Muscle_Figs_BW

Muscle_Figs_BW - rate of change in length. Properties Used...

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Skeletal Muscle Structure -1 Muscle Fascicle Fiber Myofibril T-tubules Sarcoplasmic reticulum z-disk Fig. 12-3 a,b
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Skeletal Muscle Structure - 2 Fig. 12-3 c-f
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Skeletal Muscle Structure - 3 0 Fig. 12-8
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Cross-Bridge Cycling 1 2 3 4 5 6 ATP Ca 2+- depen- dent step Actin Myosin
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0 Muscle fiber Schwann cell nAChR Acetylcholine (ACh) α -motor neuron Na channels Neuromuscular Junction I Na (+I Ca ) exceed I K ACh opens a non-specific cation channel Large EPSP (Endplate Potential)
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Excitation- Contraction Coupling cytosol lumen of t-tubule lumen of SR dihydropyridine receptor Ca 2+ -release channel (ryanodine receptor) Ca 2+ ATPase + + + + - - - - Ca 2+ Ca 2+ 0 The Triad Junction t tubule SR SR T-tubules Sarcoplasmic reticulum (SR)
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How Ca 2+ Triggers Contraction Relaxed 10 -8 M Ca 2+ Cycling > 10 -7 M Ca 2+
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Force-Length Relationship Length Force L o Experiment: Fix muscle at various lengths, measure force produced.
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Force - Velocity Relationship + (Shortening) Velocity - (Lengthening) Load (force) F 0 = maximum force developed V 0 = maximum velocity of shortening 0 Experiment: Apply a fixed load to the muscle, measure
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Unformatted text preview: rate of change in length. Properties Used to Classify Muscle Fibers 1. Whether ion channels in sarcolemma allow action potentials (all-or-none twitch) or not (graded or tonic contractions). 2. Rate of cross-bridge detachment during contraction, related to ATPase activity of myosin isoform. Determines V . 3. Number of Ca 2+-pumps in SR, determines rate of relaxation. - #2 and #3 together determine twitch duration -4. Number of mitochondria and capillary density, which determine capacity for oxidative phosphorylation and fatigue resistance. Motor Units Picture 5 Type IIa/FR IIb/FF I/S Fatigue Muscle Unit Moto-neuron Twitch Motoneuron Action Potentials Should show more fibers How the Brain Controls the Motor Pool +-Asynchronous Activation Smoothes Contractions Unfused Tetanus of a Single Motor Unit Smooth Contraction of Many Motor Units Force...
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This note was uploaded on 05/03/2010 for the course BISC 307L taught by Professor Herrera during the Spring '08 term at USC.

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Muscle_Figs_BW - rate of change in length. Properties Used...

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