12Microanatomy: Nerve Tissue

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Back 1

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Back 2

cytoplasm with nissl substance = rER
blue = myelin

Front 3

All CNS cell types except ___ are derived from the ___

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-microglia
-neural tube

Front 4

Origin of microglia?

Back 4

bone marrow

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Back 5

Hippocampus: part of cortex
H&E does not tell much about neurons, can’t see axons

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Back 6

Silver nitrate to see purkinje cells
Cellebellar lesions - ataxia

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Dendrites:
Proximal parts have Nissl substance.
More distally, Nissl substance is absent and therefore, dendritic arbors cannot be fully appreciated when one uses Nissl stains

Front 8

Nissl bodies are made up of

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rER and polysomes

Front 9

Some neurons, such as Purkinje cells of the cerebellum, have dendrites characterized by short protrusions. These protrusions are called ___ (3 names). They are specialized regions of synaptic contact.

Back 9

spines, thorns or gemmules

Front 10

Do dendrites display an action potential?

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No, they display a graded potential, i.e. their membrane potential becomes more positive or more negative depending on input

Front 11

The terminal arborizations of axons are called

Back 11

telodendria

Front 12

Neurofilaments:
-relative amount compared to microtubules in axons
-function

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Neurofilaments predominate, i.e. are more abundant than microtubules, and are believed important in maintaining axonal diameter;
increased neurofilaments --> increased axonal diameter

Front 13

Fast Axonal Transport:
Microtubule dependent
Anterograde component uses ___ as a motor protein
Retrograde component uses ___ as a motor protein
Substances that disrupt microtubules or that prevent their assembly will prevent or inhibit fast axonal transport

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-kinesin
-dynein

Front 14

___ is material that cannot be digested.

Back 14

Lipofuscin

Front 15

Rabies virus binds to ___ receptor of motor neurons innervating infected muscle cells
___ transported to cell body where it can replicate

Back 15

-acetylcholine
-Retrogradely

Front 16

Toxins such as ___ (3) are retrogradely transported

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tetanus toxin, a protease, and ricin toxin

Front 17

At synapse, influx of CA2+ due to depolarization causes what?

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Neurotransmitter release

Front 18

After neurotransmitter release, the membrane is taken up/retrieved by ___-coated vesicles

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clathrin

Front 19

Gray matter astrocytes

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protoplasmic astrocytes

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White matter astrocytes

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fibrous

Front 21

Fibrous astrocytes:
have long slender processes packed with 10nm intermediate filaments that are composed of the protein ___.

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glial fibrillary acidic protein (GFAP)

Front 22

Protoplasmic astrocytes stain ___ intensely with antibodies to GFAP

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less

Front 23

The end-feet of astrocytes line the inner portion of the pia matter to form

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glia limitans

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Astrocytes

Front 25

Around the capillaries are astrocytic ___
Experimental studies show that astrocytes induce capillaries to form the ___

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-endfeet
-blood brain barrier

Front 26

Tumors involving cells derived from ___ are the most common type of primary brain tumor. They comprise 80-90% of all glial tumors in adults.
HAVE A TENDENCY TO BECOME MORE ___ WITH TIME
frequently disseminate via the CSF to other regions of the ___, but seldom metastasize to the rest of the body
mean survival ___

Back 26

-astrocytes
-ANAPLASTIC
-CNS
-8-10 months

Front 27

-Chronic demyelinating disease of the CNS
Multiple, focal plaques of demylenization
-___, which is myelinated by oligodendroglia, often affected.

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-Multiple Sclerosis (MS)
-Optic nerve

Front 28

Multiple Sclerosis (MS):
-Prevalence 1 in ___ in USA
Pathogenesis undetermined
May be autoimmune
Antibodies to central myelin
-Characterized by ___ and relapse
-CNS plaques (___) formed by ___

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-1000
-remission
-scars
-astrocytes

Front 29

Unilateral visual impairment.
Diplopia (double vision).
Paresthesias (pins and needles)
Ataxia (unsteadiness)
Vertigo (dizziness)
Fatigue
Paresis (muscle weakness)
Dysarthria (speech problems)
Mental disturbances

Back 29

MS:
Symptoms in declining order of frequency.

Front 30

Back 30

Multiple, focal plaques of demylenization
CNS plaques (scars) formed by astrocytes

Front 31

-When the CNS is injured, the microglial nuclei enlarge and elongate. These cells are then called ___ by pathologist
-Increased damage causes the microglia to become phagocytic. They are then called ___ by pathologists.

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-rod cells
-gitter cells

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CNS INJURY:
CNS injury in adults causes permanent deficits
In adults, CNS regeneration severely limited
-Astrocytes react to injury – ___
-Form a ___
that inhibit axonal regeneration
-___express protein that prevent axonal growth

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-gliosis
-glial scar
-Oligodendroglia

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Back 33

Front 34

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Front 35

Guillan-Barre´ Syndrome:
Acute inflammatory polyradiculoneuropathy
Affects ___ myelin only
Usually bilateral, symmetrical, motor weakness
-Evidence of ___ (3) around axons
May be an autoimmune disease
Severe cases can lead to death
Most cases resolve in 2-4 weeks.

Back 35

-PNS
-T-cells, plasma cells and macrophages

Front 36

Peripheral Nerve Regeneration:
When injured, peripheral nerves can regenerate
Regenerate best when ___, i.e. when CT sheaths intact
___ play a critical role by -
Becoming phagocytic
Synthesizing essential growth-promoting factors and cytokines

Back 36

-crushed
-Schwann cells

Front 37

Peripheral Nerve Regeneration:
Average rate of regeneneration

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1-3mm/day

Front 38

When an axon is severed, the neuronal cell body undergoes a number of structural and molecular changes.
These changes are generally believed to be a neuronal response to a loss of ___.
These changes reflect an attempt by the neuron to regenerate its severed axon

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-target-derived neurotrophic factors

Front 39

When an axon is severed (axotomy), the neuron exhibits the ___.
-The cell body ___.
-There is a dissolution of Nissl substance called ___.
-The nucleus moves to an ___ position.
These changes begin within 24-48 hours and reach a peak at about 2 weeks.

Back 39

-axonal reaction
-swells
-chromatolysis
-eccentric

Front 40

Regenerative response:
___ are among genes up-regulated - Needed for growth cone and axon regeneration
-___ genes and genes associated with synaptic transmitters are down-regulated.

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-Actin and tubulin
-Neurofilament

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Severed axon:
___ portion degenerates back to the next node of Ranvier - retrograde degeneration
___ portion begins to degenerate because separated from synthetic machinery of the cell
anterograde or ___ degeneration

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-Proximal
-Distal
-Wallerian

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The axonal reaction:
Biochemical changes -
-Decrease in synthesis of less-essential proteins - ___
Increase in synthesis of proteins needed for axonal regeneration -

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-neurofilament proteins, transmitter proteins
-tubulin and actin proteins

Front 43

Within hours of injury, the severed axon produces a ___.
It is a motile structure that has a concentration of receptors for ___

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-growth cone
-neurotrophic factor and laminin