Mader Chapter 7
1-5 on page 133
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Skeletal – voluntary (attached to skeleton)
Cardiac – involuntary (heart)
Smooth – involuntary (walls of hollow
internal organs)
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Produce movement – picking up an object
Resist movement – posture, blood pressure
(Newton’s 3rd Law: muscles generate a force
(static tension) that exactly opposes and
equal but opposite force being applied to a
body part
Generate heat – contraction of our muscles
accounts for > 75% of all heat generated by
the body – shivering thermogenesis
Stabilizing joints – stabilize & strengthen
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A group of many individual cells, all w/same
origin and insertion and all with the same
function (p. 115)
Arranged in bundles called fascicles
Each bundle is enclosed in a sheath of fibrous
connective tissue called fascia
Each fascicle contains 12 to 1000s of individual
muscle cells – called muscle fibers
The outer surface of the whole muscle is covered
with several more layers of fascia – at the ends
all come together forming tendons
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Tube shaped 3 cm – 30 cm (thigh)
Can contain more than one nucleus just
under the cell membrane (skeletal)
Nearly entire cell is packed with long
cylindrical structures in parallel called
myofibrils
Myofibrils are packed with contractile
proteins called actin and myosin
When myofibrils contract the muscle cell also
contracts
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Each skeletal muscle fiber is a long, cylindrical
cell w/multiple oval nuclei just beneath the
sarcolemma (plasma membrane) surface
Fibers are large, 10 to 100 m in diameter,
and up to hundreds of centimeters long
Sarcoplasm, similar to cytoplasm of other
cells, but has numerous glycosomes
(=organelle full of glycogen) and a unique
oxygen-binding protein called myoglobin,
similar to hemoglobin
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A single myofibril within one muscle cell (in
your biceps) can contain > 100,000
sarcomeres arranged end to end.
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100,000 sarcomeres all shortening at once
produces a muscle contraction
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Understanding muscle shortening is simply
understanding how a single sarcomere works
From Z to shining Z
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2 kinds of proteins
Myosin – thick filaments interspersed @
regular intervals with a different protein
Actin – thin filaments that are structurally
linked to the Z-line
Myosin filaments are completely contained
within the sarcomere
Muscle contractions depend on the
interaction of these 2 filaments
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Nerves activate skeletal muscles
Activation releases calcium
Calcium starts the sliding filament
mechanism
Contraction ends when nerve activation ends
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Sliding filament model of contraction
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http://video.google.com/videosearch?ndsp=1
8&um=1&hl=en&q=sliding%20filament%20of
%20contraction&ie=UTF-8&sa=N&tab=iv#
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grants.hhp.coe.uh.edu/clayne/6397/Unit3.ht
m
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Lots of mitochondria form ATP by aerobic
cellular respiration
Muscles contain creatine phosphate (high E
storage supply) used to regenerate ATP
indirectly
ATP produced anaerobically when oxygen
supply is limited
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Continued intake of oxygen (panting) to
complete the metabolism of lactic acid (built
up anaerobically)
Lactic acid is transported to the liver and
broken down into carbon dioxide and water