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Neuro > Glia (1) > Flashcards

Glia (1) Flashcards

1
Q

Glial cell discovery = 4

A
  1. 1846 Rudolf Virchow coins term “neuroglia”-
    analogous to connective tissue
  2. Late 19th century Ramón y Cajal and del Río
    Hortega further classify glial cells
  3. 1970s Discovery of GFAP as a marker for
    astrocytes
  4. NOW - Increasing evidence of vital importance
    of glial cells in maintenance and normal function
    of nervous system
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2
Q

What are glial cells in CNS?

A
  1. Astrocytes
  2. Microglia
  3. Oligodendrocytes
  4. Radial Cells
  5. Ependymal cells
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3
Q

What are glial cells in PNS?

A
  1. Schwann cells
  2. Satellite cells in ganglia
  3. Enteric glial cells
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4
Q

What is OEG or OEC?

what does it do?

A

Olfactory Ensheathing Glia/cells

These cells are specialised glia that support the growth and regeneration of olfactory neurons, guiding their axons from the nasal epithelium to the olfactory bulb.

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5
Q

Explain astrocytes?

A

Partners to neurons
“housekeepers”

help maintain
- the environment around neurons,
- regulate blood flow,
- support synapse function.

-astrocyte process ensheaths the synapse
- Astrocyte end-feet wrap around the blood vessel

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6
Q

explain oligodendrocytes

A

myelinating cells - of axons for quick transmission in CNS

wraps myelin around multiple axons

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7
Q

explain microglia

A

immune effector cells

they act as the brain’s immune defense, clearing away dead cells and responding to injury.

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8
Q

ependymal cells

A

enclose ventricles

Lining the fluid-filled ventricles and playing a role in the production and circulation of cerebrospinal fluid (CSF).

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9
Q

Where does GLIA and NEURONS derive fro?

A

neuroectoderm

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10
Q

oligodendrocytes derived from?

A

ventricular zone of neural tube

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11
Q

astrocyte embryological origin

A

ventricular zone of neural tube

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12
Q

ependymal cells embryological origin

A

ventricular region of neural tube

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13
Q

microglia embryological origin

A

exception - hematopoietic stem cells

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14
Q

Six major stages of neural development

A
  1. neural precursor cells (NPCs) from ectoderm
  2. differentiation into NEURONS AND GLIA
  3. MIGRATION
  4. AXON EXTENSION
  5. SYNAPTIC CONNECTIVITY (type, number, and cellular location)
  6. modification of neural connections
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15
Q

Birth to postnatal week 3
=5

A

birth
1. neurogenesis
2. gliogenesis

postnatal week 3
3. synaptogenesis
4. synapse maturation
5. synaptic pruning

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16
Q

what are radial glia?
= 5

A
  1. ELONGATED CELLS
  2. RETAIN CONTACT WITH VENTRICULAR AND PIAL SURFACES
  3. act as SCAFFOLD for migrating neurons and glial progenitors
  4. this occurs in CEREBRAL CORTEX and other regions
  5. Also AREAS WITH NO APPARENT RADIAL GLIAL FIBRES
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17
Q

RADIAL GLIA transform into?

A
  1. some into ASTROCYTES for the REMODELLING, REMOVAL OF OLD CONTACTS AND ESTABLISHMENT OF NEW CONTACTS
  2. transform into NEURONS - sibling relationships
  3. some PERSIST in regions such as HIPPOCAMPUS and CEREBELLUM

Radial Glia to Neurons: During development, many radial glia cells can divide asymmetrically, producing one radial glial cell and one neuron. This means the neuron and radial glial cell are “siblings” as they originate from the same progenitor cell.
Sibling Relationship: This relationship highlights the close developmental connection between radial glia and the neurons they generate. The radial glia serve as both scaffolding for migrating neurons and as progenitor cells that give rise to neurons.

Why Some Radial Glia Persist:
Hippocampus: Radial glia persist here as they continue to serve as neural stem cells throughout life. The hippocampus is one of the few regions in the brain where neurogenesis (the formation of new neurons) continues into adulthood, which is important for processes like learning and memory.
Cerebellum: In the cerebellum, radial glia persist and contribute to the maintenance and organization of the cerebellar architecture. They may also play roles in the development and plasticity of cerebellar circuits, important for motor control and coordination.

