Glial cells (cells of NS)

Question 1

What is Glia Greek for?

Answer 1

Glue

Question 2

What are the two divisions of glial cells?

Answer 2

• Macroglia
• Microglia

Question 3

What are the types of macroglia?

Answer 3

• Astrocytes
• Radial glia
• Oligodendrocytes
• Bergmann glia
• Ependymal cells
• Tanycytes
• Schwann cells

Question 4

What is a mesoderm?

Answer 4

The early stages of an embryo

Question 4

What is a mesoderm?

Answer 4

The early stages of an embryo

This is made up of 3 layers that form into parts of the NS

Question 5

What are the 3 layers of the mesoderm (embryo)?

Answer 5

Macroglia = ectoderm

Schwann cells = neural crest (specific type of ectoderm)

Microglia = Mesoderm

Question 6

How do glia compare to neurones?

Answer 6

Glia don’t have dendrites or axons like neurones

Much smaller than neurone

Glia don’t have synapses

Morphologically distant from neurones

Question 7

How do glial cells communicate?

Answer 7

By gap junctions coupled rather than synapses

Question 8

What are the 3 different types of glia?

Answer 8

• Microglia = mesoderm
• Schwann cells = neural crest
• Macroglia = ectoderm

Question 9

Where are glial cells present?

Answer 9

In the central and peripheral NS

Question 10

Do glial cells conduct action potentials

Answer 10

NO!

Question 11

Who discovered Astrocytes?

Answer 11

1893, Von Lenhossek

(Astrocyte = star like morphology)

Question 12

What are the two types of astrocytes?

Answer 12

• Fibrous astrocytes
• Protoplasmic astrocytes

Question 13

What is the structure of an astrocyte?

Answer 13

• Processes happen in end feet - these project to what they’re connecting to
• Endfeet contact blood vessels & neurones directly
• Arguably most diverse glial cell in the CNS

Question 14

What are the 7 functions of an astrocyte?

Answer 14

• Uptake & buffering of extracellular K+ (place it somewhere else)
• Remove glutamate from the synapse
• Metabolic support to neurones
• Regulate blood flow according to neuronal activity
• Supply NT precursors to neurones
• Protect neurones against toxic compounds
• Modulate neuronal activity

Question 15

What are astrocytes extremely sensitive to?

Answer 15

K+

Question 16

How do astrocytes provide metabolic support to neurones?

Answer 16

Glial cells store energy for neurones when there’s not enough energy available

Question 17

Give an example of astrocytes supplying NT precursors to neurones

Answer 17

e.g. GABA and glutamate

Question 18

Give an example of a toxic compound that astrocytes protect neurones from

Answer 18

Ammonium detoxification

Question 19

Where are fibrous astrocytes founds?

Answer 19

In white matter tracts of:
- Brain
- Spinal cord
- Optic nerve
- Nerve fibre layer of retina

Question 20

What do fibrous astrocytes do?

Answer 20

Processes contact blood vessels & axons at the nodes of Ranvier

Question 21

What do fibrous astrocytes look like?

Answer 21

• Few. long processes (up to 300um)
• Soma arranges in rows between axon bundles
• Lots of overlap between processes

Question 22

Why does white matter appear white?

Answer 22

There are lots of axons running through with myelin so appear white

Question 23

Where in the white matter are astrocytes located?

Answer 23

They are arranged around the axon and blood vessels

Question 24

Where are protoplasmic astrocytes present?

Answer 24

In grey matter tracts of brain and spinal cord

Question 25

What do protoplasmic astrocytes look like?

Answer 25

- Processes contact blood vessels & neurones at the synapse & soma - Many short processors - Astrocytic domains - little overlap between processes

Question 26

Where are radial glial cells found?

Answer 26

Present in the developing brain

Question 27

What is the role of radial glial cells?

Answer 27

- Two main processes which make a connection at the ventricle wall & surface of the developing brain - Key functions: act as scaffolding to assist w neuronal mirgation in the developing brain

Question 28

What happens to radial glial cells after maturation?

Answer 28

Dissapear after maturation in most brain areas

Question 29

Where are Bergmann glia found?

Answer 29

Type of radial glial cell present in the cerebellum Cell body in the purkinje layer

Question 30

Where do Bergmann glia form connections with?

Answer 30

- Few processes that extend to the surface of the cerebellum - Processes also form contact with synapses on Purkinje neurone dendrites

Question 31

What are muller cells?

Answer 31

Type of radial glial cell present in the retina

Question 32

What do muller cells do?

Answer 32

Longitudinal processes that can make contact w synapses & blood vessels --> similar to protoplasmic astrocytes

Question 33

Where are ependymal cells found?

Answer 33

Line the ventricles

Question 34

What do ependymal cells form?

Answer 34

Form the choroid plexus

Question 35

What is the function of ependymal cells?

Answer 35

Produce & move CSF

Question 36

Where are tanycytes found?

Answer 36

Line the wall of the 3rd ventricle Long processes extend into hypothalamus

Question 37

What do tanycytes make contact with?

Answer 37

Processes make contact with neurones & blood vessels

Question 38

What is the key function of tanycytes?

Answer 38

Regulation of food intake

Question 39

What can occur if astrocytes do not function properly?

Answer 39

- Alzheimer's disease - Epilepsy - Ischemic stroke - Pain - Glioblastoma

Question 40

What is the overall role of glia?

Answer 40

Maintain homeostasis of the extracellular environment of the CNS to ensure optimum function of neurones

Question 41

Who named oligodendrocytes and why?

Answer 41

In the 1920s, Rio-Hortega (Cajal's student), stained for & named these cells oligodendrocytes Named for their apparent fewer & shorter processes than astrocytes

Question 42

What is the structure of oligodendrocytes?

Answer 42

Processes are not short but extended far to wrap around the axon

Question 43

What is the function of oligodendrocytes?

Answer 43

Produce myelin of the CNS

Question 44

Where are oligodendrocytes present?

Answer 44

Present in white matter

Question 45

How do oligodendrocytes produce myelin?

Answer 45

Each processes myelinates a single axon but different processes from a single oligodendrocyte means a single oligodendrocyte can myelinate multiple axons

Question 46

Who discovered microglia?

Answer 46

1920s, Rio-Hortega (Cajal's student) Stained for & named these cells microglia

Question 47

What are microglia like?

Answer 47

Small cells

Question 48

Where are microglia found?

Answer 48

Present throughout the brain (More in grey matter than white matter)

Question 49

What is the function of microglia?

Answer 49

Function: resident immune cells of the CNS

Question 50

What are microglia like when resting?

Answer 50

Highly ramified, microdomains that processes are sent out and retracted within for constant surveillance, express receptors for inflammatory molecule, pathogens & immune stimuli

Question 51

What are microglia like when activated?

Answer 51

Ameboid, capable of phagocytosis, pro- (M1) and and anti-inflammatory (M2)

Question 52

Who discovered Schwann cells?

Answer 52

1871, Ranvier, named these Schwann cells

Question 53

What is the function of Schwann cells?

Answer 53

Myelinate/ensheath axons of peripheral nerves

Question 54

What are myelinating Schwann cells like?

Answer 54

- Entire cells wrap around the axon - Myelinate axon above 1um diameter - Each Schwann cell myelinates on section of a single axon

Question 55

What are nonmyelinating Schwann cells like?

Answer 55

- AKA Remak cells - Ensheath multiple axons below 1um diameter into Remak fibres