Neurophysiology and special senses: spinal shock: 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 and special senses: spinal shock

Sample item

After acute complete transection of the cord at T6, the legs are flaccid with absent reflexes for several days. What mainly causes this initial areflexia?

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

The answer and the reasoning

C. Loss of tonic facilitatory descending drive to spinal neurons

Spinal neurons depend on tonic excitatory input from higher centres. When the cord is cut, they become hypoexcitable, producing spinal shock. Over days to weeks the reflexes return and become exaggerated as spinal circuits recover and denervation supersensitivity develops.

Option by option

  • A. Destruction of muscle spindles

    Muscle spindles are not destroyed by cord transection.

  • B. Failure of the neuromuscular junction

    The neuromuscular junction is preserved, and reflex recovery follows.

  • C. Loss of tonic facilitatory descending drive to spinal neurons (correct)

    Correct. Withdrawal of descending facilitation silences spinal reflexes temporarily.

  • D. Death of the anterior horn cells below the lesion

    Anterior horn cells are intact below a T6 transection and reflexes later return.

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, Loss of tonic facilitatory descending drive to spinal neurons. Spinal neurons depend on tonic excitatory input from higher centres.

Why is "Destruction of muscle spindles" not the answer?

Muscle spindles are not destroyed by cord transection.

Why is "Failure of the neuromuscular junction" not the answer?

The neuromuscular junction is preserved, and reflex recovery follows.

Why is "Death of the anterior horn cells below the lesion" not the answer?

Anterior horn cells are intact below a T6 transection and reflexes later return.

What concept does this question test?

It tests Neurophysiology and special senses: spinal shock in Physiology. When the cord is cut, they become hypoexcitable, producing spinal shock. Over days to weeks the reflexes return and become exaggerated as spinal circuits recover and denervation supersensitivity develops.

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 and special senses: spinal shock?

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.