7.3 lecture - NS organization & embryology Flashcards
1
Q
3 classifications of neurons by shape include:
A
unipolar (pseudounipolar)
bipolar
multipolar
2
Q
what are nissl bodies
A
- clumps of basophilic die in neuron soma on LM
- can be seen in H&E and multiple stains but most evident in nissl stain
- correspond to RER
3
Q
this structure forms the “receiving end” of a neuron
A
dendrite
4
Q
axodendritic synapse
A
synapse between axon & dendrite
5
Q
presynaptic element
A
specialized for release of neurotransmitter
6
Q
neurotransmitter is released from the __ element
A
presynaptic
7
Q
postsynaptic element
A
contains membrane receptors to convert chemical signal into membrane potential
8
Q
name 3 types of synapses based on anatomical location
A
axodendritic synapse (most common)
axosomatic synapse
asoaxonal synapse
9
Q
axosomatic synapse
A
between axon & cell body
10
Q
axoaxonal synapse
A
between axon and another axon
11
Q
where does the presynaptic element occur?
A
terminal bouton - at end of axon
or
bouton en passant - if along length of axon
12
Q
terminal bouton
A
presynaptic element at end of axon
13
Q
bouton en passent
A
presynaptic element before the end of axon
14
Q
where does the postsynaptic element Usually occur?
A
on the dendritic spine
15
Q
where on the neuron is an action potential typically generated?
A
axon hillock
16
Q
in a myelinated axon, spikes (APs) propagate via __ conduction
A
saltatory conduction
17
Q
saltatory conduction
A
saltatory = “jumping”
the name for action potential propagation along nodes of ranvier in a myelnated axon
18
Q
node of ranvier
A
naked axon node between myelinated internodes
19
Q
T/F action potentials travel more slowly down unmyelinated axons
A
true
APs travel more quickly by saltatory conduction down myelinated axons
20
Q
what is a myelin internode composed of?
A
wrapped cell plasma membrane
CNS - foot of an oligodendrocyte membrane
PNS - schwann cell membrane
21
Q
how many myelin internodes can be formed by…
- a schwann cell?
- an oligodendrocyte?
A
schwann cell - one myelin internode in PNS
oligodendrocyte - multiple “feet” in CNS
22
Q
how many myelin internodes can be formed by a schwann cell in the PNS?
A
one
23
Q
how many myelin internodes can be formed by an oligodendrocyte in the CNS?
A
multiple
24
Q
what is the difference between a schwann cell and an oligodendrocyte?
A
- schwann cells are located only in PNS, they form one myelin internode for a nearby axon and can support multiple unmyelinated axons which shoot through it like rods through dough
- oligodendrocytes are located only in CNS, they can form multiple myelin internodes on different axons with multiple projections or “feet” of its plasma membrane – but they do not engulf unmyelinated axons like schwann cells in the PNS
25
are unmyelinated fibers more commonly found in the CNS or PNS?
they can be found in either, i think
PNS - small fibers for slow aches / pain / temp
CNS - maybe interneurons and other short neurons
26
on EM, myelin internodes can be seen as...
alternating major dense lines (apposed cytoplasmic membrane faces), and intraperiod lines (apposed ectoplasmic membrane faces)
27
major dense line
apposed protoplasmic schwann or oligodendrocyte cell membrane faces in a myelin internode on EM (alternates with intraperiod lines)
28
intraperiod line
apposed ectoplasmic schwann or oligodendrocyte cell membrane faces in a myelin internode on EM (alternates with major dense lines)
29
inner mesaxon
the tip of the myelin sheath that lies next to the axon
30
outer mesaxon
the tip of the myelin sheath that rests atop the last layer of myelin and the transition into schwann/oligodendrocyte cell body
31
T/F inner and outer mesaxons are both parts of the same process from the schwann/oligodendrocyte cell body
false
when wrapping an axon, the support cell extends two processes, one around either side of the axon in opposite directions (grabs it like a hand and rolls into a fist). the process that winds inward around the axon is the inner mesaxon (finger); the process that extends around the outside surface of the myelin sheath and rests on top is the outer mesaxon (thumb)
32
if a myelin sheath is like a fist around a pen, which mesaxon is the finger and which is the thumb?