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18
Q

Glial cells function during development? = 4

A
  1. guidance of neurogenesis, neuronal growth and migration
  2. trophic influences (sustenance)
  3. synaptogenesis
  4. myelination and formation of vasculature

GT MS

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19
Q

Glial cells function as adult?

A
  1. blood brain barrier bbb
  2. regulation of blood flow
  3. maintenance of neural environment (ion/pH buffering, role at synapses, neurotransmitter recycling, metabolism, etc)
20
Q

Glial cells function during aging

A

change in structure

change in number

21
Q

Glial cells function during an injury

A
  1. phagocytosis
  2. proliferation and scarring
  3. can have either a NEGATIVE or POSITIVE influence on PLASTICITY AND GROWTH
  4. immune mediation
22
Q

A1 vs A2

M1 vs M2

A

A1 vs. A2 Astrocytes: A1 are pro-inflammatory and neurotoxic, while A2 are neuroprotective and reparative.

M1 vs. M2 Microglia: M1 are pro-inflammatory and can be neurotoxic, while M2 are anti-inflammatory and involved in tissue repair.

These functional subtypes illustrate how glial cells can play both protective and damaging roles in the CNS, depending on the context and signals they receive.

23
Q

Astrocytes in detail = 8

A
  1. small 3-5microM with numerous radiating processes
  2. irregular nucleus
  3. glycogen granules give a watery appearnce to the cytoplasm
  4. Identified by intracellular filaments (100nm
    in diameter) - GFAP antibody +ve
  5. Fibrous: white matter, protoplasmic: grey
    matter

6.Variety of morphologies, filament expression, enzymes and neurotransmitter
receptor and uptake components

  1. Role in neuroinflammation
  2. Tripartite synapse
24
Q

Astrocytes = MILD TO MODERATE ASTROGLIOSIS

A
  1. healthy
  2. MILD-MODERATE INSULT
  3. HYPERTROPHY + MOLECULAR AND FUNCTIONAL CHANGES
  4. TIME
  5. potential for resolution
25
Q

astrocytes = severe astrogliosis with scar formation

A
  1. healthy and then SEVERSE INSULT
  2. Persisting mature glial scar
  3. proliferated astrocytes
    + other cell types
  4. bordering along regions of overt tissue damage and inflammation due to:
    - trauma
    - ischemia
    - cytotoxicity
    - infection
    - autoimmune inflammation
  5. axons –> glial scar barrier <–inflammatory cells
26
Q

astrocytes from healthy to

A
  1. neurodegenerative astrocyte decrease Kir4 and Glt1 and increase in GFAP
    - Downregulation of essential ion and neurotransmitter
    channels and receptors; reactive; hypertrophied
  2. A1 astrocyte increse in C3
    - Lethal to oligodendrocytes & neurons, phenotype initiated by microglia,
    strong correlation to neurodegeneration, decreased phagocytic ability,
    reactive phenotype; increased with aging
  3. A2 ASTROCYRE S100a10 increase, stat3 increase
    - Promote neuronal survival;
    non-reactive phenotype
  4. EPILEPTIC ASTROCYTE decrease Glt1,Kir4 and Gs
    -Hypertrophied, dis-localization of AQP4
27
Q

OLIGODENDROCYTES in DETAIL = 6

A
  1. Small 1-3 µm cells with dense chromatin and cytoplasm
  2. Myelinating cells “interfascicular”
    – One process provides myelin of one internode of one axon
  3. Possess specialized glutamate receptors (AMPA and kainate) that are permeable to Ca2+
  4. Role in ion/neurotransmitter balance in extracellular space ?
  5. OPCs differentiate into myelinating oligodendrocytes
    throughout life
  6. Both cell types implicated in maintaining and modulating neuronal function to affect motor performance, cognition and
    emotional state
28
Q

Oligodendrocytes and myelination …Also important in this process…+ process

A

process:
1. progenitor
2. pro-oligodendrocyte
3. oligodendrocyte
4. myelinating oligodendrocyte

also important
1. axonal signalling
(Osso et al 2017)
2. mechanical stimuli
(soft enhances, stiff inhibits)

multiple axon myelination
myelin axonal processes
olig 2

29
Q

what is stacks of lamellae for?

