PNS/Anatomy/Injury Flashcards
(147 cards)
1
Q
Name 2 cell types in peripheral nerves
A
1) Firbroblasts
2) Schwann cells
2
Q
What do fibroblast generate?
A
Collagen fibers
3
Q
Fibroblasts are found in all types of what?
A
Connective tissue
4
Q
Schwann cells surround and support every what?
A
every axon in the peripheral whether or not they are myelinated
5
Q
What do Schwann cells produce in segments around the larger axons?
A
myelin sheaths
6
Q
Each nerve consists of fibers with a variety of diameters, name these 4 characteristcs
A
some myelinated, some unmyelinated. Some fibers are motor; some are sensory.
7
Q
Name the 2 classifcations systems by which axons (nerve fibers) are classifed
A
1) Based on conduction velocity
2) Based on fiber diameter
8
Q
T/F: In conduction velocity classification, when a peripheral nerve is stimulated and the response is recorded at some distal site, it can be observed that all impulses do arrive at the same time. Why or why not?
A
False, they do NOT arrive at the same time. This is due to the differences in the conduction velocities of the various fibers.
9
Q
Conduction Velocity class: Which group is the fastest? Which group is slower, and which group is slowest?
A
A - fastest
B - slower
C - slowest
10
Q
Conduction Velocity class: Which group is myelinated and unmyelinated?
A
A - myelinated
B - thinly myelinated (pregang. autonomic fibers)
C - unmyelinated
11
Q
Conduction Velocity class: Name the 4 subgroups of groups A
A
1) Alpha (alpha motor neuron)
2) Beta
3) Gamma (gamma motor neurons to muscle spindle)
4) Delta (fast pain fibers)
12
Q
Axons classified by diameter: Name the 4 groups and which is is most heavily myelinated to unmyelinated
A
I - most heavily myelinated
II
III
IV - unmyelinated
13
Q
Which classification system is mostly used in reference to sensory fibers?
A
Axons classified by diameter
14
Q
Give some examples of actual sensory fibers that use the diamter axon classification
A
Ia - muscle spindle primary endings
Ib - GTO
II - secondary muscle spindle
15
Q
Sensory receptors are associated with which type of fibers (touch)?
A
Type II
16
Q
Axon diameter group I, II, III, or IV? Sharp pain, cold, some touch
A
III
17
Q
Axon diameter group I, II, III, or IV? Slow pain, heat, itch
A
IV
18
Q
Axon diameter group I, II, III, or IV? Meissner corpuscles, Merkel endings, Pacinian corpuscles, etc., secondary muscle spindles
A
II
19
Q
Axon diameter group I, II, III, or IV? Ia - Muscle spindle primary endings, Ib - GTO
A
I
20
Q
Which classification system is used primarily for myelinated efferents?
A
The letter system primarily for myelinated efferents (A-alpha and A-gamma motor neurons) and small pain fibers (A-delta and C)
21
Q
Which classification system is used for myelinated afferents?
A
The number system for myelinated afferents (Ia from primary MS afferents, Ib from GTO, II secondary endings from MS and from some receptors of skin and joints)
22
Q
T/F: Axon diameter correlates with conduction velocity and thickness of myelin (and cell body size).
A
True
23
Q
Classification of axons by function: Large myelinated axons or (Small, unmyelinated and finely myelinated axons)? transmit sensation of proprioception, joint position and vibration
A
Large myelinated axons
24
Q
Classification of axons by function: Large myelinated axons or (Small, unmyelinated and finely myelinated axons)? transmit pain and temperature and poorly localized touch
A
Small, unmyelinated and finely myelinated axons
25
Classification of axons by function: Large myelinated axons or (Small, unmyelinated and finely myelinated axons)? Are motor (alpha and gamma) neurons
Large myelinated axons
26
Classification of axons by function: Large myelinated axons or (Small, unmyelinated and finely myelinated axons)? Autonomic NS
Small, unmyelinated and finely myelinated axons
27
What does the epineurium surround?
