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22 Cards in this Set
- Front
- Back
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No change in length
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Isometric contraction
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Force production with shortening in length
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Concentric contraction
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-Force production with lengthening m
(lower arm slowly while holding something) |
Eccentric contraction
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What happens when there are tiny tears in the muscle following eccentric contraction?
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activate signals to inc. protein sythesis-->builds muscle msass (hypertrophy)
How? IGF promotes hypertropy & cell fusion |
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Muscle allowed to shorten but maintains a constant force
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isotonic
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Force-length relationship
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Total force developed by a muscle depends on the starting length
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The amount of force produced by a muscle during an isometric contraction depends on the # of cross-bridges formed
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-More overlap, more crossbridges, shorter sarcomere
-Less overlap, fewer crossbridges, longer sarcomere |
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Length-Tension curve
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inc. length-->less overlap so 0 Force
dec. length-->creates interference btw thick & thin filaments-->interfers w/ cross-bridge formation-->dec. force |
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What are some ways to increase the amount of crossbridges formed?
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1. Inc. size/diameter of myofibrils
2. Alter # of myofibrils |
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Force depends on passive properties of the muscle
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Muscle is elastic and will resist stretch even w/o electrical stimulation.
Sources of elasticity: Titin, CT (epi,peri, endo, tendon) |
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Total length-tension curve
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Sum of passive & active components
-Passive: stretching w/o electrical stimulation -Total: F developed when muscle is electrically stimulated -Active: difference between total & passive |
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Torque produced by muscle is greater than Force applied
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In muscles, apply force near joint. This allows for limited shortening with wide displacement
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Torque
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Torque = F x Moment arm
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Distance btw joint pivot & where it perpendicularly meets the muscle
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Moment arm
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The max moment arm
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at 90 degrees & declines with greater flexion/extension
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What happens when the moment are is less
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The amount of torque dec.-->so need to produce more force to hold weight
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If put muscle at the optimal position...
If put muscle at a mechanical disadvantage (fully extended) |
The muscle weakness may be masked
Moment are small-->torque less |
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Length-velocity relationship
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Greater the load, the slower the shortening velocity
Faster the rate of cross bridge cycling, the faster the rate of shortening (myosin ATPase) Opposing load slows down crossbridge cycling |
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Speed
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How quickly muscle shortens depends on the kind of myosin & how heavy load is
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When does a muscle shorten?
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After it develops a force that is equal to the external load
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Force-velocity curve
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Vmax: max shortening velocity, no load
Fmax: eccentric contraction, peak isometric force (no shortening), 0 velocity, 0 shortening |
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What type of contractions are a common mechanism for braking movement at a joint?
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Eccentric contractions
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