Myelin-associated glycoproteins _Inhibitors of CNS axonal elongation:_ Expressed in oligodendrycytes May be important in maintaining axon-myelin complexes Axon-glial signaling

Glia and Myelination Flashcards by Payton Sterba

What is the function of clefts (incisures)?

Cytoplasic nutrients to inner leaflets

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Which cell type fits the following description?

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

Astrocytes

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

Oligodendrocytes

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

120 m/sec

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

Microglia

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Where does axon branching (collaterals) occur?

At nodes

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What are MAGs?

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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What is the function of Schwann cells?

Myelination of axons in the PNS

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Myelin structure:

Where is the outer mesaxon present?

Only in PNS

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Astrocytes often communicate with each other by what?

Gap junctions

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

Myelin-associated glycoproteins (MAGs)
Neurite inhibitors of 35 kDa (NI-35)
Nogo genes and proteins (NI-220/250)

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

Inhibitor of CNS axonal elongation

Expressed in oligodendrocytes

Chondroitin sulfate proteoglycan expressed by oligodendrocytes

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Is Guillain–Barré syndrome acute or chronic?

Acute

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True or false:

Some ependymal cells are ciliated or have microvilli.

True

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

Ependymal cells of the choroid plexus have tight junctions.

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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?

End-feet or foot processes

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

Astrocytes

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

Microglia

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What is the function of microglia?

Phagocytosis of debris in the CNS, act as macrophages.

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

Ependymal cells have desmosomal junctions but NOT tight junctions.

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What percentage of the CNS volume do glial cells occupy?

50%

Neurons are larger cells, on average

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What does ‘glia’ mean in Greek?

Glue

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Axons great than 1 µm are myelinated or unmyelinated?

Myelinated

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Multiple Sclerosis is a demyelination disease of the ________.

CNS

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Name the two types of astrocytes.

Fibrous astrocytes Protoplasmic astrocytes

These cells are the counterpart of oligodendrocytes in the PNS.

Schwann cells

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

Glia

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

Fibrous astrocytes

These cells can engulf degenerated neuronal debris.

Astrocytes

True or false: Oligodendrocytes surround only myelinated CNS axons.

True Unmyelinated axons in the CNS course unsheathed through the tissue.

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

Astrocytes

While glia have processes, they do not have \_\_\_\_\_\_\_\_\_\_\_\_.

synapses and action potentials

What property of glial cells allows repair of CNS lesions?

Glial cells retain mitotic ability into adult life.

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

In the CNS only

Guillain–Barré syndrome is a demyelinated disease of the \_\_\_\_\_.

PNS

True or false: The blood brain barrier is disrupted by Multiple Sclerosis.

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

What are the cell types of glia?

Astrocytes Oligodendrocytes Schwann cells Microglia Enpendymal cells

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

Astrocytes

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

Myelin-oligodendrocyte glycoprotein (MOGs)

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

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

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

They increase in number and size.

Myelin structure: Where is the inner mesaxon present?

In both CNS and PNS

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

Cytoplasmic

Is Multiple Sclerosis acute or chronic?

Chronic

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

Astrocytes

Describe K+ spatial buffering.

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

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

Microglia

A consequence of demyelination in the CNS is \_\_\_\_\_\_\_\_.

scarring or gliosis (sclerosis)

How many axons can one Schwann cell myelinate?

Only one segment of one axon **(May wrap more than 1 axon if axons are unmyelinated)**

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

Protoplasmic astrocytes

What are GLASTs?

Glutamate astrocyte-specific transporter They take up glutamate, which is then converted to glutamine and relased to neurons.

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

Astrocytes

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?

Central nervous system only

True or false: Schwann cells surround only myelinated peripheral axons.

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

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

In both CNS and PNS myelin

Which incisures or clefts are in the PNS?

Schmidt-Lanterman incisures

Which incisures or clefts are in the CNS?

Longitudinal incisures

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

Inhibitors of CNS axonal elongation Expressed by oligodendrocytes

What is a gliosis?

A glial scar

\_\_\_\_\_\_\_\_\_\_\_\_ is a potent inhibitor of axon outgrowth and regeneraton.

Central myelin

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

Ependymal cells

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

Astrocyte membranes were found to possess certain **_neurotransmitter receptors_** that can trigger waves of **_calcium_** inside glial cells.

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

Only have **_K+_** channels, so they are **_not_** electrically excitable.

By what ratio do glial cells outnumber neurons?

3:1 - 10:1

What are the three types of oligodendrocytes?

Perineural oligodendrocytes Interfascicular oligodendrocytes Oligodendrocytes in white matter

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

\< 2 m/sec

Multiple sclerosis affects which type of axons? Sensory, motor, or both

Both

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

50-500 Schwann cells

What are GFAPs?

Glial fibrillary acidic proteins, astrocyte specific cytoskeltal intermediate filaments

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

Guillain–Barré syndrome

Myelin structure: What are major dense lines?

Apposed cytoplasmic faces

Most CNS cancers are of _______ origin.

glial

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

Myelin-oligdendrocyte glycoproteins (MOGs)

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

They are few in number under normal conditions.

What is the function of oligodendrocytes?

Myelination of axons in the CNS

What cells form the choroid plexus?

Modified ependymal cells and associated capillaries

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

Myelin basic proteins (MBPs)

Nodes in the PNS are covered by \_\_\_\_\_\_\_\_\_\_\_. In the CNS, the nodes are \_\_\_\_\_\_\_\_.

Nodes in the PNS are covered by **_Schwann cell cytoplasm_**. In the CNS, the nodes are **_bare_**.

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

Myelin basic proteins (MBPs)

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

Microglia

What are the functions of ependymal cells?

* Provide some barrier between brain and CSF * Ciliary motion aids in CSF circulation * In choroid plexus, produce CSF

How many axons can one oligodendrocyte myelinate?

Many axons

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

Levels fall in mature PNS but not in mature CNS

Myelin structure: What are minor dense lines?

Apposed extracellular faces, also called intraperiod line