A

Stacks of Lamellae of
INSULATING MYELIN to
ENHANCE CONDUCTION

30
Q

HOW DOES OLIGODENDROCYTES WORK?

A
  1. Myelination and myelin remodelling
  2. node formation
  3. node maturation and maintenance
  4. neurotransmission
  5. metabolic support
31
Q

microglia in more information = 5

A
  1. Small cells, resting and activated states
  2. Activated in pathological states including ischemia,
    neurodegeneration, trauma and meningitis
  3. Become motile
  4. Antigen expressing cells – role in immune responses
  5. Able to secrete factors that can influence angiogenesis and
    astrocyte proliferation (complex interactions)
32
Q

microglia contribute to

A
  1. neuronal health
  2. neuronal dysfunction
  3. morphological abnormalities
33
Q

microglia in homeostasis

A
  1. enhanced learning and memory (BDNF)
  2. pruning synapses
  3. phagocytosis of cellular debris
  4. uptake of amyloid monomers/oligomers
34
Q

microglia in pathology

A
  1. impaired learning and memory (no BDNF)
  2. DESTRUCTION OF SYNAPSES
  3. DESTRUCTION OF VIABLE CELLS
  4. AMYLOID PLAQUE FORMATION
35
Q

Ependymal Cells =3

A
  1. Simple cuboidal/COLUMNAR epithelium lining ventricles, majority of which have
    CILIA and MICROVILLI
  2. Regulate composition of CSF
  3. “Tanycytes” are specialised cells on floor
    of 3rd VENTRICLE THAT CONTACT PIA AND BLOOD VESSELS OF MEDIAN EMINENCE - HORMONE RELEASE AND AXON REGROWTH
36
Q

Olfactory Ensheathing Glia IN DETAIL

A
  1. associated with OLFACTORY NERVE AND BULB
  2. PERSISTENT RENEWAL OF OLFACTORY PATHWAY THROUGHOUT LIFE
  3. therefore OEGs may be able to SUPPORT AXONAL GROWTH AND REGENERATION IN ADULT BRAIN
  4. PROMISING THERAPEUTIC target for cell replacement strategies in spinal cord injury
37
Q

cells types in PNS

A
  • schwann cells
  • satellite cells
38
Q

what do satellite cells do?

A
  1. “support cells”
  2. receptors and ion channels
39
Q

what do schwann cells do?

A
  1. myelination
  2. phagocytic activity
  3. trophic support
  4. modulation of synaptic activity
  5. presentation of antigens
40
Q

Schwann Cells in detail

A
  1. Myelinating cells of the PNS
  2. One cell myelinates one axon
     SC proliferation may contribute to regeneration
    capacity of peripheral axons
41
Q

Schwann cells proliferation may contribute to regeneration
capacity of peripheral axons ..explain how =

A
  1. Nerve crush injury intact sheath
  2. Recruitment of macrophages
  3. Mitogenic signals to SC which in turn secrete
    laminin and other adhesion molecules
  4. IL-1 release from macrophages can stimulate
    release of growth factors from SCs such as NGF,
    FGF
42
Q

cns vs pns myelin sheath

A
  1. Myelin sheath
    contains specific
    proteins that differ in
    type and amount in
    CNS vs. PNS
  2. Nodes of Ranvier
    βIV spectrin; Caspr; potassium channel Kv1.2

3.Promising therapeutic target for cell replacement strategies in spinal cord injury

43
Q

schwann cells devlopment and process

A
  1. neural crest
  2. schwann cell precursor
  3. immature schwann cells

or

  1. promylinating schwann cell
  2. myelinating schwann cell
44
Q

non myelinating schwann cells = 3

A
  1. pacinian corpuscles
  2. remak bundle
  3. terminal schwann cells of neuromuscular junction
45
Q

glia 1 summary

A
  1. Glial cells are more than just brain glue!
  2. Found in CNS and PNS
  3. Many essential roles during neural development and in adult nervous system
  4. We are still learning about role of these various cell
    types in normal physiology, ageing and pathology

Neuro (6 decks)

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