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1. exterior collagen layer
2. connected to deep fascia
3. separate muscle from surrounding tissues
1. Surround muscle fiber bundles(fascicles)
2. Contain bv and nerve supply to fascicles
1. Surrounds individual muscle cells (muscle fibers)
2. Contain cappillaries and nerve fibers contacting muscle cells
3. Contain myosatellite cells (stem cells) that repair damage.
Skeletal Muscle Fibers
1. Very Long
2. Develop through fusion of mesodermal cells (myoblasts)
3. Very large
4. Contain 100's of nuclei
1. Cell membrane of muscle fiber
2. Surrounds sarcoplasm(cytoplasm of muscle fiber)
3. A change in transmembrane potential begins contractions.
Transverse T-tubules
1. Transmit muscle fiber to contract
2. Allow entire muscle fiber to contract simultaneously
3. Same properties as sarcolemma
1. lengthwise sbdivisions in muscle fiber
2. made up of bundles of protein filaments(myofilaments)
3. Myofilaments are responsible for muscle contraction
A. thin filaments: Actin
B. Thick filaments: Myosin
Sarcoplasmic reticulum
1. Membranous structure surrounding each myofibril
2. Transmits AP's to myofibril
3. Similar in structure to smooth ER
4. Forms chambers (terminal cisternae) attached to t-tubules
1. 1 T-tubule + 2 terminal cisternae
2. Cisternae: concentrate calcium via ion pumps
-release calcium into to sarcomeres to begin contraction
1. Contractile units of muscle
2. structural units of myofibrils
3. form visible patterns in myofibrils
4. M line: center of A band (midline)
5. Z line: centers of 2 I bands (at 2 ends of sarcomere)
6. H band: area around M line; thick but no thin filaments
Zone of overlap
1. Densest, darkest area
2. thick and thin filaments overlap
1. Strands of protein
2. reach from tips of thick filaments to Z line
3. Stabilize filaments
Sarcomere function
1. T-tubules encircle sarcomere near zones of overlap
2. Calcium released from SR causes thin and thick filaments to interact
F-actin (filamentous)
1. Active sites on G-actin strands bind to myosin
2. 2 twisted rows of globular protein
Holds F-actin strands together
1. Double stranded
2. Preventsactin-myosin interaction
1. A globular protein
2. binds tropomysin to G-actin
3. Controlled by calcium
Initiating contraction
1. Calcium binds to receptor on troponin molecule
2. troponin-tropomyosin complex changes
3. exposing active site of F-actin
Sliding filament theory
1. Thin filaments of sarcomere slide toward M line alongside thick filaments
2. the width of A zone stays same
3. Z lines move closer together
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