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COT 1 (WPH) > 7.3 lecture - NS organization & embryology > Flashcards

7.3 lecture - NS organization & embryology Flashcards

1
Q

3 classifications of neurons by shape include:

A

unipolar (pseudounipolar)
bipolar
multipolar

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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
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3
Q

this structure forms the “receiving end” of a neuron

A

dendrite

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4
Q

axodendritic synapse

A

synapse between axon & dendrite

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5
Q

presynaptic element

A

specialized for release of neurotransmitter

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6
Q

neurotransmitter is released from the __ element

A

presynaptic

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7
Q

postsynaptic element

A

contains membrane receptors to convert chemical signal into membrane potential

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8
Q

name 3 types of synapses based on anatomical location

A

axodendritic synapse (most common)
axosomatic synapse
asoaxonal synapse

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9
Q

axosomatic synapse

A

between axon & cell body

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10
Q

axoaxonal synapse

A

between axon and another axon

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11
Q

where does the presynaptic element occur?

A

terminal bouton - at end of axon
or
bouton en passant - if along length of axon

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12
Q

terminal bouton

A

presynaptic element at end of axon

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13
Q

bouton en passent

A

presynaptic element before the end of axon

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14
Q

where does the postsynaptic element Usually occur?

A

on the dendritic spine

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15
Q

where on the neuron is an action potential typically generated?

A

axon hillock

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16
Q

in a myelinated axon, spikes (APs) propagate via __ conduction

A

saltatory conduction

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17
Q

saltatory conduction

A

saltatory = “jumping”

the name for action potential propagation along nodes of ranvier in a myelnated axon

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18
Q

node of ranvier

A

naked axon node between myelinated internodes

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19
Q

T/F action potentials travel more slowly down unmyelinated axons

A

true

APs travel more quickly by saltatory conduction down myelinated axons

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20
Q

what is a myelin internode composed of?

A

wrapped cell plasma membrane
CNS - foot of an oligodendrocyte membrane
PNS - schwann cell membrane

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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

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22
Q

how many myelin internodes can be formed by a schwann cell in the PNS?

A

one

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23
Q

how many myelin internodes can be formed by an oligodendrocyte in the CNS?

A

multiple

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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
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25
Q

are unmyelinated fibers more commonly found in the CNS or PNS?

A

they can be found in either, i think
PNS - small fibers for slow aches / pain / temp
CNS - maybe interneurons and other short neurons

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26
Q

on EM, myelin internodes can be seen as…

A

alternating major dense lines (apposed cytoplasmic membrane faces), and intraperiod lines (apposed ectoplasmic membrane faces)

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27
Q

major dense line

A

apposed protoplasmic schwann or oligodendrocyte cell membrane faces in a myelin internode on EM (alternates with intraperiod lines)

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28
Q

intraperiod line

A

apposed ectoplasmic schwann or oligodendrocyte cell membrane faces in a myelin internode on EM (alternates with major dense lines)

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29
Q

inner mesaxon

A

the tip of the myelin sheath that lies next to the axon

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30
Q

outer mesaxon

A

the tip of the myelin sheath that rests atop the last layer of myelin and the transition into schwann/oligodendrocyte cell body

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31
Q

T/F inner and outer mesaxons are both parts of the same process from the schwann/oligodendrocyte cell body

A

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)

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32
Q

if a myelin sheath is like a fist around a pen, which mesaxon is the finger and which is the thumb?

A

inner mesaxon - finger

outer mesaxon - thumb

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33
Q

what is the general term for non-neuronal cells in nervous tissue?

A

glial cells
or
neuroglial cells

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34
Q

T/F glia is another term for neuroglial cells

A

true

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35
Q

what are the general functions of glial cells?

A

scaffolding
metabolic support
blood-brain barrier contributions

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36
Q

why are non-neruonal cells in nervous tissue called glial cells?

