Skeletal Muscle Aging Disease Flashcards

1
Q

Larger muscles more or less fatiguable?

A

More fatiguable

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2
Q

smaller slow muscles more or less fatiguable?

A

less fatiguable

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3
Q

Muscle fibres are static?

A

lots of muscle fibre malleability

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4
Q

what is NOT a goals of intervention for muscle wasting?

A

don’t want to increase muscle fatigue

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5
Q

Myostatin if knocked out?

A

increased muscle mass gain

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6
Q

Myostatin role physiologically?

A

negative regulator

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7
Q

loss of innervation or tone leads to

A

muscle atrophy

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8
Q

Cancer Cachexia affect how much long, pancreatic, GI patients?

A

80%

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9
Q

What is ICU wasting called?

A

Critical Illness Myopathy

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10
Q

Sarcopenia definition

A

age-associated loss of skeletal muscle mass and function

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11
Q

sarcopenia dx needs 3 things:

A

<2SD

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12
Q

What age does performance decline despite exercise regime?

A

~50yr old

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13
Q

slow or fast twitch muscles affected first?

A

fast twitch first

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14
Q

weakness definition

A

inability to generate an initial force appropriate circumstances

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15
Q

Age related motor unit remodelling happens how?

A

denervation of type 2 motor units, die or reinnervation with type 1 motor units but smaller mass

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16
Q

up to how much % muscle in ageing?

A

30%

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17
Q

what replaces muscle in sarcopenia?

A

connective tissue
fat
noncontractile

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18
Q

muscle wasting acute process?

A

contraction slows before onset of severe muscle wasting

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19
Q

how does Ca2+ play a role in sarcopenia?

A

sarcoplasmic reticulum impaired release or reuptake of Ca2+

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20
Q

most susceptible motor units are?

A

Type IIb fast twitch

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21
Q

what 3 things happens to post-synaptic component in ageing?

A

wider end plates
longer nerve terminals
fewer side branches

22
Q

how to axons look in aged tissue?

A

smaller and aberrant axons, dysmyelination

23
Q

what hormone can affect sarcopenia?

A

IGF-1

24
Q

what affects muscle regen capacity?

A

satellite cells

25
Q

what happens to CT with ageing?

A

stiffer CT

more fibronectin

26
Q

how to conserve muscle strength for preventions/reversal?

A

strength training

27
Q

exercise prescription for elderly? 4 things

A

strength
aerobic exercise
flexibility
balance

28
Q

why not just give people growth hormone as they age?

A

compromises efficiency of muscle regen d/t daily wear and tear. It’s not sustainable

29
Q

focus on treatment for sarcopenia?

A

function, not just mass

30
Q

Duchenne’s onset?

A

age 2-6

31
Q

Duchenne’s symptoms?

A

generalized weakness

large calves

32
Q

Duchenne’s inheritance?

A

X-linked recessive

33
Q

why calves bigger in Duchenne’s?

A

breaking down of muscle but repairing is occuring and can keep up until eventual failure

34
Q

Duchenne’s life expectancy?

A

20years unless ventilated and corticosteroids

35
Q

What is Gower’s Sign in Duchenne’s?

A

unable to stand up without help of hands on their thighs to help

36
Q

which muscles more affected in Duchenne’s?

A

lower limb and torso, not as much upper limb

37
Q

Why occulomotor muscles spared in Duchenne’s? 3 possible reasons

A
  1. smalller muscle
  2. lower mechanical stress
  3. more sarcolemmal expression of compensatory protein
38
Q

Duchenne’s deficiency in?

A

dystrophin

39
Q

Duchenne’s mutation on which gene?

A

Xp21

40
Q

dystrophin important how in muscle?

A

combines with glycoprotein for:

  1. structural, stabilization during eccentric
  2. receiver or transducer of signals
41
Q

What is Becker’s muscular dystrophy?

A

less severe than Duchenne’s
starts later: adolescence/adulthood
can make some dystrophin

42
Q

what is dystrophin like in Becker’s muscular dystrophy?

A

smaller amounts

abnormal, smaller molecules

43
Q

DMD is what kind of deletion of gene?

A

frame shift

44
Q

Becker’s muscular dystrophy gene is affected how?

A

reading frame preserved, can still make some dystrophin

45
Q

how does dystrophin stabilize sarcolemma?

A

form costameres that make mechanical links

46
Q

without costameres what happens to sarcomeres?

A

tearing of muscles, build up of Ca2+ in ECM, fibrosis and degen

47
Q

dystrophic muscles susceptible to stretch-induced injury? 3 reasons

A

Yes due to:

  1. muscle fibre branching
  2. hypercontraction: necrosis
  3. leaky dye uptake studies
48
Q

contraction-induced muscle injury cycle?

A
healthy
contraction damage
loss of Ca2+ homeostasis
muscle degen
muscle regen
49
Q

current Rx for Duchenne’s?

A

Corticosteroids

50
Q

New Duchenne’s drug targets?

A

Heat Shock Protein Hsp72