Flashcards in Muscle Structure And Adaptation Deck (47)
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1

What do muscles form from in the embryo?

β†’ Somites (paraxial mesoderm)

2

What happens to mesodermal cells during development?

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

3

What does the sclerotome consist of?

β†’ Bone
β†’ Ribs
β†’ Cartilage

4

What is the myotome?

β†’ Muscle precursors

5

What is the dermomyotome?

β†’ Myotome and dorsal dermis

6

What is the syndetome?

β†’ Tendons

7

What does the notochord do?

β†’ Induces the mesoderm to become myogenic by inducing myogenic regulatory factors

8

What do paracrine factors induce?

β†’ Myf5 and MyoD (myogenic transcription factors)

9

Describe myogenesis

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

10

What does myogenin expression mean?

β†’terminal differentiation

11

What are the structural proteins expressed when myotubes form?

β†’ Actin and myosin

12

What can embryonic fibre number be affected by?

β†’ temperature
β†’ hormones
β†’ Nutrition
β†’ Innervation

13

What happens to muscle mass after birth?

β†’ Increase in fibre size (hypertrophy)

14

What are satellite cells?

β†’ Muscle stem cells

15

What are muscle stem cells?

β†’ Undifferentiated muscle precursors that are self-renewing

16

When are MuSCs activated?

β†’ training
β†’ postnatal development

17

Why are muscle cells multinucleated?

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

18

What do myosin isoforms dictate?

β†’ Different chemomechanical transduction
β†’ ATP hydrolysis
β†’ Shortening velocity

19

What do troponin and tropomyosin isoforms dictate?

β†’ Determine sensitivity to Ca2+

20

What do titin isoforms dictate?

β†’ Elastic properties

21

What is an example of a type I fibre?

β†’ Back extensor muscle

22

What are type I fibres used for?

β†’ Posture

23

What are the properties of type I fibres?

β†’ High mitochondrial content - oxidative phosphorylation
β†’ Heavily vascularised
β†’ Sustained contraction
β†’ Abundant myoglobin

24

What are the properties of type II fibres?

β†’ High force contraction
β†’Fatigue easily
β†’ Less mitochondria - glycolytic respiration
β†’ Poorly vascularised

25

What ratio of muscle fibres do untrained individuals have?

β†’ 50:50 fast to slow

26

What ratio of muscle fibres do long distance runners have?

β†’ 60-70% slow

27

What ratio of muscle fibres do sprinters have?

β†’ 80% fast

28

What are properties of powerlifters muscles?

β†’ Hypertrophied
β†’ Highly glycolytic
β†’ Fatigue easily
β†’ High muscle to total body mass ratio
β†’ muscle size interferes with locomotion

29

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

β†’ 2B
β†’ 2A
β†’ 2X
β†’ 1
β†’ embryonic is the slowest

30

What is MHCexoc?

β†’ extraocular myosin heavy chain