# Thread: Membrane potential

1. 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.

All help appreciated.

2.

3. 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.

4. 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.

5. 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?

6. Guys, I know it's nice to help people, but doing their homework for them really doesn't help anyone in the long run.

7. Firstly, this isn't my homework.
Secondly, i haven't got the official answer yet.

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