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Sem 3 MSK > Muscle Structure And Adaptation > Flashcards

Muscle Structure And Adaptation Flashcards

1
Q

What do muscles form from in the embryo?

A

→ Somites (paraxial mesoderm)

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2
Q

What happens to mesodermal cells during development?

A

→ They go through a mesenchymal transition
→ The cells become columnar and form a transient cavity
→ They undergo an epithelial mesenchymal transition to form the sclerotome

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3
Q

What does the sclerotome consist of?

A

→ Bone
→ Ribs
→ Cartilage

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4
Q

What is the myotome?

A

→ Muscle precursors

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5
Q

What is the dermomyotome?

A

→ Myotome and dorsal dermis

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6
Q

What is the syndetome?

A

→ Tendons

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7
Q

What does the notochord do?

A

→ Induces the mesoderm to become myogenic by inducing myogenic regulatory factors

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8
Q

What do paracrine factors induce?

A

→ Myf5 and MyoD (myogenic transcription factors)

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9
Q

Describe myogenesis

A

→ Notochord induces mesoderm to become myogenic
→ Paracrine factors induce Myf5 and MyoD which leads to myogenic commitment
→ myoblasts proliferate
→ Exit the cell cycle due to myogenin expression
→Structural proteins are expressed and myotubes form
→ Myotubes align and fuse parallel to each other
→ Biphasic muscle development : primary and secondary
→ Satellite cells : regeneration and post natal growth

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10
Q

What does myogenin expression mean?

A

→terminal differentiation

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11
Q

What are the structural proteins expressed when myotubes form?

A

→ Actin and myosin

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12
Q

What can embryonic fibre number be affected by?

A

→ temperature
→ hormones
→ Nutrition
→ Innervation

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13
Q

What happens to muscle mass after birth?

A

→ Increase in fibre size (hypertrophy)

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14
Q

What are satellite cells?

A

→ Muscle stem cells

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15
Q

What are muscle stem cells?

A

→ Undifferentiated muscle precursors that are self-renewing

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16
Q

When are MuSCs activated?

A

→ training

→ postnatal development

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17
Q

Why are muscle cells multinucleated?

A

→ They are big and long cells
→ huge production of structural proteins
→ this needs to occur along the length of the muscle fibre

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18
Q

What do myosin isoforms dictate?

A

→ Different chemomechanical transduction
→ ATP hydrolysis
→ Shortening velocity

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19
Q

What do troponin and tropomyosin isoforms dictate?

A

→ Determine sensitivity to Ca2+

20
Q

What do titin isoforms dictate?

A

→ Elastic properties

21
Q

What is an example of a type I fibre?

A

→ Back extensor muscle

22
Q

What are type I fibres used for?

A

→ Posture

23
Q

What are the properties of type I fibres?

A

→ High mitochondrial content - oxidative phosphorylation
→ Heavily vascularised
→ Sustained contraction
→ Abundant myoglobin

24
Q

What are the properties of type II fibres?

A

→ High force contraction
→Fatigue easily
→ Less mitochondria - glycolytic respiration
→ Poorly vascularised

25
Q

What ratio of muscle fibres do untrained individuals have?

A

→ 50:50 fast to slow

26
Q

What ratio of muscle fibres do long distance runners have?

A

→ 60-70% slow

27
Q

What ratio of muscle fibres do sprinters have?

A

→ 80% fast

28
Q

What are properties of powerlifters muscles?

A 
→ Hypertrophied
 → Highly glycolytic 
 → Fatigue easily 
 → High muscle to total body mass ratio
 → muscle size interferes with locomotion
29
Q

What is the order that MHC can split ATP in from fastest to slowest?

A 
→ 2B 
 → 2A 
 → 2X 
 → 1
 → embryonic is the slowest
30
Q

What is MHCexoc?

A

→ extraocular myosin heavy chain

31
Q

What is MHCperi?

A

→ perinatal myosin heavy chain

32
Q

What are the gene differences between males and females in terms of skeletal muscles?

A

→ >3000 genes

→ males have a larger fibre cross-sectional area

33
Q

What is the difference between females and males in type I fibres?

A

→ males - 36%

→ females - 44%

34
Q

What is the difference between females and males in type II fibres?

A

→ males - 41%

→ females - 34%

35
Q

What is testosterone needed for?

A

→ development of the male reproductive system

36
Q

What does testosterone develop?

A

→ Muscle + bone mass
→ body hair
→ deep voice

37
Q

What kind of a steroid is testosterone?

A

→ Anabolic

38
Q

What does testosterone do to muscle cells?

A

→ Commitment of mesenchymal pluripotent cells into myogenic lineage

39
Q

What does testosterone inhibit?

A

→ inhibits adipogenesis

40
Q

What does testosterone stimulate?

A

→ Satellite cell replication
→ muscle protein synthesis
→ fibre hypertrophy

41
Q

What are the three adverse effects that synthetic anabolic steroids can have?

A

→ Increase BP
→ affect the heart
→ Shrinkage of testicles

42
Q

What can be used for muscle mass loss?

A

→ testosterone

43
Q

How does muscle recover from a minor injury such as a sprain?

A

→ Damaged muscle fibres necrose
→ There is an inflammatory response and neutrophils and macrophages respond to the damaged muscle fibre
→ There is an increase in satellite cell proliferation
→ they fuse with muscle fibres and regenerate them

44
Q

How does muscle recover from laceration?

A

→ incomplete laceration

→ fibrotic tissue forms

45
Q

What is sarcopenia?

A

→ age related loss of muscle mass

46
Q

How much does muscle mass decrease after 30?

A

→ 3-8% decrease after 30

→ higher after 60

47
Q

What is loss of muscle mass associated with?

A

→ gain in fat mass

→ decreased satellite cell number and recruitment

Sem 3 MSK (4 decks)

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