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SF1_Histology > Neurocytology II > Flashcards

Neurocytology II Flashcards

1
Q

The 4 types of support cells of the CNS:

A
  1. ependymal cells
  2. oligodendrocytes
  3. astrocytes
  4. microglia
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2
Q

In the CNS, neuroepithelium gives rise to which support cells?

A
  • ependymal cells
  • oligodendrocytes
  • astrocytes
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3
Q

In the CNS, macrophages/monocytes give rise to which support cell?

A
  • microglia

MICROGLIA ARE NOT DERIVED

FROM CNS CELLS

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4
Q

Ependymal cells are epithelial cells that line:

A

ventricles of the brain and spinal canal cord

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5
Q

What cells are these?

A

ependymal cells

(left behind in central canal when neurons and other support cells migrate away)

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6
Q

Ependymal cell structure:

A
  • simple cuboidal/columnar shape
  • cilia and microvilli on apical surface
  • held together by desmosomes
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7
Q

Why can CSF freely travel through ependymal cell linings of the central canal in the CNS?

A
  • ependymal cells are only held together by desmosomes.
  • no tight junctions
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8
Q

What is this an image of?

A

Ciliated/microvilli of ependymal cells

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9
Q

Function of choroid plexus:

A

production of CSF

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10
Q

The choroid plexus is lined with:

A
  • ependymal cells with tight junctions that prevent easy transfer of material.
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11
Q

What is this an image of?

A

microglia

(smallest glial cell)

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12
Q

Role of microglia:

A
  • phagocytose nonviable neurons and glial cells in development and injury.
  • can release growth factors during development.
  • can recruit leukocytes to cross the blood-brain barrier.
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13
Q

Most distinct organelle of astrocytes:

A
  • intermediate filaments (glial filaments)
  • made of GFAP
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14
Q

What is this an image of?

A

astrocytes in the white matter of the spinal cord

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15
Q

Astrocytes connect:

A
  • neurons to capillaries
  • neurons to pia mater
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16
Q

Astrocytes surround:

A
  • Nodes of Ranvier
  • synapses
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17
Q

Role of astrocytes:

A
  • regulating “tightness” of blood-brain barrier
  • structural support/barrier to CNS
  • K+ sinks (regulate ionic environment)
  • neurotransmitter take-up at synapses
  • immune response
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18
Q

What is this an image of?

A

astrocytes projecting to a capillary

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19
Q

Factors released from astrocytes influence formation of:

A
  • tight junctions between endothelial cells of capillaries
  • influence integrity of the blood brain barrier.
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20
Q

What CNS support cells influence the integrity of the blood brain barrier?

A

astrocytes

  • influence endothelial cell tight junctions
  • regulate blood flow through capillaries in brain
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21
Q

What cells are the myelin-producing cells in the CNS?

A

oligodendrocytes

22
Q

Segments of myelin on CNS axons that are interrupted by Nodes of Ranvier are called:

A

internodal segments

23
Q

One oligodendrocyte may myelinate up to how many axons simultaneously?

A

40-50

24
Q

What is this an image of?

A

oligodendrocyte

myelinated CNS axons

25
Q

Intraperiod line:

A
  • light line in myelin in between myelin sheets
  • formed by proteins that hold together the myelin wrapping during mylination
26
Q

Major dense line:

A
  • dark line in myelin interior of myelin sheet
  • formed by the closely apposed cytoplasmic faces of the plasma membrane of oligodendrocytes during myelination
27
Q

Proteolipid protein:

A
  • a protein located in the intraperiod lines of myelin that holds myelin sheets together in the CNS
28
Q

What is this an image of?

A
  • major dense lines (dark) and intraperiod lines (light) in myelin
29
Q

How can you tell if a myelinated axon is in the CNS or PNS?

A
  • CNS myelinated axons have no cell bodies near them
    • oligodendrocytes send arms out
30
Q

What is this an image of?

A

myelinated axon in CNS

NO CELL BODY AROUND

31
Q

Paranodal regions:

A
  • areas near Nodes of Ranvier in the myelin sheath that still contain cytoplasm of the oligodendrocyte
  • tongue-like processes
32
Q

What is this an image of?

A
  • paranodal region (lumps of cytoplasm)
  • arrow = Node of Ranvier
33
Q

Saltatory conduction:

A
  • action potential jumping from node to node in myelinated axons
34
Q

Support cells in the PNS:

A
  • Schwann cells (associated with PNS nerve fibers)
  • Satellite cells (associated with cell bodies)
35
Q

In which nervous system are both myelinated and unmyelinated axons surrounded by support cells?

A

PNS

UNMYELINATED AXONS IN THE CNS ARE NAKED

36
Q

Function of Schwann Cells:

A
  • myelinate peripheral neurons
  • produce growth factors
  • phagocytose debris
37
Q

Difference in Schwann Cell numbers between myelinated and unmyelinated axons in the PNS:

A
  • unmyelinated:
    • Schwann cells surround around 20 axons
  • myelinated:
    • Schwann cells surround ONE axon
38
Q

What is this an image of?

A

unmyelinated axons surrounded by a Schwann cell in the PNS

39
Q

What is this an image of?

A

unmyelinated axons surrounded by a Schwann cell in the PNS

40
Q

Difference in internodes between PNS and CNS:

A
  • CNS:
    • one oligodendrocyte produces many internodes
  • PNS:
    • one Schwann cell produces one internode
    • many Schwann cells per axon
41
Q

Major dense lines and intraperiod lines are present in both:

A

PNS (Schwann cells) and CNS (oligodendrocytes)

42
Q

What protein holds together myelin sheets in the CNS?

A
  • proteolipid protein
  • located within intraperiod lines
43
Q

What protein holds together myelin sheets in the PNS?

A
  • Po (glycoprotein)
  • located within intraperiod lines
44
Q

In what nervous system are axons surrounded by connective tissue and basal lamina?

A

PNS

45
Q

What are the three coats of connective tissue surrounding PNS axons?

A
  1. endoneurium (immediately surrounds axon)
  2. perineurium
  3. epineurium (exterior)
46
Q

Perineurium holds together:

A
  • fascicles (groups of PNS axons, each surrounded by endoneurium)
47
Q

What covers unmyelinated and myelinated axons in the PNS?

A
  • Schwann cells, basal lamina, connective coats
48
Q

Order of layers surrounding an axon in the PNS:

A
  1. basal lamina (interior)
  2. endoneurium
  3. perineurium
  4. epineurium (exterior)
49
Q

What happens if you cut a PNS axon near the cell body?

A

cell body dies

50
Q

What happens if you cut a PNS axon far from the cell body?

A
  • If the basal lamina, endoneurium, perineurium and epineurium are intact, peripheral nerves may regrow along the tubes formed by these structures after axonal degeneration.
51
Q

How do axons regrow in the PNS after being lesioned?

A
  • Schwann cells line up on the remaining basal lamina and produce growth factors that “encourage” the sprouting processes to grow down the tubes.
52
Q

What is the regneration of axons following an axonal laceration dependent on?

A
  • arrangement of glial cells and connective tissue coats that provide a path for axonal growth

SF1_Histology (7 decks)

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