inner mesaxon - finger
| outer mesaxon - thumb
33
what is the general term for non-neuronal cells in nervous tissue?
glial cells
or
neuroglial cells
34
T/F glia is another term for neuroglial cells
true
35
what are the general functions of glial cells?
scaffolding
metabolic support
blood-brain barrier contributions
36
why are non-neruonal cells in nervous tissue called glial cells?
glia = glue
| glial cells support neurons with scaffolding, metabolic support, etc (they do not literally stick neurons together)
37
name 5 neuroglial cells and their locations
```
astrocytes (CNS)
microglia (CNS)
oligodendrocytes (CNS)
schwann cells (PNS)
satellite cells (PNS)
```
38
astrocyte function
astrocytes are like the connective tissue of the CNS (which has no connective tissue)
- structure (glial fibrillary acidic protein)
- space filler
- stabilize ionic medium
- provide metabolic support
- proliferate and form scar in CNS damage
39
2 types of astrocytes
```
fibrous astrocyte (white matter)
protoplasmic astrocyte (grey matter)
```
40
fibrous astrocyte
astrocyte in white matter (axons)
41
protoplasmic astrocyte
astrocyte in grey matter (neuron soma)
42
this cell type takes up excess neurotransmitter and helps regulate the ion composition of the fluid around neurons
astrocyte
43
an astrocyte in white matter is called
fibrous astrocyte
44
an astrocyte in grey matter is called
protoplasmic astrocyte
45
microglial function
macrophage of the CNS
| phagocytic cell patrolling brain and spinal cord
46
oligodendrocyte function
form multiple myelin internodes on CNS axons
47
this glial cell is part of the mononuclear phagocytic system MPS
microglia
48
where are microglia derived from?
from monocytes in bone marrow
49
the smallest type of neuroglial cell is the
microglia
| macrophage of the CNS
50
macroglia include
all glial cells other than microglia
- astrocytes
- oligodendrocytes
- schwann cells
- satellite cells
51
schwann cell function
- form single myelin internode on PNS axon
| - support unmyelinated axons like dough punched with rods
52
satellite cell function
```
encapsulate neuron soma in PNS ganglia
(usually multiple satellites per soma)
-protective cushion
-structural
-nutrient supply
```
53
how many satellite cells surround one neuron soma in a PNS ganglion?
usually multiple
53
how many satellite cells surround one neuron soma in a PNS ganglion?
usually multiple
54
T/F one satellite cell wraps around a neuron soma in a PNS galngion like a schwann cell wraps around an axon
false
| multiple satellite splat on a soma to cover it, NOT just one wrapping around it
54
T/F one satellite cell wraps around a neuron soma in a PNS galngion like a schwann cell wraps around an axon
false
| multiple satellite splat on a soma to cover it, NOT just one wrapping around it
55
this cell forms multiple myelin internodes in the CNS
oligodendrocyte
55
what is the unique intermediate filament in astrocytes?
GFAP glial fibrillary acidic protein
| -useful for antibody staining
56
this cell in the PNS forms one myelin internode and can support multiple unmyelinated axons as well
schwann cell
56
this cell in the PNS forms one myelin internode and can support multiple unmyelinated axons as well
schwann cell
57
these cells cover a neuron soma in PNS ganglia, providing a cushion and nutrients
satellite cell
57
these cells cover a neuron soma in PNS ganglia, providing a cushion and nutrients
satellite cell
58
what is the unique intermediate filament in astrocytes?
GFAP glial fibrillary acidic protein
| -useful for antibody staining
58
what is the unique intermediate filament in astrocytes?
GFAP glial fibrillary acidic protein
| -useful for antibody staining
59
what characteristic of astrocytes can make them easily identifiable through antibody staining?
GFAPs
glial fibrillary acidic proteins
special intermediate filaments unique to astrocytes
59
what characteristic of astrocytes can make them easily identifiable through antibody staining?
