Skeletal Muscle I: Organisation And Contraction Flashcards
1
Q
Antagonistic muscles
A
Flexor and extensors
2
Q
Flexor
A
Brings two muscles together
3
Q
Extensors
A
Moves two bones apart
4
Q
Nebulin
A
Aligns actin
5
Q
Titin
A
Elastic fibres that stabilise myosin
6
Q
Myosin
A
Thick filament- bare region, 15 micrometers
7
Q
Actin
A
Thin filament 7 micrometers
8
Q
During contraction
A
H zone and I bands shorten
9
Q
Troponin complex
A
T- binds to tropomyosin
I- binds actin
C- binds Ca2+
10
Q
Phosphocreatine- muscles at rest
A
ATP+creatine—>ADP + phosphocreatine
Enzyme- creatine kinase
11
Q
Phosphocreatine- working muscles
A
Phosphocreatine+ADP—> Creatine + ATP
Enzyme- creatine kinase
12
Q
ATP is used for
A
Myosin ATPase
Ca2+-ATPase
Na+-K+-ATPase
13
Q
Contraction and relaxation
A
- ACh from stomatic motor neuron at neuromuscular junction
- Na+ entry through ACh receptor channel causing muscle action potential
- AP in T-tubules cause conformational changes in DHP
- DHP opens RyR—> Ca2+ into cytoplasm
- Ca2+ binds to troponin
- Myosin heads-power stroke
- Actin filament slides to center of sarcomere
- Sarcoplasmic Ca2+-ATPase —> Ca2+ to SR
- Decrease in cytosolic [ca2+] —> Ca2+ unbinds troponin
- Tropomyosin recovers binding site, elastic elements pull filament back
14
Q
The power stroke
A
- Tight binding in the rigor state
- ATP binds to myosin, releasing actin
- myosin head hydrolyses ATP, energy rotates head to cocked position. Myosin binds weakly to actin
- Ca2+ signal -> tropomyosin moves off the binding site. Actin filament moves towards the M-line. Head swivels, Pi released
- Released ADP
