31.The T tubules
b.provide a means of rapidly transmitting ACh : 1417083
31.The T tubules
b.provide a means of rapidly transmitting ACh to the central portions of the muscle fiber
c.provide attachment sites for ACh
d.perform b and c
e.do not do any of the above
32.An action potential rapidly spreads to the central portions of a muscle cell by means of
e.both a and c
33.Binding of ____ to myosin permits the cross-bridge to ____.
a.ATP; bind with actin
b.ATP; detach from actin
c.calcium; bind with actin
d.calcium; detach from actin
e.None of the above correctly complete the sentence.
34.The sarcoplasmic reticulum stores ____ when a muscle is relaxed and releases it for binding to ____ during contraction.
35.Of the steps in excitation-contraction below, which step occurs before the others?
a.Exposed actin sites bind with myosin cross bridges.
b.Sodium channels open in the fiber's membrane.
c.Calcium is released from the sarcoplasmic reticulum.
d.Troponin binds calcium.
e.Attachment of ATP allows for cross bridge detachment.
36.Which statement is not true about cross bridges?
a.They are a component of thin filaments.
b.They are comprised of myosin.
c.They have an actin binding site.
d.They have an ATPase binding site.
e.They provide power stroking.
a.span the gap between a lateral sac of the sarcoplasmic reticulum and a T tubule
b.are believed to serve as Ca2+ channels
c.bind to and pull the thin filaments inward toward the A band's center during contraction
d.have characteristics a and b
e.are none of the above
38.Which statement is incorrect about cross bridges?
a.They are globular myosin heads that protrude from the thick filaments.
b.They bend during muscle contraction.
c.They attach and detach from actin during muscle contraction.
d.They are not found in the I band.
e.They bind with troponin during contraction.
39.During a cross-bridge cycle in skeletal muscle,
a.the cross bridge is energized when it splits ATP into ADP and P
b.the cross bridge must bind with ATPase before a power stroke will occur
c.Ca2+ causes tropomyosin to move off of the myosin’s actin-binding sites
d.ADP binds to the cross bridge at the end of the power stroke
e.both a and b occur
40.Cross bridge interaction between actin and myosin in skeletal muscle is directly blocked by