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MUSCLE STRUCTURE AND PHYSIOLOGY
J. Rosenbluth, April 2009
MUSCLE
• Skeletal muscle
– Contraction mechanism
– Excitation-contraction coupling
• Gross properties of skeletal muscle
• Cardiac, obliquely striated and smooth
muscles
• Pathology/Clinical examples
Skeletal muscle band pattern
Double “antiparallel” array of
myofilamnts (H.E.Huxley)
Sliding filament model
Myosin molecules
Myosin filament formation
Low-angle X-ray diffraction of
skeletal muscle (meridional pattern)
Actin double helix
Decorated F-actin
Decorated F-actin
attached to Z-disc
Double hexagonal array
(vertebrate skeletal muscle)
Low-angle X-ray diffraction of
skeletal muscle (equatorial pattern)
Crossbridge position during relaxation
(top) vs contraction (bottom)
Cross-bridge Cycle
– Attached
– Released
– Cocked
– Force generating
– Attached
Focal contraction
(amphibian skeletal muscle)
Triads (amphibian)
Skeletal muscle triad (amphibian)
Triad model
(Franzini-Armstrong, C.)
Actin filament with Tr and Tm
Tropomyosin movement
Pennate Muscles
Length-Tension
Relationship
Load-Velocity Relationship
Twitch vs Tetanic Tension
Cat Gastrocmenius
Muscles Have Heterogenous Properties
Twitch Contractions
Skeletal Muscle Fatigue
Cardiac muscle
Obliquely striated muscle
(Ascaris), stretched
Ascaris obliquely striated muscle
Smooth muscle
(“Myoelastic tissue”)
Smooth muscle (cross section)
Smooth muscle
(Science 148:1337-1339)
Smooth muscle
ABRM
ABRM
“Pseudohypertrophy”
(Duchenne dystrophy)
Charcot-Marie-Tooth disease
Spinal muscular atrophy