Introduction to Neuropathology- Myopathology

Question 1

What is an “onion bulb” characteristic of?

Answer 1

segmental demyelination

Question 2

Lost muscle is replaced with _____.

Answer 2

adipose and collagen

Question 3

This is a group of 100-200 myofibers all innervated by the same motor neuron.

Answer 3

the motor unit

Question 4

What is myopathy?

Answer 4

primary disease of muscle characterized by:

• proximal weakness
• elevated CK
• EMG changes

Question 5

All fibers in a motor unit are of the same ______ type, either _____ or ______.

Answer 5

histochemical; type 1 or type 2

Question 6

Describe type 1 muscle fibers.

Answer 6

• more oxidative enzymes
• more mitochondria
• more myoglobin
• increased tonic firing
• decreased rate of contraction and relaxation

Question 7

Which muscle fiber type?

• more glycolytic enzymes
• increased rate of fatigue

Answer 7

type 2 (fast-white)

Question 8

What comprises the DAC?

Answer 8

• dystroglycans (2)
• sarcoglycans (5)

Question 9

What are the 3 patterns of peripheral neuropathy?

Answer 9

1. Wallerian degeneration
2. distal axonopathy
3. segmental demyelination

Question 10

This is an enzyme that moves phosphate from creatine phosphate to ADP.

Answer 10

creatine kinase (CK)

Question 11

This is distal weakness and atrophy with normal CK and different EMG changes.

Answer 11

denervation

Question 12

Where do capillaries run in a muscle?

Answer 12

in the endomysium

Question 13

During contraction, actin and myosin _____ to shorten the sarcomere by 20%.

Answer 13

slide into each other

Question 14

In muscular dystrophy, _____ increase and replace lost muscle, also causing stiffness.

Answer 14

endomysial fibrous and adipose tissue

Question 15

This is the distance btw two z-bands.

Answer 15

a sarcomere

Question 16

What is perineurium?

Answer 16

a sheath of special, fiber-like cells that tie the axons of each fascicle together

Question 17

When the sarcolemma is damaged, _____ leaks into the serum.

Answer 17

creatine kinase (CK)

Question 18

_____ filaments are attached to z-bands.

Answer 18

Actin

Question 19

Myofibers contain 2 kinds of contractile filaments: ____ and _____.

Answer 19

myosin and actin

Question 20

Describe type 2 muscle fibers.

Answer 20

• more glycolytic enzymes
• increased rate of fatigue

Question 21

What causes distal axonopathy?

Answer 21

• drugs
• industrial poisons (pesticides, organic phosphates, solvents)

Question 22

Which muscle fiber type?

• more oxidative enzymes
• more mitochondria
• more myoglobin
• increased tonic firing
• decreased rate of contraction and relaxation

Answer 22

type 1 (slow-red)

Question 23

What is the motor unit?

Answer 23

group of 100-200 myofibers all innervated by the same motor neuron

Question 24

Actin filaments are attached to _____.

Answer 24

z-bands

Question 25

What nerves are most affected by distal axonopathy and why?

Answer 25

large axons bc they have the highest metabolic and nutritional demands

Question 26

What determines if the fibers in a motor unit are type 1 or type 2?

Answer 26

the nerve supply

Question 27

What is endoneurium?

Answer 27

the small amount of matrix in between individual axons

Question 28

What neuropathies can show segmental demyelination?

Answer 28

* inflammatory demyelinative neuropathies * Charcot-Marie-Tooth disease

Question 29

What causes Wallerian degeneration?

Answer 29

* trauma * peripheral nerve infarction * neoplastic infiltration

Question 30

What are the 2 fiber types in muscles?

Answer 30

1. type 1 (slow-red) 2. type 2 (fast-white)

Question 31

Myofibers are bound to the extracellular matrix by chain of proteins consisting of ____ and \_\_\_\_\_\_.

Answer 31

* dystrophin * the dystrophin-associated complex (DAC)

Question 32

What does CK do?

Answer 32

it's an enzyme that moves phosphate from creatine phosphate to ADP

Question 33

In \_\_\_\_\_, degeneration of the axon and myelin develops first in the most distal parts of the axon.

Answer 33

distal axonopathy

Question 34

What is a sarcomere?

Answer 34

the distance btw two Z-bands

Question 35

Each muscle is wrapped by a fibrocollagenous sheath called the \_\_\_\_\_\_.

Answer 35

perimysium

Question 36

What is the other source of energy that isn't used for muscle contraction, but to replenish ATP?

Answer 36

phosphocreatine

Question 37

Muscle disease can be placed into 2 broad categories: _____ and \_\_\_\_\_.

Answer 37

* myopathy * denervation atrophy

Question 38

What is the rate of axonal growth in Wallerian degeneration?

Answer 38

1-2 mm/day (faster if closer to the cell body)

Question 39

The immediate source of energy for muscle contraction is \_\_\_\_\_\_.

Answer 39

hydrolysis of ATP

Question 40

What is segmental demyelination?

Answer 40

the breakdown and loss of myelin over a few segments, but the axons remain intact and the neuronal body doesn't change

Question 41

What is Wallergian degeneration?

Answer 41

an axon is transected and central chromatolysis occurs (smooth cytoplasm, displaced nucleus) to disintegrate and degrade the old axon and grow a new one from the proximal stump

Question 42

What is an "onion bulb" formation?

Answer 42

concentric layers of Schwann cell processes and collagen around an axon

Question 43

This is primary disease of muscle characterized by proximal weakness, elevated CK, and EMG changes.

Answer 43

myopathy