A

glia = glue

glial cells support neurons with scaffolding, metabolic support, etc (they do not literally stick neurons together)

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37
Q

name 5 neuroglial cells and their locations

A 
astrocytes (CNS)
microglia (CNS)
oligodendrocytes (CNS)
schwann cells (PNS)
satellite cells (PNS)
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38
Q

astrocyte function

A

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
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39
Q

2 types of astrocytes

A 
fibrous astrocyte (white matter)
protoplasmic astrocyte (grey matter)
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40
Q

fibrous astrocyte

A

astrocyte in white matter (axons)

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41
Q

protoplasmic astrocyte

A

astrocyte in grey matter (neuron soma)

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42
Q

this cell type takes up excess neurotransmitter and helps regulate the ion composition of the fluid around neurons

A

astrocyte

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43
Q

an astrocyte in white matter is called

A

fibrous astrocyte

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44
Q

an astrocyte in grey matter is called

A

protoplasmic astrocyte

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45
Q

microglial function

A

macrophage of the CNS

phagocytic cell patrolling brain and spinal cord

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46
Q

oligodendrocyte function

A

form multiple myelin internodes on CNS axons

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47
Q

this glial cell is part of the mononuclear phagocytic system MPS

A

microglia

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48
Q

where are microglia derived from?

A

from monocytes in bone marrow

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49
Q

the smallest type of neuroglial cell is the

A

microglia

macrophage of the CNS

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50
Q

macroglia include

A

all glial cells other than microglia

  • astrocytes
  • oligodendrocytes
  • schwann cells
  • satellite cells
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51
Q

schwann cell function

A
  • form single myelin internode on PNS axon

- support unmyelinated axons like dough punched with rods

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52
Q

satellite cell function

A 
encapsulate neuron soma in PNS ganglia
(usually multiple satellites per soma)
-protective cushion
-structural
-nutrient supply
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53
Q

how many satellite cells surround one neuron soma in a PNS ganglion?

A

usually multiple

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53
Q

how many satellite cells surround one neuron soma in a PNS ganglion?

A

usually multiple

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54
Q

T/F one satellite cell wraps around a neuron soma in a PNS galngion like a schwann cell wraps around an axon

A

false

multiple satellite splat on a soma to cover it, NOT just one wrapping around it

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54
Q

T/F one satellite cell wraps around a neuron soma in a PNS galngion like a schwann cell wraps around an axon

A

false

multiple satellite splat on a soma to cover it, NOT just one wrapping around it

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55
Q

this cell forms multiple myelin internodes in the CNS

A

oligodendrocyte

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55
Q

what is the unique intermediate filament in astrocytes?

A

GFAP glial fibrillary acidic protein

-useful for antibody staining

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56
Q

this cell in the PNS forms one myelin internode and can support multiple unmyelinated axons as well

A

schwann cell

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56
Q

this cell in the PNS forms one myelin internode and can support multiple unmyelinated axons as well

A

schwann cell

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57
Q

these cells cover a neuron soma in PNS ganglia, providing a cushion and nutrients

A

satellite cell

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57
Q

these cells cover a neuron soma in PNS ganglia, providing a cushion and nutrients

A

satellite cell

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58
Q

what is the unique intermediate filament in astrocytes?

A

GFAP glial fibrillary acidic protein

-useful for antibody staining

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58
Q

what is the unique intermediate filament in astrocytes?

A

GFAP glial fibrillary acidic protein

-useful for antibody staining

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59
Q

what characteristic of astrocytes can make them easily identifiable through antibody staining?

A

GFAPs
glial fibrillary acidic proteins
special intermediate filaments unique to astrocytes

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59
Q

what characteristic of astrocytes can make them easily identifiable through antibody staining?

A

GFAPs
glial fibrillary acidic proteins
special intermediate filaments unique to astrocytes

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60
Q

what is a GFAP?

A

glial fibrillary acidic proteins

special intermediate filaments unique to astrocytes

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60
Q

what is a GFAP?

