Skeletal Muscle Aging Disease Flashcards
Larger muscles more or less fatiguable?
More fatiguable
smaller slow muscles more or less fatiguable?
less fatiguable
Muscle fibres are static?
lots of muscle fibre malleability
what is NOT a goals of intervention for muscle wasting?
don’t want to increase muscle fatigue
Myostatin if knocked out?
increased muscle mass gain
Myostatin role physiologically?
negative regulator
loss of innervation or tone leads to
muscle atrophy
Cancer Cachexia affect how much long, pancreatic, GI patients?
80%
What is ICU wasting called?
Critical Illness Myopathy
Sarcopenia definition
age-associated loss of skeletal muscle mass and function
sarcopenia dx needs 3 things:
<2SD
What age does performance decline despite exercise regime?
~50yr old
slow or fast twitch muscles affected first?
fast twitch first
weakness definition
inability to generate an initial force appropriate circumstances
Age related motor unit remodelling happens how?
denervation of type 2 motor units, die or reinnervation with type 1 motor units but smaller mass
up to how much % muscle in ageing?
30%
what replaces muscle in sarcopenia?
connective tissue
fat
noncontractile
muscle wasting acute process?
contraction slows before onset of severe muscle wasting
how does Ca2+ play a role in sarcopenia?
sarcoplasmic reticulum impaired release or reuptake of Ca2+
most susceptible motor units are?
Type IIb fast twitch
what 3 things happens to post-synaptic component in ageing?
wider end plates
longer nerve terminals
fewer side branches
how to axons look in aged tissue?
smaller and aberrant axons, dysmyelination
what hormone can affect sarcopenia?
IGF-1
what affects muscle regen capacity?
satellite cells
what happens to CT with ageing?
stiffer CT
more fibronectin
how to conserve muscle strength for preventions/reversal?
strength training
exercise prescription for elderly? 4 things
strength
aerobic exercise
flexibility
balance
why not just give people growth hormone as they age?
compromises efficiency of muscle regen d/t daily wear and tear. It’s not sustainable
focus on treatment for sarcopenia?
function, not just mass
Duchenne’s onset?
age 2-6
Duchenne’s symptoms?
generalized weakness
large calves
Duchenne’s inheritance?
X-linked recessive
why calves bigger in Duchenne’s?
breaking down of muscle but repairing is occuring and can keep up until eventual failure
Duchenne’s life expectancy?
20years unless ventilated and corticosteroids
What is Gower’s Sign in Duchenne’s?
unable to stand up without help of hands on their thighs to help
which muscles more affected in Duchenne’s?
lower limb and torso, not as much upper limb
Why occulomotor muscles spared in Duchenne’s? 3 possible reasons
- smalller muscle
- lower mechanical stress
- more sarcolemmal expression of compensatory protein
Duchenne’s deficiency in?
dystrophin
Duchenne’s mutation on which gene?
Xp21
dystrophin important how in muscle?
combines with glycoprotein for:
- structural, stabilization during eccentric
- receiver or transducer of signals
What is Becker’s muscular dystrophy?
less severe than Duchenne’s
starts later: adolescence/adulthood
can make some dystrophin
what is dystrophin like in Becker’s muscular dystrophy?
smaller amounts
abnormal, smaller molecules
DMD is what kind of deletion of gene?
frame shift
Becker’s muscular dystrophy gene is affected how?
reading frame preserved, can still make some dystrophin
how does dystrophin stabilize sarcolemma?
form costameres that make mechanical links
without costameres what happens to sarcomeres?
tearing of muscles, build up of Ca2+ in ECM, fibrosis and degen
dystrophic muscles susceptible to stretch-induced injury? 3 reasons
Yes due to:
- muscle fibre branching
- hypercontraction: necrosis
- leaky dye uptake studies
contraction-induced muscle injury cycle?
healthy contraction damage loss of Ca2+ homeostasis muscle degen muscle regen
current Rx for Duchenne’s?
Corticosteroids
New Duchenne’s drug targets?
Heat Shock Protein Hsp72
