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Flashcards in Neurocytology II Deck (101):
1

The most numerous cells in the CNS and PNS

-outnumber neurons 3-10:1

Support cells

2

Most brain tumors, either benign or malignant, are
of

Glial origin

3

What are the four types of support (glial) cells in the central nervous system?

Ependymal cells, oligodendrocytes, astrocytes, and microglia

4

Gives rise to ependymal cells, oligodendrocytes, and astrocytes

Neuroepithelium

5

Thought to be of the macrophage-monocyte origin

-Do not come from the CNS

Microglia

6

Epithelial cells that line the ventricles of the brain and spinal canal of the spinal cord

-remnants of the original epithelium

Ependymal Cells

7

Line the central canal after neurons and other support cells have migrated away

Ependymal cells

8

Ependymal cells in most areas of the CNS are bound together by

Adhering (NOT occluding) junctions

9

Found in the ventricle or central canal and can enter and communicate with interstitial spaces of the CNS

Cerebrospinal fluid

10

In specific locations in the ventricle ependymal cells are modified to form the special secretory epithelium of the

Choroid plexus

11

What type of structure is the choroid plexus?

A vascular structure

12

The choroid plexus produces

Cerebrospinal fluid

13

Regulate transfer of cerebrospinal fluid

Ependymal cells

14

originate from outside neural tube and are members of the mononuclear phagocytic cell population

-are phagocytic

Microglia

15

Can eliminate nonviable neurons and glial cells in development

Microglil cells

16

In adults, microglial cells can eliminate

Inactive synapses

17

In areas of neural damage, microglial cells can eliminate

Dying cells

18

Produce molecules associated with the immune
system that can recruit leukocytes across the blood brain barrier to interact with astrocytes and modulate immune function

Microglial cells

19

Star shaped support cells

Astrocytes

20

The most distinct organelles that astrocytes have are glial filaments (intermediate filaments) made of

-allows astrocytes to be studied in vivo and in a culture dish

Glial fibrillary acidic protein (GFAP)

21

Often lie between neurons and capillaries and send processes to the basal lamina of the capillary

Astrocytes

22

May lie at the interface of neuron and pia mater and send processes to the basal lamina in contact with the pia

Astrocytes

23

Provide structural support for the nervous system

Astrocytes

24

Astrocytes may regulate the ionic environment by serving as

K+ sinks

25

Astrocytes are often found around the initial segment and at the

Node of Ranvier

26

Astrocytes are linked by?

-permit passage of small ions

Gap Junctions

27

Can segregate one synapse from other synapses

Astrocytes

28

Astrocytes can accumulate neurotransmitters. This suggests that they must be partially responsible for

Terminating synaptic transmission

29

Have receptors present on astrocytes and can regulate astrocyte function

Neurotransmitters

30

Astrocytes project to

Capillaries

31

Factors released from astrocytes influence the formation of tight junctions between

Endothelial cells of capillaries

32

Influence the integrity of the blood brain barrier

Astrocytes

33

Factors released from astrocytes also regulate blood flow in the capillaries of the

Brain

34

Astrocytes also participate in the

Immune response

35

Divide and remove neuronal debris during injury

Astrocytes

36

The myelinating cells of the central nervous system

Oligodendrocytes

37

In the CNS, unmyelinated axons have no

Ensheathment

38

The myelin sheath produced by oligodendrocytes begins at the end of the

Initial segment

39

The myelin sheath produced by oligodendrocytes ends at the region of the

Axon terminal

40

The myelin sheath is interrupted at regular intervals by

noes of Ranvier

41

Segments of myelin between the nodes of ranvier are called

Internodal segments

42

In human development, myelination begins at the

-accelerates in the last trimester

14th week of gestation

43

Much of myelination occurs

-can last for several years

Postnatally

44

Forms when the oligodendrocyte sends out processes which wrap axons in a spiral manner

Myelin

45

Formed by the close apposition of the cytoplasmic faces of the plasma membrane when oligodendrocytes wrap axons

Dark major dense lines

46

Represent apposed extracellular faces of the plasma membrane of adjoining wrappings

Lighter stained intraperiod lines

47

Serves as an insulating coat of high resistance that isolates the axon from extracellular electrical influences

The myelin sheath formed by oligodendrocytes

48

Areas near the Nodes of Ranvier where edges of the spirally wrapped lamellae are separated at the major dense lines

Paranodal regions

49

Results in a series of tongue -like processes with oligodendrocyte cytoplasm

Paranodal regions

50

Tongues of oligodendrocytes are closely associated with the axolemma at the

Paranodal regions

51

At the paranodal regions, signals are thought to be transmitted between the

-Loss of these signals may result in MS or AD

Axon and oligodendrocyte

52

Serves as an insulating coat of high resistance that isolates the axon from extracellular electrical influences

