betterfuture

2+ Year Member
Feb 16, 2016
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Anybody do the "Ion channel effects on neuron membrane potentials" KA passage.

I could not follow through what the 2nd paragraph meant.

A scientist is studying neurons in vitro to determine what occurs at a newly discovered ion channel. When many of these channels are opened, the membrane potential changes from -60 mV to -50 mV. The resulting membrane potential after opening many of these channels with a decreased extracellular concentration of sodium ions is -60 mV, with a decreased extracellular concentration of chloride ions is -50 mV, and with a decreased extracellular concentration of calcium ions is -50 mV.
Maybe I was not able to follow through what was going in and what was already in. Can someone break it down?
 

theonlytycrane

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Mar 23, 2014
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There's some ion channels opening and ions are moving either in or out.

The sodium channel is opened with a decreased extracellular concentration of Na+ and the membrane potential goes to -60 mV (more negative). Sodium must be moving out of the cell.

The chloride channel is opened with a decreased extracellular concentration of Cl- and the membrane potential goes to -50 mV (less negative). Chloride must be moving out of the cell.

The calcium channel is opened with a decreased extracellular concentration of Ca2+ and the membrane potential goes to -50 mV (less negative). It looks like Ca2+ is staying in the cell.
 
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betterfuture

2+ Year Member
Feb 16, 2016
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Ok I am confused. Like always:confused:

What is the resting membrane potential? 60 mV? If so, when the ion channels open, the voltage does not change. Yet they mention the extracellular fluid has a decreased [C] of Na+1. Doesn't that imply that sodium has moved inside the cell since there is a decreased concentration of Na+1? Same questions go for the other two ions.
 
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theonlytycrane

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Mar 23, 2014
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