Thursday, April 11, 2013

Behind the scenes: Subendocardial fibres lack phase 1

Hello everyone!

I know my "Why are there differences in cardiac action potential in different parts of the heart?" post is not like the regular posts where I tell the usual facts and mnemonics and it seems out of place.

So I thought of doing a behind the scenes version of it. Who said only videos have behind the scenes? Each writing, each painting, each piece of art has a behind the scenes!

Let's get to it =D

Behind the scenes of:

Why are there differences in cardiac action potential in different parts of the heart?

My quest started off with the statement, "Subendocardial fibres lack phase 1"
And when you Google "Subendocardial fibres" it tells you about "Purkinje fibers" which is not the same.

The lord is testing me
"Why do subendocardial fibres lack phase 1?" seemed impossible to answer at first!
"Quit, don't quit? Noodles, don't noodles? You are too concerned about what was and what will be." —Oogway (Kung Fu Panda)
I decided to keep going. After poking around here and there I discovered that purkinje fibers have a prominent phase 1. That means subendocardial fibers can NOT be purkinje fibres.

The heart cells in the subendocardial region lack phase 1 and the conducting cells (Purkinje fibres) in the same region have a prominent phase 1.
I believed there was beauty in how it was created. How our bodies are designed. But I didn't know why.
"What a piece of work is a man! How noble in reason, how infinite in faculty! In form and moving how express and admirable! In action how like an angel, in apprehension how like a god! The beauty of the world. The paragon of animals. And yet, to me, what is this quintessence of dust?"
I had to push further to find out why..

I learnt there was a difference: Cells in different regions of the heart do not have the same action potential. We have a tendency to generalize things and principles to everything. The statement was a mind opener for me!
"We are all equal in the fact that we are all different. We are all the same in the fact that we will never be the same. We are united by the reality that all colors and all cultures are distinct & individual. We are harmonious in the reality that we are all held to this earth by the same gravity. We don't share blood, but we share the air that keeps us alive."
 ― C. JoyBell C.
I learnt why was there a difference: The repolarization phenomenon being different in every cells. Repolarization in a cell occurs because the action pulse has only a certain duration; thus the cell repolarizes at a certain instant of time after its depolarization, not because of the repolarization of an adjoining cell.

Because it's the differences make life interesting!
"Sunshine is delicious, rain is refreshing, wind braces us up, snow is exhilarating; there is really no such thing as bad weather, only different kinds of good weather."
― John Ruskin
Then I learnt what causes the difference: The potassium channels conductance. The action potential notch is due to the presence of a transient outward current (Ito), which diminishes in amplitude from the epicardial to endocardial surfaces.
"There is little difference in people, but that little difference makes a big difference. The little difference is attitude. The big difference is whether it is positive or negative." 
― W. Clement Stone
I learnt why is that necessary: Help the heart contract in an organized fashion and prevent haywire spread of cardiac excitation.
"You can become blind by seeing each day as a similar one. Each day is a different one, each day brings a miracle of its own. It's just a matter of paying attention to this miracle."
 ― Paulo Coelho
In the process I also learnt that without something pushing you to find the answers it's just impossible to keep looking. Thank you for being my reason.
"Passion rebuilds the world for the youth. It makes all things alive and significant."
 ―Ralph Waldo Emerson
 And that's how I ended up finding my answers to the all my questions. It took me three days of asking and three hours of Google search to get to my answer. And I'd like to end by quoting the last quote on hard work :D
"So if you wanna do something, if you've thought about something you wanna do, take it head on. Decide that you're gonna face it; that whatever shortcomings you have, that you're gonna stiffen yourself there; whatever training that is required, that you're gonna get that training; that you're gonna get started right now; do what you can, where you are, with what you have and never be satisfied."
 ― Les Brown
That's all!
Hope you had fun learning with me and see you in the next post xoxo


  1. I've told u many times before too.. but each time I read this post of yours, there's something that motivates me. Or may be everything of it. And at the end I realise, you are a great inspiring soul yourself! Thank you very much for such a beautiful post. :)

    1. That's one of the most beautiful thing anyone has ever told me. Thank you! (:


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