Peripheral N.

Question 1

Where does myelin come from to surround some axons?

Answer 1

myelin membranes of extended/flattened processes of a single Schwann cell

Question 2

Unmyelinated axons have what covering?

Answer 2

Cytoplasmic processes of Schwann cells surround 2+ unmyelinated axons

Question 3

How does radiculopathy differ from polyneuropathy?

Answer 3

Radiculo- nerve roots, a segmental deficits

polyneuro- symmetrical, socks/gloves deficits

Question 4

What are the 2 main ways that axons undergo degeneration?

Answer 4

Wallerian and

axonopathy

Question 5

How can the differences of Wallerian and Axonal degeneration be described?

Answer 5

Wallerian- degeneration distal, many nerves at a time, trauma/ischemia

axonal- proximal, 1 axon at a time, toxins/chronic dz

Question 6

What is the sequence of changes in axonopathy/wallerian degeneration?

Answer 6

1- fragmentation
2- phagocytosis
3- regeneration ( SC proliferation, endoneurial fibrosis and sprouting)

Question 7

How is neuronopathy different from Wallerian and axonal degenerations?

Answer 7

progressive degeneration of entire neuron (incl body) over time

Question 8

What causes the pattern of degeneration of demyelination?

Answer 8

1 schwann cell produces one segment of myelin, thus the pattern of degeneration is segmental

Question 9

How do peripheral nerves regenerate? What occurs if unsuccessful?

Answer 9

axonal sprouting into Schwann cell tubes, success-> reinnervation
failure-> neuroma

Question 10

How do newly myelinated nerves appear?

Answer 10

shorter and thinner myelin, similar diameter to undamaged nerves

Question 11

When do onion bulb changes occur?

Answer 11

After repeated episodes of demyelination-remyelination

Charcot-Marie-Tooth

Question 12

What elements make up thin, thick filaments and z-bands?

Answer 12

actin
myosin
alpha actinin

Question 13

What is the NADH and ATPase stain profile for type 1 muscle fibers?

Answer 13

NADH: dark
ATPase: pale

Question 14

What is the NADH and ATPase stain profile for type 2 muscle fibers?

Answer 14

NADH-pale

ATPase- dark

Question 15

What is the physiology of type 2 fibers? speed, nutrient, mitochondria.

Answer 15

fast-abundant glycogen- few mitochondria

Question 16

What is the physiology of type 1 fibers? speed, nutrient, mitochondria.

Answer 16

slow- abundant lipids-lots of mitochondria

Question 17

What is included in the motor unit?

Answer 17

• anterior horn cell and its axon and terminal branches

- muscle fiber

Question 18

How is myopathy different from neuropathy? pattern weakness, reflexes, sensory sx, m. bx.

Answer 18

proximal pattern of weakness
normal reflexes
absent sensory sx
bx shows necrosis/inflammation

Question 19

What happens during denervation atrophy?

Answer 19

denervation causes muscle fibers to reabsorb contractile elements-> atrophy and angulation