Gastrointestinal: hepatic arterial buffer response: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Gastrointestinal: hepatic arterial buffer response

Sample item

In a patient with portal vein thrombosis, hepatic arterial flow increases. What is the mechanism?

ADirect sympathetic vasodilatation of the hepatic arteryBReduced portal flow lets adenosine accumulate, dilating the hepatic arteryCIncreased pressure in the hepatic veinsDRising portal oxygen content

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Reduced portal flow lets adenosine accumulate, dilating the hepatic artery

Adenosine is washed out of the space of Mall by portal blood flow. When portal flow falls, adenosine accumulates and relaxes hepatic arterial smooth muscle, which partly compensates and maintains total hepatic flow. This is the hepatic arterial buffer response.

Option by option

A. Direct sympathetic vasodilatation of the hepatic artery
The response is local and does not depend on sympathetic vasodilators.
B. Reduced portal flow lets adenosine accumulate, dilating the hepatic artery (correct)
Correct. Reduced washout of adenosine dilates the hepatic artery.
C. Increased pressure in the hepatic veins
Hepatic venous pressure is not the signal for this response.
D. Rising portal oxygen content
Portal oxygen content falls when flow is reduced, not rises.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Reduced portal flow lets adenosine accumulate, dilating the hepatic artery. Adenosine is washed out of the space of Mall by portal blood flow.

Why is "Direct sympathetic vasodilatation of the hepatic artery" not the answer?

The response is local and does not depend on sympathetic vasodilators.

Why is "Increased pressure in the hepatic veins" not the answer?

Hepatic venous pressure is not the signal for this response.

Why is "Rising portal oxygen content" not the answer?

Portal oxygen content falls when flow is reduced, not rises.

What concept does this question test?

It tests Gastrointestinal: hepatic arterial buffer response in Physiology. When portal flow falls, adenosine accumulates and relaxes hepatic arterial smooth muscle, which partly compensates and maintains total hepatic flow. This is the hepatic arterial buffer response.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Gastrointestinal: hepatic arterial buffer response?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.