Intro to Neuropath Flashcards by A B

Neurons

1) main function
2) structure
3) replicative or non-replicative in brain?

1) transfer information in NS

2) large round, vesicular nucleus with inner nucleolus
dark Nissl substance (RER)
axons have neurofilaments = specialized intermediate fibers + tubules

3) non-replicative in brain

How well did you know this?

Not at all

Perfectly

describe neurofilaments and neurotubules

what are they crosslinked by?

neurofilament = specialized cytoskeletal intermediate fibers (10 nm)

neurotubules = intermediate fibers that form tubules (20-26 nm) made of alpha/beta tubulin

crosslinked by tau protein and microtubule assoc proteins

How well did you know this?

Not at all

Perfectly

what happens if axon of neuron damaged?

what is it called?

central chromatolysis

Nissl disappears
soma swells
nucleus displaced to side

How well did you know this?

Not at all

Perfectly

neurons are particularly vulnerable to __ and ___ due to high metabolic rate

what changes are seen to reflect necrosis under these conditions?
name?
features?

anoxic injuries and low blood glucose

ischemic/red neuron

cell shrink
eosinophilic as lose basophilic Nissl substance
mitochondria condense
nuclei become pyknotic (DNA condenss)

How well did you know this?

Not at all

Perfectly

Astrocytes

- functions

clear NT from cleft
structural support for blood vessels in BBB
maintain ionic equilbirum

How well did you know this?

Not at all

Perfectly

role of astrocytes in brain injury

effective or not?

1) scar formation
astrocyte hyperplasia and hyperplasia helps close gaps after neuron debris removed

2) incr synth of GFAP, filament elongation to allows astrocyte to extend processes across lesion
3) creates thick network but NOT effective b/c can’t fill gap

How well did you know this?

Not at all

Perfectly

oligodendroglia
- function

regeneration?

myelin cells of CNS
nutrition role for deep cortex + basal ganglia

little regeneration in injury

How well did you know this?

Not at all

Perfectly

multiple sclerosis mechanism

death of oligodendroglia

How well did you know this?

Not at all

Perfectly

ependymal cells
- function?

regenerative?

ciliated cells lining ventricles for CSF movement

inert / limited regeneration from damage

How well did you know this?

Not at all

Perfectly

what happens if ependymal cells are injured?

seen in what diseases

then are permanently damaged

seen in hydrocephalus, bacterial ventriculitis, viral infection

How well did you know this?

Not at all

Perfectly

microglia
function?

difference in structure btwn surveillance and activated state?

sentinel cells activated by neuron damage, replicate, phag debris

surveillance = long nuclei + short processes
activated = large nuclei + cytoplasm grows into highly branched patterns

How well did you know this?

Not at all

Perfectly

microglia are replenished by…

activated microgllia secrete what?
function of secretion?

replenished by blood monocytes and transform into brain macrophage

secrete neuronal trophic factors
assist in recovery
also secrete neurotoxins and cytokins for inflamm/kill neurons

How well did you know this?

Not at all

Perfectly

significance of RER aka Nissl substance

what happens when axon transected (axotomy)

Nissl = stacks of RER and reflect active protein synth

when axon transected, Nissl subtance disaggregates

How well did you know this?

Not at all

Perfectly

basic components of neuronal cytoskleeton

crosslinked by?

made of longitudinally arranged neurofilaments (10 nm long) and neurotubules (20-26 nm long)
crosslinked and fastened by tau protein + microtubule assoc proteins

How well did you know this?

Not at all

Perfectly

function of tau and MAPs?

anchor cytoskeleton to membrane + organelles

How well did you know this?

Not at all

Perfectly

mechanism of alzheimer’s diz at cell level?

abnormal paired helical filaments of hyperphosphorylated tau in perikaryon

perikaryon = cell body distinct from nucleus and form forms neurofibrillary tangles

How well did you know this?

Not at all

Perfectly

how are silver stains used in histology of CNS

appears what color

visualizing axons and dendrites
- silver deposits on cytoskeletal elements dense in neuron

appears black

How well did you know this?

Not at all

Perfectly

most common silver stain

used to stain what?

Bielschowsky stain = shows normal axons and dendrites + neurofibrillary tangles of Alzheimer’s

How well did you know this?

Not at all

Perfectly

Where is GFAP found?

What are Rosenthal fibers?

Glial fibrillary acidic protein

makes up intermediate filaments of astrocytes
component of Rosenthal fibers in diseases

How well did you know this?

Not at all

Perfectly

What are Rosenthal fibers?

Rosenthal fibers = homogenous, eosinophilic, elongated, or glob inclusion in astrocytes from longstanding gliosis, tumors or metabolic disease

mutations of GFAP cause what

describe disease

describe course of disease

Alexander disease

widespread deposits of Rosenthal fibers
causes white matter degeneration

slow progressing, fatal in children affecting myelin sheath

When and where is myelin first formed?

