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Hacking your Health > Week 5 - Skeletal Muscle Physiology > Flashcards

Week 5 - Skeletal Muscle Physiology Flashcards

1
Q

what tissue is muscle separated by?

A

connective

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2
Q

what does collagenous connective tissue comprise of?

A

epimysium, perimysium, endomysium, fasiculi

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3
Q

what are myofibrils made from?

A

actin and myosin

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4
Q

what excitable membrane surrounds muscle cells?

A

sacrolemma

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5
Q

what is the cellular fluid within muscle fibre?

A

sarcoplasm - contains enzymes, organelles, myofibrils

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6
Q

what membranous network runs through muscle fibre?

A

sarcoplasmic reticulum - stores and releases Ca and contains ATP pumps

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7
Q

what invaginations run from sacrolemma through muscle cell?

A

tranverse tubules - they speed up transmission of AP, reducing electrical delay

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8
Q

what in muscle membranes are crucial in conversion of electrical impulse to CA2+?

A

dihydropyrodine

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9
Q

what are thick myofilaments comprised of?

A

200 myosin subunits containing actin and Ca2
= binding site

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10
Q

what are thin myofilaments comprised of?

A

200 actin molecules with tropomyosin

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11
Q

what is troponin-tropomyosin Tr-T complex essential for?

A

regulation of muscle contractions

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12
Q

how does Tr-T complex regulate muscle contraction?

A

blocking of myosin binding siteson actin thin filaments

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13
Q

what disables Tr-T complex?

A

influx of Ca2+ into cell

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14
Q

what are myofibrils made of?

A

thin and thick filaments

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15
Q

what is the smallest unit of a myofibril?

A

sacromere

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16
Q

describe structure of sacromere

A

I bands surround the middle A band
the I bands are thin filaments, A is thick filaments in centre
M line is the anchoring of thick filament in centre of H-Zone (centre of A band)
Z-disc (anchors thin filaments in both I bands)

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17
Q

what is the largest protein in the body?

A

titin

18
Q

function of titin in relation to skeletal msucle?

A

acts as a scaffold to sacromere

19
Q

what happens in the sliding filament theory?

A

myosin motor heads move from one actin to the next
thin filamnets slide past thick filaments
myosin heads pull Z-lines closer together
acromere shortens
H-zone and I band shorten, reducing Z-disk difference
A band stays same length

20
Q

what is cross-bridge cycling?

A

1) ATP binds to mysoin head - myosin dissociates from actin
2) hydrolysis of ATP to ADP + P - weak binding of myosin head to actin
3) P is released - conformational change of myosin heavy chain head ‘power stroke’
this results in pulling of thin filaments
4) ADP is released - tight myosin to actin binding ‘rigor’
cycle goes again - pull and push motion

21
Q

name the 3 types of muscle fibre

A

I, IIa and IIx

22
Q

what 2 muscle fibres are oxidative?

A

I and IIa

23
Q

what muscle fibres are anaerboic/ glycolytic?

A

IIx

24
Q

how do you determine muscle fibre types in muscle sample?

A

muscle biopsy and staining
homogenise a sample and measure denisty of myosin and actin

25
Q

which muscle fibre is most fatiguable?

A

IIx (fast)

26
Q

which muscle fibre is least fatiguable?

A

I (slow)

27
Q

which muscle fibre has few mitochondria?

A

IIx

28
Q

which muscle fibre is high in myoglobin?

A

I (slow)

29
Q

what is muscle plasticity?

A

muscles have ability to change their form and function to suit environment

30
Q

what are the 3 mechanims for undergoing muscle plasticity?

A

change in fibre size, number and type

31
Q

what is wolfs law?

A

bones will adapt based on mechanical stress placed on them, if no stress it will weaken

32
Q

what is muscle atrophy?

A

a reduction in muscle mass - protein degradation

33
Q

what is muscle hypertrophy?

A

a gain in muscle mass - protein anabolism
‘an increase in the mass or cross sectional area of a single fibre’

34
Q

what occurs when there is a change in fibre size?

A

muscle atrophy and hypertrophy

35
Q

what is muscle hyperplasia?

A

an increase in muscle fibre number - does not occur in humans

36
Q

how many isoforms (I, IIa and IIx) can an adult express?

A

usually 50% type 1 and type II

37
Q

what isoforms are present in an endurance athlete?

A

> 90% type I

38
Q

what isoforms are present in a track sprinter?

A

> 80% type II

39
Q

in relation to isforms, what happens during high activity levels?

A

type IIx converts to IIa

40
Q

in relation to isoforms, what happens during low activity levels?

A

type IIa to IIx

41
Q

what are hybrid fibre types?

A

unique forms of fibres that express more than one myosin isoform

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