71.Fatigue the failure of a muscle fiber to maintain ____ : 1417087
71.Fatigue is the failure of a muscle fiber to maintain ____ as a result of previous contractile activity.
72.Muscular fatigue can be caused by
a.lactic acid accumulation
b.depletion of ATP
c.depletion of ACh
d.only two of the above
e.a, b, or c
73.Which of the following does not directly influence motor neurons?
a.primary motor cortex
d.afferent neurons (through intervening interneurons)
e.None of the above
74.When a muscle atrophies, its muscle fibers
b.decreases in mass and becomes weaker
c.increase in diameter
d.undergo mitotic cell division
e.dissolve and are replaced by fibrous scar tissue
75.In the body's lever systems, the fulcrums are represented by the
76.With the type of lever system exemplified by flexion of the elbow joint, when an object is held in the hand, the
a.power arm of the lever is the distance between the elbow joint and the insertion of the biceps muscle
b.load arm of the lever is the distance between the elbow joint and the hand
c.velocity and distance moved by the hand is amplified at the expense of the biceps muscle having to exert considerably greater force than the actual load that is moved
d.answers a, b, and c are correct
e.answers a and b are the only correct answers
77.Which statement below is characteristic of most of the body's lever systems?
a.They work at mechanical advantage.
b.They work at a mechanical disadvantage.
c.Muscles must exert greater forces than the load.
d.Both a and b
e.Both b and c
78.Enlargement of muscle due to weight lifting is primarily a result of
a.enlargement of individual myofilaments
c.increased production of actin and myosin
d.increases in the number of cells
e.Both b and d
79.The corticospinal system
a.consists of fibers originating in the primary motor cortex and terminating on motor neurons
b.involves the motor regions of the cortex, cerebellum, basal nuclei, and thalamus
c.is primarily concerned with regulation of body posture
d.has characteristics a and b
e.has characteristics b and c
80.Conscious initiation of muscle contraction is controlled by
a.the spinal cord
b.the brain stem
c.the cerebral cortex
e.none of the above