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Neuroscience > Glia > Flashcards

Glia Flashcards

1
Q

types of vertebrate glial cells

A

astroglia

microglia

oligodendroglia

Schwann cell

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2
Q

astroglia

- features + functions

A

star-shaped
symmetrical
common in CNS

nutritive + support function

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3
Q

microglia

- features + function

A

small
mesodermally-derived

defensive function
- role in breaking down cells + material in brain
= can lead to disease

BUT keeps brain free of pathogens

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4
Q

oligodendroglia

- features + function

A

asymmetrical

forms myelin around axons in brain + spinal cord (CNS)

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5
Q

Schwann cell

- features + function

A

asymmetrical

wraps around peripheral nerves to form myelin

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6
Q

classification of cell types

  • neural cells
  • neuronal cells
  • glia
  • macroglia
A

neurones + glia

neurones

microglia + microglia

astrocytes
radial cells
oligodendroglia
Schwann cels

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7
Q

myelinating glia

  • 2 types
  • function
A

oligodendroglia
(in CNS)

Schwann cells
(in PNS)

insulates axons
-> increases rate of action potential transfer

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8
Q

radial glia

  • function
  • produce
A

provide scaffold throughout CNS for neurones to migrate via during development

matrix + adhesion proteins

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9
Q

radial glia

- in adults

A

persist as different types of cells

e.g. Muller glia cells in retina

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10
Q

ependymal cells

- structure

A

lines central canal + ventricles in brain

cuboidal cells but no basement membrane

beating cilia when lining ventricles

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11
Q

ependymal cells

- specialised forms participate in…?

A

secretion of CSF

= cerebral spinal fluid

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12
Q

origins of cell types

  • neurones, astrocytes + oligodendrocytes
  • Schwann cells
  • microglia
A

neural tube

neural crest

yolk sac + macrophages (i.e. blood)

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13
Q

gliogenesis

- doesn’t involve..?

A

microglia

Schwann cells

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14
Q

gliogenesis

- process

A

neural stem cells
1) -> form neurones

OR
2) -> glial-restricted precursors

A) -> astrocyte precursors
-> type-1 astrocytes

OR

B) ->O2A progenitors
-> forms oligodendrocytes
OR
->type 2 astrocytes

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15
Q

which glia are in the CNS?

A

astrocyte
oligodendrocyte
microglia

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16
Q

dual origin of microglia

A

primitive macrophages from yolk sac blood islands migrate into brain
-> eventually become microglia

may come from blood directly
- from monocytes that invade the brain

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17
Q

evidence for monocytic origin of microglia

A

bone marrow chimeras:
show the brain becomes populated by donor-specific cells of haemopoietic origin

immunocytochemical studies:
show changes in morphology as monocytes transform to microglia

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18
Q

types of microglia

A 
ameboid
- round cells clustered
- found in development 
concentrated in corpus collosum
- proliferate

ramified

  • adult form found in brain
  • don’t proliferate when resting
19
Q

activation states of adult microglia

A

resting

  • fine processes
  • OX-42

activated

  • thick processes
  • larger cell body
  • vimentin
  • OX-42
  • proliferate
  • migrate

phagocytic (break down cells)

  • globular cell
  • lack projections
  • vimentin
  • OX-42
  • OX-8
  • proliferate
20
Q

blood-brain barrier

- define

A

semipermeable barrier
caused by vasculature + brain cells

prevents passage of cells and large molecules

21
Q

microglia

- functions

A

resting cells

  • support + protect neurones
  • release GFs

antigens activate microglia
-> migrate to antigen
+ secrete toxic substances + pro-inflammatory cytokines

remove damaged neurones

myelin fragments convert to phagocytic state
- consume cell debris from dead neurones

