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Neuroscience II > PNS Anatomy/injury > Flashcards

PNS Anatomy/injury Flashcards

0
Q

What do fibroblasts generate? Where are they located?

A

Generate collagen fibers. Located in all types of CT

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1
Q

What are the two types of peripheral nerve cell types?

A

Fibroblasts and Schwann cells

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2
Q

What do Schwann cells do?

A

Surround and support every axon in the PNS (doesn’t matter if they are myelinated or not)

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3
Q

How so Schwann cells produce myelin sheaths around axons?

A

Produce myelin sheath in segments

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4
Q

What do nerves contain?

A

Consists of fibers of different diameters, some myelinated some not. Some are motor, some are sensory

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5
Q

What are they two ways nerve fibers are classified!

A
  1. Conduction velocity

1. Fiber diameter

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6
Q

What type of nerve haas the fastest conduction velocity?

A

The A group which consists of myelinated sensory and motor fibers

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7
Q

How is the A fiber group subdivided?

A

Alpha, beta, gamma, and delta

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8
Q

What are the second fastest fiber type?

A

B fibers which are thinly myelinated (preganglionic autonomic fibers?)

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9
Q

What is the slowest fiber type?

A

C fibers which are unmyelimated.

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11
Q

What are the classifications of fiber diameter?

A

I, II, III (myelinated), IV (unmylinated)

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12
Q

What is the outermost wrapping of the neuron?

A

Epineurium

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13
Q

What is the middle wrapping of the neuron?

A

Perineurium

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14
Q

What is the innermost wrapping of the neuron?

A

Endoneurium

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15
Q

What does the epineurium mostly consist of?

A

Collagen fibers and fibroblasts

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16
Q

Where is the epineruium thickest? Thinnest?

A

Thick at the nerve trunk and thins out as the nerve branches towards its termination

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17
Q

What other structure is the epineurium continuous with at the level of the spinal nerve?

A

The dura mater

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18
Q

What protective function does the epineurium have?

A

Protects fasiculi from compressive forces

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19
Q

What does the perineurium surround?

A

Surrounds the fasicles

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20
Q

What does the perineurium consist of?

A

Collagen fibers and connective tissue cells

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21
Q

What type of junctions does the perineurium consist of and what do they do?

A

Tight junctions that closes off each fascicle from the fascicles around it

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22
Q

What is the function of the perineurium?

A

Maintains intrafasicular fluid pressure and accounts for elasticity and tensile strength of nerve

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23
Q

What does endoneurium surround?

A

Individual nerve fibers

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24
Q

What supplies the endo-, peri-, and epi- neurium with blood?

A

arterioles

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25
Q

What is Neurapraxia?

A

Transitory localized conduction block with no signs of denervation due to local damage to neural membrane

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26
Q

How long is full recovery from Neurapraxia?

A

Days to weeks

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27
Q

What is Axonotmesis?

A

Axon disruption but endoneurial sheath remains intact.

28
Q

What type of degeneration takes place with Axonotmesis?`

A

Wallerian degeneration

29
Q

What does recovery time for a peripheral nerve depend on?

A

distance necessary for regrowth. nerve grows 1mm/day 1in/month

30
Q

What is Neurotmesis?

A

complete transection of nerve with disruption of axon and endoneurium

31
Q

What type of degeneration takes place with Neurotmesis?

A

Wallerian degeneration

32
Q

What are some causes of Neurotmesis?

A

Cut, crush, or severe stretch injury

33
Q

3 types of compressive injuries?

A

Acute, intermittent, or chronic

34
Q

What does iatrogenic mean?

A

caused by medical examination or treatment

35
Q

In an acute compressive injury which is involved first sensory or motor loss?

A

Sensory involved before motor

36
Q

What is Wallerian degeneration?

A

Process of degeneration that occurs following injury to an axon

37
Q

What happens to the distal myelin and axon hours after the injury?