The Myelin sheath

53

Bare regions of axon which are specialized for high capacitance and low electrical resistance

Nodes of Ranvier

54

Nodes of Ranvier contain high levels of

Ion channels

55

During the passage of an action potential down the axon, as each node becomes active, an inward ionic current flows down the axon core to depolarize the next node and bring it to

Spike threshold

56

This results in the action potential jumping from node to node, which is called

Saltatory conduction

57

Concentrations of sodium channels are found at the

Nodes of Ranvier

58

Support cells in the peripheral nervous system (PNS) are known as

Schwann cells or satellite cells

59

Associated with peripheral nerve fibers

Schwann cells

60

Associated with cell bodies

Satellite cells

61

Support cells in the PNS surround all peripheral neurons, regardless of whether they are

Myelinated or unmyelinated

62

Produce growth factors and phagocytose debris at lesion cites

Schwann cells

63

The most well understood function that Schwann cells exhibit is

Covering and myelinating peripheral neurons

64

Cover all peripheral nerves

Schwann cells

65

In the case of unmyelinated axons, one Schwann cell may be associated with as many as

20 unmyelinated axons

66

Unlike in myelinated axons, Schwann cells covering unmyelinated axons do not contain any

Gaps

67

In the PNS, even unmyelinated axons lie within the arms of

Schwann cells

68

Unlike in the PNS, in the CNS, axons can be

Naked

69

In the case of myelinated axons, one Schwann cell produces one internode associated with one

Axon

70

In the CNS, one oligodendrocyte can form many

Internodes

71

In the PNS, one Schwann cell can form

One internode

72

When Schwann cells wrap an axon, inner leaflet opposition results in

Major dense lines

73

When Schwann cells wrap an axon, outer leaflet adhesion results in

Intraperiod lines

74

In the CNS, the adhering protein is a transmembrane protein called

PLP

75

In the PNS, the adhering protein is a transmembrane glycoprotein called

Po

76

Differences in the adhering proteins in the CNS and PNS may account for distinct

Demyelinating disease

77

Modified dense fibrous connective tissue with
contractile cells that form a semipermeable barrier

Perineurium

78

In the PNS, axons surrounded by Schwann Cells are surrounded by

-Not true for the CNS

CT coats and the endoneurium, perineurium, and epineurium

79

One major difference between the CNS and PNS is that in the CNS, unmyelinated axons have no form of

Ensheathment

80

In the PNS unmyelinated and myelinated axon are covered by Schwann cells that are covered by a

Basal lamina and connective tissue coats

81

Nerve injury is serious since mature neurons can't

Divide

82

In the PNS, functional reconnections may form if the cell body is not

Damaged

83

May regrow along the tubes formed by the basal lamina, endoneurium, perineurium, and epineurium following axonal degredation as long as these structures are in tact

Peripheral nerves

84

Line up on the remaining basal lamina and produce growth factors that “encourage” the sprouting processes to grow down the tubes

Schwann cells

85

Regeneration of nerves in the PNS is more likely if the lesion is near the

Terminal (NOT the cell body)

86

In the lesioned CNS, the nerve and its myelin sheath degenerate on both sides of the

Lesion site

87

In the lesioned CNS, debris is removed by

Proliferating microglia and astrocytes

88

Being used in some cases to enhance the regeneration of CNS neurons through their production of specific molecules

Glial Cells

89

Differences in the ability of CNS and PNS neurons to regenerate may depend, at least in part, on the arrangement of the glial cells and the presence or not of

Connective tissue coats (endoneurium, etc) surrounding the neurons

90

Another term for support cells is

Glial cells

91

The place where capillaries are in close contact with ependymal cells and ependymal cells are altered so that they now have tight junctions

Choroid plexus

92

Ependymal cells of the choroid plexus control what passes into the

Ventricle

93

Regulate immune response in brain and also eliminate
nonviable neurons and glial cells

Microglial cells

94

Lie between neurons and capillaries or between neurons and pia matter

Astrocytes

95

Send processes from grey matter to white matter and help prevent spinal chord from collapsing

Astrocytes

96

In a rapidly firing active synapse, astrocytes closely surround the synapse so that the neurotransmitter is efficiently moved from

One cell to another

97

When a synapse is inactive, astrocytes
opens it's arms so neurotransmitter can

Diffuse away

98

Keep electron dense material from moving from one
compartment to another

Tight junctions in endothelial cells

99

One oligodendrocyte can wrap

40-50 axons

100

The area of a myelin sheet where the two ends overlap

Intraperiod line

101

Protein that holds myelin sheets together in CNS

PLP

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