Input resistance

BilZ0r BilZ0r at TAKETHISOUThotmail.com
Tue Aug 17 18:17:57 EST 2004


Thanks very much!

jonesmat at physiology.wisc.edu (Matt Jones) wrote in
news:b86268d4.0408171136.26bd6314 at posting.google.com: 

> BilZ0r <BilZ0r at TAKETHISOUThotmail.com> wrote in message
> news:<Xns9548CCC6B2C2BBilZ0rhotmailcom at 202.20.93.13>... 
>> I can't find the answer to this anywhere, I've been googling for an
>> hour or so...
>> 
>> In the sentance "5-HT bath applied on the hippocampal neurons caused
>> a dose-dependent hyperpolarisation and a drop in input resistance";
>> what do they mean by input resistance? And what are the physiological
>> correlates of it?
>> 
>> I get the feeling its basically means a drop in membrane resistance,
>> and hence less current is needed to alter the cells potential
>> differnce? 
> 
> 
> I think my last post got cancelled, so here it is again:
> 
> Yes, they basically mean membrane resistance. The input resistance is
> however much resistance the headstage encounters as it tries to
> "input" current into the system. If the system is considered as the
> pipette plus the cell, the input resistance will be the sum of the
> series resistance (pipette to cell) and the membrane resistance (cell
> to ground). Assuming the series resistance is small, this will be
> dominated by the membrane resistance. If series resistance is big
> compared to the membrane resistance, there are a bunch of measurement
> problems that arise (e.g., series resistance errors).
> 
> The physiological correlate of a drop in input resistance is the
> opening of ion channels. The fact that they get a hyperpolarization,
> coupled with a drop in input resistance, means that the ion channels
> that are opening have a reversal (or equilibrium) potential negative
> to the resting potential. Therefore either chloride or potassium
> channels. Probably potassium channels for 5HT3 receptors.
> 
> PS: 
>> 
>> I get the feeling its basically means a drop in membrane resistance,
>> and hence less current is needed to alter the cells potential
>> differnce? 
> 
> Right idea, but wrong direction. A drop in resistance means that
> *more* current is needed to alter the potential. Ohm's law: V = IR. If
> R goes down, then V goes down for the same amount of I. Need to make I
> bigger to get the same V.
> 
> 
> 
> Matt
> 




More information about the Neur-sci mailing list