Yet another FA (2004) error?

[rxfudd]

P. 321, line 2 under "Antiarrhythmics - Na" Channel blockers (class I)":

Decrease slope of phase 4 depolarization....

Replace phase 4 with phase 0?

---

Members don't see this ad.

 

[StringBean]

FA is correct. Na+ channel blockers do decrease the slope of phase 4.

 

[AlexRusso]

Some more that I can think of off the top of my head...

1. Page 90 ..JGA..FA claims that JG cells secrete erythropoietin..on page 360 they say that its the endothelial cells of the peritubular capilaries that do this....as far as i know, and I looked this up, recent research suggests that its the mesangial cells that do this.

2. Page 171 in the diagram they have the arrow for Pyruvate kinase (from PEP to Pyruvate) as a double headed arrow suggesting that this is a reversible enzyme. This is about as far from the truth as you can get b/c Pyr. Kinase is one of the irreversible enzymes of glycolisis and in order to go from pyruvate to PEP in gluconeogenesis you have to go Pyruvate -->OAA--->malate--->OAA--->PEP

I started a thread about FA errors a while back but it got lost somewhere, I guess not too many people were actually studying back then. Now that more of us are geting ready I think it would be nice to have a listing of errors we've found.

 

[AlexRusso]

FA is correct. Na+ channel blockers do decrease the slope of phase 4.

That is true since phase 4 due to If a sodium current

 

[rxfudd]

Yeah, now I see what they mean. Still, I think of class I ARs as mainly decreasing phase 0 slope (even if they do also decrease phase 4) - FA really doesn't even mention this. Thanks for the explanation.

 

[Idiopathic]

I dont know if I completely agree with that. At the most it should be an ancillary effect, right? The primary effect of class 1a and 1c is QT prolongation (while 1b decreases phase 0 upstroke). Where does phase 4 factor into this?

 

[mpp]

Class I's are sodium channel blockers. The depolarization of pacemaker cells is mediated by If (Na+ channels) during phase 4. Hence, the Class I's decrease their firing.

 

[BamaAlum]

I dont know if I completely agree with that. At the most it should be an ancillary effect, right? The primary effect of class 1a and 1c is QT prolongation (while 1b decreases phase 0 upstroke). Where does phase 4 factor into this?

This is partly correct. Class 1A acts at the I(f) Na channels, thus decreasing the slope of Phase 4. The prolonged QT comes from the fact that they and Class III affect the Potassium rectifer channels, thus slowing repolarization. This is why Class 1A and III can cause torsades.

 

[VALSALVA]

This is slightly off topic, but I came across a Kaplan Q-Bank error today. The answer Q-Bank was looking for was ulceratic colitis...except it wasn't one of the options. Naturally, the explanation began with, "this is a classic case of ulceratic colitis." HA!! Anyone else seen this one?

 

[phllystyl]

I started a thread about FA errors a while back but it got lost somewhere, I guess not too many people were actually studying back then. Now that more of us are geting ready I think it would be nice to have a listing of errors we've found.

Use search and bump it up man. you know the interWEB!

 

[Idiopathic]

My point is this...what is the natural 'slope' of the th phase 4 anyway? Obviously the nodes have a distinct phase 4 slope to them, but the ventricles dont. What is there to decrease? Is it a 'subclinical' slope?

 

[mpp]

That's what we're talking about...the phase 4 slope of the pacemaker nodal cells.

Another error: First Aid, 2004 edition, page 82
Teres minor - should say 'laterally rotates the arm' (not medially rotates)

Of the rotator cuff muscles, only subscapularis medially rotates.

 

[Idiopathic]

phase 4 slope of nodal cells is Ca++ dependent, no?

edit: i see now that it is dependent on all three...regardless, the class I drugs do not have their primary effect here. I have read the the 1a class are better for abnormal atrial rhythms, but not 1b and 1c. Any comments?

 

[drchris33]

I thought Phase 0 of nodal cells was calcium dependent. I think phase 4 is the "funny" sodium channels, that spontaneously depolarize.

Also found out that the Sphincter of Oddi is called the Sphinter of odd (version 2002). That that was funny

I also found an error, not sure if it was on COMLEX qbank or USMLEasy website, but I had a question regarding dobutamine. It was asking about dobutamine's MOA; I selected beta-agonist. The correct answer on there was mixed alpha and beta. I looked in two other sources, in addition to First Aid, and all of them say that B1> B2. Anyone else know any different?

 

[KyGrlDr2B]

I thought Phase 0 of nodal cells was calcium dependent. I think phase 4 is the "funny" sodium channels, that spontaneously depolarize.

Also found out that the Sphincter of Oddi is called the Sphinter of odd (version 2002). That that was funny

I also found an error, not sure if it was on COMLEX qbank or USMLEasy website, but I had a question regarding dobutamine. It was asking about dobutamine's MOA; I selected beta-agonist. The correct answer on there was mixed alpha and beta. I looked in two other sources, in addition to First Aid, and all of them say that B1> B2. Anyone else know any different?

When I had pharm, we learned that dobutamine was a racemic mixture--one part is a B agonist and the other an alpha agonist.

 

[Idiopathic]

"2 dopes had a carving lab" or "2 dobermans could carve up a labrador" (depending on your feelings about dogs)

dobutamine and dopamine = a/B agonist
carvedilol and labetalol = a/B antagonist

 

[Idiopathic]

I thought Phase 0 of nodal cells was calcium dependent. I think phase 4 is the "funny" sodium channels, that spontaneously depolarize.

Yes, sorry...

 

[mpp]

This is slightly off topic, but I came across a Kaplan Q-Bank error today. The answer Q-Bank was looking for was ulceratic colitis...except it wasn't one of the options. Naturally, the explanation began with, "this is a classic case of ulceratic colitis." HA!! Anyone else seen this one?

Not a mistake though. The question stem describes UC then asks what would you likely find in a relative. UC is not one of the answer choices...but another correct choice is: Crohn's (versus the other GI answer choices like Celiac, Whipple, etc).

 

[KyGrlDr2B]

mpp, do you have qbank and first aid memorized??

*Jealous*

 

[Idiopathic]

I saw this Q too, its funny how recognizable they get when you look at them a few times.

 

[mpp]

mpp, do you have qbank and first aid memorized??

*Jealous*

I'm working on it. Unfortunately my test is in 5 days...don't think I'll quite make it.

 

[AlexRusso]

I'm working on it. Unfortunately my test is in 5 days...don't think I'll quite make it.

Good luck..you sound like you know your stuff. You'll do fine.

 

[KyGrlDr2B]

I'm working on it. Unfortunately my test is in 5 days...don't think I'll quite make it.

Mpp, I think you're going to do great! You really seem to know your material. I have less than 2 weeks and still feel overwhelmed.

 

[drchris33]

Thanks for the replies on the dobutamine issue. However, I don't remember learning that in pharm, and what really sucks, is that I have looked in three different Pharm books and they all just address that it is a beta agonist. The only thing I have found different is that in Lipponcott's Pharm, it does mention that it is available in a racemic mixture, but that is it.

I am sure you guys know what you are talking about, not trying to say you are wrong, just stating what I have found

-C