CHAPTER 5Excitable Tissue: Muscle 113
- The functions of tropomyosin in skeletal muscle include
A) sliding on actin to produce shortening.
B) releasing Ca2+ after initiation of contraction.
C) binding to myosin during contraction.
D) acting as a “relaxing protein” at rest by covering up the sites
where myosin binds to actin.
E) generating ATP, which it passes to the contractile
mechanism.
- The cross-bridges of the sarcomere in skeletal muscle are made
up of
A) actin.
B) myosin.
C) troponin.
D) tropomyosin.
E) myelin.
- The contractile response in skeletal muscle
A) starts after the action potential is over.
B) does not last as long as the action potential.
C) produces more tension when the muscle contracts isometri-
cally than when the muscle contracts isotonically.
D) produces more work when the muscle contracts isometri-
cally than when the muscle contracts isotonically.
E) decreases in magnitude with repeated stimulation.
5. Gap junctions
A) are absent in cardiac muscle.
B) are present but of little functional importance in cardiac
muscle.
C) are present and provide the pathway for rapid spread of exci-
tation from one cardiac muscle fiber to another.
D) are absent in smooth muscle.
E) connect the sarcotubular system to individual skeletal mus-
cle cells.
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Science, 2007.
Fung YC: Biomechanics, 2nd ed. Springer, 1993.
Hille B: Ionic Channels of Excitable Membranes, 3rd ed. Sinaver
Associates, 2001.
Horowitz A: Mechanisms of smooth muscle contraction. Physiol Rev
1996;76:967.
Kandel ER, Schwartz JH, Jessell TM (editors): Principles of Neural
Science, 4th ed. McGraw-Hill, 2000.
Sperelakis N (editor): Cell Physiology Sourcebook, 3rd ed. Academic
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