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Neuro > Cells of the CNS > Flashcards

Cells of the CNS Flashcards

1
Q

How is the CNS organised?

A

Into functional regions/nuclei

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2
Q

List the types of glial cells

A
  1. Astrocytes
  2. Microglia
  3. Oligodendrocytes
  4. Ependymal cells
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3
Q

How many neurons and glia are there in the brain?

A

In adult brain ~ 1 x 1011 neurons; ~ 5-fold more glia

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4
Q

Describe the cell composition of the brain

A

Typically: neurons 10-20%
astrocytes ~ 50%
microglia ≤ 20%

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5
Q

Is the cell composition dependent on brain region?

A

Yes

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6
Q

Give examples of cell compositions in different regions of the brain

A
  • astrocytes out number neurons in cortex

- neurons out number astrocytes in cerebellum

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7
Q

Describe the steps of brain formation

A

Neurogenesis (Neural stem cells make neurons) —> Gliogenesis (then they make glia), synaptogenesis —> Synaptic pruning (particular networks undergo planned death)

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8
Q

What does the post-mitotic nature of neurons mean for cell number?

A

Their number declines with age

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9
Q

What does post-mitotic mean?

A

No longer dividing

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10
Q

Which regions of the brain exhibit adult neurogenesis?

A

olfactory bulb, hippocampus and striatum

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11
Q

Which cells of the brain divide by mitosis throughout life?

A

Astrocytes, oligodendroctyes, ependymal cells

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12
Q

Where do microglia come from?

A

– derived from bone marrow stem cells
(same as macrophages, leukocytes):
precursor cells cross in to brain early in development before blood brain barrier forms

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13
Q

What is the cell body also known as?

A

Soma

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14
Q

What is the part of the neuron that initiates the action potential called?

A

Axon hillock

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15
Q

What is another name for nerve terminals?

A

Synaptic boutons

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16
Q

What does neuronal morphology depend on?

A

Function and neuron type

17
Q

What does the number of dendritic branches correlate to, give examples?

A

The number of synaptic contacts

motor neurons ~ 9000; Pukinje cells ~ 1 x 10^6

18
Q

What are interneurons?

A

Neurons completely within CNS

19
Q

Describe interneurons

A

axons tens-hundreds mm

- small cell body (5 mm)

20
Q

What are efferent neurons?

A

neurons directly controlling glands/muscles e.g. motor neurons

21
Q

Describe efferent neurons

A
  • axon length can be ˃ 1 m

- cell body > 100 mM

22
Q

Which are the most common glial cells in the CNS?

A

Astrocytes

23
Q

What do astrocytes do?

A

1.Modulate brain oxygen levels by regulating blood flow via end feet at BBB
2.Regulate glucose and other metabolites to neurons
3.Remove excessive neurotransmitters at synapses allowing precise signalling
4.Take up K+ at synapses – essential for neuronal signalling
5.Release factors that control synapse formation
e.g. brain derived neurotrophic factor (BDNF)
6.Cause physical barriers between different neuronal circuits
7.Part of the neuroinflammation response – become mobile

24
Q

Describe astrocyte morphology

A

astrocyte leaflet lies close to dendrites, synapses and axons of neurons; sparse around soma

25
Q

What are microglia like under resting conditions?

A

stationary but continually sending out and retracting projections

26
Q

What happens to the morphology go microglia upon activation?

A

have amoeboid shape, become mobile

27
Q

What do microglia interact with?

A

neurons (synapses and dendrites), astrocytes, blood vessels

28
Q

Describe the functions of microglia

A

phagocytose dying neurons / bacteria, present antigens to immune cells
implicated in synaptic formation, maintenance and pruning

29
Q

Where are oligodendrocytes found?

A

white matter

30
Q

What do oligodendrocytes do?

A

They form the myelin sheath around axons

31
Q

How do oligodendrocytes get into the brain (development)?

A

Oligodendrocyte precursor cells migrate to destination

Proliferation controlled by neurons and astrocytes

32
Q

Describe oligodendrocyte morphology

A

Mature oligodendrocytes envelop up to 50 axonal segments.
Each segment termed an internode and are several hundred mm long.
Internodes separated by nodes of Ranvier

33
Q

Where are ependymal cells found?

A

In the choroid plexus

34
Q

Describe ependymal cell morphology

A

Columnar epithelial-like cells containing cilia and microvilli

35
Q

What do ependymal cells do?

A

They are involved in producing CSF

36
Q

Give examples of diseases and the spcific neuronal population deaths which they are associated with

A
  • Amyotrophic lateral sclerosis: upper and lower motor neurons
  • Huntington’s disease: neurons of the basal ganglia
  • Parkinson’s disease: dopaminergic neurons of substantia nigra
37
Q

What diseases are associated with Activation of microglia and astrocytes?

A

Parkinson’s disease, Alzheimer’s disease, neuronopathic Gaucher disease

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