Question

watch the following animation and answer the three questions below by completing the quiz part of the tutorial.
muscle contraction summary & quiz

1. the sliding filament theory states that, during muscle contraction and relaxation,

a. actin & myosin filaments shorten, then lengthen
b. actin & myosin filaments change positions relative to one another
c. troponin & tropomyosin slide past one another

1. during muscle contraction, calcium ions bind to

a. troponin
b. tropomyosin
c. actin
d. myosin

1. after a myosin head has performed a power stroke, it must first bind to ______ in order to perform another power stroke.

a. actin
b. troponin
c. tropomyosin
d. atp

Explanation:

1. For question 13: The sliding filament theory core principle is that actin and myosin filaments do not change length, but slide past each other to shorten or lengthen the sarcomere during contraction/relaxation.
2. For question 14: In muscle contraction, calcium ions released from the sarcoplasmic reticulum bind to troponin, which shifts tropomyosin to expose actin binding sites.
3. For question 15: After a power stroke, the myosin head remains attached to actin until it binds ATP, which causes the myosin head to detach and reset for another stroke.

Answer:

1. b. Actin & myosin filaments change positions relative to one another
2. a. Troponin
3. d. ATP