Sarcomere Labeling Quiz
Questions: 16 · 10 minutes
1. Which change best explains why the I band and H zone become narrower during contraction?
Thick and thin filaments both become substantially shorter
Z discs dissolve and release the attached filaments
Thin filaments slide farther over thick filaments, increasing overlap
Thick filaments slide outward past the Z discs
2. During contraction, which change should be shown for the I band?
It becomes narrower as overlap increases
It stays fixed because actin does not move
It shifts outside the Z discs
It widens as thick filaments shorten
3. Which landmark lies at the center of a sarcomere and helps organize the thick filaments?
Z disc
M line
I band
Actin-binding site
4. A bracket on a diagram covers the entire length occupied by thick filaments, from one end of the thick filaments to the other. Which label belongs on the bracket?
H zone
I band
A band
Z disc
5. Which structure marks each boundary of one sarcomere?
A band
M line
H zone
Z disc
6. A label identifies a region centered on the M line and containing thick filaments without thin-filament overlap. Which term is correct?
I band
H zone
Z disc
Zone of overlap
7. A cross-section is taken from a point between a Z disc and the end of the nearest thick filaments. Which filament type should be present there?
Thick filaments only
Thin filaments only
Neither thick nor thin filaments
Both thick and thin filaments
8. A student compares a relaxed sarcomere with a contracted one. Where should the Z discs appear in the contracted sarcomere?
Farther apart, beyond the thin filaments
At the same distance because only the H zone moves
Closer together, with a shorter sarcomere
Joined together at the M line
9. If a diagram marks the distance from one Z disc to the central M line, what fraction of a sarcomere is marked?
One complete sarcomere
One quarter of a sarcomere
One half of a sarcomere
Two sarcomeres
10. On a sarcomere diagram, which band extends across the full length of the thick filaments, including areas where they overlap thin filaments?
A band
I band
H zone
Z disc
11. To which sarcomere structure are thin filaments anchored at their outer ends?
Ends of neighboring thick filaments
M line
Center of the H zone only
Z disc
12. A label points to the lighter central portion of the A band where thin filaments do not overlap thick filaments. What is it?
H zone
I band
Zone of overlap
Z disc
13. As thin filaments slide toward the center during contraction, what generally happens to the H zone?
It narrows and may become difficult to see
It widens while the A band narrows
It becomes the new boundary of the sarcomere
It moves from the center to the Z disc
14. Which elastic protein links thick filaments toward the Z disc and helps the sarcomere return toward its resting length?
Troponin
Titin
Tropomyosin
Nebulin
15. Two diagrams show the same sarcomere before and during contraction. Which labeled band should remain approximately the same length?
I band
H zone
Distance between Z discs
A band
16. Which region contains thin filaments but no thick filaments in a relaxed sarcomere?
A band
H zone
M line
I band