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Electrical current [was Consciousness]

Mark Zarella zarellam at nospam.twcny.nospam.rr.com
Sat Nov 22 10:55:03 EST 2003


r norman wrote:
> On Sat, 22 Nov 2003 05:21:23 GMT, Mark Zarella
> <zarellam at nospam.twcny.nospam.rr.com> wrote:
> 
> 
>>>The propagation of action potentials in neurons involves ionic currents 
>>> AND electrical conduction.
>>
>>Care to explain the difference?  I think this conversation is awfully 
>>close to bordering on semantics.  So I suppose a definition of 
>>electrical current and ionic current is in order.  I think we all agree 
>>that ionic current can simply be characterized as the net flow of charge 
>> due to translational motion of ions.  So is "electrical current" that 
>>current due to electron flow only, or can it be characterized simply by 
>>net flow of charge?
> 
> 
> It is posible to find definitions of "electric current" on the web
> saying that is is the flow of electrons.  But then you can find all
> sorts of nonsense on the web.
> 
> More properly electrical current is the rate of movement of electrical
> charge.  And even more properly you must allow displacement current in
> which charges do not move.  Displacement current, I = C dV/dt, is
> usually called capacitative current in neurobiology terminology, and
> is a major factor in current flow in neurons.
> 
> So in a typical action potential you have ionic current through
> membrane channels caused by electrochemical gradients across the
> mmbrane, you have capacitative current across the membrane where no
> ions actually flow caused by temporal gradients in electrical
> potential, you have ionic current down the axon caused by spatial
> gradients in electrical potential, you have electron transport through
> the redox reactions at the surface of your Ag/AgCl  recording or
> stimulating electrodes, you have electron flow though your electronic
> equipment, you have hole flow through P type semiconductors in the
> equipment, you may even have electrons tunneling through barriers in
> some semiconductor devices or ions flowing in plasmas in your display
> devices.  Are there any other forms of current that I have forgotten?
> 
> 

Those definitions are pretty standard, though I think not having them 
posted led to thet source of confusion in this discussion.




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