A

glial fibrillary acidic proteins

special intermediate filaments unique to astrocytes

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61
Q

define ganglia

A

collections of neuron cell bodies outside the CNS (in the PNS)

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61
Q

define ganglia

A

collections of neuron cell bodies outside the CNS (in the PNS)

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62
Q

a discrete group of neuron soma in the CNS is called a __

A

nucleus

e.g. brainstem nucleus, paraventricular nucleus, etc

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62
Q

a discrete group of neuron soma in the CNS is called a __

A

nucleus

e.g. brainstem nucleus, paraventricular nucleus, etc

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63
Q

what is the synapse between motor neuron and muscle called?

A

neuromuscular junction

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63
Q

neuromuscular junction

A

synapse between motor neuron and muscle

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64
Q

the post-synaptic region of the plasmalemma of muscle is called the…

A

motor end plate

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64
Q

motor end plate

A

the post-synaptic region of the plasmalemma of muscle

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65
Q

is there a motor end plate on smooth muscle?

A

in rudimentary form

neuromuscular junction is most specialized in skeletal muscle

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65
Q

is there a motor end plate on cardiac muscle?

A 
probably not so much... but possibly...
scarce innervation (autoelectrogenic)
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66
Q

neurophil

A

synaptically dense mesh of axons & dendrites

  • most prominently in grey CNS matter
  • but maybe possible in PNS ganglia?
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66
Q

neurophil

A

synaptically dense mesh of axons & dendrites

  • most prominently in grey CNS matter
  • but maybe possible in PNS ganglia?
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67
Q

3 meninges covering brain

A 
dura mater (outer)
arachnoid mater (middle)
pia mater (inner)
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67
Q

3 meninges covering brain

A 
dura mater (outer)
arachnoid mater (middle)
pia mater (inner)
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68
Q

this meninge of the brain is extremely tough

A

dura mater

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68
Q

this meninge of the brain is extremely tough

A

dura mater

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69
Q

what is the subarachnoid space?

A

space between arachnoid & pia mater usually filled with cerebral spinal fluid

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69
Q

what is the subarachnoid space?

A

space between arachnoid & pia mater usually filled with cerebral spinal fluid

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70
Q

this is a common site of brain hemorrhage

A

subarachnoid space

space between arachnoid & pia mater usually filled with cerebral spinal fluid

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70
Q

this is a common site of brain hemorrhage

A

subarachnoid space

space between arachnoid & pia mater usually filled with cerebral spinal fluid

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71
Q

2 classes of peripheral neurons

A

sensory

motor

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71
Q

2 classes of peripheral neurons

A

sensory

motor

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72
Q

these neurons control skeletal muscle

A

motor neurons

72
Q

these neurons control skeletal muscle

A

motor neurons

73
Q

what is the synapse between motor neuron and muscle called?

A

neuromuscular junction

73
Q

what is the synapse between motor neuron and muscle called?

A

neuromuscular junction

74
Q

neuromuscular junction

A

synapse between motor neuron and muscle

74
Q

neuromuscular junction

A

synapse between motor neuron and muscle

75
Q

the post-synaptic region of the plasmalemma of skeletal muscle is called the…

A

motor end plate

75
Q

the post-synaptic region of the plasmalemma of skeletal muscle is called the…

A

motor end plate

76
Q

motor end plate

A

the post-synaptic region of the plasmalemma of skeletal muscle

76
Q

this nervous system has one long efferent nerve (no efferent ganglia)

A

somatic

77
Q

is there a motor end plate on smooth muscle?

A

no

no motor neuron, no voluntary control, no motor endplate

77
Q

is there a motor end plate on smooth muscle?

A

no

no motor neuron, no voluntary control, no motor endplate

78
Q

is there a motor end plate on cardiac muscle?

A

no

no motor neuron, no voluntary control, no motor endplate

78
Q

is there a motor end plate on cardiac muscle?

A

no

no motor neuron, no voluntary control, no motor endplate

79
Q

how do motor neurons pass out of the spinal cord?

