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KIN 3600
lec 20
| Question | Answer |
|---|---|
| Excitation – contraction | Excitation of muscle coupled with concentration by regulation of sarcoplasmic Ca++ concentration |
| Coupling agent | Calcium |
| Since the release of calcium is faster than the reuptake | muscle shortening is faster than the relaxation |
| Rate of increase calcium comes in the cell faster than | the rate of decrease calcium leaving the cell |
| High calcium = | Continuous contraction |
| Recycle contractions cycle | Resting state -Cocked & Energy used (Ca++) Stimulation -Ca++ release from SR Formation - Strong bond Power stroke - Release ADP Cross bridge completion - ATP binds to bridge & Form weak bond Resting state - Re-cocked & Ca++ back to SR |
| Muscle Twitch | - 1 twitch = 1 single contraction - Short stimulation |
| 3 phases of muscle twitch | 1. latent period 2. contraction phase 3. relaxation phase |
| PHASE 1 | - Latent Period (Electromechanical delay) - 5ms - Stimulated but did not respond |
| PHASE 2 | - Contraction phase - (40ms) |
| PHASE 3 | - Relaxation phase - (50ms) - Longer |
| Refractory period | - 5ms - Muscle does not respond to simulation |
| Why do muscles contract faster than the relaxation phase? | Ca++ influx is faster than the outflux |
| Muscles responsible for fast movements | Short twitch time |
| Muscles responsible for slow movements | Long twitch time |
| Twitch Summation | stimulation of muscle fiber before the completion of previous twitch results in a stronger contraction - Ca++ is being pumped & pumped |
| Underlying mechanism of Twitch Summation | - Pre-stretching of SEC by the first twitch - Not enough time available to pump all Ca++ back to SR & Out of the cell – resulting progressive increase in sarcoplasmic Ca++ concentration |
| Wave summation | Progressive ^ sarcoplasmic Ca++ without all getting pumped back into SR |
| Fused tetanus | - Continuous contraction with no relation - No change in sarcoplasmic & Ca++ concentration |
| All in-vivo muscular contractions | are tetanic contraction |
| Treppe Effect | Stimulate muscle with low energy frequencies not to cause tetanic contraction (5Hz) |
| Treppe Effect responds by | - Progressive increment in tension for up to 30-40 contractions - Failure to relax completely |
| Treppe Effect caused by | - ^ Na+ & K+ concentration or sarcoplasm, ^ rate of ca++ release of SR - Progressive influx of Ca++ into the cell - Lack of time available to pump the Ca++ back into the SR & out of the cell |
| Types of muscle fibers | -Slow Twitch Oxidative (ST, SO, R) or Type I -Fast twitch oxidative – Glycolytic (FOG) or Type IIA -Fast twitch glycolytic (FT, FG) or Type IIX or Type IIB (rats) |
| The main characteristics of Type IIX fibers | -High contractile speed (2-3 times faster than ST) -High activity of myosin (ATPase, CPK, & Anaerobic Glycolytic enzymes) -Larger diameter -High maximal tension (2-3x higher than ST) -High capacity for anaerobic glycogenolysis -SR network |
| Calculation of Specific Tension | cross-sectional area / Force produced |
Created by:
rmart11
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