A

They begin to fragment and the neurotubules and neurofilaments become disarrayed

38
Q

What type of swelling occurs along the axon distal to the injury?

A

Varicose swelling

39
Q

HOw long after injury does it take for the axon to become discontinuous (no action potentials can propagate along the length)?

A

48-96 hours

40
Q

When do Schwann cells activate and what do they do in the Wallerian degeneration process?

A

activate w/in 24 hrs of injury, undergo mitosis and help mast cells get rid of degenerated distal nerve segment and myelin

41
Q

How is the myelin degenerated in Wallerian Degeneration?

A

phagocyizedby mast cells, aided by Schwann cells

42
Q

How long does it take for the site of injury to be cleared?

A

1 week-several months post injury

43
Q

What happens if there is severe injury and the endoneurium is disrupted?

A

capillaries are disrupted causing hemorrhage. Much inflammation follows and a dense fibrous scar can form

44
Q

What do Schwann Cells do to facilitate correct nerve regrowth?

A

They form stacks to guide the growth of growth cones from the regenerating axons

45
Q

What is chromatolysis?

A

Process by which nucleus in cell body becomes eccentric and and the Nissl substance breaks down

46
Q

What can happen to the DRG’s with injury?

A

Injury can trigger apoptosis and 20-50% of DRG cells may die. More likely if injury is proximal

47
Q

In what type of injury is functional recovery more likely?

A

Neruopraxia or Axonotmesis where endoneurial tube is intact

48
Q

What happens to muscle with denervation?

A 
Severe atrophy (~70% reduction in x-sectional area by two months)
intramuscular fibrosis with proliferation of connective tissue
49
Q

What can happen to motor units with reservation?

A

Can result in giant motor units where collaterals of a single alpha motor neuron innervate a large number of all the same type muscle fiber

50
Q

How long will receptors wait to be reinnervated?

A

up to a year

51
Q

5 things regeneration results in?

A 
more axons due to collaterals
smaller diameter initially
Thinner myelin initially but eventually recovers
more myelin segments
slower conduction velocities
52
Q

What is another name for Guillian-Barre?

A

Postinfectious Polyneuritis

53
Q

Who does Guillian-Barre syndrome usually affect?

A

young adults-early middle age

54
Q

When does Guillian-Barre syndrome usually appear?

A

After particular type of respiratory infection

55
Q

What is physiologically happening with Guillian-Barre syndrome?

A

Lymphocytic sensitization to peripheral nerve antigen. Patchy difuse segmental demyelinization of peripheral nerves occurs

56
Q

What are some symptoms of Guillian-Barre syndrome?

A

Severe ascending weakness (hours to days after)
areflexia
elevated CSF protein
possible cranial nerve and respiratory involvement (phrenic nerve)
mild sensory loss;disproportionate motor loss

57
Q

How long does Guillian-Barre syndrome progress for? Stay stable? Recovery time

A

progress over 10 days, stay stable for 2 weeks, 6mo-2 year recovery time

58
Q

How many people do not fully recover from Guillian-Barre syndrome?

A

10%

59
Q

What are some indicators of incomplete recovery from Guillian-Barre syndrome?

A

more than 3 weeks from max weakness to initial improvement
reduced motor nerve conduction velocities
EMG evidence of denervation
respiratory support

60
Q

What is CIPD?

A

Chronic Inflammatory Demyelinating Polyneuropathy

61
Q

What is CIPD sometimes confused for

A

Guillian-Barre syndrome

62
Q

What is CIPD?

A

A chronic progressive autoimmune mediated inflammation of peripheral myelin

63
Q

What type of course does CIPD follow?

A

A relapsing/remitting course

64
Q

IN CIPD, what type of innervation is involved (sensory/motor)?

A

Both equally

65
Q

Do people return to prior fan with CIPD?

A

No

66
Q

WHat are some treatments for CIPD?

A

Short term steroids
plasmapheresis
IV IGg

Neuroscience II (13 decks)

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