Each peripheral nerve (i.e. radial n., femoral n.)
28
What two things does the epineurium consists mostly of?
collagen fibers, and fibroblasts
29
Where is the epineurium (what % of cross sectional area) thick at and when does it thin out?
Is thick at the nerve trunk (30-75% of cross sectional area) and thins out as the nerve branches towards its termination.
30
What is the epineurium continuous with at the level of the spinal nerve?
Is continuous with the dura mater at level of spinal nerve.
31
What does the epineurium protect, and from what?
Protects fasciculi from compressive forces
32
What does the Perimeurium lie deep to?
epineurium
33
What does the perineuium surround?
Fascicles
34
What 2 things is the perineurium composed of?
1) Collagen fibers
| 2) Connective tissue cells
35
What are the cells of the perineurium connected by?
tight junctions and in effect closes off each fascicle from the fascicles around i
36
What does the perineurium maintain in the fasicle? What 2 things does this account for in the nerve?
- Maintains intrafascicular fluid pressure
| - The fluid pressure accounts for the elasticity and tensile strength of the nerve
37
What does the endoneurium consist of?
Loose connective tissue
38
Where does the endoneurium extend from?
Perineuium
39
What does the endoneurium surround?
Individual nerve fibers
40
What supplies the blood to the epi-, peri-, and endoneurium? What is it suspectible to?
- Arterioles
| - Peripheral vascular disease
41
Define neurapraxia
transitory localized conduction block with no signs of denervation
42
What causes neurapraxia?
Due to local damage to neural membrane
43
How long is the recovery period for neurapraxia? Is there lasting damage to the nerve?
Full recovery in days or weeks.
| No lasting damage to nerve
44
What type of injury may occur with neurapraxia?
Mild compression injury likely
45
Give an example of neurapraxia.
- Leg falling asleep
| - Limb going numb
46
Define Axonotmesis. What happens to the axon and what remains intact?
axon disruption but endoneurial sheath remains intact
47
What type of degeneration and regrowth takes place in axonotemsis?
Wallerian degeneration and regrowth occurs
48
With Axonotemsis, how long is the length of recovery?
Depends on distance necessary for regrowth
49
Aonotemsis, what type of injury is likely?
Streth injury (Erb's palsy)
50
In Axonotmesis, what happens in stretch injuries? (what breaks before what)?
Axon breaks before myelin sheath
51
Define neurotmesis
Complete transection of nerve with disruption of axon and endoneurium
52
What type of degeneration occurs in axonotmesis?
Wallerian degeneration takes place
53
In axonotmesis, what is required for reinnervation?
regrowth
54
What can cause a neurotmesis?
Caused by cut, crush, or severe stretch injury
55
Name 3 types of traumatic injuries to the nerve
1) Laceration
2) Crush (Compression)
3) Stretch
56
Name the 3 types of compressive injuries to the nerve
1) Acute
2) Intermittent
3) Chronic
57
Acute, intermittment, or chornic intermittent injury? May be occupational (i.e. carpal tunnel)
Intermittent
58
Acute, intermittment, or chornic intermittent injury? One time event
Acute
59
Acute, intermittment, or chornic intermittent injury? May occur with longstanding intermittent or with constant pressure
Chronic
60
What can cause a chronic compression injury that is caused by constant compression?
