BRS physiology question

[stronghold]

Question no. 5 on page 100. The explanation for the answer is not related and even supports another choice. It asks if the ejection fraction increases there will be a decrease in :
A) Cardiac output
B) End-systolic volume
C) heart rate
D) pulse pressure...

When I read the question, I thought of the the formular ejection fraction = stroke volume / end-diastolic volume. So the relationship is inverse between ejection fraction and end-diastolic volume. Although BRS answers the question as C) heart rate, it provides an unrelated explanation that end-systolic volume decreases!!

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[esrever]

maybe an error in BRS Phys of that edition. I have 4th edition. Same question it is.
a. Cardiac Output
b. end-diastolic Volume
c. end-systolic volume
d. heart rate

 

[MilkIsGood]

it was just an error.

 

[Zzmed]

Apparently there's a mistake here.
As the explanation says, there is an increase in EF when for example we administrate a positive inotropic agent. In this case heart rate increases.
When i read the question, i automatically answered B. Because when there is an increase in EF, a higher fraction of EDV is ejected and the blood remaining is much less (decrease in ESV).

BUT, if you go a little bit further: inotropic agent--> initially HR increase --> EF increase --> ESV decrease --> HR decreases finally (or else the heart will start failing because there will be no blood to eject, not enought time for blood to return from venous circulation).

 

[Wordead]

Apparently there's a mistake here.
As the explanation says, there is an increase in EF when for example we administrate a positive inotropic agent. In this case heart rate increases.
When i read the question, i automatically answered B. Because when there is an increase in EF, a higher fraction of EDV is ejected and the blood remaining is much less (decrease in ESV).

BUT, if you go a little bit further: inotropic agent--> initially HR increase --> EF increase --> ESV decrease --> HR decreases finally (or else the heart will start failing because there will be no blood to eject, not enought time for blood to return from venous circulation).

Positive inotropes dont necessarily act on heart rate, main effect is on contractility.

Also an increase in HR would not increase the ejection fraction. If anything it could decrease it (ie tachycardia).

 

[stronghold]

Guys, regardless to the choices, what is the effect of increase of ejection fraction on ESV, EDV and heart rate?

 

[Jonari]

Question no. 5 on page 100. The explanation for the answer is not related and even supports another choice. It asks if the ejection fraction increases there will be a decrease in :
A) Cardiac output
B) End-systolic volume
C) heart rate
D) pulse pressure...

When I read the question, I thought of the the formular ejection fraction = stroke volume / end-diastolic volume. So the relationship is inverse between ejection fraction and end-diastolic volume. Although BRS answers the question as C) heart rate, it provides an unrelated explanation that end-systolic volume decreases!!

Guys, regardless to the choices, what is the effect of increase of ejection fraction on ESV, EDV and heart rate?

I seriously hate cardio physio, unfortunate because I know it's one of the more important physio topics on the board. I find cardio pathophysio easier...anyways, to answer your question on the relationship with EDV and ESV with increased EF, they would rise and decrease, respectively.

Increased EF --> more blood going into the system --> more will be coming back --> increased EDV. Greater FStarling relationship/contractility --> decreasing ESV.

Even, mathematically, the equation works out:

EF = (EDV - ESV)/EDV


0.2 = (10-8)/10


Now with increased EDV and decreased ESV

0.5 = (12-6)/12


Edit: Forgot about heart rate...ok, so since EF is increased, means more blood is going into circulation, correct? Means greater CO.... CO = HR x TPR. It's easier for the body to control HR over TPR, *I think* (still have to review cardio physio again). To compensate for increase in CO, there will be a decrease in the heart rate.

God, I hope I'm correct, exam is in 27 days.

 

[stronghold]

Thanks Jonari!! I like your new picture

 

[Zzmed]

. To compensate for increase in CO, there will be a decrease in the heart rate.

Exactly what i said above in more simple words...

 

[Jonari]

Exactly what i said above in more simple words...

don't you hate that...you post something first...come back to a thread, and another person basically said the same the same thing and ends up getting credit for it.

 

[Zzmed]

don't you hate that...you post something first...come back to a thread, and another person basically said the same the same thing and ends up getting credit for it.

Obviously I don't want to say that! And you know it...

BUT, if you read carefully all the thread you 'll see that after my post it is said that I was wrong. I had a mistake in my post (positive inotropic agents increase HR) but my conclusion is correct.

Everything i said was for the sake of clarity. To help the guy that asked to understand that we say the same thing...
So, next time, before you rush and say something, just think about it a little bit more before you say it...
Thanks

And good luck with your exam. You 'll be fine

 

[Jonari]

Obviously I don't want to say that! And you know it...

BUT, if you read carefully all the thread you 'll see that after my post it is said that I was wrong. I had a mistake in my post (positive inotropic agents increase HR) but my conclusion is correct.

Everything i said was for the sake of clarity. To help the guy that asked to understand that we say the same thing...
So, next time, before you rush and say something, just think about it a little bit more before you say it...
Thanks

And good luck with your exam. You 'll be fine

I'm still confused, why are you telling me this?

 

[Wordead]

Obviously I don't want to say that! And you know it...

BUT, if you read carefully all the thread you 'll see that after my post it is said that I was wrong. I had a mistake in my post (positive inotropic agents increase HR) but my conclusion is correct.

Everything i said was for the sake of clarity. To help the guy that asked to understand that we say the same thing...
So, next time, before you rush and say something, just think about it a little bit more before you say it...
Thanks

And good luck with your exam. You 'll be fine

Just to clarify, you said increased HR -> increased EF. This is not true.

Increased EF does decrease HR, you were right about that.

Just in case.

 

[Zzmed]

Just to clarify, you said increased HR -> increased EF. This is not true.

Increased EF does decrease HR, you were right about that.

Just in case.

Exactly..