A

ventral root

79
Q

pleomorphic vesicles indicate a __ synapse

A

inhibitory

80
Q

what are the characteristics of a neuromuscular junction that can help you distinguish it from a nervous system synapse?

A
  • 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
Q

this neuron type passes out of the spinal cord through the ventral root

A

motor neuron

81
Q

what kind of neurons exist in the ventral root

A

motor neurons

81
Q

what kind of neurons exist in the ventral root

A

motor neurons

82
Q

how do sensory neurons pass into the spinal cord?

A

through the dorsal root, after passing through the dorsal route ganglion

82
Q

how do sensory neurons pass into the spinal cord?

A

through the dorsal root, after passing through the dorsal route ganglion

83
Q

this neuron type passes into the spinal cord through the dorsal root

A

sensory neuron

83
Q

this neuron type passes into the spinal cord through the dorsal root

A

sensory neuron

84
Q

what kind of neurons exist in the dorsal root?

A

sensory neurons

84
Q

what kind of neurons exist in the dorsal root?

A

sensory neurons

85
Q

what is a motor neuron?

A

an efferent neuron that conducts signals from CNS to effectors (can be somatic or autonomic, sympathetic or parasympathetic, all have motor neurons)

85
Q

what is a motor neuron?

A

an efferent neuron that conducts signals from CNS to effectors (can be somatic or autonomic, sympathetic or parasympathetic, all have motor neurons)

86
Q

what is a sensory neuron?

A

an afferent neuron that conducts signals from periphery to CNS (can be somatic or autonomic, sympathetic or parasympathetic, all have sensory neurons)

86
Q

what is a sensory neuron?

A

an afferent neuron that conducts signals from periphery to CNS (can be somatic or autonomic, sympathetic or parasympathetic, all have sensory neurons)

87
Q

how is a motor neuron different from an efferent neuron?

A

i think they are basically the same thing…

87
Q

how is a motor neuron different from an efferent neuron?

A

i think they are basically the same thing…

88
Q

what organelles are found in dendrites?

A 
microtubules
mitochondria
ER (in Large dendrites)
ribosomes (in Large dendrites)
neurofilaments (in Large dendrites)
89
Q

on EM of a dendrite cross section, what are three circular structures that are likely to be observed?

A 
from large to small:
mitochondria
microtubules
neurofilaments (in Large dendrites)
ER (in Large dendrites)
ribosomes (in Large dendrites)
90
Q

what kind of cytoskeletal filaments are prevalent in dendrites?

A

microtubules (always prevalent)

neurofilaments (in Large dendrites)

91
Q

which has larger cross sectional area, microtubules or neurofilaments? which is likely to be seen in a dendrite?

A

microtubules are larger
microtubules will always be seen, slightly larger
neurofilaments many be found in large dendrites

92
Q

what is a dendritic spine?

A

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
Q

3 classes of connective tissue investments in the CNS

A

trick!
no connective tissue in the CNS
space is filled by astrocytes

94
Q

T/F dendritic spines are dynamic and can move and grow

A

true

95
Q

how many efferent neurons to conduct a parasympathetic motor signal?

A

2 - peripheral ganglia in or near effector organs / tissues

96
Q

how many efferent neurons to conduct a sympathetic motor signal?

A

2 - paravertebral ganglia (sympathetic chain)

97
Q

how many afferent neurons to conduct a sensory signal from any division of the nervous system

A

1 - pseudounipolar neurons with soma in the dorsal root ganglia

98
Q

this nervous system has short preganglionic and long postganglionic efferent nerves

A

sympathetic

99
Q

this nervous system has long preganglionic and short postganlionic efferent nerves

A

parasympathetic

100
Q

this nervous system has one long efferent nerve (no efferent ganglia)

A

somatic

101
Q

which membrane surface has more associated protein, protoplasmic or ectoplasmic?

A

protoplasmic

102
Q

postsynaptic density

A

a histological term for postsynaptic element (appears as a density due to density of receptors)

103
Q

how to tell an excitatory synapse from an inhibitory synapse on EM?

