Physiology question

[Amy B]

Hi all,

I have a question, which is probably very trivial but I packed away my textbooks and I started thinking about this and it is driving me crazy......

I know that if the resting membrane potential becomes too large the cell will be inexcitable because the RMP is too far from threshold ( -60 mV) for action potential production. If the RMP becomes too depolarized, the neuron also becomes inexcitable..... So my question is if it becomes depolarized does that mean the number becomes more positive?

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[sdeel]

Yes, depolarization is the membrane potential becoming more positive and yes it can become hyperpolarized, thus in the very + range. But if the cell stays this way the cell would be in a constant state of contracture, the opposite of which would be true if the cell was hypopolarized. Hope it helps and look forward to meeting you next year. Have you checked out the student webpage? The moderator supposed to be posting pics of our April Fools GAGs on the faculty and yes the DEAN.

 

[PACtoDOC]

Hyperpolarized would make the membrane potential more negative, as in the -70 or -80 range. Less polarized would make the membrane potential less negative like -40 or -50 instead of the normal -60mV or so.

 

[Kalel]

To the OP: I'm not sure that you understand what you are asking, your question seemed a littel confusing to me. I will try to answer your question anyways. If acted upon by an outside force or if the cell loses energy, it's resting potential can rise to a positive number or a higher negative number. If the membrane potential was changed to a number above threshold (let's say that threshold was -65 mV) by some outside force (ie voltage clamp), what would happen is that the neuron would fire it's action potential once, and then it would not be able to fire again until it's membrane potential was dropped to below threshold because it's sodium channels responsible for firing the action potential would remain in their deactivated state. Were you asking what would happen if the cell became hyper-polarized (ie more negative)? All that would happen there is that the cell would require more energy or a greater stimulus to fire an action potential. Anyways, I know that this neurophys stuff is confusing, but I did research on it during undergrad, so if you have any other questions, I'd be happy to try to answer them for you.

 

[sdeel]

whoops kinda contridicted myself, just mistyped. Kelel has a much bette explanation and as such probably got that A in phsio

 

[Amy B]

Originally posted by Kalel
what would happen is that the neuron would fire it's action potential once, and then it would not be able to fire again until it's membrane potential was dropped to below threshold because it's sodium channels responsible for firing the action potential would remain in their deactivated state.

This is actually what I was wondering. If it was raised to the more postive number what would be the result. I remembered it had something to do with the Na channels but I didn't know how that all tied together.

Thanks to all for the reponses.

Sdeel: Thanks for you help also. I have really enjoyed looking over your class page. The photos are great. And I can't wait to see the gag photos. So you guys did some pranks this week. Were they good ones?