Exam 4 Flashcards
(356 cards)
Composition of muscle tissue
- Muscle cells, myocytes
- Connective tissue, containing blood and nerves, transmits muscular contraction forces
Sarcoplasm
Striated muscle Cytoplasm
Sarcolemma
Striated muscle plasma membrane
Sarcoplasmic reticulum
Striated muscle smooth ER
sarcomere
Structural unit of myofibril in striated muscle
Myofilaments
Actin and myosin filaments in striated muscle
Myofibrils
Elongated contractile thread in striated muscle
Myofiber/muscle fiber
Single muscle cell in striated muscle
Skeletal muscle
• arises by fusion of myoblasts and differentiation
Mesoderm—> Myoblast—> Large multi nucleated cells—> syncytium + Differentiation in the skeletal muscle fibers
Endomysium
Sheath of fine connective tissue that surrounds individual muscle fibers, Fine RT fibers and ground substance, tiny nerves and blood vessels run parallel to muscle fibers
Perimysium
Thick CT sheath that surrounds groups of muscle fibers (Fascicles/bundles). Continuous with tendon fibers, large nerves and blood vessels
Epimysium
Dense CT cells that surrounds collection of fascicles (entire muscle). Major nerves and blood vessels
General features of myofiber
• Single cell, myocyte
•  Striated, voluntary
• Well developed Sarcoplasmic reticulum
• Multi nucleated
• Nuclei at cell periphery
Myofibril
• multiple myofibrils per cell
• tiny contractile threads within Sarcoplasm
• Extend entire length of cell, filled with myofilaments (Actin and myosin)
• Responsible for appearance of cross striations
Myofibril bands
Dark bands: A band divided by H band
M line: divides H band
Light band: I band divided by Z line
Sarcomere: length between adjacent Z lines
Thin filaments
Actin, tropomyosin, troponin
Extend from Z line through A band to edge of H band
Thick filaments
Myosin
Extends length of a band, thin cross-bridges extending from each myosin filament towards neighboring actin filaments
M line
• Dense line at center of H band
• Contains Myomesin, C protein, and other proteins for special arrangement
• lattice arrangement maintained by interconnection of thick myosin filaments
Z line/ The matrix
• region where ends of actin filaments attach in adjacent sarcomeres
• Alpha actinin protein, Titin, Nebulin, etc
Sarcoplasm
• between myofibrils
• Beneath Sarcolemma
• Around nuclei
• Mitochondria appear in the same area
• Numerous invaginations along cell surface, forming the T tubules
Sarcoplasmic reticulum
Network of cisterns and membranous tubules running between and around myofibrils
• Forms collars at A-I Junctions in skeletal and Z lines of cardiac
• binds and releases calcium
Skeletal muscle triads
T tubule + 2 terminal cisternae or sarcoRetic 
• Facilitates transmission of electrical impulse from Sarcolemma to Interior depths of cells at A-I junctions
Actin- thin filaments
1.) G actin: Globular actin Polymerizes to form F actin
2.) F actin: two helically wound strands of polymerized G Actin 
Myosin
• four light chains and two heavy chains
• Heavy chain: light meromyosin and heavy meromyosin