.telalink.net> <36523785.484B17DE@pop3.concentric.net> <912019876.8168.0.nnrp-08.d4e44203@news.demon.co.uk> <73im3f$ogr@dfw-ixnews3.ix.netcom.com> <912075256.24982.0.nnrp-03.d4e44203@news.demon.co.uk> Reply-To: kkollins@concentric.net NNTP-Posting-Host: ts001d16.spr-ma.concentric.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.02 [en]C-DIAL (Win95; U) Xref: biosci bionet.biophysics:4576 bionet.microbiology:15173 bionet.neuroscience:26038 I'll be grateful if you continue your discussion... Learning's Fun. ken collins Andrew K Fletcher wrote: > 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. > " > 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. > > 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 .