Muscle Tissue Flashcards
Muscle fibers of skeletal muscle characteristics and function?
- Function: force generation
- multinucleated
- nuclei at periphery
- rich capillary network to meet metabolic demands
- collagenous CT
Purpose of connective tissue in skeletal muscle?
- transfers force to bone
- contains high amounts collagenous
- fibers aligned parallel to greatest force
Where does skeletal muscle develop from?
Somites (dermomyotomes)
Process of skeletal muscle development?
- Dermomyotome splits off into dorsal and ventral muscle masses
- Myoblasts (single cells) migrate from somite
- Myoblasts fuse together and make multinucleated cells called Myotubes
- process called syncytium
Sarcoplasm?
muscle cell cytoplasm
Sarcolemma?
muscle cell membrane
Outer layer of muscle cell membrane?
- interacts with ECM and coatings
- transmits force
Inner layer of muscle cell membrane?
- true cell membrane
- lipid layer
Muscle cell contents?
- primarily myofibrils packed into tubes
- gives striated appearance
Cardiac Muscle characteristics?
- Net like organization
- striated
- complex junctions
- intercalated discs (transmits force)
- found only in heart - Fatigue Resistance
- one or two nuclei
- larger more numerous T tubules
- extensive Mitochondria (continuously functioning)
Skeletal muscle organization of Myofibril?
- A band: made of Myosin thick filaments
- I band: made of Actin, Troponin, Tropomyosin thin filaments, attached to Z line
- Z band: filament anchoring site
- H band: middle of A band
- M line: myosin anchoring site
Length of Sarcomere?
extends from one Z line to the next Z line
Sarcomere thick filaments?
Myosin (A band)
- Myosin contains enzyme ATPase which hydrolyzes ATP to ADP + P (cofactor: Actin)
- reaction binds Myosin heads to Actin
- two heavy chain- tail region
- four light chain- globular heads
- hinge region- aids in movement of head
Sarcomere thin filament?
Actin (I band):
- F and G actin
- Troponin (T, C, I)- bound to Tropomyosin, prevents Actin and Myosin binding
- Tropomyosin- binds to F actin
- Globular actin (G) binds Myosin
- moves in response to calcium
What does Myosin anchor to?
M line
What does Actin anchor to?
Z line
Steps of Muscle contraction in the myofiber?
- Influx of calcium
- Calcium binds Troponin
- Troponin moves to expose Actin binding site
- Myosin heads bind to Actin binding site
- Hinge region of Myosin deforms (as a result of ATP hydrolysis)
- Power stroke- Myosin moves against Actin
-result of hundreds of actin/myosin cross bridges happening