27. What actually shortens when a muscle fiber contracts?
        A)    thickand thin filaments
        B)    A bands,M lines, and Z discs
        C)   sarcomeres, H zones, and I bands
        D)    both band c

28.Sarcoplasmic reticulum is the name given to which of thefollowing?    
a.Rough endoplasmic reticulum in smooth muscle cells
b.Smooth endoplasmic reticulum in cells of the epimysium
c.Smooth endoplasmic reticulum in all muscle cells
d.Rough endoplasmic reticulum in cardiac muscle cells

29.Which of the following actions is caused by skeletalmuscle?
a.Vasoconstriction
b.Vasodilation
c.Pupillary dilation
d.Eye movements
e.Heartbeat

30.Which of the following does NOT occur in a muscle during acontraction?
a.Thick and thin filaments interact
b.Muscle fibers stretch
c.Thick and thin filaments \"slide\" past one another
d.Muscle fibers shorten

31. A nerve impulse triggers the release of what chemical at aneuromuscular junction?
        A)   adenosine triphosphate (ATP)
        B)   acetylcholinesterase (AChE)
        C)   acetylcholine (ACh)
        D)    none ofthe above

32 .Rigor mortis demonstrates that skeletal muscle tissue
        A)    normallyrequires energy to end as well as to start a contraction
        B)    cansurvive and function for some time after the heart stopsbeating
        C)   maintains powerful contractions even with no ATP, until autolysisoccurs
        D)    all ofthe above