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  #1  
Old 08-03-2011
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Question More positive than the resting membrane potential!

Which of the following changes would you expect to make the membrane potential of a muscle more positive than the normal (resting ) level?

A. increased conductance to potassium
B. increased conductance to chloride
C. decreased conductance to sodium
D. increased extracellular potassium concentration
E. increased extracellular chloride conductance..
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  #2  
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B. increased conductance to chloride
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Old 08-03-2011
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E: letting Cl go out
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Old 08-03-2011
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membrane potential more positive ( from -90 to -70)

d.increased extracellular potassium concentration
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Old 08-03-2011
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the answer is B
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Old 08-03-2011
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D. Hyperkalemia increases resting membrane potential (more positive)
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Old 08-04-2011
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i am confused about a and d, ill jus go with a!
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Old 08-04-2011
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well the answer is B...explanation in kaplan LN is...increased extracellular cl would hyperpolarise due to its effects on the cl equilibrium potential!!!!!...can any one explain this!!!!
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Old 08-04-2011
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Did you see this in Kaplan Q bank?
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Old 08-04-2011
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what is the reason why it is not A???
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Old 08-04-2011
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Quote:
Originally Posted by usluipek View Post
Did you see this in Kaplan Q bank?
nope it is in the kaplan lecture notes in the review questions..
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Quote:
Originally Posted by heman466s View Post
nope it is in the kaplan lecture notes in the review questions..

page no. pls.
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Old 08-04-2011
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Quote:
Originally Posted by USMLE2011m View Post
page no. pls.


Q no 7 of review questions of excitable tissue!!
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Quote:
Originally Posted by heman466s View Post
Q no 7 of review questions of excitable tissue!!
this is just a typo.
The correct answer is D. increased extracellular potassium concentration.
You can always use the nernst equation.

btw, anyone have the 2009 Kaplan errata?
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Finally I found the question and the answer is D!

http://www.aippg.net/forum/f18/membr...le-cell-63587/

If you still have problem understanding this concept, check this video!
(check min 12'...)
http://www.cvphysiology.com/Arrhythmias/A007.htm

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Yes now i think its D

Thanx bebix Cleared an important concept.
So now
A) increased conductance to K will cause more efflux of K leading to more negative membrane pot.
B) increase chloride conductance will lead to more influx of chloride leading to more negative membrane pot.
C) decreSED CONDUCTance OF Na will lead to less influx of Na leading to more negative memb. pot.
D) Increased K conc will lead to more influx of K ion into the cell leading to Increased memb. pot.
E) Increased Cl will lead to increased Cl influx leading to more negative memb. Pot.

Correct me i am getting it wrong
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Quote:
Originally Posted by usmle2011 View Post
Yes now i think its D

Thanx bebix Cleared an important concept.
So now
A) increased conductance to K will cause more efflux of K leading to more negative membrane pot.
B) increase chloride conductance will lead to more influx of chloride leading to more negative membrane pot.
C) decreSED CONDUCTance OF Na will lead to less influx of Na leading to more negative memb. pot.
D) Increased K conc will lead to more influx of K ion into the cell leading to Increased memb. pot.
E) Increased Cl will lead to increased Cl influx leading to more negative memb. Pot.

Correct me i am getting it wrong
so wt is happening in case of benzodiazepene n barbiturate where Cl- conductance is affected ???increase in opening frequency of Cl channels in case of BZs plss clear this concept
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Quote:
Originally Posted by qurat21 View Post
so wt is happening in case of benzodiazepene n barbiturate where Cl- conductance is affected ???increase in opening frequency of Cl channels in case of BZs plss clear this concept
Well the role of BZs is an inhibitory one so it increases the intracellular cloride conc. making the resting membrane potential more negative than normal ... Therefore a higher than normal positive potential is needed to overcome this state and evoke an action potential ... This happens even in muscle that is why BZs cause relaxation of muscle
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However I'd like to add that these drugs are GABA selective so the chloride inhibition only occurs at high doses since GABA is not present in the muscle cell
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Quote:
Originally Posted by bebix View Post
Finally I found the question and the answer is D!

http://www.aippg.net/forum/f18/membr...le-cell-63587/

If you still have problem understanding this concept, check this video!
(check min 12'...)
http://www.cvphysiology.com/Arrhythmias/A007.htm



thanx bebix...very helpful!!
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  #21  
Old 05-26-2014
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thts why hyperkalemia causes arrythmia due to increased memb. potential.
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