Intro to Skeletal Muscle Pathology

Question 1

What is the obvious manifestation of muscle pathology?

Answer 1

Muscle weakness

Question 2

What are the Oxford grading scale scores?

Answer 2

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

Question 3

In a healthy muscle cross-section where are the nuclei found?

Answer 3

In the periphery of the fiber

Question 4

In a glycogen phosphorylase stain what stains darker?

Answer 4

Muscles with higher levels of glycogen phosphorylase (Type IIX)

Question 5

What is nuclear clumping found in?

Answer 5

Neuropathy

Question 6

What is increased internal nuclei found in?

Answer 6

Myopathy

Question 7

What is fiber type grouping found in?

Answer 7

Neuropathy

Question 8

What is the major determining factor of the type of muscle fibers?

Answer 8

The nerve that innervates it

Question 9

What will infiltrate the muscle fibers when it is denervated?

Answer 9

Macrophages

Question 10

What is the most severe muscular dystrophy disease?

Answer 10

Duchenne muscular dystrophy

Question 11

What occurs to muscle size in DMD?

Answer 11

Psuedo-hypertrophy due to fibrosis and lipid accumulation in the muscle

Question 12

Which muscles are more affected in DMD?

Answer 12

Proximal more so than distal muscles

Question 13

What happens to the endomysium in muscular dystrophy?

Answer 13

Endomysial fibrosis

Question 14

What protein is affected in MD?

Answer 14

Dystrophin

Question 15

What is dystrophin?

Answer 15

A protein found in the cytoskeleton of muscles

Question 16

What are the functions of the cytoskeleton?

Answer 16

Tension sensor
Signal transductor
Scaffolding structure

Question 17

What color does dystrophin appear when stained?

Answer 17

Yellow

Question 18

What is the calcium dependent proteolytic protein?

Answer 18

Calpain

Question 19

What are the 3 proteolytic pathways in muscle hypothesized for DMD necrosis (loss of calcium homeostasis)?

Answer 19

Lysosomal proteases
Ca2+ dependent Calpain
ATP dependent ubiquitin proteasome pathway

Question 20

How is calpain activated?

Answer 20

Loss of calcium homeostasis

Question 21

What are three affected metabolic pathways of muscle?

Answer 21

Glycogen phosphorylase (Glycogenolysis)
Cytochrome b deficiency
Fat metabolism (carnitine transferase)

Question 22

What are principle symptoms of mitochondrial oxidative disorders?

Answer 22

Exercise intolerance and persistent lactic acidosis

Question 23

What occurs to muscle fibers in hyperthyroidism?

Answer 23

Transformation from Type-I to Type-II fibers

Question 24

What is hyperkalemic periodic paralysis?

Answer 24

Mutation in Na+ channel; in presence of high K+ levels Na+ channels fail to inactivate properly (flaccid paralysis)

Question 25

What can statins on occasion cause?

Answer 25

Rhabdomyolysis