COLLEEN M. SPECHT
v102nq9f at ubvms.cc.buffalo.edu
Thu Oct 10 12:22:21 EST 1996
In article <53i9gk$ss5 at highway.leidenuniv.nl>, Schaap at rullf2.medfac.leidenuniv.nl (Jeroen Schaap) writes:
>In article <52ov40$4q2 at gap.cco.caltech.edu>,
>Maybe it is theoretically possible to take a segment of an axon an
>determine which the direction is. But I am not mentioning any
>electrophysiological properties. I am not very sure, but I believe the
>cytoskeleton grows in one direction, with helices turning in a special
>direction. Theoretically, I stress, it might be possible to determine
>the direction of the cytoskeleton in an axon-segment and with that the
>direction of the propagation of action potentials in 'normal'
> Second, I can also imagine antidromic ap's could have an
>influence on the membrane potential of the soma/ axon hillock by means
>of electrotonic interaction. But results will be very difficult to
>interpretate. Because the different potentials involved in an ap as a
>function of time, there will be no simple elevation of depression of
>membrane potential. I don't know whether some slow channels have been
>proved on axons -please help me with this- but they could de- or
>hyperpolarize the soma.
i don't think anyone would argue this point - and there is really no reason to
think that this couldn't take place. however, sodium/potassium atp-ase used a
considerable amount of energy to prevent this from happening. and even if a
tiny current did make it to the hillock (which i would think a tiny current
always does...) it in not enough to make an a.p.
> Third, why couldn't any action potential be generated on an
>axon, by means of axo-axonic synapses etc. Off course the axons don't
>have the ap generating mechanism, axon hillock, but nevertheless, why
>couldn't the 'axonic synapses' depolarize enough in order to generate an
again, this would theoretically work, but has not yet been found. there IS
such a thing as the axoaxonic synapse, which results in presynaptic inhibition.
to generate an action potential you would need many many many such synapses on
a single axon i would think (this is what has not yet been found).
>Things are never that simple they seem to be.
but jeroen, were they simple wouldn't they bore you?
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