Myology
-Study of muscles
Functions of skeletal muscle tissue
-Body movement
-Maintenance of posture: muscle tone (continual contraction) keeps body from collapsing/falling
-Temperature regulation: heat produced when muscles contract
-Storage and movement of materials: sphincters (circular muscles around openings) open and close
-Support: helps hold organs in place ex: abdominal and pelvic floor muscles
Gross Anatomy
-made up of muscle fibers=muscle cells
-each skeletal muscle is an organ
-many skeletal muscles work in groups
Tendons/Aponeuroses
-tendons attach many skeletal muscles to bones (dense regualr CT)
-aponeuroses: flattened sheetlike tendon
Endomysium
-surrounds muscle fiber
Fasicles
-groups of muscle fibers
Perimysium
-surrounds fasicles
Epimysium
-surround sentire muscle
Deep Fascia
-surrounds all the CT wrappings
Superficial Fascia
-subcutanious layer is superficial to deep fascia
Sarcolemma
-muscle cell membrane
Sarcoplasm
-cytoplasm of skeletal fibers
Internal characterists of muscle cell (sarcoplasmic reticulum)
-has organelles like lysosomes, ribosomes, and ER called sarcoplasmic reticulm
-SR function: store calcuim ions Ca2+ and releases them when muscle contracts
Transverse Tubules (T-tubules)
-conduct nerve impulses quickly from sarcolema through muscle fiber
Compositon of Muscle Fibers
-mainly made of myofibrils
-run length of muscle-as long as muscle fiber
-no nuclear or cellular wrapping
Myofilaments
-compose myofibrils
-many needed to run length of muscle
-protein filaments
-each thick myofilament surrounded by 6 thin myofilaments
-arrangement of thick and thin filaments gives muscle its striations
Myosin
-thick myofilaments
-fixed length
Actin
-thin myofilaments
I Bands
-light bands (I-LIGHT)
-thin myofilaments only
A Bands
-dark bands (A=DARK)
-overlapping thick and thin myofilaments
Z disc (Z Line)
-dark structure in the middle of an I band
-thick myofilaments only
H Zone (H Band)
-a lighter central region in the middle of an A band
M Line
-dark line in the middle of H zone
-thick myofilaments attach here
Sarcomere
-run from Z disc to Z disc
-functional contractile unit
-many along length of muscle fiber
-shorten and narrow when muscle contracts
Sliding Filament Model of Contraction
When Muscle Contracts:
-thick and thin myofilaments slide over one another
-length of each sarcomere shortens and narrows, muscle contracts
-H zones narrow and I bands narrow
**Z disc, M line, A band, thick and thin myofilaments stay the same size (do not shorten or narrow)
