Muscle Physiology

Question 1

What are the layers of skeletal muscle starting as a whole

Answer 1

Whole muscle (bundles of fascicles) -> fascicle -> muscle fibre (myocyte) -> myofibril

Question 2

What connective tissue surrounds the whole muscle

Answer 2

Epimysium

Question 3

What connective tissue surrounds a fascicle

Answer 3

Perimysium

Question 4

What connective tissue surrounds A muscle fibre

Answer 4

Endomysium

Question 5

Name for myocyte development

Answer 5

Myogenesis

Question 6

Steps of myogenesis

Answer 6

Myoblasts (mesodermal) fuse to form myotubes then undergo terminal differentiation into myocytes (muscle fibres)

FGF- fibroblast growth factor is used

Question 7

When does terminal differentiation occur

Answer 7

When FGF is low

Question 8

Where is contractile machinery assembled

Answer 8

In cytoplasm

Question 9

Why is there dark-light banding in myofibrils

Answer 9

difference in size of thick and thin filaments due to abundance of proteins. Myosin-thick-has more protein

Question 10

How can short cells produce long muscles?

Answer 10

Packaging- parallel or pennate

Question 11

Parallel vs pennate

Answer 11

Parallel- lower force, higher ROM, good endurance

Pennate- higher force, lower ROM

Question 12

What arrangement of fibres provides best packing

Answer 12

Pennate packs more fibres into same space

Question 13

Actin role

Answer 13

Muscle organization

Question 14

Myosin role

Answer 14

Force generating ATPase

Question 15

Sarcomere sections

Answer 15

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

Question 16

How does actin form

Answer 16

Helical coils of G-actin (globular) polymerize to form F-actin

Question 17

F-actin is unstable- so what is used to stabilize

Answer 17

Nebulin, tropomyosin, troponin

Question 18

How does myosin form

Answer 18

Subunits polymerize in a tail to tail formation

Question 19

Two regions of myosin

Answer 19

Tail region
Cross bridge region

Question 20

Role of myosin light chains and where they are found

Answer 20

Important for myosin ATPase activity
Found on globular heads

Question 21

Components of thin filament and their roles (5)

Answer 21

1. CapZ: stabilizes end, keeps f-actin as f-actin
2. Alpha-actinin: anchors actin to thin filament centre (to z-line)
3. Tropomodulin: binds and caps minus end of actin, regulating actin length
4. Troponin: is a trimer. TnC- contains EF hands (4 hands for 4 Ca binding sites), TnT and TnI- interact with tropomyosin
5. Actin

Question 22

Thick filament components and roles

Answer 22

1. Titin: structural, flexibility, stability
2. Myomesin: connect thick filament bundles and equalize contractile force exerted
3. C-protein: assembly and stabilization of thick filament
4. Myosin

Question 23

Myosin heads contain

Answer 23

Heavy chains, essential/structural light chains, regulatory light chains

Question 24

Function dystroglycans and location

Answer 24

Force transfer
Prevent damage ex. Shearing

Extra cellular and in sarcolemma

Question 25

Function dystrophin and location

Answer 25

Link cytoskeleton to transmembrane proteins
Males have one copy

In cytoplasm

Question 26

Function sarcoglycans and location

Answer 26

Bridge transmembrane proteins

In sarcolemma

Question 27

Why do we need to link muscle cytoskeleton to ECM

Answer 27

Maintain structural integrity and prevent sarcolemma rupture

Question 28

What is included in the dystrophin-glycoprotein complex

Answer 28

Transmembrane sarcoglycans
Membrane associated dystrophin

Question 29

What does a defect in dystrophin gene cause

Answer 29

Duchenne Muscular Dystrophy
- degenerative muscle disease