Nernst equation question - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-15-2011
INCOGNITO's Avatar
USMLE Forums Guru
 
Steps History: Step 1 Only
Posts: 343
Threads: 127
Thanked 524 Times in 192 Posts
Reputation: 534
Question Nernst equation question

a 32 year old man is recovering from third-degree burns over 50% of his body surface area. His serum potassium is low(2.9mEq/L) which is common in healing burn victims.
He exhibits postural hypotension and skeletal muscle weakness. If Eq potential (nernst potential) for K+ in a nerve cell was -105mV and Eq potential for Na+ was +55mV.
What would be an approximate value for the resting membrane potential for a nerve cell in this man assuming normal membrane permeability..?

a)+80mV
b)+52mV
c)+22mV
d)-50mV
e)-98mV
f)-45mV

I know answer but don't know the explanation..so plz explain it simply..
AND IS THIS USUALLY MLE type QUESTION?
Reply With Quote Quick reply to this message
The above post was thanked by:
zeal7 (01-30-2013)



  #2  
Old 06-15-2011
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 646
Threads: 52
Thanked 761 Times in 256 Posts
Reputation: 772
Default

-98mv...

characteristic of any cell is that the equilibrium potential is near to the potential of K+

so pick the answer closest to K+...

calculation in this condition is very difficult and complicated.. will only confuse u more.
Reply With Quote Quick reply to this message
The above post was thanked by:
Dr. Mexito (05-27-2012), INCOGNITO (06-16-2011), sami trailer (01-31-2013), usluipek (06-16-2011), zeal7 (01-30-2013)
  #3  
Old 01-30-2013
billy's Avatar
USMLE Forums Guru
 
Steps History: Not yet
Posts: 444
Threads: 109
Thanked 369 Times in 208 Posts
Reputation: 379
Post

nice que
Reply With Quote Quick reply to this message
 
  #4  
Old 01-30-2013
USMLE Forums Scout
 
Steps History: Not yet
Posts: 52
Threads: 1
Thanked 20 Times in 16 Posts
Reputation: 30
Default

hyokalemia... results in less + ions outside plasma membrane hence RMP becomes less negative since plasma membrane has ungated K ch , potassium ions will move out bringing RMP closer to equilibrium potential of K;
Reply With Quote Quick reply to this message
The above post was thanked by:
zeal7 (01-30-2013)



Reply

Tags
Cell-Biology-, Physiology-, Step-1-Questions

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
USMLE step 1 - Nernst equation? Tig2575 USMLE Step 1 Forum 1 05-17-2011 07:50 AM
Hardy-Weinberg equation help docnas USMLE Step 1 Forum 1 01-21-2011 07:43 AM
Hardy Weinberg Equation, Please Help achistikbenny USMLE Step 1 Forum 6 07-03-2010 12:56 AM
Hardy- weinberg equation!!! fauzan USMLE Step 1 Forum 7 12-30-2009 12:23 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)