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Musculo-Skeletal > 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 does the sclerotome consist of?

A

→ Bone
→ Ribs

→ Cartilage

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3
Q

What is the myotome?

A

→ Muscle precursors

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4
Q

What is the syndetome?

A

→ Tendons

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5
Q

What does the notochord do?

A

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

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6
Q

What do paracrine factors induce?

A

→ Myf5 and MyoD (myogenic transcription factors)

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7
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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8
Q

What are the structural proteins expressed when myotubes form?

A

→ Actin and myosin

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9
Q

What can embryonic fibre number be affected by?

A

→ temperature
→ hormones

→ Nutrition
→ Innervation

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10
Q

What happens to muscle mass after birth?

A

→ Increase in fibre size (hypertrophy)

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11
Q

What are satellite cells?

A

→ Muscle stem cells

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12
Q

What are muscle stem cells?

A

→ Undifferentiated muscle precursors that are self-renewing

→return to quiescence when not needed

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13
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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14
Q

What do myosin isoforms dictate?

A

→ Different chemomechanical transduction
→ ATP hydrolysis

→ Shortening velocity

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15
Q

What do troponin and tropomyosin isoforms dictate?

A

→ Determine sensitivity to Ca2+

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16
Q

What do titin isoforms dictate?

A

→ Elastic properties

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17
Q

What is an example of a type I fibre?

A

→ Back extensor muscle

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18
Q

What are type I fibres used for?

A

→ Posture

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19
Q

What are the properties of type I fibres?

A

→ High mitochondrial content - oxidative phosphorylation
→ Heavily vascularised

→ Sustained contraction
→ Abundant myoglobin
→small diameter

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20
Q

What are the properties of type II fibres?

A

→ High force contraction
→Fatigue easily

→ Less mitochondria - glycolytic respiration
→ Poorly vascularised
→large diameter

21
Q

What ratio of muscle fibres do untrained individuals have?

A

→ 50:50 fast to slow

22
Q

What ratio of muscle fibres do long distance runners have?

A

→ 60-70% slow

23
Q

What ratio of muscle fibres do sprinters have?

A

→ 80% fast

24
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

25
Q

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

A

→ 2B
→ 2A

→ 2X
→ 1
→ embryonic is the slowest

26
Q

What is MHCexoc?

A

→ extraocular myosin heavy chain

→movements of the eyeball and upper eyelid

27
Q

What does testosterone inhibit?

A

→ inhibits adipogenesis

28
Q

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

A

→ Increase BP
→ affect the heart

→ Shrinkage of testicles

29
Q

What can be used for muscle mass loss?

A

→ testosterone

30
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

31
Q

How does muscle recover from laceration?

A

→ incomplete laceration

→ fibrotic tissue forms

32
Q

What is sarcopenia?

A

→ age related loss of muscle mass

→Atrophy of muscle fibres- associated with type I fibres to express Type II phenotype

33
Q

What is loss of muscle mass associated with?

A

gain in fat mass
→ decreased satellite cell number and recruitment
→Anabolic resistance – reduced protein synthesis in response to hormonal stimulation or resistance exercise

34
Q

Which heavy chains do type I and type II fibres express?

A

→Slow twitch fibres (type I) express type I myosin heavy chain
→Fast twitch fibres (type II) express type II MHC

35
Q

What type of fibres are present in the eye muscle(lateral rectus)?

A

mainly type II fast twitch

36
Q

What types of fibres are present in calf muscle(gastrocnemius)?

A

mixed type I & II

37
Q

What type of fibres are present in soleus(calf)?

A

more type 1 slow twitch

38
Q

What does the motor unit consist of?

A

→a motor neuron and the set of muscle fibres within a muscle that it innervates

39
Q

What is the range of motor unit sizes?

A

→10 to many 100s of muscle fibres

40
Q

What is neurone pool?

A

→A muscle may be innervated by 10s to 100s of motor MNs

41
Q

Describe incomplete tetanus

A

→the muscle goes through quick cycles of contraction with a short relaxation phase for each

42
Q

What is complete tetanus?

A

→If the stimulus frequency is so high that the relaxation phase disappears completely, contractions become continuous

43
Q

What happens during tetanus?

A

→the concentration of Ca++ ions in the sarcoplasm allows virtually all of the sarcomeres to form cross-bridges and shorten, so that a contraction can continue uninterrupted

44
Q

Describe the difference in firing rates in fast and slow motor units

A

→Fast motor units need higher firing rates to generate tetanic forces than slow motor units

→Slow motor units are recruited first, followed by fast units for higher levels of force generation

45
Q

What is the difference between spatial and temporal summation?

A

→Spatial summation occurs when multiple presynaptic neurones together release enough neurotransmitter to exceed the threshold of the postsynaptic neurone.
→Temporal summation occurs when one presynaptic neurone releases neurotransmitter many times over a period of time. Time dependent

46
Q

What is muscle hyperplasia?

A

→Increase in muscle mass due to formation of new muscle fibres

47
Q

What is the difference between hyperplasia and hypertrophy?

A

→Hyperplasia refers to the process where cells in an organ or tissue increase in number

→Hypertrophy is when these cells in an organ or tissue increase in size

48
Q

How is smooth muscle tone achieved?

A

→Driven by reflex arcs from muscle spindles (sectioning dorsal roots abolishes resting tone)
→activation of a few motor units at a time

49
Q

Compare hypertonia and hypotonia

A

→hypotonia- absence of the low-level contractions that lead to muscle tone
→hypertonia- excessive muscle tone. present with muscle rigidity (as seen in Parkinson’s disease)

Musculo-Skeletal (6 decks)

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