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