Neurophysiology: Monro-Kellie doctrine: 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 · Neurophysiology: Monro-Kellie doctrine

Sample item

A slowly enlarging intracranial mass causes no rise in pressure at first. Which mechanism buffers the early rise in volume?

ADisplacement of CSF and venous bloodBCompression of the brain parenchymaCOutward expansion of the skull vaultDAn immediate rise in arterial inflow

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

The answer and the reasoning

A. Displacement of CSF and venous blood

The skull is a rigid box containing brain, blood and cerebrospinal fluid. When one component enlarges, CSF and venous blood are displaced to compensate, and pressure rises steeply only when this reserve is exhausted.

Option by option

A. Displacement of CSF and venous blood (correct)
Correct. CSF and venous blood are displaced first, delaying a pressure rise.
B. Compression of the brain parenchyma
Brain tissue is not compressible enough to absorb a mass.
C. Outward expansion of the skull vault
The adult skull is rigid and cannot expand.
D. An immediate rise in arterial inflow
Arterial inflow does not buffer a volume increase and would worsen it.

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 A, Displacement of CSF and venous blood. The skull is a rigid box containing brain, blood and cerebrospinal fluid.

Why is "Compression of the brain parenchyma" not the answer?

Brain tissue is not compressible enough to absorb a mass.

Why is "Outward expansion of the skull vault" not the answer?

The adult skull is rigid and cannot expand.

Why is "An immediate rise in arterial inflow" not the answer?

Arterial inflow does not buffer a volume increase and would worsen it.

What concept does this question test?

It tests Neurophysiology: Monro-Kellie doctrine in Physiology. When one component enlarges, CSF and venous blood are displaced to compensate, and pressure rises steeply only when this reserve is exhausted.

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 Neurophysiology: Monro-Kellie doctrine?

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.