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Thread: Membrane potential

  1. #1 Membrane potential 
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    Hello everyone, I'm new to this forum and I'm a bit :?

    Anyway I have 2 questions which are proving rather difficult!

    Recording electrodes are placed into a nerve cell to measure the membrane potential at a particular site. When the physiologist glances at the recording and sees that the membrane at that instant has a potential of (x)mV the conclusion is that the portion of the membrane being recorded is:

    A At the phase of an action potential when the inside of the cell becomes more positive than the outside
    B At the phase of an action potential when the inside of the cell becomes less negative than the outside
    C Not in the normal resting state
    D Depolarised
    E All of the above are correct


    In the first question, x is 50mV and in the second, -90mV.

    Explanations please!!!!!!!
    All help appreciated.


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  3. #2  
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    The resting potential for a cell is about -70 mV

    at +50 mV, the cell is fully depolarized. D is right. (maybe A also)

    at -90 mV, the cell is hyperpolarized. C is right. (maybe B also)

    For a full explanation, see the notes on anatomy.

    I'm tempted to use the answer choices A and B, but I don't think the cell as a whole changes in charge. If the choices said that the inside of the cell membrane (instead of just inside the cell), than I would use A and B. But I don't think our cell becomes mini electrodes, I think it's only a difference in potential across the membrane.

    If you are just looking for a quick and dirty answer for a multiple choice homework: at 50 mV it's D. at -90 mV it's C.

    But if you can select more than one choices, I'd put: D and A, then C and B. Maybe I'm just over-analyzing the cell charge part.


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  4. #3  
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    At 50mV, if A is correct then isn't B also correct and also C leading to the actual answer being E?

    Read A and B carefully.

    Thanks for your reply.
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  5. #4  
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    haha you're right on. A and B seems to be saying the same thing, so E would be the right ans. Well, what's the official answer? Did you get it yet?
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  6. #5  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Guys, I know it's nice to help people, but doing their homework for them really doesn't help anyone in the long run.
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  7. #6  
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    Firstly, this isn't my homework.
    Secondly, i haven't got the official answer yet.
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