babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
which of the following changes would be expected to make membrane potential of a muscle cell more positive than the normal (resting) cell:
a) increased potassium conductance
b) increased conductance to chloride
c) decreawed conductance to sodium
d) increased extracellular potassium concentration
e) increased extracellular chloride concentration
please, comment on your opinion
thank you
|
| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
|
The answer is D. Increasing the K+ outside the cell causes at the very least a more positive resting membrane potention because it decreases the concentration gradient of K+. Further if you increase the K+ to a very high level it will result in the reversal of the concentration gradient and flow of K+ into the muscle cell leading to depolarization .
So now I hope you atleast have faith in this forum!! Good question when are you taking the test?
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
the correct answer listed was B
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
my exam is in Feb, but i feel like i am sliding in a comatose state...had to push it from Jan to Feb to do one more reading
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
totally diagree with B, but that's what was given as a correct answer
|
| jamdoc
Forum Elite
Topics: 30
Posts: 244
|
answer is D. cl- ion equilibrium potential is -90mv so no matter what the conductance to chloride ion is, there is no net movement.
___________________
Dont worry.Nobody knows 100%
|
| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
|
Thats what kaplan says, where did you get the question from ? usmle rx ?
I'm doing the same thing as you. I thought I would get one more reading in and thus postponed a month. Now its just been really hard to keep reading the last ten days or so. I blame some of this on the fact that my beloved Dallas Cowboys took a nose dive. Truly tragic...I might not ever recover. Good luck on your test.
Edited by Ancylostoma on 01/08/07 - 09:27 PM
|
| drdido
Forum Junior
Topics: 6
Posts: 56
|
I believe the answer is D. According to BRS .. increased Cl- conc would lead to inhibition of the cell membrane, drawing it further away from membrane's pot threshold and away from initiating an AP.
If you increase the conductance of K+ out of the cell, then you make the cell more positive internally and that would evetually lead to excitation as you surpass the threshold.
Ancylostoma... can u further explain what you mentioned above please "Further if you increase the K+ to a very high level it will result in the reversal of the concentration gradient and flow of K+ into the muscle cell leading to depolarization . " thx
dido
___________________
Get me the hell out of this!
|
| MRMAVERICK
Forum Guru
Topics: 40
Posts: 713
|
the answer is definitely d
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
thank you very much, guys, now i know that i am not retarded (at least one point against it), but this question (with answer) actually comes from Kaplan Physio book, so it must be a mistake they have there. there is also very weird explanation that is very hard to correlate with actual question...
Ankylostoma, don't take it so close, it's just a game and put it this way....lose or wiin, these guys have a job ano no one is losing it, and you on the other hand, if will not concentracte and WIN will not be in the same situation
when is your exam?
|
| jsknetsdude
Forum Junior
Topics: 4
Posts: 63
|
more positive than the normal
increased conductance to chloride is the answer .. dont go into AP details .. the Q is simple .. the Cl a neg ion to be pumped outside ..
There fore more Na would be needed to achieve the theroshold for AP .. if you consider AP i.e.
___________________
JSK .. O Lord !! Increase my capacity to Absorb knowledge ..
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
when we increase conductance in Cl, doesn't INFLUX of Cl increase?
|
| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
|
I'm going to take my exam a month from now. So i'm about to gear up for a serious last study blitz. Hopefully I want to finish my kaplan questions and usmle world and then take the exam
|
| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
|
goog luck to you i'm just few days behind. you'll do just fine, i'm sure
|
| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
|
lol, the smileys cure all, thanks ,good luck to you again !!
|
| Luckyall
Forum Guru
Topics: 11
Posts: 592
|
B) is totally wrong
No matter wht the CL conductance is there will be NO net difusion of CL in a steady state sit. b/c CL is already at its Eq. Pot, nor a change in Conductance of CL in a steady state sit. alter cell's Eq. potential !!!!!!
|
| Luckyall
Forum Guru
Topics: 11
Posts: 592
|
B) is totally wrong
No matter wht the CL conductance is there will be NO net difusion of CL in a steady state sit. b/c CL is already at its Eq. Pot, nor a change in Conductance of CL in a steady state sit. alter cell's Eq. potential !!!!!!
|
|
| |
| | | | | | | | | | | | | | | | | |
