Ion channel effects on neuron membrane potentials KA Passage

[betterfuture]

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.
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Maybe I was not able to follow through what was going in and what was already in. Can someone break it down?

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[theonlytycrane]

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.

 

[betterfuture]

Ok I am confused. Like always

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.

 

[theonlytycrane]

can you link the passage? I'll take a look

 

[betterfuture]

https://www.khanacademy.org/test-pr...-tut/e/neuron-membrane-potentials---passage-1

 

[theonlytycrane]

https://www.khanacademy.org/test-pr...-tut/e/neuron-membrane-potentials---passage-1

Yeah the passage is pretty crappy like most of the KA stuff and their new layout. I would just know how the Na+/K+ pump works, that Na+ is usually on the outside of the neuron and K+ is usually on the inside of the neuron.

 

[betterfuture]

Lol