1. True or False: The primary reason for muscle fatigue is the buildup of Ca2+ ions in the muscle fiber.
A skeletal muscle fiber is said to be fatigued when it can no longer contract despite continued neural stimulation. The cause of muscle fatigue varies with the level of muscle activity. After short peak levels of activity, such as running a 100-meter dash, fatigue may result from the exhaustion of ATP and CP reserves or from the drop in pH that accompanies the buildup of lactic acid. After prolonged exertion, such as running a marathon, fatigue may involve physical damage to the sarcoplasmic reticulum that interferes with the regulation of intracellular Ca2+ concentrations. Muscle fatigue is cumulative--the effects become more pronounced as more muscle fibers are affected. The result is a gradual reduction in the capabilities of the entire skeletal muscle.
2. If an intervening rest period is imposed on active muscle,
a. it will then be able to generate much more force.
b. the development of fatigue will be delayed. c. muscle hypertrophy can be prevented.
d. muscle atrophy can be prevented.
In a resting skeletal muscle, the demand for ATP is low. More than enough oxygen is available for the mitochondria to meet that demand, and they produce a surplus of ATP. The extra ATP is used to build up reserves of CP and glycogen. Resting muscle fibers absorb fatty acids and glucose that are delivered by the bloodstream. The fatty acids are broken down in the mitochondria, and the ATP generated is used to convert creatine to creatine phosphate and glucose to glycogen.
Quick Reply
