1. Structure of Skeletal Muscle (Chapter 13; pp. 369-371)
Jennifer Howard
March 22, 2006

2. Skeletal Muscle Cells Aka: muscle fibers, myofibers, myocytes
Multinucleate
long, spindle-shaped
Sarcoplasm
Sarcolemma
0.1cm to 30cm
Diameter:
0.001cm to
0.01 cm

3. Muscle Contents
fasicles = packages of muscle cells
myofibrils contain myofilaments (protein chains) – actin and myosin = responsible for muscle contraction

4. Myosin Regulatory Light Chain (RLC) Essential Light Chain (ELC)
Myosin = hexameric protein with 2 heavy chains + 2 pairs of different light chains
Regulatory Light Chain (RLC)
Essential Light Chain (ELC)

5. Actin tropomyosin, troponin
actin (F-actin, filamentous actin) = 2 intertwined chains of G-actin (globular)
tropomyosin, troponin

6. Muscle Contraction and Relaxation
Nerve impulse  Ca2+ binds to troponin  myosin binding sites on actin unblocked  myosin heads bind to actin (ATP  ADP + Pi)  myosin pulls actin (contraction)
Action is coordinated in all myofilaments of the myofiber and the muscle contracts as one unit
Ca2+ carried away  myosin-actin linkage loosens  troponin and tropomyosin block actin binding sites  actin and myosin return to original positions

7. References
Pasternak, J.J. An Introduction to Human Molecular Genetics (2nd Edition). Hoboken: John Wiley & Sons, Inc., pp
accessed on 19 March
accessed on 19 March. 2006