Heart Anatomy Question

[jgalt42]

A bit stuck on what the true answer is. This is from the back of my anatomy textbook. The textbook says the answer is B, but my prof says its C.

Which of the following conditions would be caused if the amount of blood entering the ascending aorta with each contraction of the heart were increased?

A) The atrioventricular valves would not close.
B) The amount of blood sent to the lungs for oxygenation would decrease
C) Stimulation by the sympathetic nervous system would accompany this change
D) The amount of blood entering the right atrium of the heart would have been increased.
E) The heartbeat would be speeded up by the parasympathetic nervous system

My justification for B is that the heart would compensate for such a large ventricular contraction with a smaller atrial contraction in the next cardiac cycle.

C could also work as this is the direct response of NE into the pacemaker cells.

Which one is the best answer?

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[Scilencer]

Basically it's asking what happens when stroke volume increases...it's worded awkwardly but SNS activity will lead to increased SV so C makes the most sense... Tbh this wording kinda sucks so don't worry too much.

 

[Didierdrogba]

I think C is incorrect. Shouldn't SNS be decreased, and Parasympathetic be increased due to carotid arch baroreflex?

 

[JShephard]

I think C is incorrect. Shouldn't SNS be decreased, and Parasympathetic be increased due to carotid arch baroreflex?

Yeah. Unless it's saying before the change instead of after.

 

[notbobtrustme]

Isn't it D because what the heart pumps has to equal what it receives....

 

[madchemist89]

Between answers B and C, I believe that B is the better answer. The increased blood flow in the arch of the aorta will stimulate the baroreceptor causing increased firing, leading to a decrease in sympathetic outflow and increase parasympathetic outflow. Therefore, contractility and heart rate will be reduced. Cardiac output = SV x HR. Cardiac output will be decreased, leading to decreased blood entering the lungs.

 

[Didierdrogba]

Isn't it D because what the heart pumps has to equal what it receives....

After reading this question for the 10th time, I conclude that this is a really poorly asked question

 

[calvnandhobbs68]

Definitely E guys

E) The heartbeat would be speeded up by the parasympathetic nervous system

To add to the consensus, this is a horribly written question and answer set.

 

[evilbooyaa]

'Speeded up'. lol.

Ok, it's not A. Clearly.

B might be right assuming that you essentially have a second inlet into the ascending aorta that contracts in-sync with the heart. B is saying that your stroke volume is not going up (because the SNS causes your stroke volume to go up through increased contractility). Then, perhaps the carotic arch baroceptors would cause enough of an effect to decrease lung perfusion. Looking at it twice, however, this seems pretty unlikely since you have an increased functional stroke volume. Maybe if you had a IVC catheter that was removing the same amount of blood that you were injecting into the ascending aorta... then maybe.

C is the physiologic cause of the effect proposed in the question stem, which is probably why your professor said C was the answer. Because he's thinking physiologically, not some crazy scenario where there is a magical increase in ascending aorta volume without an increase in stroke volume.

D might be right besides the incorrectly used 'would have been'. If it said 'would be increased', then that is correct. Increase in stroke volume means that more blood fills into the right atrium compared to prior to the SV increase.

E is wrong. PNS slows down the heart rate.

So, agree with general consensus above about it being a horribly written question, and one that has multiple answers. However, I would say the physiologic answer (and most likely the 'most correct' one) is C.


However OP, your explanation for B is incorrect.

My justification for B is that the heart would compensate for such a large ventricular contraction with a smaller atrial contraction in the next cardiac cycle.

A large ventriular contraction would not coincide with a smaller atrial contraction. Your left ventricle feeds your ascending aorta. Your right ventricle feeds your lungs.

 

[Morsetlis]

Terribly worded question. Increased SV is not a "cause", it is an effect.

 

[GadRads]

Pressure changes in the chambers of the heart drive closure/opening of AV valves. Nothing in the question leads to A.

An increase in stroke volume/cardiac output should increase venous return. Therefore B is wrong.

C is possible. Sympathetics increase contractility of myocytes which increase SV. However this will cause the increased output not accompany it, so this answer is iffy and likely wrong.

D is true since it follows the frank-starling mechanism. Increased venous return--> increased preload --> increased stroke volume-->cardiac output (assuming same heart rate).

E. Parasympathetics slow down SA nodes which slow down heart rate.

I think D is the best answer

A bit stuck on what the true answer is. This is from the back of my anatomy textbook. The textbook says the answer is B, but my prof says its C.

Which of the following conditions would be caused if the amount of blood entering the ascending aorta with each contraction of the heart were increased?

A) The atrioventricular valves would not close.
B) The amount of blood sent to the lungs for oxygenation would decrease
C) Stimulation by the sympathetic nervous system would accompany this change
D) The amount of blood entering the right atrium of the heart would have been increased.
E) The heartbeat would be speeded up by the parasympathetic nervous system

My justification for B is that the heart would compensate for such a large ventricular contraction with a smaller atrial contraction in the next cardiac cycle.

C could also work as this is the direct response of NE into the pacemaker cells.

Which one is the best answer?

 

[je355804]

Definitely E guys

E) The heartbeat would be speeded up by the parasympathetic nervous system

To add to the consensus, this is a horribly written question and answer set.

OP did you copy and paste this question or did you type it in? If you typed it, were there perhaps some misspelled words? Where did this question come from?