i.e. Iatrogenic (cast too tight, setting fractures)
| Postural, Biomechanical, Callus formation
61
Acute/Intermittment or Chornic compression? Neurapraxia
Acute/Intermittment
62
Acute/Intermittment or Chornic compression? May develop into axonotmesis
Chornic
63
Acute/Intermittment or Chornic compression? reduced NCV over compressed segment
Acute/Intermittment
64
Acute/Intermittment or Chornic compression? NCV further reduced or abolished, reduction/loss of touch/pressure
Chronic
65
Acute/Intermittment or Chornic compression? Paresthesia (an abnormal sensation, typically tingling or pricking), especially at night
Acute/Intermittent
66
Acute/Intermittment or Chornic compression? Sensory involved before motor
Acute/Intermittent
67
Acute/Intermittment or Chornic compression? pain and temp spared
Acute/Intermittent
68
Acute/Intermittment or Chornic compression? symptoms develop rapidly (depends)
Acute/Intermittent
69
Acute/Intermittment or Chornic compression? symptoms short-lived, reversible
Acute/Intermittent
70
Acute/Intermittment or Chornic compression? motor denervation changes with atrophy
Chronic
71
Acute/Intermittment or Chornic compression? pain, hyperesthesia (excessive physical sensitivity, esp. of the skin), allodynia (pain due to a stimulus which does not normally provoke pain)
Chornic
72
Acute/Intermittment or Chornic compression? symptoms and deficits progressive
Chornic
73
Acute/Intermittment or Chornic compression? external decompression may not alleviate
Chornic
74
Name 4 other causes of Neuropathy
1. Disease related - Guillian Barre, diabetes
2. Metabolic – alcoholism, diabetes
3. Toxins – Heavy Metals
4. Genetics – Charcot
75
Distal segment in wallerian degeneration: What begins hours after the injury?
Fragmentation of axon and myelin
76
Distal segment in wallerian degeneration: These two neuro__ become disarrayed
Neurotubules and neurofilaments become disarrayed
77
Distal segment in wallerian degeneration: What type of swelling occurs along the axon?
Varicose swelling
78
Distal segment in wallerian degeneration: What occurs by 48-96 hours to the axon?
Neurotubules and neurofilaments become disarrayed
79
Distal segment in wallerian degeneration: What occurs to the myelin by 36-48 hours? What phagocytizes it?
Myelin degeneration is advanced by 36-48 hours (phagocytized by mast cells)
80
Distal segment in wallerian degeneration: What type of cells help in phagoytizing and in recovery? When do they actvate upon injury? What do they actually do?
Schwann cells also help in phagocytizing and in recovery. They activate within 24 hours of injury, undergo mitosis and help the mast cells get rid of degenerated distal nerve segment and myelin
81
Distal segment in wallerian degeneration: How long does the site of injury clear post-injury?
Site of injury is cleared 1 week- several months post-injury
82
Distal segment in wallerian degeneration: At the site of injury, what are the only 2 things that remain?
All that remains is the endoneurial sheath (if that has not been disrupted by injury) and Schwann cells
83
Distal segment in wallerian degeneration: In more severe injuries when endoneurium is disrupted, what 2 things typically occur?
capillaries and hemorrhage results
84
Distal segment in wallerian degeneration: Much inflammation follows as a result and what can form?
Fibrous scar can form, axons cannot grow through scar tissue
85
Distal segment in wallerian degeneration: In mild to moderate injuries, what do Schwann cells do?
form stacks to guide the growth of growth cones from the regenerating axons
86
Proximal segment in wallerian degeneration: Cell body - Within 6 hours, what happens with the nucleus and Nissl (chromatin) substance?
Nucleus becomes eccentric (off-center) and Nissl substance breaks down
87
Proximal segment in wallerian degeneration: Define Chromatolysis
In a cell body, the nucleus becomes eccentric and the Nissle (chromatin) substance breaks down
88
Proximal segment in wallerian degeneration: What happens with the Schwann cells?
Schwann cells proliferate and phagocytize the proximal segment but this may be minimal in mild injuries
89
Proximal segment in wallerian degeneration: What occurs more likely if the injury is more proximal? (It can trigger this and __-__% of these cells die)
can trigger apoptosis (programmed cell death) and 20-50% of DRG cells may die
90
Wallerian degeneration: Functional recovery more likely to occur in which 2 types of neuropathies? Why? What neuropathy is it likely to not occur? Why?
1) Neurapraxia
2) Axonotmesis
Because endoneurial tube is intact.
91
Wallerian degeneration: Functional recovery is not likely to occur in which types of neuropathies? Why?
