Nerves Flashcards

1
Q

Nerve Response to Loading

A
"TARD"
Type
Amount
Rate
Duration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Factors of Nerve Excursion

A
  1. Elongation of nerve bed = adjacent segments move towards
  2. Shortening of nerve bed = adjacent segments move away
  3. Adjacent segments move first –> as movement continues more distal segments undergo excursion
  4. Adjacent segments have the greatest magnitude of excursion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Steps of Nerve Rupture

A
  1. Nerve straightens
  2. Fascicles straighten
  3. Axons straighten + tension (remove undulations)
  4. After 4% strain axons rupture
  5. Some fascicles rupture
  6. Critical number of fascicles rupture –> failure of entire nerve and plastic deformation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Nerves Under Compression

A
  1. uniform circumferential
    - displaces contents transversely and longitudinally
    - force greatest at edge of cuff due to the shearing forces
  2. lateral (between 2 flat surfaces)
    - change in shape but not volume = no increase in endoneurial pressure
    - less damaging
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Axonal Crush/Transection

A
  1. neuropraxia = temporary conduction block (schwann cell damage)
  2. axonotmesis I = loss of axon continuity
  3. axonotmesis II = loss of axon + endoneurium continuity
  4. axonotmesis III = loss of axon + endoneurium + perineurium continuity
  5. neurotmesis = complete transection of nerve trunk
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Axonal Transection Stimulates:

A

“Wearing My Dad’s Socks”

  1. Macrophage infiltration (1-4 days)
  2. Wallerian degeneration (2-4 days) = distal axonal degeneration + myelin fragmentation
  3. Schwann cell differentiation = detach from axons, proliferate, recruit macrophages to clear cellular/myelin debris
  4. Schwann cells Align longitudinally + express stimulating factors to direct nerve regrowth toward target organ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Chronic Nerve Compression Injury

A

“Injury Gradually Saves Face”

  1. Axonal integrity initially preserved (neuropraxia)
  2. Gradual macrophage infiltration (several weeks)
  3. Schwann cell turnover, proliferation + apoptosis (peaks at 4 weeks) triggered by Schwann cell mechanosensitivity
  4. Focal demyelination (7-10 days) –> remyelination (2-4 weeks) –> new thinner myelin sheath –> decreased conduction velocity but normal NMJ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Chronic Nerve Compression Causing Intraneural Oedema

A
  1. ischaemic damage to endoneurial capillary endothelial cells
  2. damage to blood-nerve barrier
  3. increased intraneural pressure
  4. impairs intraneural blood flow + axoplasmic flow
  5. fibroblasts activated + fibrosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Nerve Pathology Risk Factors

A

Diabetes
Thyroid disease
Nerve disorder (predisposes for secondary nerve disorder = double crush phenomena)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly