12_Neuro 1.2 Glia And Myelination

Front 1

Glia cells outnumber neurons by (ratio range), but occupy about (%) of CNS volume because neurons are (larger/smaller) cells.

Back 1

1. 3:1 - 10:1
2. 50%
3. Larger

Front 2

Describe glia cells in regard to their shape similarity to neurons and mitotic ability:

Back 2

They have processes by no synapses and no action potential. They also maintain mitotic ability into adult life and are most common CNS cancer.

Front 3

What are the five glial cell types?

Back 3

1. Astrocytes
2. Oligodendrocytes
3. Schwann
4. Microglia
5. Ependymal

Front 4

Describe the size, shape, and relative frequency of Astrocytes.

Back 4

1. Largest
2. Star-shaped; many long processes
3. Most numerous

Front 5

What is AAC check 3

Back 5

Prepare Solution Board

Front 6

Describe the differences bn Fibrous and Protoplasmic astrocytes:

Back 6

1. Fibrous have long thin proceses and found in white matter
2. Protoplasmic have shorter, thicker processes and found in gray matter

Front 7

Astrocytes have "end-feet" - what doe they do?

Back 7

They contact and surround blood vessels; they also line the ventricles as well as contact neurons.

Front 8

What is GFAP and what is it used for?

Back 8

They are astrocyte cytoskeletal intermediate filaments called Glial Fibrillary Acidic Proteins. They are connective tissue of the CNS that fill the spaces not occupied by neurons and blood vessels.

Front 9

What is a Gliosis?

Back 9

Scar tissue made from proliferation of astrocytes after neuronal damage.

Front 10

Describe K+ spatial buffering
1. What cells are involved?
2. How does it work?

Back 10

1. Astrocytes
2. K ions released from spiking neurons are taken up by astrocytes to maintain neuronal membrane potential. Glial cells only have K channels so they respond to changes in extracellular K+ with changes in Vm but are not excitable.

Front 11

1. Describe how astrocytic processes remove neurotransmitters and metabolites.
2. What does this aid in?
3. How do the astrocytes deal with glutamate? (p16)

Back 11

1. Processes surround synapses and actively remove neurotrans and metabs from synaptic cleft:
2. Rapid removal of transmitters and metabolites result in rapid termination of synaptic signal
3. Astrocytes have GLAST (glutamate astrocytes-specific transporter) that take up glutamate, convert to glutamine, and release to neurons.

Front 12

T or F: Astrocytes have neurotransmitter receptors.

Back 12

T - they can trigger electrical and biochemical events inside glial cells.

Front 13

T or F - Astrocytes contribute to, though not the basis for, the blood brain barrier.

Back 13

True

Front 14

T or F - Astrocytes do not communicate with each other.

Back 14

F - They communicate via gap junctions, providing glial signaling

Front 15

What is meant by "glial guides"

Back 15

It describes astrocytes that serve as guides for neuronal migration during development.

Front 16

T or F - A subset of astrocytes can serve as stem cells.

Back 16

True - they can generate neurons and glia

Front 17

Describe Oligodendrocytes:
1. Size relative to astrocyte
2. Relative number of processes
3. Shape of nuclei

Back 17

1. Smaller than astrocytes
2. Fewer processess
3. Round nuclei

Front 18

What is the main function of Oligodendrocytes?

Back 18

Myelination of axons in CNS - doing so by extending processes to an axon to myelinate it.

Front 19

What is a potent inhibitor of axon outgrowth and regeneration?

Back 19

Central myelin made by Oligodendrocytes

Front 20

What is the major role of Schwann Cells?

Back 20

Myelination of axons in the PNS

Front 21

Compare Schwann and Oligodendryocytes with respect to the number of axons they can myelinate.

Back 21

1. One Schwann cell will only myelinate one segment of one axon, however, a single axon in the PNS can be myelinated by 50-500 Schwann cells.
2. One Oligodendrocyte cell can myelinate many axons.

Front 22

Which glial cell wraps around one or more peripheral axons whether myelinated or unmyelinated?

Back 22

Schwann cells

Front 23

Describe Microglia:
1. Size
2. Cell body shape
3. Relative number of processes

Back 23

1. Small
2. Oval cell body
3. Many short processes

Front 24

What is the major role of Microglia?

Back 24

They serve as CNS macrophages where they phagocytose debris

Front 25

What is the relative frequency of Microglia? Under what conditions might this change?

Back 25

1. They are few in number under normal conditions
2. Increase in number and size when neurons undergo degeneration

Front 26

Describe Ependymal cells (i.e. shape, cell type, what does it line)

Back 26

Cuboidal or Columnar epithelial cells that line the inside of the neural tube (central canal and ventricles)

Front 27

T or F - Some ependymal cells are ciliated or have microvilli

Back 27

T

Front 28

What is it about the Ependymal cell lining of the ventricles that allow substances in the CSF to penetrate the brain?

Back 28

They have desmosomal junctions - not tight junctions - that allow substances to cross.

Front 29

What are the three functions of the Ependymal Cells?

Back 29

1. Provide barrier between brain and CSF
2. Ciliar motion aids in CSF circulation
3. In Choroid Plexus, produces CSF

Front 30

Describe myelination by Oligodendrocytes vs Schwann cells with respect to mesaxons.

Back 30

Oligo (CNS) have only an inner mesaxon
Schwann (PNS) cells have both inner and outer mesaxons

Front 31

Does myelin thickness increase or decrease with axon diameter?

Back 31

It increases

Front 32

What is the major structural protein of myelin in CNS and PNS?

Back 32

Myelin Basic Protein

Front 33

Explain what Major Dense Lines and Minor Dense Lines appose (see p18)

Back 33

Major appose cytoplasmic faces
Minor appose extracell

Front 34

Where MBP typically found in myelin structure?

Back 34

Major Dense Line

Front 35

T or F: MBP is often a basis for CNS autoimmune disease.

Back 35

T

Front 36

What is MOG? T or F It is implicated as a target antigen in autoimmune aspects of CNS demyelinating disease.

Back 36

Myelin-Oligodendrocyte Glycoprotein. True

Front 37

Define saltatory conduction:

Back 37

Jumping from node to node (of Ranvier)

Front 38

What kind of gates are found in the Nodes of Ranvier

Back 38

Voltage-gated Na channels.

Front 39

Where does axon branching (aka collaterals) always occur?

Back 39

At the nodes of Ranvier

Front 40

Describe how the nodes differ in PNS vs CNS

Back 40

PNS = nodes are covered by Schwann Cell Cytoplasm
CNS = Nodes are bare

Front 41

What is the function of Clefts (Incisures)? What are they specifically called in PNS and CNS?

Back 41

Nutrition of cytoplasm in inner leaf.
1. PNS = Schmidt-Lanterman
2. CNS = Longitudinal incisures

Front 42

What are unmyelinated axons in the PNS surrounded by? (2 things)

Back 42

1. Schwann Cell cytoplasm
2. Basal Lamina

Front 43

What are the two major functions of Myelin?

Back 43

1. Insulation; Decreased iconic flux across axolemma, conserves cellular ATP
2. Increase conduction velocity (up to 120m/s). Unmyelinated fibers conduct at <2m/s

Front 44

MS affects both of these types of axons:

Back 44

Sensory and Motor

Front 45

What NS does MS and Guillain-Barre Syndrome affect?

Back 45

MS = CNS (think brain)
GBS = PNS