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7 Cards in this Set
- Front
- Back
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Three properties of a muscle that is concerning us in this chapter |
Excitability- respond to chemicals released from nerve cells Conductivity- ability to propagate electrical signals over membrane Contractility - ability to shorten and generate force |
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Describe the five stages of muscle contractions |
Nerve impulses reaches an axon terminal & synaptic vesicles release acetylcholine ACh diffuses to receptors on the sarcolemma and Na+ channels open and Na+ rushes to cell A muscle action potential spreads over sarcolemma and down transverse tubules SR releases Ca+2 into sarcoplasm Ca+2 binds to troponin and causes troponin- tropomyosin complex to move and reveal myosin binding sites an actin the contraction cycle begins |
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Describe what happens to filaments of muscle |
Myosin cross bridges pull on thin filaments Thin filaments slide inward Z Discs come toward each other Sarcomeres shorten the muscle fiber shorten the muscle shortens |
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Force of muscle contraction depends on the length of the sarcomere Too stretched = Too contracted = |
Too stretched = less over lap less cross bridges Too contracted = good overlap but Z-discs crumpled myosin heads z discs block this process - wrist flexors making a fist |
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If the force generated by the muscle is greater than the external force = |
Concentric |
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If the force generated by the muscle is equal to the external force = |
Isometric |
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If the force generated by the muscle is less that the external force = |
Eccentric |