Without tube (as in neurotmesis) sprouting axons have little guidance
92
Wallerian degeneration: What can begin as soon as 24 hrs post-injury up to months later depending on severity?
Regrowth
93
Wallerian degeneration: Axons will sprout many what?
Collaterals
94
Wallerian degeneration: What is the typically rate of regrowth of a nerve?
1mm/day or approximately 1 inch/mo
95
Wallerian degeneration: What happens if axon grows down wrong tube, when end organ is reached?
no connection is made
96
Wallerian degeneration: SEVERE atrophy of muscle takes place with denervation (__% reduction in cross sectional area by __ months
SEVERE atrophy of muscle takes place with denervation (70% reduction in cross sectional area by 2 months
97
Wallerian degeneration: In the denervation effect on muscle, what can occur with proliferation of connective tissue?
Intramuscular fibrosis
98
Wallerian degeneration: Denervation Effect on Muscle-What may result in the giant muscle motor units? How long does this reorganization of the motor unit take?
Reinnervation
| -1 year to 18 months after injury
99
Wallerian degeneration: Denervation Effect on Muscle-Muscle reinnervation may be in__ or in__
incomplete or inefficient
100
Wallerian degeneration: Denervation Effect on Muscle: What happens with the axons originally of one fiber type when they reinnervate?
They reinnervate into other fiber types
101
Wallerian degeneration: Denervation Effect on Muscle: T/F-All muscle fibers are reinnervated
False, Not all muscle fibers are reinnervated
102
Wallerian degeneration: Denervation Effect on Muscle: What makes muscle contraction inefficient?
Connective tissue thickening (fibrosis) within muscle make contraction inefficient
103
Wallerian degeneration: Effect on Sensory: What can still happen 6-12 months post injury?
Re-establishment of sensation to the original pattern
104
Wallerian degeneration: Effect on Sensory: What happens with the receptors?
Receptors wait for up to a year in a dormant state to be reinnervated
105
Wallerian degeneration: Effect on Sensory: Effective reinnervation depends on axons doing what?
Regenerating down the correct endoneurial tube to make contact with original receptor. This doesn’t always happen
106
Wallerian degeneration: Regeneration results in: More or less axons due to collaterals?
More
107
Wallerian degeneration: Regeneration results in: Diameter?
Smaller diameter initially
108
Wallerian degeneration: Regeneration results in: What happens with the myelin?
Thinner, but eventually recovers
109
Wallerian degeneration: Regeneration results in: more or less myelin segments?
More myelin segments
110
Wallerian degeneration: Regeneration results in: Slower or quicker conduction velocity?
Slower
111
Demyelinization: What happens with AP conduction?
AP conduction can be slowed or blocked
112
Demyelinization: What causes this?
A. Certain conditions or diseases
113
Demyelinization: If cause is an inflammatory process as in Guillian Barre, what 3 things can happen?
1) damage may be permanent
2) axon may be damaged and/or
3) conduction block may be complete
114
Postinfectious Polyneuritis (Guillian-Barre syndrome)-incidence rate?
1.6/100,000/yr worldwide
115
Postinfectious Polyneuritis (Guillian-Barre syndrome)-How old are people when it occurs?
young adults, early middle age
116
Postinfectious Polyneuritis (Guillian-Barre syndrome)-When does it usually appear after?
Infectious illness
117
Postinfectious Polyneuritis (Guillian-Barre syndrome)-Lymphocytic sensitization to what?
