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25 Cards in this Set

  • Front
  • Back
Describe Type I muscles fibers
Slow-twitch (red) fibers

rich in Mitochondria & Oxidative enzymes
Describe Type II muscle fibers
Fast-twitch (white) fibers

Poor in Mitochondria
What determines the type of fiber a myocyte contains?
Motor neuron
Define Neurogenic Atrophy
disease of the Anterior Horn cell or its axon
Describe the pathology seen in Neurogenic Atrophy
Initial: individual atrophic angular fibers

Later: Groups of atrophic angular fibers
Neurogenic Atrophy
What is seen here?
What helps in diagnosis Neurogenic Atrophy?
Fiber typing = after reinnervation, a cluster of Type I fibers are adjacent to a cluster of Type II fibers
Fiber-typing used to diagnose Neurogenic Atrophy
What is seen here?
What diseases can cause Neurogenic Atrophy?
1. ALS
2. Vasculitis
3. Trauma
4. Nerve compression (spinal cord disease)
List 3 Inflammatory Myopathies
1. Dermatomyositis
2. Polymyositis
3. Inclusion Body Myositis
-perifascicular pattern of injury
What is seen here?
What is the clinical presentation of Dermatomyositis?
Rash + weakness + muscle pain

*has an association with Cancer (Lung CA)
What is the immune target of Dermatomyositis? What is it mediated by?

Antibodies + Complement
Polymyositis = lack of skin involvement
-Endomysial process
-inflammation tends to occur within the meat of muscle
-nuclei are also sometimes not at the periphery
What is seen here?
Inclusion Body Myositis
-rimmed vacuoles that may contain Beta-amyloid & tau within
What is seen here?
Describe the clinical features of Inclusion Body Myositis
1. occurs in Distal muscles first
2. Older subjects
3. Resistant to therapy = not responsive to steroids
4. Rimmed vacuoles
pathology of Dystrophies
-fiber size variation
-increased central nuclei
-degeneration, necrosis
What is seen here?
Describe the pathology of Dystrophy
1. Fiber size variation
2. increased central nuclei
3. degeneration, necrosis
4. regeneration
5. fibrosis
Dystrophy characterized by X-linked inheritance with a mutation in the dystrophin gene
Duchenne & Becker Muscular Dystophy
Central Core Disease (congenital myopathy)
-central pallor
-disorganized sarcomeres with deficiency of ATPase
What is seen here?
Nemaline Myopathy (congenital myopathy)
-Rod-like inclusions derived from the Z-disc
What is seen here?
Myotubular (Centronuclear) Myopathy
-desmin, loss of myofibrillar material (EM)
What is seen here?
Mitochondrial Myopathy
-aggregates of abnormal mitochondria
-Ragged red fibers
-Cytochrome oxidase negative fibers
What is seen here?
-aggregates of abnormal mitochondria
-Ragged red fibers
-Cytochrome Oxidase negative fibers
Mitochondrial Myopathy
Mitochondrial Myopathy

Proximal weakness
-other neurological symptoms
-lactic acidosis
What disease is this? What does it cause?