GFAPs
glial fibrillary acidic proteins
special intermediate filaments unique to astrocytes
60
what is a GFAP?
glial fibrillary acidic proteins
| special intermediate filaments unique to astrocytes
60
what is a GFAP?
glial fibrillary acidic proteins
| special intermediate filaments unique to astrocytes
61
define ganglia
collections of neuron cell bodies outside the CNS (in the PNS)
61
define ganglia
collections of neuron cell bodies outside the CNS (in the PNS)
62
a discrete group of neuron soma in the CNS is called a __
nucleus
| e.g. brainstem nucleus, paraventricular nucleus, etc
62
a discrete group of neuron soma in the CNS is called a __
nucleus
| e.g. brainstem nucleus, paraventricular nucleus, etc
63
what is the synapse between motor neuron and muscle called?
neuromuscular junction
63
neuromuscular junction
synapse between motor neuron and muscle
64
the post-synaptic region of the plasmalemma of muscle is called the...
motor end plate
64
motor end plate
the post-synaptic region of the plasmalemma of muscle
65
is there a motor end plate on smooth muscle?
in rudimentary form
| neuromuscular junction is most specialized in skeletal muscle
65
is there a motor end plate on cardiac muscle?
```
probably not so much... but possibly...
scarce innervation (autoelectrogenic)
```
66
neurophil
synaptically dense mesh of axons & dendrites
- most prominently in grey CNS matter
- but maybe possible in PNS ganglia?
66
neurophil
synaptically dense mesh of axons & dendrites
- most prominently in grey CNS matter
- but maybe possible in PNS ganglia?
67
3 meninges covering brain
```
dura mater (outer)
arachnoid mater (middle)
pia mater (inner)
```
67
3 meninges covering brain
```
dura mater (outer)
arachnoid mater (middle)
pia mater (inner)
```
68
this meninge of the brain is extremely tough
dura mater
68
this meninge of the brain is extremely tough
dura mater
69
what is the subarachnoid space?
space between arachnoid & pia mater usually filled with cerebral spinal fluid
69
what is the subarachnoid space?
space between arachnoid & pia mater usually filled with cerebral spinal fluid
70
this is a common site of brain hemorrhage
subarachnoid space
| space between arachnoid & pia mater usually filled with cerebral spinal fluid
70
this is a common site of brain hemorrhage
subarachnoid space
| space between arachnoid & pia mater usually filled with cerebral spinal fluid
71
2 classes of peripheral neurons
sensory
| motor
71
2 classes of peripheral neurons
sensory
| motor
72
these neurons control skeletal muscle
motor neurons
72
these neurons control skeletal muscle
motor neurons
73
what is the synapse between motor neuron and muscle called?
neuromuscular junction
73
what is the synapse between motor neuron and muscle called?
neuromuscular junction
74
neuromuscular junction
synapse between motor neuron and muscle
74
neuromuscular junction
synapse between motor neuron and muscle
75
the post-synaptic region of the plasmalemma of skeletal muscle is called the...
motor end plate
75
the post-synaptic region of the plasmalemma of skeletal muscle is called the...
motor end plate
76
motor end plate
the post-synaptic region of the plasmalemma of skeletal muscle
76
this nervous system has one long efferent nerve (no efferent ganglia)
somatic
77
is there a motor end plate on smooth muscle?
no
| no motor neuron, no voluntary control, no motor endplate
77
is there a motor end plate on smooth muscle?
no
| no motor neuron, no voluntary control, no motor endplate
78
is there a motor end plate on cardiac muscle?
no
| no motor neuron, no voluntary control, no motor endplate
78
is there a motor end plate on cardiac muscle?
no
| no motor neuron, no voluntary control, no motor endplate
79
how do motor neurons pass out of the spinal cord?
ventral root
79
pleomorphic vesicles indicate a __ synapse
inhibitory
80
what are the characteristics of a neuromuscular junction that can help you distinguish it from a nervous system synapse?
