Biology · Support and Movement
Work through this past-paper style MCQ, then read the full explanation. Practice more biology questions on mMCQ with adaptive practice and topic analytics.
Which of the following changes in length during sarcomere contraction?
- A
Thick filaments
- B
M-line
- C
H-zone
- D
All of these options are correct
The H zone—the central region of the A zone—contains only thick filaments and is shortened during contraction. Remember that the actin and myosin filaments themselves do not change length, but instead slide past each other.
Thick filaments from the A band. They are surrounded by thin filaments on two sides linearly. When a muscle contracts, its length remains the same. Hence, this option is incorrect.
During muscle contraction, the thin filaments slide past the thick filaments or M-line.
The H-zone is the bright region in the middle of a sarcomere. It is because the edges of thick filaments they are overlapped with thin filaments, hence making the region crowded and appear dark under a microscope. However, in the middle, where only thick filaments are present, the region appears lighter and brighter. This region is called Hthe -zone. When the muscle contracts, thin filaments move towards the center of thick filaments, making the H-zone smaller. So, this option is correct.
As only option C is correct, this option is incorrect.
Tagged under Biology · Support and Movement · 2021