glial cells

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30 Terms

1
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what are the 4 types of glial cells?

- astrocytes

- oligodendrocytes

- microglia

- ependymal cells

2
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what shape are astrocytes?

star shaped

3
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where are astrocytes found?

central nervous system

4
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what percentage of glial cells do astrocytes make up?

20-40%

5
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what are 5 functions of astrocytes?

- provide metabolic support

- regulate extracellular ionic environment

- neurotransmitter uptake

- modulating synaptic transmission

- promotion of myelination by oligodendrocytes

6
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what is the main way that astrocytes provide metabolic support?

they store glycogen which can be broken down into glucose to provide fuel for neurons

7
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what is another way that astrocytes provide metabolic support?

store lactate which is useful in periods of high energy consumption or ischaemia

8
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why is it important for the astrocytes to provide the energy for the brain?

it has a constant requirement for glucose but it is unable to store or produce glycogen itself

9
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why do astrocytes need to regulate the extracellular ionic environment?

high levels of ions like potassium can cause spontaneous depolarisation of the neuron

10
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how do astrocytes regulate the extracellular ionic environment?

they remove excess potassium ions from the extracellular space

11
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how do astrocytes take up neurotransmitters?

contain specific transporters for several neurotransmitters such as glutamate

12
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why do astrocytes need to uptake neurotransmitters?

rapid removal of neurotransmitters from extracellular space is required for normal function of neurons

13
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how do astrocytes modulate synaptic transmission?

release ATP to increase the production of adenosine which inhibits synaptic transmission

14
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what is the main role of oligodendrocytes?

insulating the axons in the CNS

15
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how do oligodendrocytes insulate the axons?

produce a myelin sheath which wraps around the axon

16
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how many axonal segments can a single oligodendrocyte myelinate?

50

17
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what are oligodendrocytes the equivalent to?

Schwann cells in the PNS

18
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what germ layer do astrocytes, oligodendrocytes and ependymal cells arise from?

ectoderm

19
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what germ layer do microglia arise from?

mesoderm

20
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what is the main role of the microglia?

phagocytic and immunocompetent cells

21
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when are the microglia activated?

in response to tissue damage

22
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what happens when microglia are activated?

they can recognise foreign antigens and initiate phagocytosis to remove foreign material

23
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what can microglia also do?

function as antigen presenting cells if needed

24
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what is the ependyma?

thin lining of ventricles in the brain and spinal cord

25
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what is the ependyma made up of?

ependymal cells

26
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what are the ependymal cells attached to?

the basal membrane of the cells is attached to astrocytes

27
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what is the main function of the ependymal cells?

produce cerebrospinal fluid as part of the choroid plexus

28
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what are the ependymal cells covered in?

cilia and microvilli

29
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what do the cilia do?

allow for circulation of CSF

30
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what do the microvilli do?

allow for absorption of CSF