Are neurons impermeable to Na+?

[Lazerous]

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Top Score 2 question 19 choice E says:

At rest neurons are impermeable to Na+ so the cell remains polarized

Is this true? I thought it was slightly permeable and there is even a special protein to provide facilitated diffusion but the Na-K pump does it's job of pumping out Na ions to keep the potential, no?

 

[klpennin]

Yeah, I was confused about that question too, but the other answer is definately wrong (saying somthing about [Na] being higher on the inside of the cell).

 

[211183]

I think what you initially said is correct... it's impermeable to Na+ until the "gates" open...I think that K+ is permeable though-- which is what helps keep the gradient...hmm..

 

[211183]

Actually you know what, I remember reading both in two different sources, so now im just as confused as you. I rmember taking that test and picking that answer because I knew the rest were definitely wrong.

 

[Chesnok]

just eliminate wrong answers ; - inside is negative, outside is positive --> gradient in normal cell

 

[Albuterol]

if you think about the cell membrane...charged molecules are impermeable so i'd have to agree with topscore.

AP cliffs says the gradient is maintained by the large negatively charged proteins on the inside of the cell so thats what gives the cell its overall negative charge. the K+ leak channels contribute to the negative charge by flowing out of the cell, down its gradient.

 

[Lazerous]

just eliminate wrong answers ; - inside is negative, outside is positive --> gradient in normal cell

Oh, I picked the right answer. I was just confused about this one choice.

Also in Cliff's AP I recall that they show a picture a an axon membrane that has facilitative proteins for both Na and for K and in between those two facilitative proteins is an active protein a.k.a. the Na-K pump...

 

[doc3232]

If I am not mistaken it is NEARLY impermeable.
Basically, it is barely permeable to K and Na. I think this is why I everyone is confused. Most books say it is not because the amount of Na and K passing is so small that it is nearly negligible.