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41 Cards in this Set
- Front
- Back
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Motor Unit |
Motor neuron and the muscle fibre it innervates *Smallest amount of muscle that can be activated voluntarily |
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What is coordinated largely by nervous system |
Gradation of force in skeletal muscle |
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What is the most important means of controlling muscle tension |
Recruitment of motor units |
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All fibres in motor unit contract... |
Simultaneously |
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To increase muscle force, you can.. |
Recruit more motor units Increase frequency |
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Every AP that enters the postsynaptic cell is going to produce an |
Endplate potential |
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Neuromuscular junction steps |
1. Transmitter synthesized & stored in vesicles 2. AP reaches synaptic terminal 3. Depolarization - opening voltage gated Ca+ 4. Influx of Ca2+ through Ca+ channels 5. Ca2+ causes vesicles to fuse with membrane 6. Retrieval of vesicular membrane from PM 7. Transmitter released into cleft - exocytosis 8. Transmitter binds to receptor molecules 9. Open/Close of postsynaptic channels 10. Postsynaptic current causes excitatory/inhibitory potential that changes excitability of postsynaptic cell |
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Clostridium botulinum toxin |
Affects docking of vesicles so less ACh released |
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Curare/M.gravis |
Binds to ACh nicotinic receptors so blocks ACh induced muscle contraction |
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Neostigmine |
Inhibits Acetyl cholinesterase, leaving more ACh in cleft, counteracting effects of ACh reducing agents |
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Downer cows and ACh |
Decreases ACh release: hypthermia, weak pulse, decreased rumen contraction |
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Excitation-Contraction coupling steps *Depolarization of motor end-plate is coupled to muscle contraction |
1. AP propagates along sarcolemma and down T-Tubules 2. Depolarization changes DHP receptor in T-tubule 3. DHP opens linked to opening of Ryanodine receptor on SR 4. Ca2+ released from SR 5. Ca2+ binds to troponin 6. Formation of cross-bridges (myosin-actin) 7. Ca2+ removed and sequestered in SR 8. Tropomyosin block restored - contraction ends |
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DHP |
Dihydropyridine receptor |
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DHP in skeletal vs cardiac muscle |
Skeletal: Voltage sensitive Cardiac: Ca2+ channels |
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Formation of Cross-Bridges |
Myosin (ADP and Pi) and Actin |
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Power stroke |
Pi released to cause power stroke then: -Myosin head tilts toward M line -ADP released -Actin pulled to M line (Sliding filament) -Myosin head detaches from actin with ATP binding |
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Factors affecting skeletal muscle contraction |
Muscle length and tension Energy Supply |
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Muscle is... |
Plastic |
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Muscle is plastic, means... |
Muscle adapts to meet habitual level of demand placed on it |
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Isotonic contraction |
Muscle length shortened when tensed/force generated |
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Isometric contraction |
Muscle length constant when tensed |
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Types of isotonic contraction |
Concentric Eccentric |
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Concentric muscle contraction |
Decrease muscle length |
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Eccentric muscle contraction |
Increase muscle length (tension developed is less than load on muscle) |
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Eccentric muscle activity occurs at what point in gait phases? |
E2 phase (the yield) |
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Muscle twitch phases |
Latent phase Contraction phase Relaxation phase |
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Latent phase |
Time from stimulus to contraction *due to time it takes for AP to travel down T-tubules and release Ca from SR |
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Contraction phase |
Binding of actin to myosin |
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Relaxation phase |
Ca being sequestered back into SR |
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Treppe |
Muscle stimulated 2nd time immediately after relaxation phase of 1st twitch |
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Treppe results in |
Increase in tensions due to gradual increase in Ca2+ because Ca2+ pumps in SR are unable to sequester all Ca between twitches |
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Summation |
Wave summation Multiple motor unit summation (recruitment) |
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Wave summation |
2nd stimulus occurs before complete relaxation and causes greater tension because it is superimposed on an already contracted muscle |
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Wave summation results in |
Smooth, continuous muscle contraction |
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Multiple motor unit summation |
If more force required, more and larger motor units are recruited to increase tension |
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Incomplete tetanus |
Individual twitches are distinguishable |
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Complete tetanus |
Individual twitches indistinguishable because of high frequency of stimulations *No relaxation phase tension |
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Energy Metabolism in muscle - types |
Creatinine Phosphate (anaerobic) Glycolysis (anaerobic) Oxidative Metabolism (TCA cycle & Oxidative phosphorylation) |
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Creatine phosphate |
1. Excess energy stored as creatine phosphate 2. Creatine kinase: enzyme for rapid ATP generation 3. ATP and Creatine Posphate - enough for 10-15 seconds |
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GLycolysis |
1. 2 ATP molecules/glucose - enough for 2 mins 2. Type 2B fibres 3. Glycogen about 1% of muscle weight |
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Oxidative metabolism |
1. 36 ATP molecules/glucose 2. Type 1 fibres 3. Lipids - prolonged, endurance training |
