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Mechanics of Single Fiber Contraction I

How does fatigue affect muscle contraction? Muscle fibers contract in response to neural stimulation and then relax. If stimuli are applied in rapid succession then the fiber will contract further and remain contracted as long as the stimulation is supplied. In this way a muscle will remain contracted for long periods. Muscle fatigue is the loss of ability to contract after extended periods of contraction. Different types of fibers vary in their resistance to fatigue. Endurance training encourages the development of fibers that are resistant to fatigue.

View the animation below, then complete the quiz to test your knowledge of the concept.






1During twitch summation...
A)a muscle fiber under continuous stimulation and contraction becomes unable to contract at all until it has rested.
B)muscle fiber stimulations are such that muscle fibers are able to contract and then completely relax before the next contraction.
C)the stimuli arrive at the muscle fiber so rapidly that there is no muscle relaxation between stimuli, but rather, a continuous contraction of the muscle fiber.
D)the stimuli arrive at the muscle fiber at such a rate that the muscle fiber is unable to completely relax between stimuli, and sequential contractions exhibit an equal contractive force that is greater than when the muscle fiber is allowed to rest completely.
E)a second stimulus arrives at the muscle before complete relaxation of the first contraction, causing the second contraction to have greater tension than the first one.



2During fused tetanus...
A)a muscle fiber under continuous stimulation and contraction becomes unable to contract at all until it has rested.
B)muscle fiber stimulations are such that muscle fibers are able to contract and then completely relax before the next contraction.
C)the stimuli arrive at the muscle fiber so rapidly that there is no muscle relaxation between stimuli, but rather, a continuous contraction of the muscle fiber.
D)the stimuli arrive at the muscle fiber at such a rate that the muscle fiber is unable to completely relax between stimuli, and sequential contractions exhibit an equal contractive force that is greater than when the muscle fiber is allowed to rest completely.
E)a second stimulus arrives at the muscle before complete relaxation of the first contraction, causing the second contraction to have greater tension than the first one.



3During unfused tetanus...
A)a muscle fiber under continuous stimulation and contraction becomes unable to contract at all until it has rested.
B)muscle fiber stimulations are such that muscle fibers are able to contract and then completely relax before the next contraction.
C)the stimuli arrive at the muscle fiber so rapidly that there is no muscle relaxation between stimuli, but rather, a continuous contraction of the muscle fiber.
D)the stimuli arrive at the muscle fiber at such a rate that the muscle fiber is unable to completely relax between stimuli, and sequential contractions exhibit an equal contractive force that is greater than when the muscle fiber is allowed to rest completely.
E)a second stimulus arrives at the muscle before complete relaxation of the first contraction, causing the second contraction to have greater tension than the first one.



4A complete muscle contraction is called a muscle twitch.
A)True
B)False



5A short rest period after a muscle fiber experiences fatigue will allow that muscle fiber to contract again equally as long as it did before the fatigue.
A)True
B)False







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