Biology Support & Movement NUMS 2022
PMDC Verified Question 60 of 75
Which event does not occur during muscle contraction?
A
I-band shortens
B
A-band shorten
C
H-zone disappears
D
Z-line move closer
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: A-band shorten
Concept:

The Sliding Filament Theory constraints.

Formula:

N/A (Conceptual)

Solution:

  • During contraction, actin filaments are dragged inward, causing the overall sarcomere (Z to Z) to shorten.


  • Consequently, the I-band shortens and the central H-zone shrinks and disappears.


  • However, the A-band represents the physical length of the thick myosin filaments themselves. Since protein polymers do not magically shrink, the A-band's length remains absolutely constant.


Why other options are incorrect:

Options A, C, and D are all classic defining events that do occur during sliding filament contraction.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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