A 
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
Q

a symmetric synapse is a __ synapse

A

inhibitory synapse

  • pre and post synaptic densities are same density
  • pleomorphic vesicles (altered shape)
  • wider
105
Q

an asymmetric synapse is a __ synapse

A

excitatory synapse

  • postsynaptic density is darker than presynaptic density
  • vesicles are round
  • narrower
106
Q

pleomorphic vesicles indicate a __ synapse

A

inhibitory

107
Q

what are the characteristics of a neuromuscular junction that can help you distinguish it from a nervous system synapse?

A

a

108
Q

how can you determine the location of a synaptic active site on EM?

A

the presynaptic vesicles may be queued / clustered at the synaptic sites, ready for release

109
Q

what does a multipolar neuron look like on LM?

A

non-circular nucleus, can probably see multiple branches coming out before lost in surrounding tissue

110
Q

T/F dendrites contain RER

A

~true

Large dendrites may have RER

111
Q

is a neuron typically very actively transcribing or relatively quiescent?

A

actively transcribing
euchromatic
prominent nucleuolus

112
Q

how large / small is a nueronal soma compared to surrounding glial cells?

A

very large
soma nucleus is larger than surrounding glia
soma nucleolus is about = surrounding glial nuclei

113
Q

how do glial cells compare to neuron cell bodies in size?

A

they are much smaller

just the somal nucleolus is ~ the size of surrounding glial cell nuclei

114
Q

what do nissl bodies look like on EM?

A

stacks of ER

115
Q

golgi stain

A

stains only 1-5% of neurons (no one really knows why…) makes easier to visualize neuron and processes

116
Q

if a stain illustrates just one neuron or only a few, what kind of stain is it probably?

A

golgi stain

stains only 1-5% of neurons (no one really knows why…) makes easier to visualize neuron and processes

117
Q

the angle between branching dendrites is…

A

usually < 90 degrees

118
Q

the angle in a branching axon is…

A

usually ~90 degrees

119
Q

how do dendrites change with distance from cell body?

A

they taper off and end not too far away

120
Q

what kind of glial cell is found in dorsal root ganglia?

A

satellite cell
subclass of schwann cell that splats onto pseudounipolar soma to protect / nourish
-found around all PNS soma / ganglia

121
Q

where are satellite cells found?

A

in PNS ganglia splatting onto neuron soma

122
Q

what do satellite cells look like on LM?

A

like a light staining layer with multiple peripheral nuclei around a neuron soma (round and unipolar (pseudounipolar) if in the dorsal root ganglia)

123
Q

what do unipolar (pseudounipolar) neurons look like on LM?

A

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
Q

on EM of a dendrite cross section, what are three circular structures that are likely to be observed?

A

from large to small:
mitochondria
microtubules
neurofilaments

125
Q

most of the nonstaining space between neuronal soma in a nissl stain is occupied by…

A

astrocytes (“connective tissue” of the CNS)

or perhaps oligodendrocytes (more associated with axons)

126
Q

which has larger cross sectional area, microtubules or neurofilaments? which is likely to be seen in a dendrite?

A

microtubules are larger

both are likely to be seen, microtubules will be slightly larger

127
Q

what is a dendritic spine?

A

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
Q

how can you tell an astrocyte from an oligodendrocyte on EM?

A

GFAP glial fibrillary acidic protein

appears like a dense cable of fibers in an astrocyte

129
Q

this glial cell is very dynamic, moves through nervous tissue quickly, and is responsible for immune surveillance in the CNS

A

microglia

130
Q

glial function in CNS:

  • physical support
  • control of microenvironment
  • myelin synthesis
  • defense / immune
A

astrocyte - physical support
astrocyte - control of microenvironment
oligodendrocyte - myelin synthesis
microglia - defense / immune

131
Q

are there nissl bodies in axons and dendrites?

A

large dendrites maybe (may have R & RER)

axons no - no RER or free ribosomes

132
Q

are there mitochondria in axons and dendrites on EM?

