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GATE 2022 BM – Question 44

Mammalian Cell Biology, Human Anatomy and Physiology · Nervous System · 2 marks · Multiple choice

Which statement about axonal ATP requirement is true?

  1. A myelinated axon needs more ATP than an unmyelinated axon of equal diameter and length
  2. An unmyelinated axon needs more ATP than a myelinated axon of equal diameter and length
  3. Both need the same ATP at equal diameter and length
  4. An unmyelinated axon always needs more ATP regardless of diameter and length

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Correct answer: (B) An unmyelinated axon needs more ATP than a myelinated axon of equal diameter and length

Explanation

For equal geometry and comparable activity, myelination restricts most action-potential ionic exchange to nodes of Ranvier. Fewer ions then need to be pumped back across the membrane per impulse, reducing ATP demand. Thus B. D overgeneralizes by discarding geometry and other conditions.

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