Question

(9/25/25) formative assessment assignment: chapter 6 the muscular system part 1 (suggested
10 of 16
the thin filaments are composed of the contractile protein called actin, plus some (1 ) proteins that play a role in allowing (or preventing)
binding of myosin heads to actin. the thin filaments are anchored to the z disc (a disclike membrane). notice that the light i band includes parts of two
adjacent (2 ) and contains only the thin filaments. although they overlap the ends of the thick filaments, the thin filaments do not extend into the
middle of a relaxed sarcomere, and thus the central region (the h zone) looks a bit lighter. when the actin - containing thin (3 ) slide toward each
other during contraction, the h zones disappear because the actin and myosin filaments completely overlap.
another very important muscle fiber organelle—the sarcoplasmic reticulum (sr)—is a specialized smooth (4 ) reticulum (not shown in figure
6 - 3). the interconnecting tubules and sacs of the sr surround every myofibril just as the sleeve of a loosely crocheted sweater surrounds your arm. the
major role of this elaborate system is to store calcium and to release it on demand when the muscle fiber is (5 ) to contract. as you will see,
calcium provides the final go signal for contraction.
o 1 stimulated 2 regulatory 3 sarcomeres 4 filaments 5 endoplasmic
o 1 endoplasmic 2 stimulated 3 regulatory 4 sarcomeres 5 filaments
o 1 sarcomeres 2 filaments 3 endoplasmic 4 stimulated 5 regulatory
o 1 filaments 2 endoplasmic 3 stimulated 4 regulatory 5 sarcomeres
o 1 regulatory 2 sarcomeres 3 filaments 4 endoplasmic 5 stimulated

Explanation:

1. The thin filaments have regulatory proteins in addition to actin that control myosin - actin binding.
2. The light I - band includes parts of two adjacent sarcomeres.
3. During muscle contraction, the thin filaments (filaments containing actin) slide.
4. The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum.
5. Calcium is released from the SR when the muscle fiber is stimulated to contract.

Answer:

1. regulatory
2. sarcomeres
3. filaments
4. endoplasmic
5. stimulated