61.If the load a muscle increased, eventually a load will : 1417086
61.If the load on a muscle is increased, eventually a load will be reached at which the velocity of shortening becomes zero. At this point, the muscle contraction is referred to as
62.Energy sources available to form ATP in muscle fibers in the absence of oxygen include
d.creatine phosphate and glycolysis
e.chemiosmosis and glycolysis
63.The first means by which ATP is produced at the onset of contractile activity is
a.transfer of energy and phosphate from creatine phosphate to ADP
d.degradation of myoglobin
e.none of these
64.During aerobic exercise, the primary means for ATP production in muscle fibers involves
a.can store small amounts of O2
b.increases the rate of O2 transfer from the blood into muscle fibers
c.is abundant in fast-glycolytic fibers
d.can perform a and b
e.has characteristics a and c
66.Select the correct statement about the summation of simple twitches.
a.They can occur because of the long duration of the action potential in a muscle fiber.
b.They reduce the tension in a muscle.
c.They result from the slow stimulation of a muscle fiber.
d.The effect is unrelated to the refractory periods of action potentials.
e.The twitches resulting from separate action potentials.
67.Which of the following statements about the different types of muscle fibers is incorrect?
a.The higher the ATPase activity, the faster the speed of contraction.
b.Muscles with a high glycolytic capacity and large glycogen stores are more resistant to fatigue.
c.Muscles with high ATP-synthesizing ability are more resistant to fatigue.
d.Oxidative types of muscle fibers contain myoglobin.
e.Muscle fibers containing large amounts of myoglobin have a dark red color in comparison to the paler fibers, which have little myoglobin.
68.Fast-glycolytic (type IIx) muscle fibers
a.have high myosin-ATPase activity
b.can carry out oxidative phosphorylation
e.have all of the above characteristics
69.Fast-oxidative (type IIa) fibers
a.contain very few mitochondria
b.can be converted into fast-glycolytic fibers by regular resistance activities
c.are most abundant in muscles specialized for maintaining low-intensity contractions for long periods of time without fatigue
d.have characteristics b and c
e.have none of the above characteristics
70.The muscle cells of a marathon runner's legs would exhibit all these characteristics except
a.high resistance to fatigue
b.low myoglobin content
c.low glycogen content
e.slow speed of contraction