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neuron triggering

jamie morken foster at uvic.ca
Tue Feb 16 18:48:18 EST 1999


Hi all,

Richard Norman wrote...
>And then the excitability of the neuron can be plastic, so that threshold
might vary.
>Once a second messenger signalling mechanism cuts loose and starts to
phosphorylate
>all sorts of cell proteins, and possibly starts activating gene control
mechanisms, there is
>no telling how, how much, or for how long, the cell is likely to change.


Is there another way that the neurons firing voltage can change besides
your above example?
Will the neuron fire differently if the firing voltage is reached in one
case and surpassed in another case?


Richard Norman wrote...
>The "inputs" are synaptic events which summate in a horribly non-linear
way.
>This is caused in part by the notion of "reversal potential" -- the
amplitude of
>synaptic effect depends on the local membrane potential at the moment.
It is
>also caused by the fact that synapses alter the membrane conductance, and

>therefore influence the current loops that carry the potential from the
site of the
>synapse to the spike initiation zone.  Even an excitatory synapse "short
circuits"
>the membrane and reduces the effect of more distant excitation.


Can you explain how/why the synapses short circuit the membranes?  I
assume an excitory
synapse would want as little short circuiting of the membrane as possible,
so as to carry as much
voltage to the spike initiation zone as possible.  Does an inhibitory
synapse release chemicals that
purposely short circuit the membrane?  Or is there a different method
inhibitory neurons use to reduce
neuron firing, such as sending a negative voltage (aka reverse potential?)
towards the spike initiation zone?
Thanks,

Jamie Morken




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