Respiratory system: pulmonary vascular response to exercise: 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 · Respiratory system: pulmonary vascular response to exercise

Sample item

During strenuous exercise cardiac output may rise three to four-fold, yet mean pulmonary arterial pressure increases only slightly. What is the main mechanism?

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

The answer and the reasoning

B. Recruitment of closed capillaries and distension of open ones, which lowers pulmonary vascular resistance

The pulmonary circulation is a low-pressure, low-resistance system. With rising flow, collapsed capillaries are recruited and open vessels distend passively, so resistance falls and pressure changes little. Sympathetic control of the pulmonary vessels is weak.

Option by option

  • A. Redirection of flow through the bronchial circulation

    The bronchial circulation carries only 1 to 2 percent of cardiac output and does not take the load.

  • B. Recruitment of closed capillaries and distension of open ones, which lowers pulmonary vascular resistance (correct)

    Correct. Recruitment and distension reduce resistance as flow rises.

  • C. Active sympathetic beta-mediated dilatation of pulmonary arterioles

    Sympathetic dilatation is a minor effect in the pulmonary vessels.

  • D. Opening of a right-to-left shunt through the foramen ovale

    A right-to-left shunt would cause hypoxaemia and does not occur normally.

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.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Recruitment of closed capillaries and distension of open ones, which lowers pulmonary vascular resistance. The pulmonary circulation is a low-pressure, low-resistance system.

Why is "Redirection of flow through the bronchial circulation" not the answer?

The bronchial circulation carries only 1 to 2 percent of cardiac output and does not take the load.

Why is "Active sympathetic beta-mediated dilatation of pulmonary arterioles" not the answer?

Sympathetic dilatation is a minor effect in the pulmonary vessels.

Why is "Opening of a right-to-left shunt through the foramen ovale" not the answer?

A right-to-left shunt would cause hypoxaemia and does not occur normally.

What concept does this question test?

It tests Respiratory system: pulmonary vascular response to exercise in Physiology. With rising flow, collapsed capillaries are recruited and open vessels distend passively, so resistance falls and pressure changes little. Sympathetic control of the pulmonary vessels is weak.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Respiratory system: pulmonary vascular response to exercise?

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.