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Neuroanatomy > Glia and Myelination > Flashcards

Glia and Myelination Flashcards

1
Q

What is the function of clefts (incisures)?

A

Cytoplasic nutrients to inner leaflets

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2
Q

Which cell type fits the following description?

  • Star-shaped bodies, many long processes
  • Vascular “end-feet” which contact and surround blood vessels
A

Astrocytes

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2
Q

Which glial cells in the CNS are amller than strocytes, have fewer processes, and have round nuclei?

A

Oligodendrocytes

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2
Q

In myelinated axons, conduction velocity can reach up to _______.

A

120 m/sec

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3
Q

When neurons in the CNS degenerate, their cellular debris is phagocytosed primarily by which glial cell type?

A

Microglia

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3
Q

Where does axon branching (collaterals) occur?

A

At nodes

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4
Q

What are MAGs?

A

Myelin-associated glycoproteins

Inhibitors of CNS axonal elongation:

  • Expressed in oligodendrycytes
  • May be important in maintaining axon-myelin complexes
  • Axon-glial signaling
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4
Q

What is the function of Schwann cells?

A

Myelination of axons in the PNS

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5
Q

Myelin structure:

Where is the outer mesaxon present?

A

Only in PNS

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6
Q

Astrocytes often communicate with each other by what?

A

Gap junctions

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6
Q

What are the three types of inhibitors of CNS axonal elongation expressed in oligodendrocytes?

A
  1. Myelin-associated glycoproteins (MAGs)
  2. Neurite inhibitors of 35 kDa (NI-35)
  3. Nogo genes and proteins (NI-220/250)
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7
Q

What is a neurite inhibitor of 35 kDA (NI-35)?

A

Inhibitor of CNS axonal elongation

Expressed in oligodendrocytes

Chondroitin sulfate proteoglycan expressed by oligodendrocytes

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7
Q

Is Guillain–Barré syndrome acute or chronic?

A

Acute

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8
Q

True or false:

Some ependymal cells are ciliated or have microvilli.

A

True

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8
Q

To form the CSF/brain barrier, what do ependymal cells of the choroid plexus have?

A

Ependymal cells of the choroid plexus have tight junctions.

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9
Q

What is the name for the structure on astrocytes that contacts and surrounds blood vessels and also line the ventricles as well as contact neurons?

A

End-feet or foot processes

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9
Q

Which cells have processes that surround synapses and actively remove many neurtransmitters and metabolites from the synaptic cleft (glutamate-glutamine cycle)?

A

Astrocytes

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9
Q

Which cells may be activated in MS, Parkinson’s, Alzheimer’s, and AIDS-related dementia?

A

Microglia

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9
Q

What is the function of microglia?

A

Phagocytosis of debris in the CNS, act as macrophages.

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9
Q

What do ependymal cells lining the ventricles have that allow some substances in the CSF to penetrate the brain?

A

Ependymal cells have desmosomal junctions but NOT tight junctions.

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11
Q

What percentage of the CNS volume do glial cells occupy?

A

50%

Neurons are larger cells, on average

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12
Q

What does ‘glia’ mean in Greek?

A

Glue

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13
Q

Axons great than 1 µm are myelinated or unmyelinated?

A

Myelinated

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13
Q

Multiple Sclerosis is a demyelination disease of the ________.

A

CNS

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15
Q

Name the two types of astrocytes.

A

Fibrous astrocytes

Protoplasmic astrocytes

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16
Q

These cells are the counterpart of oligodendrocytes in the PNS.

A

Schwann cells

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17
Q

What is the name for the supporting elements of the CNS and PNS?

A

Glia

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17
Q

These astrocytes have long, thin processes and are found in the white matter.

A

Fibrous astrocytes

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18
Q

These cells can engulf degenerated neuronal debris.

A

Astrocytes

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19
Q

True or false:

Oligodendrocytes surround only myelinated CNS axons.

A

True

Unmyelinated axons in the CNS course unsheathed through the tissue.

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20
Q

A subset of which cells int he adult brain can serve as stem cells to generate neurons and glia?

A

Astrocytes

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22
Q

While glia have processes, they do not have ____________.

A

synapses and action potentials

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23
Q

What property of glial cells allows repair of CNS lesions?

A

Glial cells retain mitotic ability into adult life.

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24
Q

Where can myelin-oligodendrocyte glycoprotein (MOGs) be found?

A

In the CNS only

24
Q

Guillain–Barré syndrome is a demyelinated disease of the _____.

A

PNS

25
Q

True or false:

The blood brain barrier is disrupted by Multiple Sclerosis.

A

True

Disruption of the blood brain barieer and acute inflamamtion occurs with Multiple Sclerosis.

27
Q

What are the cell types of glia?

A

Astrocytes

Oligodendrocytes

Schwann cells

Microglia

Enpendymal cells

28
Q

Which glial cells function to provide structure support and repair and are known as the “connective tissue of the CNS”?

A

Astrocytes

29
Q

Which myelin protein is implicated as a target antigen in autoimmune aspects of CNS demyelinating diseases?

A

Myelin-oligodendrocyte glycoprotein (MOGs)

30
Q

Schwann cells provide growth-promoting factors. Name the three main factors.

A
  1. Laminin (in the Schwann cell basal lamina)
  2. NgCAM/L1 (cell adhesion molecule)
  3. Nerve growth factor (secreted by Schwann cells)
31
Q

When neurons undergo degeneration, what happens to the number and size of microglia?

