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19 Cards in this Set
- Front
- Back
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The twitch begins _________ after the muscle action potential because..
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a few milliseconds after the action potential because it takes time for calcium to be released...then it takes time for TnC to become saturated with calcium, and it takes time to overcome the elastic properties of muscle
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What is the most notable elastic element at the sarcomere level?
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titin
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When you first start curling a dumbbell, what causes the isometric contraction (muscle not yet shortened)?
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elastic components (titin and tendons) must first be overcome before you can progress from isometric contraction (no shortening) to isotonic
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How does muscle summation progress as you increase the stimulus frequency?
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more stimulus frequency--less time to relax--stronger tension
single twitch > temporal summation > unfused tetanus > fused tetanus |
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The optimal resting length of a muscle fiber for the most forceful contraction is...
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not too short or not too stretched out (right in the middle)
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The rate of crossbridge cycling (velocity) is maximum at low or high load (force)?
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velocity is at a maximum with 0 force. As load (force) increases, velocity decreases
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Fast twitch fibers: type I or type II?
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Type II
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Slow twitch fibers: type I or type II?
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Type I
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Which has a large tetanic force--fast or slow twitch fibers?
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fast twitch
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What is the difference between type I and type II fibers?
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type II (fast twitch) has higher myosin ATPase activity and a larger cross area (more myofibrils)
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Type II A are __________ fast twitch fibers and Type II B are _________ fast twitch fibers.
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Type II A: fatigue resistant
Type II B: fatigable |
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Type I muscle fibers have how many types?
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only one type I fiber. it is slow to fatigue, slow to contract and has low tetanic force
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What is the backup energy source for skeletal muscles, which requires large amounts of ATP?
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phosphocreatine. creatine kinase transfers a phosphate from phosphocreatine to ADP to form ATP
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Type I and type II A fibers rely on _____________ for energy.
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the citric acid cycle
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Type II B fibers rely on ___________ for energy.
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anaerobic glycolysis
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What type of muscle fibers have a lot of mitochondria, myoglobin and are well supplied with blood vessels?
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type I (slow twitch) and type II A (fast twitch fatigue resistant). These fibers are collectively called "oxidative-glycolytic fibers"
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Oxidative-glycolytic fibers are white or red?
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red. includes type I and type II A
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Which fibers have slow myosin ATPase activity?
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type I
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When the nervous system rotates through motor units to allow some to rest while others are contracting during submaximal sustained force, this is called...
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asynchronous recruitment
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