Good Day Samuel,
Your question is interesting.
Most introductions to membrane potentials concentrate on stable resting
membrane potentials that are occassionally depolarized to threshold
precipitating voltage dependent action potentials. In fact, many neurons
have oscillating membrane potentials or either endogenous or exogenous
origins. The "value" of such neurons becomes obvious when examining neural
circuits such as central pattern generators. A rhythmic drive is essential
to such circuits. Consider it an issue of inertia. Active circuits are
more likely to respond to modulations than inactive circuits.
What is interesting is that phasing of oscillating membrane potentials can
result in multiple output patterns for relatively simple circuits. The
medical significance is that central pattern generators underlie virtually
all motor functions in diverse taxons including mammals. Rhythmic
circuits are probably the norm in all central integrating centers and
probably in sensory pathways as well.
Simple models exist for pacemaker cardiac muscle cells, single unit smooth
muscle, as well as more complex systems such as the crustacean
stomatogastric nervous system. Most of these models invoke changes in
various ionic conductances that hyperpolarize (IPSPs) or depolarize
(EPSP's) cells thus delaying or facilitating oscillations. Neuromodulators
and feedback inhibition play essential roles in these systems. It is nifty
stuff but it is accessible if you know the basic models of membrane
potentials.
rlh
At 12:40 PM +0000 4/22/98, Piman wrote:
>I am a French maths student and I am studying the modelisation of the
>nervous membrane: Hodgkin-Huxley and Fitzhugh-Nagumo.
>That talks about the trigger effect: if the tension of the membrane is high
>(more than 100 mV), there are oscillations: temporal sum.... (I don't know
>the English words...)
Richard Hall
Comparative Animal Physiologist
Division of Sciences and Mathematics
University of the Virgin Islands
St. Thomas, USVI 00802
809-693-1386
rhall at uvi.edu
