Neuromuscular Junction

Question 1

What is a neuromuscular junction?

Answer 1

Site where motor neuron excites muscle fiber. Axon terminal with motor end plate.

Question 2

What are the three layers of muscle fiber?

Answer 2

Epimysium, perimysium, endomysium.

Question 3

What is Muscular Dystrophy?

Answer 3

Group of inherited disease, loss of muscle mass, progressive weakness.

Question 4

What are the two types of MD?

Answer 4

Duchenne and Becker.

Question 5

What is DMD?

Answer 5

Duchenne muscular dystrophy, x-linked recessive caused by mutation in DMD gene, absence of dystrophin. Muscle cell damage every time muscle contracts/ relax, dead cells replaced with connective tissue.

Question 6

What is the DMD gene?

Answer 6

Largest known gene for dystrophin, anchor protein for muscle cell structural framework and cytoskeleton in ECM.

Question 7

What is X-linked?

Answer 7

Mutation in X chromosome, only pass down one X-chromosome for males.

Question 8

What are the S&S for DMD?

Answer 8

Onset occurs 3-5 years, progressive muscle degeneration, weakness in proximal muscles, impaired motor, respiratory muscles, fatigue, lumber hyper lordosis (curvature in lower spine), toe walking to compensate. Gower’s sign, pseudohypertrophy of calf muscle (due to replacement with CT).

Question 9

What is the Gower’s sign?

Answer 9

Weakness in proximal muscle, not able to lift trunk without using arms and hand to brace.

Question 10

Which medications are used to cure DMD?

Answer 10

Eteplirsen, deflazacort.

Question 11

What is Becker Muscular Dystrophy?

Answer 11

Mutation in DMD, but dystrophin remain, milder S&S, onset occurs later in childhood/ adolescence.