Intro to Skeletal Muscle Pathology Flashcards
What is the obvious manifestation of muscle pathology?
Muscle weakness
What are the Oxford grading scale scores?
0/5: No contraction
1/5: Visible/palpable muscle contraction no movement
2/5: Movement with gravity eliminated
3/5: Movement against gravity only
4/5: Movement against gravity some resistance
5/5: Movement against gravity full resistance
In a healthy muscle cross-section where are the nuclei found?
In the periphery of the fiber
In a glycogen phosphorylase stain what stains darker?
Muscles with higher levels of glycogen phosphorylase (Type IIX)
What is nuclear clumping found in?
Neuropathy
What is increased internal nuclei found in?
Myopathy
What is fiber type grouping found in?
Neuropathy
What is the major determining factor of the type of muscle fibers?
The nerve that innervates it
What will infiltrate the muscle fibers when it is denervated?
Macrophages
What is the most severe muscular dystrophy disease?
Duchenne muscular dystrophy
What occurs to muscle size in DMD?
Psuedo-hypertrophy due to fibrosis and lipid accumulation in the muscle
Which muscles are more affected in DMD?
Proximal more so than distal muscles
What happens to the endomysium in muscular dystrophy?
Endomysial fibrosis
What protein is affected in MD?
Dystrophin
What is dystrophin?
A protein found in the cytoskeleton of muscles
What are the functions of the cytoskeleton?
Tension sensor
Signal transductor
Scaffolding structure
What color does dystrophin appear when stained?
Yellow
What is the calcium dependent proteolytic protein?
Calpain
What are the 3 proteolytic pathways in muscle hypothesized for DMD necrosis (loss of calcium homeostasis)?
Lysosomal proteases
Ca2+ dependent Calpain
ATP dependent ubiquitin proteasome pathway
How is calpain activated?
Loss of calcium homeostasis
What are three affected metabolic pathways of muscle?
Glycogen phosphorylase (Glycogenolysis) Cytochrome b deficiency Fat metabolism (carnitine transferase)
What are principle symptoms of mitochondrial oxidative disorders?
Exercise intolerance and persistent lactic acidosis
What occurs to muscle fibers in hyperthyroidism?
Transformation from Type-I to Type-II fibers
What is hyperkalemic periodic paralysis?
Mutation in Na+ channel; in presence of high K+ levels Na+ channels fail to inactivate properly (flaccid paralysis)
What can statins on occasion cause?
Rhabdomyolysis
