Skeletal Muscle Flashcards
Red, slow twitch fibers
for endurance-resist fatigue
type 1 fibers
white, fast twitch fibers
strength training
Selectively destroyed in prolonged steroid use
type 2 fibers
- X-Linked
- Increase in CK
- Pelvic and shoulder girdle weakness
- Mutation in dystrophin gene
- Macrophages invade and engulf necrotic material
- muscles appear large because theyre replaced by fat (pseudohypertrophy)
Duchennes MD
Mild from of Duchennes
Dystrophin is truncated
Beckers MD
- Most common form of adult MD
- Autosomal Dominant
- atrophy of type 1 fibers, hypertrophy of type 2 fibers
- circumferentially oriented sarcomeres
- cataracts, testicular atrophy, GI issues, balding, arrythmias
myotonic dystrophy
- Mutation on chromosome 19-ryanodine receptor
- malignant hyperthermia
- rhabdomyolsis
- hypotonia and decreased DTR
- central pallor, target formations
Central Core Disease
- Red, Rod like inclusions in sarcoplasm
- Congenital hypotonia and kyphoscoliosis
- Peripheral Inclusions
Rod/Nemaline Myopathy
- Proximal Muscle weakness
- mutated dynamin 2
- Bilateral ptosis
- centrally located nucleus
central nuclear myopathy
Symmetrical proximal muscle weakness
Increased serum muscle enzymes
non-suppurative inflammation
General features of all inflammatory myopathies
CD8+ infiltrate
MHC1 antigen expression
lung disease and raynauds
Responsive to steroids
Polymyositis
Rimmed Vacuoles
Cytoplasmic inclusions-stain with congo red
Not responsive to steroids
Inclusion body myositis
- Deposits IgG, IgM and complement in capillary walls
- B cell and CD4+ infiltrate
- Rash on upper eyelids (heliotrope)
- Perifascicular atrophy
Dermatomyositis
- Muscle fatigue-worse throughout day
- autoantibodies to Ach receptor
- increased risk of thymoma
- ptosis, and diplopia
myasthenia gravis
muscle weakness
wasting
fatigability of proximal muscles and trunk
Small cell lung cancer
Eaton Lambert Syndrome
Acid Maltase deficiency
accum of membrane bound glycogen
severe hypotonia and areflexia
Pompe Disease
Debranching enzyme deficiency
growth retardation
liver dysfunction
Cori Disease
Myophosphorylase deficiency
severe cramping during exercise-cannot make lactate
Tx-avoid vigorous exercise
non-membrane bound glycogen
McArdle Disease
- Proximal muscle weakness and atrophy
- Denervation and peripheral neuropathy
- Accum. of lipid in sarcoplasm outside mitochondria
Carnitine Deficiency
- Paracrystalline inclusions on EM
- Can’t metabolize long chain fatty acids
- Pain after exercise with myoglobinuria
carnitine palmitoyltransferase deficiency
- Ragged red fibers-accum of mitochondria
- Deficient in complex IV
Mitochondrial Disease
opthalmoplegia
retinal pigment degeneration
cardiac arrythmia
ragged red fibers
kearns-sayre syndrome (one of the mitohondrial diseases)
- myoglobin released into blood
- positive urine dipstick for blood
- no RBC’s on urinalysis
- acute renal failure
- can occur after influenza, alcoholism
- scattered necrosis, degeneration and regeneration
rhabdomylosis
Target fibers type grouping atrophy angular configurations of fibers replacement of fibers by adipose tissue
Denervation
- Floppy Baby
- infants show progressive weakness, on’t live past 1 year
- clusters of hypertrophied pale type 1 fibers
Werdnig Hoffman (late onset is kugelberg welander)
- Type 2 fiber angular atrophy
- No increase in CK
- Usually related to chronic problem-being treated with steroids
Steroid myopathy
