To all the cardio ppl

[LapisLazuli]

I have an actual question about the heart, not why you guys are doing this or what the hours are like...

Its probably elementary for you guys: What's the most important factor that regulates coronary blood flow?
Isn't it just aortic blood pressure? My question book is too good for my crappy textbook, so I can't even find answers. Couldn't the answer also technically be "autoregulation by local chemical factors", like metabolic factors?
God, I wish I had a better book (I'm still undergrad)

The choices are:
A. neural regulation by the ANS
B. intraventricular pressure during ventricular systole
C. autoregulation by local chemical factors
D. aortic b.p.
E. circulating epinephrine

I would say D, but I'm not sure if that's too easy.
I hope this doesn't sound like a "do my homework for me" post. Honestly, what better source of answers is there?

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[ckent]

i'm pretty sure that the correct answer is C. Blood supply to the heart is mostly supplied during diastole, so unless the diastolic pressure bottoms out, I think that the heart isn't all that dependent on the aortic pressure. The heart is one of those "priority organs" during shock, ie the body will vasoconstrict almost all other vessels (and compromise other organs) to maintain blood flow to the heart and brain.

 

[phillymed]

which textbook are you using?
if you can, try and check the Berne and Levy one, its probably the most reliable forthis.
I would think C also,
A agree, circulating Epi could be a bit dangerous. I am not sure about that bid on diastole. IN skeletal muscle, local metabolites play a big role in vasodialation. when you excercise or what ever you increase the pH of the blood vessles and they dialate, it would make sense that in thea heart is the same.
Let us know when you get the correct answer.

 

[ys]

The answer is C. Adenosine is probably the most important chemical mediator of coronary autoergulation. Nitric oxide also plays a part. Non-chemical autoregulation also plays a part, reactive hyperemia leads to greater blood flow during diastolye, since the coronary vessels get occluded during systole. Hope this helps.

 

[LapisLazuli]

I checked Berne and Levy, and C is the actual answer. Thanks for recommending that book, it seems pretty helpful. In their words, "Changes in coronary blood flow are caused primarily by caliber changes of the coronary resistance vessels in reponse to the metabolic demands of the heart."

It didn't list ade and NO specifically, but fortunately I have you guys for that.

Thanks!