8. Assuming two skeletal muscle fibers have the same myosin ATPase activity, and both are producing an equal force, but one fiber is longer than the other one. Which of the following best describes their shortening velocities? I A. Long fiber has a higher velocity during isotonic contraction than the short one B. Long fiber has a higher velocity during isometric contraction than the short one C. Long fiber has a lower velocity during isotonic contraction than the short one D. Long fiber has a lower velocity during isometric contraction than the short one E. Both fibers have the same velocity during isotonic contraction F. Both fibers have the same velocity during isometric contraction

12. The _________________________ is the main functioning unit of muscle fibers and where the “action” takes place.  It is bordered at each end by _____________. A. sarcomere; Z lines B. actin; H bands C. myofilament; M lines D. tropomyosin; I bands

Which of the following statements relating to the developmental aspects of muscles is false? a. All muscle tissue types arise from myoblasts b. Skeletal muscles become amitotic while smooth muscles regenerate throughout life c. Sarcopenia begins by age 30 and is irreversible d. Body strength per unit muscle mass is the same in both sexes  e. none of the above   Which of the following structures is located in the head region of the thick filament myosin? a. actin binding site b. ATP binding site c. ATPase enzyme d. all of the above e. none of the above

7. Explain the sliding filament theory of muscle contraction.

1. Describe a skeletal muscle fiber's microanatomy, including structures such as the sarcolemma, sarcoplasmic reticulum, transverse tubules, myofibrils (sarcomere structure).

62.