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Biomechanics
CH 6 Biomechanics of skeletal muscle
| Question | Answer |
|---|---|
| What are the 4 principle characteristics of muscle tissue? | Excitability, Contractility, Extensibility, Elasticity |
| Excitability | Ability to receive an respond to a stimulus |
| Contractilty (irritability) | ability of a muscle to contract and produce a force |
| Extensibility | ability of a muscle to be stretched without tissue damage |
| Elasticity | ability of a muscle to return to its original shape after shortening or extension |
| How many muscle fibers make up one cell? | 1 |
| How long is an individual muscle fiber? | 1mm to 600mm |
| What determines strength? | Muscle fiber diameter |
| Why is muscle fiber important? | influences fiber contraction and muscle shortening |
| What is muscle connective tissue? | allows for structural support and force transmission |
| 3 layers of Connective Tissue? | Epimysium, Perimysium, Endomysium |
| Epimysium | Wraps entire muscle; tough outer coat |
| Perimysium | Wraps fascicles; provided pathway for major blood vessels and nerves |
| Endomysium | Wraps fibers |
| Satellite cells | -involved in muscle repair -stimulate during muscle training |
| Where is the satellite cell located? | between plasmalemma and basement membrane |
| Muscle repair steps | 1. injuried muscle fiber 2. proliferation & migration of satellite 3. fusion of myoblasts 4. myofibrilar synthesis & assembly 5. Regenerated muscke fiber 6. Become nucleli |
| Sarcolemma | sheath around the fibers of skeletal muscle |
| Sarcoplasmic reticulum | specialized type of smooth Endoplasmic reticulum that regulates the calcium |
| Transverse Tubule (T-tubules) | extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells. |
| Myofibrils | Units responsible for contraction & relaxation |
| How many myofibrils are in 1 muscle fiber? | thousands (1000-8000) |
| What happens when a muscle grows? | myofibrils increases |
| Thick filaments | -myosin -A-Band |
| Thin filaments | -actin -I-Band |
| I-band | light colored |
| A-band | Dark color |
| Z-line | -The support of the thin filament -line between the I-band |
| M-line | -The support of the thick filament -line between the A-band |
| Does the I-band shorten? | No, it slide past |
| Why doesn't myosin pull at the same time? | they lose force |
| H-zone | Thick filament where there is no overlap of actin |
| How is force generated? | by a muscle fiber that is directly proportional to the # of myosin cross-bridges that are strongly bound to the actin filament |
| What allows the cross-bridges to attach to the actin? (on-off switch) | Calcium and troponin |
| What causes the sacrolemma to have an action potential? | Synaptic clef |
| Excitation-contraction coupling | t-system signals the release of calcium on-off switch |
| How does a muscle contract & relaxation | 1.Generated action potential 2.Release ACh from presynaptic nerve terminal 3.Binding ACh on muscle fiber 4.Depolarization of sarcolemma 5.Action potential through T-tubules 6.Signaling SR to release calcium 7.Calcium bind to troponin |
| How does a muscle contract & relaxation(2) | 8. tropomyosin exposes binding sites 9.Actin-myosin interaction 10.Pumping calcium back into SR 11.Troponin.Tropomyosin takes back actin/myosin 12.Muscle relaxation |
| Innervation Ratio | # of muscle fibers for that motor neuron 1 motor neuron : # of fiber muscles |
| Why does fast twitching reach peak force faster than slow twitch? | Calcium pumps in the SR with faster isoforms |
| Sedentary people | 50% slow 50% fast where athletes may differ |
| How to change type IIX -> IIA | both strength training & endurance |
| how to change type IIA -> I | extensive endurance training |
| Agonist | acts to cause a movement |
| Antagonist | acts to slow or stop movement |
| Stabilizer | acts to stabilize a body part against some other force |
| Neutralizer | acts to eliminate an unwanted action produced by an agonist |
| Synergist | acts to perform the same action as another muscle |
| When muscles work as agonist, what type of contraction? | Concentric (against resistance) |
| What are the types of contractions? | concentric, eccentric, isometric |
| Concentric | shortening (against) |
| Eccentric | lengthening (with) |
| Isometric | no lengthening |
Created by:
rmart11
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