RE: [HAPS-L] "I'm going to pick a fight" - Braveheart

["Ford, Dayton" <dford@xxxxxxxxxx>]

To be honest, because I teach physiology only, I haven't looked at an integrated A&P book in years. What did I miss about the series-elasic elements?

Dayton

________________________________

From: HAPS-L-owner@xxxxxxxxxxx on behalf of Ken Saladin
Sent: Fri 2/10/2006 8:24 PM
To: HAPS-L@xxxxxxxxxxx
Subject: Re: [HAPS-L] "I'm going to pick a fight" - Braveheart



	Okay. Would someone please explain to me the rationale behind referring to calcium as the second messenger in the IP3/DAG second messenger system, rather than IP3 and DAG.


That's a good question, Dayton. Thanks for bringing it up. I delayed responding mostly because I was too busy when this thread started, but partly because I was afraid I might be one of the guilty parties calling calcium a second messenger. I thought maybe I had been swayed by Ganong and Guyton into doing so when I was writing my first edition, and just retained that in the 2nd and 3rd because nobody ever questioned it. But in deciding to address this tonight, I went back to see exactly what I did say and I was relieved to see that I named IP3 and DAG as the second messengers and calcium as the third messenger in the IP3 system (A&P 3rd ed., p. 660). So I'm less guilty than I thought I was.

Nevertheless, I have perpetuated some other common textbook errors. It took me a while to give up saying that muscle twitches follow an all-or-none law. Everybody was saying they did and so I did too. It was Alan Magid's remarks on HAPS-L that swayed me to abandon that and invoke the all-or-none law only for action potentials (whether in muscle or nerve cells). More recently, Alan's comments, again, have persuaded me to drop the concept of the series-elastic components of muscle -- too late for the 4th edition of A&P just out this year, but just in time for the 2nd edition of Human Anatomy. 

In writing textbooks for the freshman-sophomore level, I am reluctant to contradict the textbooks written for medical students and professionals unless I know of very clear arguments and authority for doing so. Yet I've always been a bit of an iconoclast and I'm almost delighted to divest myself and my books of old scientific myths when I know they're no longer tenable. I often catch hell for this from reviewers and users, and spend a lot of time -- it sometimes seems -- e-mailing my sources to people. 

Ken