Blood and immunity: leukotrienes: 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 · Blood and immunity: leukotrienes

Sample item

A man with asthma has bronchoconstriction that is not relieved by antihistamines but improves with montelukast. Which mediators are being blocked?

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

The answer and the reasoning

C. Cysteinyl leukotrienes made by the lipoxygenase pathway

Cysteinyl leukotrienes LTC4, LTD4 and LTE4, derived from arachidonic acid by 5-lipoxygenase, were formerly called slow-reacting substance of anaphylaxis. They are powerful bronchoconstrictors and increase vascular permeability, and montelukast blocks their receptor.

Option by option

  • A. Prostacyclin made by cyclooxygenase

    Prostacyclin is a bronchodilator and vasodilator, not a bronchoconstrictor.

  • B. Histamine acting on H1 receptors

    Histamine acts on H1 receptors, but antihistamines did not help here.

  • C. Cysteinyl leukotrienes made by the lipoxygenase pathway (correct)

    Correct. Cysteinyl leukotrienes cause bronchoconstriction, and montelukast antagonises them.

  • D. Bradykinin acting on endothelial receptors

    Bradykinin is not the target of montelukast.

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 C, Cysteinyl leukotrienes made by the lipoxygenase pathway. Cysteinyl leukotrienes LTC4, LTD4 and LTE4, derived from arachidonic acid by 5-lipoxygenase, were formerly called slow-reacting substance of anaphylaxis.

Why is "Prostacyclin made by cyclooxygenase" not the answer?

Prostacyclin is a bronchodilator and vasodilator, not a bronchoconstrictor.

Why is "Histamine acting on H1 receptors" not the answer?

Histamine acts on H1 receptors, but antihistamines did not help here.

Why is "Bradykinin acting on endothelial receptors" not the answer?

Bradykinin is not the target of montelukast.

What concept does this question test?

It tests Blood and immunity: leukotrienes in Physiology. They are powerful bronchoconstrictors and increase vascular permeability, and montelukast blocks their receptor.

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 Blood and immunity: leukotrienes?

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.