M9: Muscle Physiology

Question 1

When a muscle contracts, which area of the sarcomere shortens?

A. Z-line
B. H zone
C. I band
D. A band
E. B & C

Answer 1

Answer: E

I band:
is the area where only thin filaments exist (the Z line zig zag down the middle of this band). It shortens during contraction.

H zone:
is the center of a sarcomere; it is an area that consists of only myosin filaments. During a muscle contraction, the myosin pulls the actin filaments toward the center, shortening the H zone.

Question 2

Power stroke

Answer 2

is the part of the muscle contraction/ or cross bridge when myosin pulls the thin filaments toward the center of the sarcomere, shortening the H zone. This event requires ATP