A

They increase in number and size.

31
Q

Myelin structure:

Where is the inner mesaxon present?

A

In both CNS and PNS

31
Q

On which face of the myelin membrane are myelin basic proteins (MBPs) found?

A

Cytoplasmic

31
Q

Is Multiple Sclerosis acute or chronic?

A

Chronic

33
Q

The largest & most numerous glial cells are of which type?

A

Astrocytes

35
Q

Describe K+ spatial buffering.

A

K+ ions released by spiking neurons are taken up by astrocytes so that the neuronal membrane potential is maintained.

36
Q

Which cells are recruited during infection, injury, and seizure?

A

Microglia

37
Q

A consequence of demyelination in the CNS is ________.

A

scarring or gliosis (sclerosis)

38
Q

How many axons can one Schwann cell myelinate?

A

Only one segment of one axon

(May wrap more than 1 axon if axons are unmyelinated)

40
Q

These astrocytes have shorter, thicker processes and are found in the gray matter.

A

Protoplasmic astrocytes

41
Q

What are GLASTs?

A

Glutamate astrocyte-specific transporter

They take up glutamate, which is then converted to glutamine and relased to neurons.

43
Q

These cells fill spaces not occupied by neurons and blood vessels. They surround synapses.

A

Astrocytes

45
Q

During a neurology rotation, you are asked to examine a patient diagnosed with multiple sclerosis. You recall that this demyelinating disease affects which part of the nervous system?

A

Central nervous system only

47
Q

True or false:

Schwann cells surround only myelinated peripheral axons.

A

False

Schwann cells surround ALL peripheral axons, whether myelinated or unmyelinated.

48
Q

Where can myelin-associated glycoprotein (MAGs) be found?

A

In both CNS and PNS myelin

48
Q

Which incisures or clefts are in the PNS?

A

Schmidt-Lanterman incisures

49
Q

Which incisures or clefts are in the CNS?

A

Longitudinal incisures

51
Q

What is the function of Nogo genes and proteins (NI-220/250) and where are they expressed?

A

Inhibitors of CNS axonal elongation

Expressed by oligodendrocytes

53
Q

What is a gliosis?

A

A glial scar

54
Q

____________ is a potent inhibitor of axon outgrowth and regeneraton.

A

Central myelin

56
Q

Which cells make up the cuboidal or columnar epithelial layer lining the inside of the neural tube (cerebral ventricles, central canals)?

A

Ependymal cells

58
Q

Astrocyte membranes were found to possess certain _________ that can trigger waves of ___ inside glial cells.

A

Astrocyte membranes were found to possess certain neurotransmitter receptors that can trigger waves of calcium inside glial cells.

59
Q

Glial cells have only ____ channels. Are they electrically excitable?

A

Only have K+ channels, so they are not electrically excitable.

61
Q

By what ratio do glial cells outnumber neurons?

A

3:1 - 10:1

62
Q

What are the three types of oligodendrocytes?

A

Perineural oligodendrocytes

Interfascicular oligodendrocytes

Oligodendrocytes in white matter

63
Q

In unmyelinated axons, action potentials pass continously along the axolemma, causing the conduct velocity to be ______.

A

< 2 m/sec

64
Q

Multiple sclerosis affects which type of axons?

Sensory, motor, or both

A

Both

66
Q

A single axon in the PNS can be myelinated by how many Schwann cells?

A

50-500 Schwann cells

67
Q

What are GFAPs?

A

Glial fibrillary acidic proteins, astrocyte specific cytoskeltal intermediate filaments

67
Q

This disease is an autoimmune disease against one’s own myelin proteins in the PNS.

A

Guillain–Barré syndrome

68
Q

Myelin structure:

What are major dense lines?

A

Apposed cytoplasmic faces

70
Q

Most CNS cancers are of _______ origin.

A

glial

72
Q

Which myelin proteins can be found on the surface of myelin sheath and oligodendrocytes?

A

Myelin-oligdendrocyte glycoproteins (MOGs)

73
Q

Under normal conditions, roughly how many microglia cells are there?

A

They are few in number under normal conditions.

75
Q

What is the function of oligodendrocytes?

A

Myelination of axons in the CNS

76
Q

What cells form the choroid plexus?

A

Modified ependymal cells and associated capillaries

77
Q

What is the basis for CNS autoimmune disease (experimental allergic encephalomyelitis)?

A

Myelin basic proteins (MBPs)

78
Q

Nodes in the PNS are covered by ___________. In the CNS, the nodes are ________.

A

Nodes in the PNS are covered by Schwann cell cytoplasm. In the CNS, the nodes are bare.

79
Q

What are the major structural proteins of myelin in CNS and PNS?

A

Myelin basic proteins (MBPs)

80
Q

These glial cells are the smallest and have oval cell bodies and many short processes.

A

Microglia

81
Q

What are the functions of ependymal cells?

A
  • Provide some barrier between brain and CSF
  • Ciliary motion aids in CSF circulation
  • In choroid plexus, produce CSF
82
Q

How many axons can one oligodendrocyte myelinate?

A

Many axons

83
Q

MAGs have high levels in developing CNS and PNS. What are their levels in mature PNS and CNS?

A

Levels fall in mature PNS but not in mature CNS

84
Q

Myelin structure:

What are minor dense lines?

A

Apposed extracellular faces, also called intraperiod line

Neuroanatomy (7 decks)

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