Term
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Definition
| Minimal strength stimuli required to initiate contraction |
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Term
Periods of Muscle Twitch
(Force over Time curve) |
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Definition
Latent Phase(impulse travel; ca++ release)
Contraction
Relaxation |
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Term
| Summation/Twitch types (3 types) |
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Definition
Complete relaxation between twitches
Wave summation: incomplete tetanus (partial relaxation)
Complete tetanus (increasing strength w/ each successive twitch; no relaxation. Sustained or Tetanic contraction). Most common in muscles. |
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Term
Recruitment
~
Multiple Motor Unit Summation |
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Definition
Motor axons connect to mx muscle fibers; fewer fibers per axon=greater control (such as eye); more fibers per axon associated with larger muscles.
~
As intensity of stimulation increases, additional motor units are 'recruited' for action, until all available are at work. |
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Term
| Asynchronous Motor Summation |
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Definition
| Different sets of muscle fibers stimulated so that they may be alternated ('relay team'); see graph in notes. If properly timed, force level is maintained throughout use of alternating muscle units. |
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Term
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Definition
| Sustained contraction, essentially. Associated with collapse upon loss of consciousness. |
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Term
| Optimal contraction length |
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Definition
| Not overly compressed or extended (think of sarcomere). |
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Term
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Definition
| Lactic Acid buildup, damage to muscle fibers. |
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Term
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Definition
| Muscle Twitches develop same force per twitch, however in a whole muscle, not all fibers are stimulated at once, and the frequency of impulses regulates strength. |
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Term
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Definition
| Slow; Red (myoglobin); Always oxidative/aerobic, fatigue resistant. More mitochondria |
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Term
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Definition
Fast, White (less vascular), less mitochondira and respiratory capacity. Greater SR, faster ATPase, rapid contraction.
Either Glycotic (fatigue-able due to lactic acid buildup and ATP supply)
OR
Oxidative (fatigue resistant). |
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Term
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Definition
| Intermediate; fast(er) and w/ moderate oxidative capacity. |
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Term
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Definition
All muscles have combined fiber types, but in different proportions reflecting specialized functions.
***Long distance runners up to 90% Type I |
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Term
| Muscle Use and Disuse; Hypertrophy + Atrophy |
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Definition
Hypertrophy: forcefully exercised, enlargement due to additional filaments but no new muscle fibers.
Atrophy: Disuse, muscles shrink. Mitochondria levels drop, capillary networks/respiratory capacity diminished. Can shrink 50% in size in few months. |
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