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Neurocytology 2 Flashcards

1
Q

What type of cell is the most numerous in the CNS and the PNS?

A

Support cells.

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2
Q

What is the origin of most brain tumors (benign or malignant)?

A

Brain tumors are of glial origin.

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3
Q

What types of support cells does the neuroepithelium give rise to?

A

1) Ependymal cells
2) Astrocytes
3) Oligodendrocytes

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4
Q

What is the origin of microglia?

A

Microglia are thought to be of the macrophage-monocytes origin.

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5
Q

Do microglia come from the CNS?

A

No, they do NOT.

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6
Q

What are ependymal cells?

A

Epithelial cells that line the:

1) Ventricles of the brain
2) Spinal canal of the spinal cord

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7
Q

What are ependymal cells remnants of?

A

They are remnants of the neuroepithelium.

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8
Q

What kind of junctions are associated with ependymal cells?

A

Adhering junctions.

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9
Q

Since ependymal cells are held together by adhering junctions,

A

CSF in the ventricles or central canal can enter and communicate with the interstitial spaces of the CNS.

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10
Q

What is found on the apical surface of the ependymal cells?

A

Cilia.

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11
Q

What is the function of the cilia on the ependymal cells?

A

Moving the CSF in the ventricles or central canal.

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12
Q

What happens when a capillary is in close proximity to ependymal cells?

A

The ependymal cells become modified to form the choroid plexus.

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13
Q

How are the ventricle ependymal cells modified?

A

There are tight junctions between them.

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14
Q

What is a choroid plexus?

A

A secretory epithelium that produces CSF.

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15
Q

What is the function of the cells in the choroid plexus?

A

To regulate transfer of materials from the capillary into the ventricle.

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16
Q

What does “microglia” mean?

A

The smallest glia.

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17
Q

What is the function of microglia?

A

1) Phagocytic
- Can regulate the immune response
- Can eliminate nonviable neurons and glial cells
- Can eliminate inactive synapses
- Can eliminate dying cells
- Can produce molecules associated with the immune system

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18
Q

What is the prominent intermediate filament in astrocytes called?

A

Glial filaments.

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19
Q

What are glial filaments made of?

A

Glial fibrillary acidic protein (GFAP).

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20
Q

Where are astrocytes found?

A

1) Between neurons and capillaries

2) Between neurons and pia matter

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21
Q

What is the function of astrocytes?

A

To provide structural support to the NS.

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22
Q

What do astrocytes serve as?

A

They serve as K+ sinks that regulate the ionic environment.

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23
Q

Where are astrocytes found?

A

They are found at the initial segment of the axon and at the Nodes of Ranvier.

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24
Q

How are astrocytes linked?

A

They are linked by gap junctions that permit the passage of small ions.

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25
What segregates one synapse from other synapses?
Astrocytes.
26
How do astrocytes accumulate neurotransmitters?
Via neurotransmitter receptors.
27
What can astrocytes do as a result of stimulation by neurotransmitters?
1) Change their permeability of ion channels 2) Change their morphology 3) Change their content of neurotrophic factors that keep neurons alive and functioning normally 4) Change their ability to take up neurotransmitters
28
What is the relationship between astrocytes and capillaries?
Factors released from the astrocytes regulate blood flow in the capillaries of the brain.
29
Where does the barrier lie morphologically?
The barrier lies at the level of the endothelial cells and their tight junctions.
30
What do the factors released from the astrocytes influence?
1) Formation of tight junctions between the endothelial cells of capillaries 2) Passage of materials across the endothelial cells
31
What type of cell produces the myelin sheath?
Oligodendrocytes.
32
Where does the myelin sheath begin and end?
The myelin sheath begins at the end of the initial segment and ends at the region of the axon terminal.
33
What is the myelin sheath interrupted by?
The myelin sheath is interrupted by Nodes of Ranvier.
34
What are the segments of myelin between the nodes called?
These segments are called internodal segments.
35
How does the myelin form?
When the oligodendrocyte sends out processes, which wrap around axons.
36
About how many axons can 1 oligodendrocyte myelinate?
40-50 axons.
37
How are the major dense lines formed?
By the close apposition of the cytoplasmic faces of the plasma membrane.
38
What do the intraperiod lines represent?
They represent apposed extracellular faces of the plasma membrane.
39
What are the outer surfaces of the plasma membrane are held together by?
A protein called Proteolipid Protein.
40
What does the myelin sheath serve as?
An insulating coat.
41
Where are paranormal regions located?
They are located near the Nodes of Ranvier.
42
At the paranodal regions, signal are transmitted between what?
Signals are transmitted between the axon and the oligodendrocyte.
43
What happens if these signals are lost?
This may result in diseases such as MS and Alzheimer's disease.
44
What do the Nodes of Ranvier contain?
High levels of sodium channels.
45
What are the Nodes of Ranvier specialized for?
High capacitance and low electrical resistance.
46
What is saltatory conduction?
Action potential jumping from 1 Node of Ranvier to the next.
47
Which support cells in the PNS is associated with peripheral nerve fibers?
Schwann cells.
48
Which support cells in the PNS is associated with cell bodies?
Satellite cells.
49
What do support cells in the PNS surround?
They surround all peripheral neurons, myelinated and unmyelinated.
50
What are the functions of Schwann cells?
1) Produce growth factors 2) Phagocytose debris at lesion sites 3) Myelinate peripheral neurons
51
In the case of unmyelinated axons, 1 Schwann cell...
Covers multiple axons and provides trophic support to them.
52
One main difference between unmyelinated axons in the PNS and the CNS is...
Unmyelinated axons in the PNS lie within the arms of Schwann cells, while in the CNS they can be naked.
53
In the case of myelinated axons, 1 Schwann cell produces...
1 internode associated with 1 axon.
54
One main difference between Schwann cells and oligodendrocytes, is that...
1 Oligodendrocyte can form many internodes, while 1 Schwann cells forms 1 internode.
55
In the PNS, what is the adhering protein called?
P0, a transmembrane glycoprotein.
56
In the PNS, the axons surrounded by Schwann cells are also surrounded by what?
Connective tissue coats.
57
What are these connective tissue coats called?
1) Endoneurium 2) Perineurium 3) Epineurium
58
What immediately surrounds the Schwann cell?
A basal lamina.
59
What produces the basal lamina?
The Schwann cell.
60
What immediately surrounds the basal lamina?
The endoneurium.
61
What surrounds the endoneurium?
The perineurium.
62
What is a perineurium?
A modified dense fibrous CT that forms a semipermeable barrier.
63
What surrounds the perineurium?
The epineurium.
64
What needs to be intact for the peripheral nerves to regrow?
The basal lamina, endoneurium, perineurium, and the epineurium.
65
What happens when the Schwann cells line the remaining basal lamina?
They produce growth factors that encourage the axons to grow.
66
If the lesion is close to the cell body, then...
The neuron may NOT recover.
67
Why can't the CNS regenerate?
The environment is different and the connective coats are absent.

Anatomy (5 decks)

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