Muscle Damage and Disease Flashcards
How are muscle fibres produced?
Satellite cells stimulated
Chemotaxis to myonucleus
Myonucleus contains actively proliferating myoblasts
Fusion of myoblasts into myotubes
Where do satellite cells reside?
Between fibre and basal lamina
What area does each nucleus control?
30µm
What type of muscle fibre has more satellite cells?
Slow
Do young or old fibres have more satellite cells?
Young
How long can damage increase after exercise?
up to 30 hours
Is concentric or eccentric exercise more damaging?
eccentric
What are the results of damage?
Streaming of the Z line
non-uniformity of the sarcomere length
Holes in membrane
When does damage spread into neighbouring sarcomeres?
On next contraction
Which type of fibre is most susceptible to damage?
type 2
What effect does damage have on power output?
Decreases
How is damage repaired?
Holes release Ca in fibre
Activates Proteases to degrade tissue
Recruits macrophages and neutrophils to remove tissue
How long is extreme damage repaired in?
Degraded in 4 days
Regenerated in 10 days
How are satellite cells activated?
Nitric oxide
What are characteristics of new muscle fibres?
Smaller diameter
Central nuclei
What do satellite cells produce?
Hepatocyte growth factors
Insulin-like growth factors
Is trained muscle more or less resistant to damage?
more
What are the dystrophies associated with skeletal muscle damage?
Duchenne
Beckers
Limb Girdle
Emery Drieffus
What mutations are there in duchenne muscular dystrophy?
X-linked deletion of Dystrophin
Actin- (N) dystrophin (C)- α dystroglycan -costamere connection is absent
Lack of lateral force support
What is Becker’s muscular dystrophy?
N-dystrophin truncation so no binding to actin.
Muscle weakness not fatal
What are mutations associated with nemaline myopathies?
Actin
Nebulin (MOST)
Tropomyosin
What are the symptoms of nemaline myopathies?
Nuclear actin rods
Sarcoplasmic actin rods
loss of actin/actinopathy
What are the 2 types of cardiomyopathies?
Hypertrophic
Dilated
What filament do cardiomyopathies effect?
cardiac myosin thickening or thinning
What cellular symptoms do cardiomyopathies have?
Disorganised myocytes
How is α-actinin varied in genetics?
4 isoforms
type 3 in fast fibres
How many people does Duchenne affect?
1/4000
How many people does Beckers affect?
1/20000