- folds in the muscle fiber membrane
- external lamina between may appear as a thin dark line between muscle plasma mebrane and axon plasma membrane
- maybe sarcomeres, actin, dense bodies
80
this neuron type passes out of the spinal cord through the ventral root
motor neuron
81
what kind of neurons exist in the ventral root
motor neurons
81
what kind of neurons exist in the ventral root
motor neurons
82
how do sensory neurons pass into the spinal cord?
through the dorsal root, after passing through the dorsal route ganglion
82
how do sensory neurons pass into the spinal cord?
through the dorsal root, after passing through the dorsal route ganglion
83
this neuron type passes into the spinal cord through the dorsal root
sensory neuron
83
this neuron type passes into the spinal cord through the dorsal root
sensory neuron
84
what kind of neurons exist in the dorsal root?
sensory neurons
84
what kind of neurons exist in the dorsal root?
sensory neurons
85
what is a motor neuron?
an efferent neuron that conducts signals from CNS to effectors (can be somatic or autonomic, sympathetic or parasympathetic, all have motor neurons)
85
what is a motor neuron?
an efferent neuron that conducts signals from CNS to effectors (can be somatic or autonomic, sympathetic or parasympathetic, all have motor neurons)
86
what is a sensory neuron?
an afferent neuron that conducts signals from periphery to CNS (can be somatic or autonomic, sympathetic or parasympathetic, all have sensory neurons)
86
what is a sensory neuron?
an afferent neuron that conducts signals from periphery to CNS (can be somatic or autonomic, sympathetic or parasympathetic, all have sensory neurons)
87
how is a motor neuron different from an efferent neuron?
i think they are basically the same thing...
87
how is a motor neuron different from an efferent neuron?
i think they are basically the same thing...
88
what organelles are found in dendrites?
```
microtubules
mitochondria
ER (in Large dendrites)
ribosomes (in Large dendrites)
neurofilaments (in Large dendrites)
```
89
on EM of a dendrite cross section, what are three circular structures that are likely to be observed?
```
from large to small:
mitochondria
microtubules
neurofilaments (in Large dendrites)
ER (in Large dendrites)
ribosomes (in Large dendrites)
```
90
what kind of cytoskeletal filaments are prevalent in dendrites?
microtubules (always prevalent)
| neurofilaments (in Large dendrites)
91
which has larger cross sectional area, microtubules or neurofilaments? which is likely to be seen in a dendrite?
microtubules are larger
microtubules will always be seen, slightly larger
neurofilaments many be found in large dendrites
92
what is a dendritic spine?
small stickings out of the dendritic plasmalemma that each receive an axon terminal from another neuron
(look like running ink into little lateral short cracks along large crack that is dendrite on LM, or like a seismograph reading)
93
3 classes of connective tissue investments in the CNS
trick!
no connective tissue in the CNS
space is filled by astrocytes
94
T/F dendritic spines are dynamic and can move and grow
true
95
how many efferent neurons to conduct a parasympathetic motor signal?
2 - peripheral ganglia in or near effector organs / tissues
96
how many efferent neurons to conduct a sympathetic motor signal?
2 - paravertebral ganglia (sympathetic chain)
97
how many afferent neurons to conduct a sensory signal from any division of the nervous system
1 - pseudounipolar neurons with soma in the dorsal root ganglia
98
this nervous system has short preganglionic and long postganglionic efferent nerves
sympathetic
99
this nervous system has long preganglionic and short postganlionic efferent nerves
parasympathetic
100
this nervous system has one long efferent nerve (no efferent ganglia)
somatic
101
which membrane surface has more associated protein, protoplasmic or ectoplasmic?
protoplasmic
102
postsynaptic density
a histological term for postsynaptic element (appears as a density due to density of receptors)
103
how to tell an excitatory synapse from an inhibitory synapse on EM?
