Effect of Class I (a, b, + c) drugs on Pacemaker cells? - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
USMLE Articles
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

Thread Tools Search this Thread Display Modes
Old 06-27-2013
USMLE Forums Guru
Steps History: Not yet
Posts: 315
Threads: 115
Thanked 161 Times in 85 Posts
Reputation: 171
Drug Effect of Class I (a, b, + c) drugs on Pacemaker cells?

In FA, and other books I've used, an effect of these drugs has been described (decreasing the slope of phase 4 depolarization)

But the Kaplan Lecturer for Pharmacology made an interesting point: the RMP in Pacemaker cells was less negative, in comparison to the more negative RMP in ventricular and atrial muscle cells.

And that Na channels tend to be in the 'ready' state, and more ready to depolarize when at the more negative potential (ventricular/atrial muscle cells).

And because the RMP is partly depolarized in SA and AV nodes (relative to ventricular/atrial muscle cells), any Na channels present there, would be inactive to begin with. This was the Kaplan Guys reasoning, and it made sense, and it helped reinforce the concept that cells 'maintained' in a sort of deplarized state, will keep their fast Na channels 'inactive'.

Is this a good way to think of it?
Reply With Quote Quick reply to this message



Quick Reply

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:
Please enter a password for your user account. Note that passwords are case-sensitive.
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.
Where you live. Leave blank if you don't want to tell.


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
Mechanism of action of Class Ib antiarrhythmic drugs dr.morphine USMLE Step 1 Forum 9 05-22-2016 11:02 PM
Class I antiarrhythmic drugs hongyee USMLE Step 1 Forum 4 05-26-2012 01:17 AM
Verapamil effects on nodal cells or ventricular cells? kenlee USMLE Step 1 Forum 1 04-04-2012 12:48 AM
Chloroquine effect on pancreatic beta cells khushboo USMLE Step 1 Forum 7 11-21-2011 02:04 PM
cells that arise from arachnoid cells ricko335 USMLE Step 1 Forum 6 09-13-2011 07:11 AM

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)