Skeletal Muscle 2 Flashcards
What are the three layers of a muscle? Plus what lines cells
epimysium- entire muscle
perimysium- fasicles
endomysium- myofibres surrounds
sarcolemma- surrounds individual cell
What are the invaginations of the sarcolemma and what do they do?
T-tubules, and they propogate AP’s into the myocyte
What are the:
- Z- discs
- H-zone
- A-band
- I-band
- M line
Z-discs; boundaries of sarcomeres
H-zone: only thick filaments + m line ( no myosin heads)
A-band: Dark part of sarcomere, Thick plus thin filaments
I-band: Light part, thin filaments.
What is the SR?
store of Ca2+
What are the terminal ends called, and what is the triads function?
Cisternae, and excitation contraction coupling
What is the composition of thick filaments?
Myosin, repeating, staggered and in opposite directions.
What are thin filaments made of?
2 strands of F-actin
What other structures are on thin filaments?
Tropomyosin, troponin complex (TnT, TnC, TnI) and nebulin(aligns fialments)
What are the functions of TnT, TnC and TnI?
TnT: positions troponin on Tm
TnC: where Ca2+ binds
TnI: inhibits myosin head binding
Cross bridge cycle:
1) What is the rigor state?
2) what follows rigor state?
3) What follows ATP binding
4) What is the relaxed state?
5) What is power stroke?
6) What follows power stroke?
1) Myosin head bound to actin tightly at 45 degrees
2) ATP binds to myosin head and it detaches from actin
3) ATP hydrolysis occurs, so ADP an Pi
4) ADP and Pi attached causes high affinity for actin, causing binding at 90 degrees.
5) Pi detaches, causing power stoke moving thin filament inwards (myosin head rotation)
6) ADP detaches, causing rigor state.
What inhibits X-bridge cycle at rest?
Tm, TnT, TnI and TnC
What happens when Ca2+ conc increases?
- TnT move and expose binding sites
- TnC binds Ca2+
Where does excitation contraction coupling occur?
Triads
What are the channels of the SR that are related to ECC?
RyR1s
What are the channels on the T-tubules related to ECC
DHPR’s