```
excitatory
-asymmetric: postsynaptic density is darker than presynaptic density
-vesicles are round
-narrower
inhibitory
-symmetric: pre and post synaptic densities are same density
-pleomorphic vesicles (altered shape)
-wider
```
104
a symmetric synapse is a __ synapse
inhibitory synapse
- pre and post synaptic densities are same density
- pleomorphic vesicles (altered shape)
- wider
105
an asymmetric synapse is a __ synapse
excitatory synapse
- postsynaptic density is darker than presynaptic density
- vesicles are round
- narrower
106
pleomorphic vesicles indicate a __ synapse
inhibitory
107
what are the characteristics of a neuromuscular junction that can help you distinguish it from a nervous system synapse?
a
108
how can you determine the location of a synaptic active site on EM?
the presynaptic vesicles may be queued / clustered at the synaptic sites, ready for release
109
what does a multipolar neuron look like on LM?
non-circular nucleus, can probably see multiple branches coming out before lost in surrounding tissue
110
T/F dendrites contain RER
~true
| Large dendrites may have RER
111
is a neuron typically very actively transcribing or relatively quiescent?
actively transcribing
euchromatic
prominent nucleuolus
112
how large / small is a nueronal soma compared to surrounding glial cells?
very large
soma nucleus is larger than surrounding glia
soma nucleolus is about = surrounding glial nuclei
113
how do glial cells compare to neuron cell bodies in size?
they are much smaller
| just the somal nucleolus is ~ the size of surrounding glial cell nuclei
114
what do nissl bodies look like on EM?
stacks of ER
115
golgi stain
stains only 1-5% of neurons (no one really knows why...) makes easier to visualize neuron and processes
116
if a stain illustrates just one neuron or only a few, what kind of stain is it probably?
golgi stain
| stains only 1-5% of neurons (no one really knows why...) makes easier to visualize neuron and processes
117
the angle between branching dendrites is...
usually < 90 degrees
118
the angle in a branching axon is...
usually ~90 degrees
119
how do dendrites change with distance from cell body?
they taper off and end not too far away
120
what kind of glial cell is found in dorsal root ganglia?
satellite cell
subclass of schwann cell that splats onto pseudounipolar soma to protect / nourish
-found around all PNS soma / ganglia
121
where are satellite cells found?
in PNS ganglia splatting onto neuron soma
122
what do satellite cells look like on LM?
like a light staining layer with multiple peripheral nuclei around a neuron soma (round and unipolar (pseudounipolar) if in the dorsal root ganglia)
123
what do unipolar (pseudounipolar) neurons look like on LM?
mostly round soma, maybe one extension for axon if in right plane of section (multipolar were distorted by multiple processes)
- still have nissl bodies and large euchromatic nucleus with prominent nucleoulus
- surrounded by light layer of satellite cells
124
on EM of a dendrite cross section, what are three circular structures that are likely to be observed?
from large to small:
mitochondria
microtubules
neurofilaments
125
most of the nonstaining space between neuronal soma in a nissl stain is occupied by...
astrocytes ("connective tissue" of the CNS)
| or perhaps oligodendrocytes (more associated with axons)
126
which has larger cross sectional area, microtubules or neurofilaments? which is likely to be seen in a dendrite?
microtubules are larger
| both are likely to be seen, microtubules will be slightly larger
127
what is a dendritic spine?
small stickings out of the dendritic plasmalemma that each receive an axon terminal from another neuron
(look like running ink into little lateral short cracks along large crack that is dendrite on LM)
128
how can you tell an astrocyte from an oligodendrocyte on EM?
GFAP glial fibrillary acidic protein
| appears like a dense cable of fibers in an astrocyte
129
this glial cell is very dynamic, moves through nervous tissue quickly, and is responsible for immune surveillance in the CNS
microglia
130
glial function in CNS:
- physical support
- control of microenvironment
- myelin synthesis
- defense / immune
astrocyte - physical support
astrocyte - control of microenvironment
oligodendrocyte - myelin synthesis
microglia - defense / immune
131
are there nissl bodies in axons and dendrites?
large dendrites maybe (may have R & RER)
| axons no - no RER or free ribosomes
132
are there mitochondria in axons and dendrites on EM?
yes
higher conc in dendrites
stray mitochondria in axons
133
what organelles are likely to be seen in an axon transverse section
neurofilaments (smaller dots)
microtubules (larger, possibly tubular)
stray mitochondria
No RER or free ribosomes
134
what does a myelinated axon look like on transverse H&E?
eosinophilic cytoplasm
| pale ring of myelin (lipid bilayer does not stain usually, though have seen it stain darker than axon in some slides)
135
what does a myelinated axon look like on osmium stain?
