IPHY 3430 3-31-11

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IPHY 3430 3-31-11
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Skeletal Muscle MetabolismUse of ATP1. Provide
power stroke of myosin2. Binding causes
detachment of cross bridge on myosin and actin
cross bridge binding site3. Active transport of
Ca into vesicles4. Action potential of muscle
membrane
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Skeletal Muscle MetabolismTemporal variation in
supply of ATP as exercise starts 1. Creatine
phosphate2. Aerobic ATP production myoglobin
donates O23. Glycolysis with lactic acid
formation
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FatigueMuscle fatigue 1) depletion of
glycogen (more low intensity) 2) accumulation
of lactic acid 3) conduction failure (K
buildup) 4) Inhibition of cross-bridge
cyclingCentral fatigue 1) brain no longer
adequately activates motor neurons
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Muscle Fiber Types Slow oxidative Fast
oxidative Fast glycolyticmyosinATPase
low high highcontrct. speed
slow fast fastfatigue resist.
high intermed. Lowoxidative phos.
activity high high lowglycolytic
activ. low intermed highmitochondria
high high lowmyoglobin high
high lowglycogen content
low intermed. Highblood
supply high high
low
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Muscle fiber types of world-class
athletesEvent slow twitch glycolytic
oxidativelong dist. 64.4 764 16.6800
m 51.9 868 14.8100 m 24.0 1287
12.9shotput 37.7 1058 4.3couch pot.
52.6 822 7.4
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Other muscle fiber dataAnimal high
oxidative low oxidativeQuarter horse 7
93heavy hunter 31
69greyhound 3 97mongrel
31 69hummingbird 100 0turkey
1 99
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Training EffectsAerobic? vascularity, FA
oxidative capacity, mitochondria, triglyceride
storage, ? lactate dehydrogenase
activityStrength ? diameter of fast,
glycolytic fibers, myosin and actin, and in
number of cells5 mo weight training --gt 11 ?
circumf., 28 ? in strength5 mo
immobiliz.--gt ? 5 circumf., 35 ? strength
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Smooth Muscle differs from skeletalactin,
myosin and intermediate filaments that serve
as cytoskeletoncan be stretched very much and
still contract actin lacks troponin, has
tropomyosinmyosin must be phosphorylated
arrangement of actin and myosin differs slow
contraction, can remain contracted for very
long periods of timemost cells myogenic, but
also some can be stimulated by PNS
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Skeletal, cardiac and smoothall use ATPall
have actin and myosinCa plays some role in
contraction initiationbut...
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Skeletal Cardiac Smoothinnervation
motor PNS, SNS PNScontr. initiat.
neurogenic myogenic bothCa source
sarcopls. ret. xtracell. xtracell.T tubules
yes yes no