peripheral nerve antigen
118
Postinfectious Polyneuritis (Guillian-Barre syndrome)-Symptoms include: a. __ weakness (severe) hours to days b. ar__ c. elevated __ protein d. possible __ nerve and __ involvement e. may have mild __ loss; disproportional __ loss f. inflammatory segmental __
a. ascending weakness (severe) hours to days
b. areflexia
c. elevated CSF protein
d. possible cranial nerve and respiratory involvement
e. may have mild sensory loss; disproportional motor loss
f. inflammatory segmental demyelination
119
Postinfectious Polyneuritis (Guillian-Barre syndrome)-May progress over __ days, stay stable for __ weeks, then __ mo to __ yrs recovery
May progress over 10 days, stay stable for 2 weeks, then 6 mo to 2 yrs recovery
120
Postinfectious Polyneuritis (Guillian-Barre syndrome)-__% do not fully recover
10% do not fully recover
121
Postinfectious Polyneuritis (Guillian-Barre syndrome)-Early indicators of possible incomplete recovery: More than 3 weeks from maximum weakness to initial __, __ motor nerve conduction velocities, EMG evidence __, R__ support
Early indicators of possible incomplete recovery:
More than 3 weeks from maximum weakness to initial improvement
Reduced motor nerve conduction velocities
EMG evidence of denervation
Respiratory support
122
Postinfectious Polyneuritis (Guillian-Barre syndrome)-Name 2 types of treatments
1) Plasmapheresis (means take out the antibodies)
2) Intravenous immunoglobulin treatment (IVIg)
Via several different mechanisms, interrupts the abnormal immune response responsible for the inflammation
123
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)-May appear initially as __ __
Guillian Barre
124
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)-Define
Is a chronic, progressive autoimmune mediated inflammation of the peripheral myelin
125
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)-Sensory and motor equally or unqually involved
Sensory and motor equally involved
126
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)-Leads to severe __ over a period of years
disability
127
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)-Name 3 treatments for CIDP
1) Steroids for short term
2) Plasmapheresis
3) IV IGg
128
Multiple Sclerosis (MS)-Define
It is a disease characterized by the appearance and relapse of neurological deficits in multiple areas of the central nervous system with primary damage to myelinated axons.
129
Multiple Sclerosis (MS)-What is MS produced by? What does it result in?
It is produced by an environmental agent in a genetically susceptible individual resulting in an alteration of immune mechanisms in the CNS.
130
Multiple Sclerosis (MS)-Classification-How many types are there?? Which one is most common?
4 types but most common is chronic relapsing-remitting
131
Multiple Sclerosis (MS)-Occurs twice as frequently in (women or men) as in (women or men)
Occurs twice as frequently in women as in men
132
Multiple Sclerosis (MS)-Mainly in (young or old) adults
Mainly in young adults (average age in U.S. is 24).
133
Multiple Sclerosis (MS)-More prevalent in __ temperate latitudes
More prevalent in north temperate latitudes (Believe it’s a genetic and environmental factors), In these areas is the most frequent cause of chronic disability in the young and middle aged populations.
134
Multiple Sclerosis (MS)-a. S__ (dysesthesia (unpleasant, abnormal sense of touch), paresthesia, anesthesia), b. M__ (decreased control and spasticity), c. V__ - Optic Neuritis, d. B__ dysfunction, e. Br__ signs, f. Cer__ signs, g. Dem__
a. Sensory (dysesthesia, paresthesia, anesthesia)
b. Motor (decreased control and spasticity)
c. Visual - Optic Neuritis
d. Bladder dysfunction
e. Brainstem signs
f. Cerebellar signs
g. Dementia
135
MS or GB? ascending weakness (severe) hours to days
GB
136
MS or GB? areflexia
GB
137
MS or GB? Sensory (dysesthesia, paresthesia, anesthesia)
MS
138
MS or GB? Motor (decreased control and spasticity)
MS
139
MS or GB? Visual - Optic Neuritis
MS
140
MS or GB? Bladder dysfunction
MS
141
MS or GB? elevated CSF protein
GB
142
MS or GB? possible cranial nerve and respiratory involvement
GB
143
MS or GB? may have mild sensory loss; disproportional motor loss
GB
144
MS or GB? inflammatory segmental demyelination
GB
145
MS or GB? Brainstem signs
MS
146
MS or GB? Cerebellar signs
MS
147
MS or GB? Dementia
MS