How long is myelin production

starts late in development in periphery

from birth –> many yrs

Describe how Schwann cells myelinate PNS axons

1) neurons induce Schwann proliferation and migration along axon length
2) Schwann cells elongate and ensheathe neuron
3) axons instruct Schwann to begin wrapping once basal lamina is formed

what induces Schwann myelination

induced by neurons thru cell-cell interactions and intrinsic gene expression program in Schwann

Role of microglia in CNS inflamm and repair @ rest vs when find injury secrete what?

microglia = first line phagocytic cells 1) @ rest, sample environment to sense foreign materials, toxins, and damage 2) when find injury/invasion --> activated --> nucleus larger and rod with ramified cyto 3) migrate to lesion, replicate, engulf damage 4) secrete cytokine and neurotoxin for neuroinflamm and can kill neurons; also secrete trophic factors for repair

what is encircling of degenerating neurons by microglia called difference from microglial nodules

neurophagia nodules = clustering of microglia aorund foci of necrotic brain tissue

what is sarcolemma? structure? function?

cell membrane of muscle cell - invaginates deep into cytoplasm of cell --> T-tubules T tubules allow depol of membrane to rapidly penetrate entire cell

what is connected to sarcolemma? how?

contractile myofibrils of muscle cells attach to sarcolemma nd ECM via dystrophin dystrophin connects cytoskeleton to membrane and dystrophin assoc complex (DAC)

describe DAC and what it is mad eof

made of 5 sarcoglycan proteins ubunits + 2 dystroglycan protein subunits bound to merosin (part of basement membrane)

mutations in dystrophin cause what? what does it cause?

Duchenne and Becker muscular dystrophy causes ongoing degneration/regen of muscle fibers causes muscle damage d/t loss of mechanical force of contraction

long term changes in DMD and becker's

degeneration faster than reegen so fibers undergo necrosis muscle replaced by fat and connective tissue --> progressive weakness

mutations in gene for DAC can lead to ___ merosin mutations found in __

limb girdle dystrophies some congenital dystrophies

describe how type 1 and type 2 fibers distrib in normal muscle and in denervation atrophy appearance in staining

proportion varies based on muscle fxn BUT ONLY 1 TYPE PER MOTOR UNIT (1 MOTOR NEURON + ALL FIBERS) (neuron determines type of fiber) appears as checkerboard under stain

what happens to type 1 and type 2 fiber distrib in denervation atrophy what happens to appearance under stain

1) when motor neuron axon cut, muscle fibers lose innerv --> atrophy 2) nearby motor unit axons sprout new growth cones to re-innerv myocytes and incorporate --> new motor unit 3) change in fiber type to assume type of new motor unit (neighbors) 4) loss of checkerboard and creates grouping

what is myelin made of? difference btwn central and peripherl myelin

myelin = 70% lipid + 30% proteins lipid is same = galactocerebroside proteins differ and usu glycosylated in PNS (not CNS)

proteins in myelin of PNS

P0 Peripheral myelin protein 22 schwann cell myelin protein Myelin basic protein

proteins in myelin of CNS

myelin assoc glycoprotein myelin oligodendrocyte protein myelin basic protein

Describe Wallerian degeneration what happens to soma RER nucleus cytoplasm due to?

when axon transected, everything distal degenerates soma undergoes chromatolysis (swells) RER disintegrates nucleus displaces to periphery cytoplasm --> smooth due to activation of protein synth to regenerate

Wallerian degeneration | How do axons regenerate?

Schwann cells distal proliferate and provide growth substrate regrows 1-3 mm per day

Describe segmental demyelination causes what? effect on conduction velocity?

due to dysfunction of Schwann cell or damage to myelin sheath (nothing wrong withaxon) loss of myelin from breakdown in few segments --> causes loss of saltatory conduction, decr conduction velocity schwann cells can make new myelin to repair but demyelin can cause loss of axons and perm damage

segmental demyelination | appearance of axon without myelin

thin regenerating myelin onion bulbs

presence of lewy body (eosinophilic body made of alpha synuclein means)

parkinson's

rounded cytoplasmic neuronal inclusion seen in

pick's disease

neurofibrillary

myopathy vs denervation

myopathy = prox weakness and atrophy elevated CK EMG changes denervation = distal weakness and atrophy normal CK diff EMG changes

signs of acute denervation

randomly distrib small, angular fibers seen | usu type 2 selective

signs of chronic denervation

type 1 and type 2 proprotion equalizes

what are bands of bugner

in wallerian degeneration | basal lamina lined endoneurial tubes that ensheath prolif schwann cells

clinical signs of nerve regeneration | order

1) autonomic 2) sensation 3) motor