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Neuroscience > Astrocytes and oligodendrites > Flashcards

Astrocytes and oligodendrites Flashcards

1
Q

What is the most abundant cell in the brain ?

A

Astrocytes

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2
Q

What are the six functions of astrocytes ?

A
  1. neurogenesis and gliogenesis
  2. neuronal guidance in development
  3. synaptogenesis and synaptic maturation
  4. Connect domains
  5. creation of BBB
  6. synaptic modulation
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3
Q

What are the two pieces of evidence for tripartite synapses?

A
  • astrocytes are excitable

- communicate bidirectionally with neurones

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4
Q

How are astrocytes excitable?

A

produce short term changes in intracellular calcium concentration through release of calcium stores from the ER

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5
Q

How do astrocytes communicate bidirectionally with neurones?

A

Detect NT from neurones

Release their own NT or gliotransmitter = able to modify electrophysiological excitability of neuron

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6
Q

What clearance do astrocytes participate in?

A

Glu (glutamic acid) clearance by converting it to glutamine

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7
Q

What type of transmitter is Glu?

A

gliotransmitter

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8
Q

What are the functions of glutamatergic signalling?

A

Synchronous depolarisation
increase postsynaptic current frequency
AMPA-receptor-dependent postsynaptic current increases

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9
Q

What is the BBB?

A

barrier between intracerebral blood vessels and brain parenchyma (made of glia and neurones)
Stops entry to brain

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10
Q

The BBB is present throughout the brain apart from which areas?

A 
circumventricular organs (CVOs)
neurohypoysis 
Pineal gland
subfornical organs 
lamina terminals
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11
Q

What junctions form in a BBB?

A

tight junctions between endo cells and astroglial endfeet

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12
Q

How do solutes cross the BBB?

A

pass through endothelial cells and mem of astrocytes (selectively permeable to essential nutrients)

Endothelial cells have specific transporters

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13
Q

What are the types of myelinating cells ?

A
  1. Oligodendrocytes - all myelinating, CNS, multiple axons

2. Schwann cells - myelinating and non, single axon

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14
Q

What is myelination dependent on ?

A

Axonal diameter

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15
Q

What is the ratio which is kept constant in the PNS and CNS ?

A

g-ratio of axons: number of myelin lamellae (1:10)

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16
Q

Explain the interdependence of glia-axons

A
  • Loss of axon = degeneration of oligodendrocytes and de-differentiation of Schwann cells
  • Absence of oligodendrocytes = axons degenerate
17
Q

What do non-myelinating Schwann cells do?

A

surround small diameter neurones
support and isolation from myelinated axons
express surface markers L1 and NCAM

18
Q

What do perisynaptic Schwann cells do?

A

At NMJ
respond to synaptic activity by ca+ waves
Modulate synaptic activity by reg extracellular ion levels and inducing postsynaptic Ach receptor aggregation

19
Q

What markers do OBECs express?

A

Glial markers: GFAP, s100, P75

Radial glial markers : nesting and vimentin

20
Q

What type of conduction does a myelin sheath facilitate?

A

saltatory conduction

21
Q

Where are action potentials propagated ?

A

Node of ranviers

22
Q

What is the composition of the myelin sheath?

A
  • 70% lipids (mostly cholesterol)
    myelin, phospholipids, glycolipids, glycospingolipids
  • 30% proteins
23
Q

What is the difference in the composition of the myelin sheath in the CNS and PNS?

A 
CNS= main protein MBP and PLP
PNS = main protein P0, PMP22 and Cx32
24
Q

What is key for saltatory conduction?

A

molecular interactions at the paranode and juxtaparanode due to clustering of the K+ and Na+ channels

25
Q

What does the loss of NCAM do?

A

Neuronal cell adhesion molecule loss from axonal surface triggers myelination

26
Q

What is L1 ?

A

Expressed at premyelination

Tags axon to be myelinated

27
Q

What do oligodendrite precursor cells differentiate into?

A

Oligodendrocytes starting to express myelin products

28
Q

What is the function of MAG and PLP in axon ensheathment?

A

stitch the spirals along the axon

wraps of myelin are fused together by them

29
Q

What happens to the myelin sheath due to MS?

A
  • autoantibioties of myelin components produced
  • involve white matter
  • demyelination (by damage to oligodendrocytes)
  • BBB breakdown, swelling and inflammation

Neuroscience (14 decks)

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