A

yes
higher conc in dendrites
stray mitochondria in axons

133
Q

what organelles are likely to be seen in an axon transverse section

A

neurofilaments (smaller dots)
microtubules (larger, possibly tubular)
stray mitochondria
No RER or free ribosomes

134
Q

what does a myelinated axon look like on transverse H&E?

A

eosinophilic cytoplasm

pale ring of myelin (lipid bilayer does not stain usually, though have seen it stain darker than axon in some slides)

135
Q

what does a myelinated axon look like on osmium stain?

A

light axon
black myelin layer
(heavy metal stain, stains lipids dark)

136
Q

what is the best way to tell a longitudinal section of a nerve from smooth muscle, tendon, or other connective tissue?

A

can spot nodes of ranvier

look like transverse lines

137
Q

why do folds in myelin sometimes appear to come apart on EM?

A

schwann cell is opening a path for communication to axon

138
Q

what do unmyelinated axons look like on EM?

A

may have microtubules & neurofilaments, possibly mitochondria, may be smaller next to myelinated axons, may be a cluster poking through schwann cell cytoplasm

139
Q

what do unmyelinated axons look like on LM?

A

frothies near a dark schwann cell nucleus

each froth is smaller than a myelinated axon

140
Q

what does a terminal bouton look like on golgi stain?

A

like a bleb at the end of an axon

141
Q 
glial function               PNS         CNS
phys support
microenvironment
myelin
defense/immune
A

glial function PNS CNS
phys support ct astro
microenvironment schw/sat astro
myelin schw oligo
defense/immune immun micro

142
Q

what are the branches at the end of an axon called?

A

collaterals

143
Q

what is an axospinous synapse?

A

axon to dendritic spine

144
Q

T/F in rare cases, dendrites can have vesicles and pre presynaptic

A

true

in rare cases

145
Q

T/F dendrites contain RER

A

~true

Large dendrites may have RER

146
Q

multiple dendrites + axon = __ neuron

A

multipolar neuron

147
Q

bipolar neuron

A

one input process (dendrite)
one output process (axon)
only found in retina & olfactory bulb

148
Q

where are bipolar neurons found?

A

only retina and olfactory bulb

149
Q

what kind of neuron is found in the retina?

A

bipolar neurons

150
Q

what kind of neuron is found in the olfactory bulb?

A

bipolar neurons

151
Q

what kind of neuron is found only in the retina and olfactory bulb?

A

bipolar neurons

152
Q

where are unipolar (pseudounipolar) nuerons found?

A

only in the dorsal root ganglia

sensory ganglia of the PNS

153
Q

this neuron is only found in the sensory ganglia of the PNS

A

unipolar (pseudounipolar)

154
Q

what is the funciton of a unipolar (pseudounipolar) neuron?

A

allow fast conduction through dorsal root ganglion (sensory) while still maintaining a cell body for protein production and function

155
Q

what kind of glial cell is found only in dorsal root ganglia?

A 
satellite cell
subclass of schwann cell that splats onto pseudounipolar soma to protect / nourish
156
Q

where are satellite cells found?

A

in dorsal root ganglia splatting onto pseudounipolar soma of sensory nerves

157
Q

what do satellite cells look like on LM?

A

like a light staining layer with multiple peripheral nuclei around a round unipolar (pseudounipolar) neuron soma

158
Q

what do unipolar (pseudounipolar) neurons look like on LM?

A

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
Q

T/F the size of a glial cell nucleus is ~ the size of a neuron nucleolus

A

true

160
Q

most of the nonstaining space between neuronal soma in a nissl stain is occupied by…

A

astrocytes (“connective tissue” of the CNS)

161
Q

what is a glial scar made up of?

A

astrocytes

162
Q

what proportion of central nervous tissue is occupied by extracellular structures?

A

0%
no extracellular structures
spaces between neurons taken up by oligodendrocytes and astrocytes

163
Q

how can you tell an astrocyte from an oligodendrocyte on EM?

