Download Muscle architectures

Muscle architectures
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Prof. Maarja Kruusmaa
Tallinna Tehnikaülikool
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Bones
Are composite materials
Type I collagen
Mineral (calcium)
Mineralisation level 60-70%
Bone is rigid supportive
material
But still capable of deforming
(ca 1%)
Safety factor 3-5%
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Elasticity and Strength of Bone
Stress-strain curve similar to
engineering materials
Stress is small, Cauchy tensor
1 ⎛ ∂ui ∂u j ⎞
⎟
ε ij = ⎜⎜
+
2 ⎝ ∂x j ∂x i ⎟⎠
σ = Eε
€
€
http://www.pt.ntu.edu.tw/hmchai/BM03/BMmaterial/Bone.htm
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Anisotropic behaviour of the Bone
http://www.pt.ntu.edu.tw/hmchai/BM03/BMmaterial/Bone.htm
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Ligaments and tendons
Tendon connects muscle to bone
transmit forces from muscle to bone
Ligaments connect bone to bone
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Skeletons
Transmit forces to the external
environment
Support body weight
Protect delicate organs
Cartalige provide low friction
movement and effective load
transfer across the ends of the
bones
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Muscles and bones as lever systems
OpenStax College. Forces and Torques in Muscles and Joints, OpenStax CNX Web site
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http://www.iscuo.org/timothyhebert/science/biol2n10.htm
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Muscle architecture
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Twitch fibers and tonic fibers
White muscles
(twitch fibers) simulated by large
nerve cells Contract rapidly Give
quick, sharp strong contractions
Fast fatigue
Red muscles (tonic muscles)
simulated by thin slow nerve cells
Contract slowly, don’t’ relax
between stimulus
Resist fatigue
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Twitch fibers and tonic fibers
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Positive and negative work
Shortening muscle does
positive work
Stretching muscle does
negative work
Concentric contraction occurs
when a load is lifted and the
muscles involved shorten.
Positive work occurs at
contraction, when the product
of the muscle moment arm and
the angular velocity are
positive.
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Eccentric and Concentric Contraction
Negative work occurs when the
product of the muscle moment
arm and the angular velocity
are negative.
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3 ways of getting out force
Developing tension while
shortening
Developing tension against an
immovable load (not
shortening)
Developing tension while
getting stretched
S.Vogel, Prime mover
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Muscle work loops
http://0-jap.physiology.org.library.pcc.edu/content/107/4/1156/F1.expansion
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Agonistic – antagonistic pairs
Most of muscles work in pairs
When one muscle lengthens the
other shortens
When one does positive work
the other does negative work
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Endoskeletons – internal skeletons
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Exoskeletons external skeletons
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Robotic exoskeleton
HAL, Tsukuba University www.biorobotics.ttu.ee
Hydrostatic structures
http://labs.bio.unc.edu/Kier/research.html
http://jeb.biologists.org/content/215/8/1247/F8.expansion.html
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Hydrostatic skeleton
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Hand tools
Muscles amplify distance
Hand tools amplify force
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