light axon
black myelin layer
(heavy metal stain, stains lipids dark)
136
what is the best way to tell a longitudinal section of a nerve from smooth muscle, tendon, or other connective tissue?
can spot nodes of ranvier
| look like transverse lines
137
why do folds in myelin sometimes appear to come apart on EM?
schwann cell is opening a path for communication to axon
138
what do unmyelinated axons look like on EM?
may have microtubules & neurofilaments, possibly mitochondria, may be smaller next to myelinated axons, may be a cluster poking through schwann cell cytoplasm
139
what do unmyelinated axons look like on LM?
frothies near a dark schwann cell nucleus
| each froth is smaller than a myelinated axon
140
what does a terminal bouton look like on golgi stain?
like a bleb at the end of an axon
141
```
glial function PNS CNS
phys support
microenvironment
myelin
defense/immune
```
glial function PNS CNS
phys support ct astro
microenvironment schw/sat astro
myelin schw oligo
defense/immune immun micro
142
what are the branches at the end of an axon called?
collaterals
143
what is an axospinous synapse?
axon to dendritic spine
144
T/F in rare cases, dendrites can have vesicles and pre presynaptic
true
| in rare cases
145
T/F dendrites contain RER
~true
| Large dendrites may have RER
146
multiple dendrites + axon = __ neuron
multipolar neuron
147
bipolar neuron
one input process (dendrite)
one output process (axon)
only found in retina & olfactory bulb
148
where are bipolar neurons found?
only retina and olfactory bulb
149
what kind of neuron is found in the retina?
bipolar neurons
150
what kind of neuron is found in the olfactory bulb?
bipolar neurons
151
what kind of neuron is found only in the retina and olfactory bulb?
bipolar neurons
152
where are unipolar (pseudounipolar) nuerons found?
only in the dorsal root ganglia
| sensory ganglia of the PNS
153
this neuron is only found in the sensory ganglia of the PNS
unipolar (pseudounipolar)
154
what is the funciton of a unipolar (pseudounipolar) neuron?
allow fast conduction through dorsal root ganglion (sensory) while still maintaining a cell body for protein production and function
155
what kind of glial cell is found only in dorsal root ganglia?
```
satellite cell
subclass of schwann cell that splats onto pseudounipolar soma to protect / nourish
```
156
where are satellite cells found?
in dorsal root ganglia splatting onto pseudounipolar soma of sensory nerves
157
what do satellite cells look like on LM?
like a light staining layer with multiple peripheral nuclei around a round unipolar (pseudounipolar) neuron soma
158
what do unipolar (pseudounipolar) neurons look like on LM?
mostly round soma, maybe one extension for axon if in right plane of section (multipolar were distorted by multiple processes)
-still have nissl bodies and large euchromatic nucleus with prominent nucleoulus
159
T/F the size of a glial cell nucleus is ~ the size of a neuron nucleolus
true
160
most of the nonstaining space between neuronal soma in a nissl stain is occupied by...
astrocytes ("connective tissue" of the CNS)
161
what is a glial scar made up of?
astrocytes
162
what proportion of central nervous tissue is occupied by extracellular structures?
0%
no extracellular structures
spaces between neurons taken up by oligodendrocytes and astrocytes
163
how can you tell an astrocyte from an oligodendrocyte on EM?
GFAP glial fibrillary acidic protein
| appears like a dense cable of fibers in an astrocyte
164
this glial cell is very dynamic, moves through nervous tissue quickly, and is responsible for immune surveillance in the CNS
microglia
165
glial function in CNS:
- physical support
- control of microenvironment
- myelin synthesis
- defense / immune
astrocyte - physical support
astrocyte - control of microenvironment
oligodendrocyte - myelin synthesis
microglia - defense / immune
166
dense connective tissue sheath around PNS nerves
epineurium
167
collagen fibers with squamous cells around PNS nerves
perineurium
168
type III collagen fibers between myelin sheaths in PNS
endoneurium
169
nervous tissue external lamina =
basal lamina surrounding schwann cells
171
what controls the microenvironment of neurons in the PNS?
schwann cells
| satellite cells
172
how to tell if an EM is from CNS or PNS?