A

GFAP glial fibrillary acidic protein

appears like a dense cable of fibers in an astrocyte

164
Q

this glial cell is very dynamic, moves through nervous tissue quickly, and is responsible for immune surveillance in the CNS

A

microglia

165
Q

glial function in CNS:

  • physical support
  • control of microenvironment
  • myelin synthesis
  • defense / immune
A

astrocyte - physical support
astrocyte - control of microenvironment
oligodendrocyte - myelin synthesis
microglia - defense / immune

166
Q

dense connective tissue sheath around PNS nerves

A

epineurium

167
Q

collagen fibers with squamous cells around PNS nerves

A

perineurium

168
Q

type III collagen fibers between myelin sheaths in PNS

A

endoneurium

169
Q

nervous tissue external lamina =

A

basal lamina surrounding schwann cells

171
Q

what controls the microenvironment of neurons in the PNS?

A

schwann cells

satellite cells

172
Q

how to tell if an EM is from CNS or PNS?

A

PNS will have the following; CNS will not

  • collagen (clusters of transversely cut cables)
  • external lamina (fuzziness) around schwann cell
173
Q

silver stains…

A

reticular fibers
intracellular material of neurons
stroma

174
Q 
glial function in PNS:
physical support -
control of microenvironment -
myelin synthesis -
defense / immune -
A

physical support - connective tissue
control of microenvironment - schwann / sat
myelin synthesis - schwann
defense / immune - immune system

175
Q 
glial function               PNS         CNS
phys support
microenvironment
myelin
defense/immune
A

glial function PNS CNS
phys support ct astro
microenvironment schw/sat astro
myelin schw oligo
defense/immune immun micro

176
Q

what is the series of events that occurs in the course of peripheral nerve regeneration

A 
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
Q

why does peripheral nerve regeneration sometimes fail?

A

if sprouting axon cannot reach schwann cell tubes and it is unable to reach target, produces traumatic neuroma

178
Q

what is a traumatic neuroma?

A

a painful tangle of axon that forms if a regenerating axon cannot reach distal schwann cell tube to complete regeneration

179
Q

what is the consequence of failed peripheral nerve regeneration?

A

traumatic neuroma

a tangle of axon that forms if a regenerating axon cannot reach distal schwann cell tube to complete regeneration

180
Q

chromatolysis

A

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
Q

how will the soma of a transected neuron compare to other intact neurons nearby?

A

soma loses nissl bodies (no need to send material down axon, chromatolysis)
-nucleus may move to periphery

182
Q

is nerve regeneration possible in the CNS?

A

extremely rare

  • no external lamina to guide axon sprouts
  • central myelin inhibits axon growth in CNS
  • astrocytes fill space with gliotic scar
204
Q

what are the following connective tissue elements formed by?

  • external lamina
  • endoneurium
  • perineurium
  • epinuerium
A

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
Q

what are the following connective tissue elements formed by?

  • external lamina
  • endoneurium
  • perineurium
  • epineurium
A

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
Q

is nerve regeneration possible in the PNS?

A 
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
220
Q

wallerian degeneration

A

the antegrade reaction in the distal part of a severed nerve… leads to distal axon and myelin being phagocytosed

221
Q

after nerve injury:
retrograde reaction is called…
antegrade reaction is called…

A

chromatolysis

wallerian degeneration

222
Q

the ventral root of the spinal cord is severed. where my you look to observe wallerian degeneration?

A

surface of striated muscle

or at the presynaptic end of another motor synapse

223
Q

what kind collagen is found in endoneurium?

A

type III (reticular)

224
Q

T/F type 1 collagen is found in endoneurium

A

false

type III collagen (reticular)

225
Q

what collagen types exist in the following connective tissue layers in peripheral nervous tissue?

  • external lamina
  • endoneurium
  • perineurium
  • epineurium
A

external lamina - type IV
endoneurium - type III
perineurium - type III and type IV
epineurium - type I

COT 1 (WPH) (25 decks)

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