Pages 187-195. Muscle fiber contraction is “all or none” ◦ There is no “in-between”...
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Transcript of Pages 187-195. Muscle fiber contraction is “all or none” ◦ There is no “in-between”...
![Page 1: Pages 187-195. Muscle fiber contraction is “all or none” ◦ There is no “in-between” contraction Not all fibers may be stimulated at one time Different.](https://reader036.fdocuments.net/reader036/viewer/2022062519/5697bf711a28abf838c7defe/html5/thumbnails/1.jpg)
Pages 187-195
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Muscle fiber contraction is “all or none”◦ There is no “in-between” contraction
Not all fibers may be stimulated at one time
Different combinations of muscle fiber contractions may give differing responses◦ Graded responses= different degrees of
skeletal muscle shortening
© 2015 Pearson Education, Inc.
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Graded responses can be produced by changing:◦ The frequency of muscle stimulation◦ The number of muscle cells being stimulated
(and therefore, recruited) at one time
more fibers= greater muscle tension◦ Muscles can contract until they run out of energy
© 2015 Pearson Education, Inc.
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Adenosine Triphosphate (ATP)◦ Immediate source◦ Stored in muscle fibers in small amounts that are
quickly used up After this initial time, other pathways must be
utilized to produce ATP
© 2015 Pearson Education, Inc.
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1. Direct phosphorylation of ADP ◦ by creatine phosphate
2. Aerobic (cellular) respiration (most ATP)
3. Anaerobic (cellular) respiration◦ glycolysis and lactic acid formation
© 2015 Pearson Education, Inc.
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Muscle cells store CP, a high-energy molecule◦ After ATP is depleted, ADP remains
◦ CP transfers a phosphate group to ADP to regenerate ATP
◦ CP supplies are used up in less than 15 seconds (About 1 ATP is created per CP molecule)
*creatine phosphate is also known as phosphocreatine
© 2015 Pearson Education, Inc.
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Figure 6.10a Methods of regenerating ATP during muscle activity.
(a) Direct phosphorylation
CP
CP ADP
ATPCreatine
Coupled reaction of creatinephosphate (CP) and ADP
Energy source:
Oxygen use:Products:
None 1 ATP per CP,creatine
15 secondsDuration of energy provision:
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– breaks down glucose without oxygen– broken down to pyruvic acid, then to lactic acid– produces about 2 ATP very quickly
– Lactic acid accumulates in the muscles and produces fatigue
– After exercise, the oxygen deficit is repaid by rapid, deep breathing
© 2015 Pearson Education, Inc.
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Figure 6.10b Methods of regenerating ATP during muscle activity.
glucoseEnergy source:
Glycolysis and lactic acidformation
(b) Anaerobic pathway
ATP2
O2
O2
Oxygen use:Products:
Duration of energy provision:
None 2 ATP per glucose,lactic acid
40 seconds, or slightly more
net gain
Releasedto blood
Glucose (fromglycogen breakdown ordelivered from blood)
Pyruvic acid
Lactic acid
Glycolysisin cytosol
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Glucose is broken down to CO2 and H2O
◦ Creates about 32 ATP per glucose molecule◦ occurs in the mitochondria◦ slower reaction, requires continuous oxygen◦ Provides hours of sustained energy
© 2015 Pearson Education, Inc.
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See page 194 for this side-by-side comparison of pathways
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Comparison of pathways
Image source:http://www.udel.edu/chem/C465/senior/fall00/Performance1/phosphocreatine.htm.html
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• Isotonic contractions– Myofilaments slide past each other during
contractions– The muscle shortens, and movement occurs– Example: bending the knee; rotating the arm
• Isometric contractions– Tension in the muscles increases– The muscle doesn’t shorten or produce
movement– Example: pushing against a wall with bent
elbows
© 2015 Pearson Education, Inc.
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Increase in muscle:◦ Size ◦ Strength◦ Endurance ◦ Aerobic (endurance) exercise=
stronger more flexible muscles greater resistance to fatigue
◦ Resistance, or isometric, exercise like weight lifting increases muscle size and strength
© 2015 Pearson Education, Inc.