1. Arrangement of a Muscle
Muscle  Fascicle  Muscle Fiber (cell)  Myofibril Myofilaments (thick/thin)

2. Muscle Fiber [cell] structure
up to .5 meter long yet only .1 mm in thickness
multinucleated (several nuclei)
Sarcolemma – the membrane around a muscle fiber
Sarcoplasm – the cytoplasm of a muscle cell
Myofibril – parallel cords of protein, several make up a muscle fiber
Sarcoplasmic Reticulum – Lattice-like network surrounding each myofibril [ Ca+ storage]
Cisterns – larger tubules of the sarcoplasmic reticulum;
2 cisternae, along with a Transverse (T) Tubule form what is known as the triad
T-Tubule – has openings that lead in from the sarcolemma surface

4. Myofibril
Parallel cords of protein, several make up a muscle fiber

5. Composition of a Myofibril
2 Types of Myofilaments:
MYOSIN- thick filament protein
ACTIN- thin filament /3 proteins [actin, troponin and tropomyosin]

7. SARCOMERE: structural and functional unit of the myofibril/ contractile unit of skeletal muscle
Composed of Actin and Myosin
Located between 2 Z Lines

8. Parts of the Sarcomere A-Band – where myosin and actin overlap
I-Band – only actin filaments
Z-line – perpendicular strands of protein fibers extend out from actin filaments
H-Zone – center of A-Band, myosin filaments, w/ no overlapping actin filaments
M-Line – center of H-Zone, proteins that attach to the center of the myosin filaments, holding them in place