REPLY Physiological and Metabolic Models (SD6192)

[System Dynamics Mailing List]

Posted by  "Alan Graham" <Alan.Graham at paconsulting.com>

Hi Ali,

There are many models of physiological and metabolic systems, a few
explicitly by System Dynamicists, and many many more that are dynamic
models differing mostly in nomenclature from "standard SD".

System Dynamics modeling of medical systems started in the 1970s with
Richard O. Foster's MIT thesis on glucose regulation and diabetes, and
my MIT thesis on endocrine regulation of the onset of puberty.  Both of
these are available online through MIT.  Erik Mosekilde has done
continuing work on dynamics of nephrons in the kidneys, at least one
publication appearing in the System Dynamics Review.  PA Consulting did
an extensive model of immune response, capable of recreating viral and
bacterial attack, and onset and treatment of rheumatoid arthritis.  (Due
to commercial circumstances, this work was never published.)  Jack Homer
did an excellent ISDC conference paper on drug resistance adaptation in
bacteria.  Doubtless I'm not recalling or missing several.

Beyond these, a significant portion of metabolic and physiological
models in the medical literature are based on rather simplified (by SD
standards) differential equations.  Given that such models aren't using
the SD skills in understanding decision-making, it's difficult to say
that they're definitely not SD models.  (Editorial:  Of course, many
such models are academic, and have the only apparent usefulness or
purpose of getting published, but truth be told, we in SD, at least in
the publications side, aren't entirely free of that particular lacuna.)

Beyond these, there's a loosely-organized movement called The Physiome
Project, whose aim is to model the entire body, in the same way that the
Genome Project mapped the entire human genome.  Google it.

Beyond these, there's a newer movement called Systems Biology, whose
goal is more comprehensive examination of most traditional topics.  And
guess what, many of the models are remarkably System Dynamics like.

Bottom line is, there's a lot done and being done with philosophy, aims
and tools very much like SD, and a small fraction of that is
"SD-branded".

Cheers,

Alan


Alan K. Graham, PhD
Federal and Defense Services
PA Consulting Group
Posted by  "Alan Graham" <Alan.Graham at paconsulting.com>
posting date  Tue, 16 Jan 2007 12:50:44 -0500