Cell Types In Brain And Spinal Cord Flashcards

1
Q

Neurons

A

Specialised for electrical signalling

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2
Q

What inputs to neurons

A

Dendrites

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3
Q

When are axons mainly formed

A

During development

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4
Q

What do action potentials propagate along

A

Along the axon from the axon hillock

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5
Q

2 types of synapses

A

Chemical
Electrical

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6
Q

Chemical synapse

A

Majority
Via neurotransmitters (glutamate , GABA, dopamine, serotonin, etc)

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7
Q

Electrical synapses

A

Less abundant
Via direct flow of ions- enable synchronised electrical activity eg brainstem (breathing) and hypothalamus (hormone secretion)

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8
Q

Chemical synaptic transmission

A

Axon potential depolarises synaptic terminal membrane
Opening of voltage-gated calcium channels leads to calcium influx
Calcium influx triggers neurotransmitter release

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9
Q

Where are excitatory synapses often concentrated

A

Dendritic spines

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10
Q

Neural plasticity

A

Changes in neuronal/synaptic structure and function in response to neural activity
Basis of learning and memory

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11
Q

Dendritic Spines

A

Dynamic structures- number, size, composition
Spine remodelling linked to neural activity

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12
Q

How do neurones differ

A

Size
Morphology
Neurotransmitter content
Electrical properties
Eg neocortex

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13
Q

Electrical synapse structure

A

No synaptic vesicles
Connexins found in both pre and post synaptic membrane
Form a gap junction to allow passage of ions

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14
Q

Betz cells

A

Upper motor neurones
Large excitatory (gluatmatergic) long projections, pyramidal cells
Vulnerable in MND

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15
Q

Medium spiny neurones

A

Striatal interneurons
Small, inhibitory (GABAergic)
Vulnerable in Huntington’s disease

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16
Q

Which neurons are vulnerable in MND

A

Betz cells

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17
Q

Which neurones are vulnerable in Huntington’s disease

A

Medium spiny neurones

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18
Q

Oligodendrocytes

A

Myelinating cells in the CNS
Unique to vertebrates
Provide metabolic support for axons

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19
Q

Myelin

A

Insulates axon segments
Enables rapid nerve conduction

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20
Q

Nodes of Ranvier

A

Gaps in myelin sheath
Saltatory conduction

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21
Q

Myelin sheath

A

Formed by wrapping of axons by oligodendrocyte processes (membranes)
Highly compacted - 70% lipid, 30% protein
Myelin specific proteins eg. Myelin basic protein (MBP) can be used as markers

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22
Q

Arborisation

A

Fine branching structure at the end of a nerve fibre

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23
Q

How do oligodendrocytes provide metabolic support to axons

A

Transferring lactate into neurones (can be used as an energy source)

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24
Q

Functions of microglia

A

Immune surveillance
Phagocytosis- debris/microbes
Synaptic plasticity- pruning of spines
Bad (M1) and good (M2) microglia

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25
Q

What percentage of myelin in lipid

A

70%

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26
Q

What percentage of myelin is protein

A

30%

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27
Q

Microglia

A

Resident immune cells of the CNS
‘Resting’ state - highly ramified, motile processes survey environment
Upon activation (eg by ATP) retract processes, become ameoboid and motile
Proliferate at sites of injury- phagocytic

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28
Q

Where do microglia originate from

A

Yolk sac progenitors that migrate into the CNS

29
Q

At what rate do microglia survey environment

A

2-3 um/min

30
Q

What can activists microglia

A

ATP

31
Q

Which form of microglia is ‘bad’

A

M1

32
Q

Which form of microglia is ‘good’

A

M2

33
Q

Astrocytes

A

Highly heterogenous - not all star-shaped
Common marker glial fibrillary acidic protein (GFAP)
Most numerous glial cells in CNS

34
Q

Why are M1 microglia ‘bad’

A

Linked to chronic inflammation

35
Q

Astrocyte functions

A

Structural- define brain micro-architecture (contribute to blood-brain barrier)
Envelope synapses- ‘tripartite synapse’- buffer K+, glutamate etc
Metabolic support- eg glutamate-glutamine shuttle
Neurovascular coupling- changes in cerebral blood flow in response to neural activity
Proliferate in disease- gliosis or astrocytosis

36
Q

Specialised astrocytes

A

Radial glia
Bergmann glia
Müller cells (retina)

37
Q

Radial glia

A

Important for brain development

38
Q

Bergmann glia

A

Cerebellum

39
Q

How do astrocytes contribute to blood-brain barrier

A

Processes of astrocytes envelope capillaries in brain

40
Q

Müller cells

A

Retina

41
Q

Motor neurone disease

A

Adult-onset neurodegenerative disease characterised by loss of upper (motor cortex) and lower (spinal cord) motor neurones

42
Q

Multiple sclerosis

A

Autoimmune demyelinating disease where immune cells attack the myelin sheath of oligodendrocytes

43
Q

Commissures

A

Tracts that cross the midline

44
Q

White matter

A

Contains abundance of myelinated tracts and commissures

45
Q

Grey matter

A

Abundant in neural cell bodies and processes

46
Q

Neuropil

A

Contains few cell bodies

47
Q

How are axons gathered in the CNS

A

Into tracts

48
Q

Nuclei

A

Abundance of neuronal cell bodies in CNS

49
Q

Ganglia

A

Cell bodies and supporting cells in PNS
eg dorsal root ganglia

50
Q

Nerves

A

Axons bundled into nerves in PNS

51
Q

MND spinal cord shows pathological changes in

A

Motor neurons
Microglia
Astrocytes

52
Q

MND symptoms are due to loss of

A

Motor neurones

53
Q

Pathological CNS lesions in MS involve

A

Neurones
Oligodendrocytes
T lymphocytes

54
Q

Acute symptoms in MS primarily reflect dysfunction of

A

Neurones

55
Q

Myelinating cells of the PNS

A

Schwann cells

56
Q

Origins of Schwann cells

A

Neural crest derived c.f. Oligodendrocytes- derived from CNS- resident neural progenitors

57
Q

What forms the blood-brain barrier

A

Endothelial cell tight junctions
Basement membrane (few fenestrations)
Astrocytes end feet
Pericytes (contractile, aid blood flow)

58
Q

What is the blood-brain barrier sensitive to

A

Inflammation
Hypertension
Trauma
Ischaemia

59
Q

Ependymal cells

A

Epithelial-like, line ventricles and central canal spinal cord
Ciliated- facilitates flow

60
Q

Functions of ependymal cells

A

CSF production, flow and absorption
Allow solute exchange between nervous tissue and CSF

61
Q

Choroid plexus

A

Frond-like projections in ventricles
Formed from modified ependymal cells- villi form around network of capillaries—> highly vascularised with a large surface area

62
Q

Function of choroid plexus

A

Main site of CSF production by plasma filtration drive by solute secretion

63
Q

Gap junctions between ependymal cells

A

Form blood-CSF barrier

64
Q

Which cells myelinate axons in CNS

A

Oligodendrocytes

65
Q

Where is CSF reabsorbed

A

Arachnoid granulations

66
Q

Ependymal cells

A

Produce CSF in choroid plexus of lateral ventricles

67
Q

Choroid fissure

A

Attachment site for choroid plexus
Above hippocampus

68
Q

Which pigmented hormone is present in the skin and what type of cell is it produced by

A

Melanin
Melanocytes