S2 Neuro Exam 1: Nervous System Injury & Repair

Front 1

Describe retrograde neuronal reaction

Back 1

1. axon reacts proximal to injury site usually to 1st node of ranvier
2. cell body undergoes metabolic changes to meet requirements for regeneration

Front 2

Describe the metabolic reaction of injured peripheral nerves (retrograde neuronal reaction)

Back 2

-dispersion of ribosomal RNA in Nissl substance (chromatolysis)
-movement of nucleus to one side (eccentricity)

Front 3

Describe anterograde or Wallerian degeneration

Back 3

-disruption of axon
-phagocytosis of axon by macrophages
-distal portion of nerve degenerates
-schwann cells remain around degenerated portion & form Bands of Bungner
-proximal stump forms multipple sprouts & follow schwann cell column (distally) back to original target

Front 4

What do Bands of Bungner do?

Back 4

synthesize trophic factors that attract & support growth of axon (essential to regeneration)

Front 5

Different types (degrees) of peripheral nerve injury & properties

Back 5

1st degree / neuropraxia:
least severe
function disrupted, no physical injury
ex, foot falling asleep
2nd degree / axonotmesis:
axons disrupted
scaffold intact
ex, nerve traction, crush injury
3rd degree / neurotmesis:
most severe
entire nerve structure disrupted
ex, cutting injury
*higher degree = least likely to recover

Front 6

*The injury of a peripheral nerve in which axons alone are injured with minimal injury of the connective tissue structure of the nerve is __________

Back 6

axonotmetesis

Front 7

complications of basic repair methods (PNS)

Back 7

-muscle tissue & sensory peripheral tissue loose innervation & undergo degeneration which may become irreversible
-muscle flaccid paralysis, loss of mass, supersensitivity
-muscle tissue atrophies & is replaced by fibrotic tissue (12-24 months is irreversible damage)
-sensory loss occurs where dermatomes do NOT overlap
-nerve retraction may form neuroma which will prevent any repair if not removed

Front 8

*Motor axons in an injured peripheral nerve that are regenerating in a distal stump typically regenerate at a speed of ____________

Back 8

1 in/month

(2mm/day)

Front 9

Basic methods used in peripheral nerve repair

Back 9

-physical therapy, electrical stimulation, & injection of trophic factors
-delay atrophy & contracture formation
(only temporarily)
-epineurial nerve suture (fasicle realign)
-nerve grafting (from sural antebrachial cutaneous)
-allografts (from cadavers)

Front 10

T/F
Surgical mismatching of fasicles in a repair improves outcome

Back 10

FALSE

produces a worse outcome

Front 11

T/F
light & discriminitive touch is lost over a larger area than pain

Back 11

TRUE


*sensory axons grow faster than motor esp gross pain sensation

Front 12

What is the result of autonomic loss (sympathetic) due to peripheral nerve damage?

Back 12

*postganglionic sympathetic axons lost
-loss of vascular control (skin becomes red and hot at early time intervals, later blue and colder than normal)
-loss of Sudomotor control (skin becomes dry and scaly)
-denervation of large area (sciatic, brachial plexus) can result in bone decalcifiction from disuse and loss of circulatory control.

Front 13

Describe the sequence of functional peripheral nerve recovery

Back 13

1. sensory recovery
-deep pain
-superficial cutaneous pain & vasomotor control
-heat & cold
-light touch & discriminative touch

Front 14

The progress of sensory regeneration can be followed by __________

Back 14

Tinel's sign

*regenerating sensory axons very sensitive to pressure
*tapping on distal nerve trunk produces tingling in area being innervated

Front 15

Describe the main difference in the response of the CNS & PNS to injury

Back 15

PNS:
-many repair mechanisms

CNS:
-don't regenerate, compensate
-reestablish blood brain barrier & isolate

Front 16

mechanisms that limit CNS repair

Back 16

-limited connective tissue
-astrocytes isolate injured areas
-blood brain barrier isolates injury from vasculature

Front 17

*The (glial-pial) scar that isolates the remaining CNS from injured areas consists primarily of the processes of

Back 17

astrocytes

Front 18

*After injury central nervous system, tissue is phagocytized primarily by ______________

Back 18

microglia


*peripheral macrophages also infiltrate injured CNS tissue

Front 19

In the CNS, __________ rapidly phagocytize damaged tissue. What do these cells essentially do?

Back 19

gitter cells (macrophages)

liquifaction= essentially dissolve necrotic tissue

Front 20

What does liquifaction eventually produce?

Back 20

damage area becomes cavity filled with ECF & CSF

*cavity isolate by glial-pial scar

Front 21

What is transneuronal degeneration?

Back 21

-in addition to the loss of the injured neuron, other neurons that are innervated by the injured neuron may undergo degeneration

Front 22

What occurs after denervation?

Back 22

muscle will show flaccid paralysis followed by l denervation supersensitivity, and the spread of extrajunctional receptors, fasciculations and rapid atrophy

Front 23

Without reinnervation, muscle degeneration will become irreversible in ____ yrs

Back 23

1-2 yrs

*set limit on amount of time available for nerve regeneration & function recovery to occur

Front 24

____________in skin will also irreversible degenerate if not reinnervated

Back 24

sensory organs

Front 25

Sensory recovery is usually ______________first followed by an incomplete recovery of _____________

Back 25

protopathic sensation

epicritic sensation.

Front 26

Surgical repair of peripheral nerves is usually limited to _________ injuries.

Back 26

neurotmesis

Front 27

Techniques of repair include epineurial suture, fascicular repair, and nerve grafting. What is a major complication of peripheral nerve injury and repair?

Back 27

Neuroma formation

Front 28

Injuries to the (PNS/CNS) is not accompanied by an appreciable amount of axonal regeneration.

Back 28

CNS

Front 29

After axonal injury, CNS neurons are generally incapable of generating a regenerative response and usually undergo a slow atrophy and cell death.
Why?

Back 29

Distal portions of CNS axons degenerate slowly, and oligodendrocytes do not form the equivalent of bands of Bugner (no groundwork for regeneration)

Front 30

T/F
The microenvironment of CNS appears to be incompatible with appreciable axonal regeneration with molecular inhibitors of axonal growth present in tissue

Back 30

TRUE