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21.According to the sliding-filament mechanism, the a.A bands slide between the

Question : 21.According to the sliding-filament mechanism, the a.A bands slide between the : 1417082

 

21.According to the sliding-filament mechanism, the

a.A bands slide between the I bands

b.thin filaments slide inward toward the center of the A band

c.Z lines slide between the T tubules

d.contractile proteins shorten, thus shortening the sarcomere

e.filaments slide past the lateral sacs of the sarcoplasmic reticulum

22.During contraction of skeletal muscle fibers, the

a.contractile proteins shorten

b.thin filaments slide inward toward the A band's center as a result of cycles of cross-bridge binding and bending

c.thick and thin filaments become tightly coiled, thus shortening the sarcomere

d.I bands slide in between the A bands

e.lateral sacs of the sarcoplasmic reticulum shorten, pulling the Z lines closer together

23.Which of the following are involved in the regulation of cross bridge attachment activity?

a.calcium ions

b.troponin

c.tropomyosin

d.all of the above

e.only b and c

24.During muscle contraction,

a.the Z lines move farther away from the thick filaments

b.the A band becomes narrower

c.the H zone becomes narrower or disappears

d.the I band remains unchanged

e.both b and c occur

25.The H zone

a.is the area within the middle of the A band where the thin filaments do not reach

b.shortens or disappears during contraction

c.contains only thick filaments

d.does not contain cross bridges

e.is all of the above

26.Which of the following changes in banding pattern occur during muscle relaxation?

a.Thin filaments move away from the Z lines.

b.I bands get wider.

c.H zones get narrower.

d.Thick filaments become longer.

e.Both b and c occur.

27.During contraction, asynchronous cycling of cross bridges

a.prevents tetany

b.prevents thick filaments from slipping backwards

c.prevents thin filaments from slipping backwards

d.utilizes less ATP

e.does not do any of the above

28.During excitation-contraction coupling,

a.the action potential travels down the T tubules

b.Ca2+ is released from the sarcoplasmic reticulum

c.Ca2+ is taken up by the sarcoplasmic reticulum

d.both a and b occur

e.both a and c occur

29.The T tubules

a.store Ca2+

b.provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fiber

c.store ATP

d.run longitudinally between the myofibrils

e.have expanded lateral sacs

30.Sequence the following events involved in muscle cell contraction:

1.Sodium channels open and sodium flows in.

2.Impulse reaches the axon's terminal.

3.ACh binds to receptors on the muscle cell membrane.

4.Synaptic vesicles fuse with neuron's membrane and release ACh via exocytosis.

5.If enough sodium moves in to the muscle cell, an impulse (action potential) develops.

a.1, 2, 3, 4, 5

b.2, 1, 3, 4, 5

c.2, 4, 3, 1, 5

d.3, 4, 5, 1, 2

e.3, 5, 2, 1, 4

 

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