Bon soir Laurent,
Sorry for putting my .02 ? in here.
"Laurent" <lorseau at ens.insa-rennes.fr> skrev i melding
news:3D34371D.EDB8F929 at ens.insa-rennes.fr...
> Thanks a lot.
> Anyway, I may have not explain correctly what I wanted, or I don't
> understand well enough what you say.
>> I have some basic notions about neurons and chemistry, but I haven't tried
> to know the whole phenomena of the synapse.
>> Here is what I wanted know if it was possible :
>> Neuron A is activated since a few msec (or less or even more).
> Neuron A suddenly desactivates.
> Wait some msec.... (delay, no signal in A's axon, nor through Synapse S)
> Synapse S from neuron A (still desactivated) to neuron B then transmits a
> signal.
Yes, and Richard said so,no ?
Neuron A activates a _potential_; ae electrical signal that courses through
the axon (which is the output from the neuron) to the end-terminal (where
the neurotransmitters are stored in vesicles [containers]).
Then this signal activates intake of Ca+ (Calsium), which releases vesicles
(small containers) with neurotransmitters inside them - those vesicles
'integrates' then with the cellular membrane and the neurotransmitters are
released outside of the cell.
Then it takes some time for these neurotransmitter to diffuse across the
synaptic cleft (the distance between the terminal of neuron A, and the
cellular wall of neuron B) were it activate _reseptors_ on neuron B.
The time it takes from when the signal activates the intake of Ca+ to the
release of the vesicles is very short.
And Richard thinks of the time for the neurotransmitter to _diffuse_ from
neuron A to neuron B; while you are thinking of the time-delay from when the
signal _activates_ the Ca+ intake.
Chemically it is the neurotransmitter which is interesting if you are
searching for a delay, so he gave you the right answer.
Hope I have helped clearifying things, Laurent.
Brian
> Is that the same delay you were talking about ?
> If this is possible, can the delay be very long ?
>> Laurent
>>> "Richard S. Norman" wrote:
>> > On Tue, 16 Jul 2002 15:24:03 +0200, Laurent
> > <lorseau at ens.insa-rennes.fr> wrote:
> >
> > >Hi !
> > >
> > >I was wondering if a natural synapse could transmit a signal after and
> > >only after (and not instantly after) the source neuron has stopped
being
> > >activated. Is this possible ?
> > >
> > >Laurent.
> >
> > Your question can be answered on many different levels of detail. How
> > much neurophysiology background do you have and how much detail do you
> > want? Are you really asking about synaptic delay?
> >
> > Generally, the synapse releases transmitter as a result of being
> > depolarized. In many cases, that means that the axon has just fired
> > an action potential. The nerve activity causes the transmitter
> > release by starting a complex process involving calcium and vesicle
> > changes (here is where all the details occur).
> >
> > It does take a brief time to crank up the machinery and here is where
> > most of the synaptic delay occurs. But if the action potential is
> > prolonged a bit, it is certainly possible for the transmitter to be
> > released before the action potential is finished, if that is what you
> > are asking. The delay can vary from a few hundred microseconds to a
> > msec or more depending on the cell and the synapse and the action
> > potential can have a similar variation in duration.
> >
> > The most important thing is the the release machinery does not require
> > that the depolarization be removed before release can occur. So, yes,
> > it is possible.
>
