Biology Support & Movement MDCAT 2015
PMDC Verified Question 73 of 75
A sarcomere is the region of a myofibril between two successive:
A
M-lines
B
I-bands
C
Z-lines
D
T-tubules
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Z-lines
Concept:

Boundaries of the sarcomere.

Formula:

N/A (Conceptual)

Solution:

  • The basic functional unit of muscle contraction is the sarcomere.


  • By standard histological definition, a single sarcomere spans the exact distance between two successive Z-lines (or Z-discs), which anchor the thin actin filaments.


Why other options are incorrect:

The M-line is the center of the sarcomere. The I-band spans across the Z-line into two adjacent sarcomeres. T-tubules are membrane invaginations, not filament boundaries.

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