neurobiology question

[jheidenr]

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Topscore exam II #19:

All of the following of neurons ar true except:

A. Refrectory periods make the backward travel of action potentials impossible.
B. The greater the diameter of the axn, the faster the impulse will travel.
C. The more heavliy the axon is myelinated, the faster the impulse will travel.
D. At rest the concentration to Na+ is greater inside the cell.
E. At rest neurons are permeable to Na+ so the cell remains polarized

Topscore says D and I agree with that, but why not E? I thought that at rest, the neuron was impermeable to Na+ and that's how it keeps the gradient. Any ideas?

 

[eric275]

Topscore exam II #19:

All of the following of neurons ar true except:

A. Refrectory periods make the backward travel of action potentials impossible.
B. The greater the diameter of the axn, the faster the impulse will travel.
C. The more heavliy the axon is myelinated, the faster the impulse will travel.
D. At rest the concentration to Na+ is greater inside the cell.
E. At rest neurons are permeable to Na+ so the cell remains polarized

Topscore says D and I agree with that, but why not E? I thought that at rest, the neuron was impermeable to Na+ and that's how it keeps the gradient. Any ideas?

I think that may be a typo.

From Kaplan: " The resting potential is created because the nueron is selectively permiable to K+, so K+ diffuses down the concentration gradient, leaving the net negative charge inside. (Nuerons are impermeable to Na+, so the cell reamins polarized) Pg 614 Kaplan Blue Book, 3rd paragraph.

It probaly should have said impermeable .

 

[DrTacoElf]

I think that may be a typo.

From Kaplan: " The resting potential is created because the nueron is selectively permiable to K+, so K+ diffuses down the concentration gradient, leaving the net negative charge inside. (Nuerons are impermeable to Na+, so the cell reamins polarized) Pg 614 Kaplan Blue Book, 3rd paragraph.

It probaly should have said impermeable .

E. At rest neurons are permeable to Na+ so the cell remains polarized

At rest neurons are permeable only to K+. I know this for a fact 🙂 Also this makes sense because the [K+] is higher inside the cell at rest so it will diffuse down its gradient and in part helps to maintain the resting membrane potential of about -70mv.

 

[ItsGavinC]

Furthermore, being permeable to Na doesn't maintain polarization, it creates hypopolarization, or lessens the polarity of the cell.

 

[jheidenr]

yes...that's what I though, just making sure. I guess there are no practice DATs out there that are perfect...