22
Q

microglial activation sequence

A
  1. activation signal
  2. retraction of extant branches
  3. motility (protrusion + retraction)
  4. locomotion
23
Q

microglia stimulators

A

viruses + bacteria

dead cells/debris

CNS toxins

ischemia (stroke-related damage)

neuronal degeneration
- release cytokines

activated astrocytes
- release cytokines

24
Q

controversy:

microglia’s role in neurodegenerative disease

A

A) certain proteins produced by neurones during these diseases e.g. amyloid
-> activate microglia + kill neurones via ROS production

vs

B) microglia don’t play an active role in killing otherwise healthy cells in brain
- microglia kill damage neurones

25
Q

astrocytes

  • 2 types
  • functions
A

protoplasmic (grey matter)

  • maintain blood-brain barrier
  • transport K+ and glucose

fibrous (white matter)

  • support + structure
  • form scar tissue
26
Q

astrocytes

  • ratio of astrocytes:neurones
  • perivascular feet
A

50:1

projections that make contact with blood vessels

27
Q

astrocyte

- functions

A

pathways

support

growth + death

calcium signallin g

glutamate

BBB

glucose transport
channels +

receptors

extracellular volume

28
Q

astrocyte

-pathways

A

in development
- provide pathways used by neurones to migrate

role in axonal guidance
-involves CAMs, cadherins, integrins, selectins

create boundaries for axonal movement

29
Q

astrocyte

- support

A

gives structure and protection to synapse

30
Q

astrocyte

- growth + death

A

release large no. of different factors:
GFs + cytokines
= important for survival and development of neurones

astrocytes proliferate around site of axon damage
- could aid repair but can form ‘glial scar’ which inhibits axonal regeneration

31
Q

astrocyte

- Ca2+ signalling

A

gap junctions between astrocytes
- allows rapid communication using Ca2+
via calcium waves

  • may coordinate synapses into synchronously firing groups
32
Q

astrocytic regulation of neural networks

A

all synapses enveloped by an astrocyte may be within that astrocyte’s domain of synaptic influence

-> one group of neurone could influence another distant grip through strictly astrocytic pathways

33
Q

glutamate

A

a neurotransmitter
released in excess
- must be removed otherwise excitotoxic death

34
Q

astrocytes

- glutamate

A

express glutamate tranporters
= GLAST + GLT-1

-> clear glutamate from synapse

glutamate converted into glutamine + returned to neurones

35
Q

astrocyte

- BloodBrainBarrier

A

astrocytes involved in BBB formation

stops immune system cells (e.g. T cells) invading
- provides immune privilege

36
Q

immunological privilege

A

rejection of allografts is greatly diminished by transplantation into the nervous system

37
Q

astrocyte

- K+ and glucose transport

A

express GLUT

K+ levels for neuronal function
- need to be higher inside neurone

38
Q

astrocyte

- channels + receptors

A

neurotransmitter receptors
e.g. seretonin receptor
helps coordinate activity of astrocytes with neurones

ion channels e.g. Ca2+ and K+
- clearance of ions that help maintain levels of ions extracellularly (=interstitial ion levels)

39
Q

astrocyte

- extracellular volume

A

astrocytic swelling due to glutamate and adenosine receptor stimulation

volume fraction decreases
-> increased conc of extracellular molecules
(= increases effective cones of neurotransmitters)

astrocytes through modulation of their size can influence excitability of neurones

40
Q

cytokines

  • produced by
  • alter
  • 2 types of response
  • different actions depending on…
A

astrocytes + microglia
+ neurones

cell survival + proliferation

pro-inflammatory or anti-inflammatory

  • point of release
  • cells they act on
  • concentration
41
Q

cytokine

- examples

A

interferons (IFN)

interleukins (IL)

tumour necrosis factor (TNF) family

42
Q

cytokine

- receptors

A

microglia, astrocytes + oligodendrocytes express receptors for many cytokines

e.g. microliga express IL-6 receptor

43
Q

signal transduction mediated by cytokine receptors

A
  1. cytokine binds to receptor
  2. triggers intracellular pathway
    e. g. Jak-Stat pathway
  3. stat proteins enter nucleus
  4. alter transcription

Neuroscience (17 decks)

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