PNS will have the following; CNS will not
- collagen (clusters of transversely cut cables)
- external lamina (fuzziness) around schwann cell
173
silver stains...
reticular fibers
intracellular material of neurons
stroma
174
```
glial function in PNS:
physical support -
control of microenvironment -
myelin synthesis -
defense / immune -
```
physical support - connective tissue
control of microenvironment - schwann / sat
myelin synthesis - schwann
defense / immune - immune system
175
```
glial function PNS CNS
phys support
microenvironment
myelin
defense/immune
```
glial function PNS CNS
phys support ct astro
microenvironment schw/sat astro
myelin schw oligo
defense/immune immun micro
176
what is the series of events that occurs in the course of peripheral nerve regeneration
```
cut/trauma
local changes
retrograde reaction (chromotolysis)
antegrade reaction
distal axon & myelin phagocytosed
schwan cells proliferate distally
schwan tubes or bands of bungner
soma begins heightened production
proximal axon sprouts
grows into tubes
schwann cells remyelinate
guide to targer
```
177
why does peripheral nerve regeneration sometimes fail?
if sprouting axon cannot reach schwann cell tubes and it is unable to reach target, produces traumatic neuroma
178
what is a traumatic neuroma?
a painful tangle of axon that forms if a regenerating axon cannot reach distal schwann cell tube to complete regeneration
179
what is the consequence of failed peripheral nerve regeneration?
traumatic neuroma
| a tangle of axon that forms if a regenerating axon cannot reach distal schwann cell tube to complete regeneration
180
chromatolysis
dissolution of nissl bodies in neuron soma in the event of nerve injury, perhaps nucleus moves to periphery
- nerve may undergo apoptosis
- if sufficient support from schwann cells and external membrane is present, peripheral nerve may regenerate after chromatolysis
181
how will the soma of a transected neuron compare to other intact neurons nearby?
soma loses nissl bodies (no need to send material down axon, chromatolysis)
-nucleus may move to periphery
182
is nerve regeneration possible in the CNS?
extremely rare
- no external lamina to guide axon sprouts
- central myelin inhibits axon growth in CNS
- astrocytes fill space with gliotic scar
204
what are the following connective tissue elements formed by?
- external lamina
- endoneurium
- perineurium
- epinuerium
external lamina - basal lamina of schwann cells (type IV collagen)
endoneurium - type III collagen fibers
perineurium - collagen fibers (III and IV) with squamous cells
epineurium - dense irregular connective tissue (type I collagen)
205
what are the following connective tissue elements formed by?
- external lamina
- endoneurium
- perineurium
- epineurium
external lamina - basal lamina of schwann cells (type IV collagen)
endoneurium - type III collagen fibers
perineurium - collagen fibers (III and IV) with squamous cells
epineurium - dense irregular connective tissue (type I collagen)
219
is nerve regeneration possible in the PNS?
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yes it can be achieved, this is the process:
cut/trauma
local changes
retrograde reaction (chromotolysis)
antegrade reaction (wallerian reaction)
distal axon & myelin phagocytosed
schwan cells proliferate distally
schwan tubes or bands of bungner
soma begins heightened production
proximal axon sprouts
grows into tubes
schwann cells remyelinate
guide to targer
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220
wallerian degeneration
the antegrade reaction in the distal part of a severed nerve... leads to distal axon and myelin being phagocytosed
221
after nerve injury:
retrograde reaction is called...
antegrade reaction is called...
chromatolysis
| wallerian degeneration
222
the ventral root of the spinal cord is severed. where my you look to observe wallerian degeneration?
surface of striated muscle
| or at the presynaptic end of another motor synapse
223
what kind collagen is found in endoneurium?
type III (reticular)
224
T/F type 1 collagen is found in endoneurium
false
| type III collagen (reticular)
225
what collagen types exist in the following connective tissue layers in peripheral nervous tissue?
- external lamina
- endoneurium
- perineurium
- epineurium
external lamina - type IV
endoneurium - type III
perineurium - type III and type IV
epineurium - type I
