Muscle Physiology Flashcards
What are the layers of skeletal muscle starting as a whole
Whole muscle (bundles of fascicles) -> fascicle -> muscle fibre (myocyte) -> myofibril
What connective tissue surrounds the whole muscle
Epimysium
What connective tissue surrounds a fascicle
Perimysium
What connective tissue surrounds A muscle fibre
Endomysium
Name for myocyte development
Myogenesis
Steps of myogenesis
Myoblasts (mesodermal) fuse to form myotubes then undergo terminal differentiation into myocytes (muscle fibres)
FGF- fibroblast growth factor is used
When does terminal differentiation occur
When FGF is low
Where is contractile machinery assembled
In cytoplasm
Why is there dark-light banding in myofibrils
difference in size of thick and thin filaments due to abundance of proteins. Myosin-thick-has more protein
How can short cells produce long muscles?
Packaging- parallel or pennate
Parallel vs pennate
Parallel- lower force, higher ROM, good endurance
Pennate- higher force, lower ROM
What arrangement of fibres provides best packing
Pennate packs more fibres into same space
Actin role
Muscle organization
Myosin role
Force generating ATPase
Sarcomere sections
A-band: thick and thin
I-band: thin only
M-line: attachment site for thick filament
Z-line: sarcomere is region between lines
H-zone: thick only
As muscle contracts: I-band and H-zone becomes shorter and sarcomere shortens
How does actin form
Helical coils of G-actin (globular) polymerize to form F-actin
F-actin is unstable- so what is used to stabilize
Nebulin, tropomyosin, troponin
How does myosin form
Subunits polymerize in a tail to tail formation
Two regions of myosin
Tail region
Cross bridge region
Role of myosin light chains and where they are found
Important for myosin ATPase activity
Found on globular heads
Components of thin filament and their roles (5)
- CapZ: stabilizes end, keeps f-actin as f-actin
- Alpha-actinin: anchors actin to thin filament centre (to z-line)
- Tropomodulin: binds and caps minus end of actin, regulating actin length
- Troponin: is a trimer. TnC- contains EF hands (4 hands for 4 Ca binding sites), TnT and TnI- interact with tropomyosin
- Actin
Thick filament components and roles
- Titin: structural, flexibility, stability
- Myomesin: connect thick filament bundles and equalize contractile force exerted
- C-protein: assembly and stabilization of thick filament
- Myosin
Myosin heads contain
Heavy chains, essential/structural light chains, regulatory light chains
Function dystroglycans and location
Force transfer
Prevent damage ex. Shearing
Extra cellular and in sarcolemma
Function dystrophin and location
Link cytoskeleton to transmembrane proteins
Males have one copy
In cytoplasm
Function sarcoglycans and location
Bridge transmembrane proteins
In sarcolemma
Why do we need to link muscle cytoskeleton to ECM
Maintain structural integrity and prevent sarcolemma rupture
What is included in the dystrophin-glycoprotein complex
Transmembrane sarcoglycans
Membrane associated dystrophin
What does a defect in dystrophin gene cause
Duchenne Muscular Dystrophy
- degenerative muscle disease
