Skeletal Muscle Flashcards
Draw a model of skeletal muscle including I-band + H-band and their components.
In contracted SkM, what ∆s? What stays the same?
H zone + I bands decrease, distance btwn Z-lines decrease
A band stays the same
What microfilaments are in the I-band? A-band? H-zone?
I-band: actin
A-band: actin + length of myosin
H-zone: myosin
What are the 3 components of the I-band?
F-actin, Tropomyosin, Troponin
What is the function of F-actin in the I-band?
Binding sites for myosin
What is the function of Tropomyosin in the I-band?
Covers myosin binding site
What is the function of Troponin in the I-band? What molecule is needed for this action? What forms as a result?
Troponin bound to Ca = conformational-∆ forces tropomyosin into groove, allows cross bridge formation
What are the 3 types of Troponin and their functions?
Troponin I: bind actin
Troponin T: at end of Tropomyosin
Troponin C: bind Ca
What is the A-band?
Length of myosin
What are the 2 components of the H-zone? What are these components made of?
Myosin tail: 2 heavy chains
Myosin head: 4 light chains contain the ATPase activity
Name the accessory proteins of SkM, where do they attach/what are their functions?
Nebulin: adjacent to actin filaments, attaches to Z-line
Titin: in elastic protein which attaches ends of the myosin molecules to the Z-line
What are the 4 steps of Sliding Filament Theory?
- Relaxed state
- Cross bridge formation
- Power stroke
- Termination / End of Contraction
What is the 1st step of Sliding Filament Theory?
Relaxed state: ATP bound to myosin head
What is the 2nd step of Sliding Filament Theory?
Cross bridge formation: ATPase converts ATP —> ADP + Pi
- allows “high energy” / ready position
- if Ca present, myosin binds to actin
What is the 3rd step of Sliding Filament Theory?
Power stroke: release ADP + Pi, actin slides over myosin
What is the 4th step of Sliding Filament Theory?
Termination / End of contraction: ATP binds myosin head, Ca pumped out of cell back into sarcoplasmic reticulum (SR)
What is the Triad of SkM? Where is it located? What does it consist of?
AI junction
T-tubule + 2 terminal cisternae of SR
In the Triad of SkM, explain the T-tubule & SR
T-tubule = sarcolemma; transmits AP
SR stores Ca w/ calsequestrin
