Week 2 Flashcards
Myoblast
-muscle mesenchymal cells
Myotubule
- composed of
- will become
- made from myoblasts fusing together to make multinucleated tubes
- eventually become myofilaments once they make enough proteins and nuclei are displaced against sarcolemma
Myofilaments
- what do they make
- classes
- make myofibrils
- classes: actin (I band) and myosin (A band)
Sarcomere
- what forms it
- where does it extend from and to
- function
- formed by I and A bands,
- boundaries are between two z lines
- contractile unit of muscle cell
Sarcolemma
-what is it
-muscle cell membrane, encases multiple myofibril, contains sarcoplasmic reticulum
What lies outside of sarcolemma?
endomysium-fascia
Transverse-tubule
- what is it?
- function?
- Invaginations of the sarcolemma that penetrate deeply into the muscle fiber around all myofibrils
- allows action potential to propagate
Sarcoplasmic reticulum
-modified smooth ER of sarcolemma, holds Ca
Skeletal muscle triad
- made of
- function
- t-tubule and two terminal cisternae of SR
- allows depolarization of the sarcolemma in a T-tubule to affect the sarcoplasmic reticulum and trigger release of Ca2+ ions into cytoplasm around the thick and thin filaments, which initiates contraction of sarcomeres
H-band
-contains myosin and creatine kinase (will transfer phosphate groups from phosphocreatine to ADP to create ATP for muscle contraction)
M line
-in middle of H zone, contains myomesin which holds thick filaments in place
F-actin
-two actin monomers forming an actin filament
Troponin complex
-what is it made of? their functions?
- Tropnin I, C,, T
- T: binds troponin to tropomyosin
- I: inhibits binding of actin to myosin
- C: binds Ca (only in striated muscle)
Tropomyosin
- extends length of 7 actin monomers and binds to troponin
- blocks myosin-binding sites preventing crossbridges from forming
Myosin II head
driving force of movement when bound to ctin