Cell Types In Brain And Spinal Cord

Question 1

Neurons

Answer 1

Specialised for electrical signalling

Question 2

What inputs to neurons

Answer 2

Dendrites

Question 3

When are axons mainly formed

Answer 3

During development

Question 4

What do action potentials propagate along

Answer 4

Along the axon from the axon hillock

Question 5

2 types of synapses

Answer 5

Chemical
Electrical

Question 6

Chemical synapse

Answer 6

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

Question 7

Electrical synapses

Answer 7

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

Question 8

Chemical synaptic transmission

Answer 8

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

Question 9

Where are excitatory synapses often concentrated

Answer 9

Dendritic spines

Question 10

Neural plasticity

Answer 10

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

Question 11

Dendritic Spines

Answer 11

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

Question 12

How do neurones differ

Answer 12

Size
Morphology
Neurotransmitter content
Electrical properties
Eg neocortex

Question 13

Electrical synapse structure

Answer 13

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

Question 14

Betz cells

Answer 14

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

Question 15

Medium spiny neurones

Answer 15

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

Question 16

Which neurons are vulnerable in MND

Answer 16

Betz cells

Question 17

Which neurones are vulnerable in Huntington’s disease

Answer 17

Medium spiny neurones

Question 18

Oligodendrocytes

Answer 18

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

Question 19

Myelin

Answer 19

Insulates axon segments
Enables rapid nerve conduction

Question 20

Nodes of Ranvier

Answer 20

Gaps in myelin sheath
Saltatory conduction

Question 21

Myelin sheath

Answer 21

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

Question 22

Arborisation

Answer 22

Fine branching structure at the end of a nerve fibre

Question 23

How do oligodendrocytes provide metabolic support to axons

Answer 23

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

Question 24

Functions of microglia

Answer 24

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

Question 25

What percentage of myelin in lipid

Answer 25

70%

Question 26

What percentage of myelin is protein

Answer 26

30%

Question 27

Microglia

Answer 27

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

Question 28

Where do microglia originate from

Answer 28

Yolk sac progenitors that migrate into the CNS

Question 29

At what rate do microglia survey environment

Answer 29

2-3 um/min

Question 30

What can activists microglia

Answer 30

ATP

Question 31

Which form of microglia is ‘bad’

Answer 31

M1

Question 32

Which form of microglia is ‘good’

Answer 32

M2

Question 33

Astrocytes

Answer 33

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

Question 34

Why are M1 microglia ‘bad’

Answer 34

Linked to chronic inflammation

Question 35

Astrocyte functions

Answer 35

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

Question 36

Specialised astrocytes

Answer 36

Radial glia Bergmann glia Müller cells (retina)

Question 37

Radial glia

Answer 37

Important for brain development

Question 38

Bergmann glia

Answer 38

Cerebellum

Question 39

How do astrocytes contribute to blood-brain barrier

Answer 39

Processes of astrocytes envelope capillaries in brain

Question 40

Müller cells

Answer 40

Retina

Question 41

Motor neurone disease

Answer 41

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

Question 42

Multiple sclerosis

Answer 42

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

Question 43

Commissures

Answer 43

Tracts that cross the midline

Question 44

White matter

Answer 44

Contains abundance of myelinated tracts and commissures

Question 45

Grey matter

Answer 45

Abundant in neural cell bodies and processes

Question 46

Neuropil

Answer 46

Contains few cell bodies

Question 47

How are axons gathered in the CNS

Answer 47

Into tracts

Question 48

Nuclei

Answer 48

Abundance of neuronal cell bodies in CNS

Question 49

Ganglia

Answer 49

Cell bodies and supporting cells in PNS eg dorsal root ganglia

Question 50

Nerves

Answer 50

Axons bundled into nerves in PNS

Question 51

MND spinal cord shows pathological changes in

Answer 51

Motor neurons Microglia Astrocytes

Question 52

MND symptoms are due to loss of

Answer 52

Motor neurones

Question 53

Pathological CNS lesions in MS involve

Answer 53

Neurones Oligodendrocytes T lymphocytes

Question 54

Acute symptoms in MS primarily reflect dysfunction of

Answer 54

Neurones

Question 55

Myelinating cells of the PNS

Answer 55

Schwann cells

Question 56

Origins of Schwann cells

Answer 56

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

Question 57

What forms the blood-brain barrier

Answer 57

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

Question 58

What is the blood-brain barrier sensitive to

Answer 58

Inflammation Hypertension Trauma Ischaemia

Question 59

Ependymal cells

Answer 59

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

Question 60

Functions of ependymal cells

Answer 60

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

Question 61

Choroid plexus

Answer 61

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

Question 62

Function of choroid plexus

Answer 62

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

Question 63

Gap junctions between ependymal cells

Answer 63

Form blood-CSF barrier

Question 64

Which cells myelinate axons in CNS

Answer 64

Oligodendrocytes

Question 65

Where is CSF reabsorbed

Answer 65

Arachnoid granulations

Question 66

Ependymal cells

Answer 66

Produce CSF in choroid plexus of lateral ventricles

Question 67

Choroid fissure

Answer 67

Attachment site for choroid plexus Above hippocampus

Question 68

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

Answer 68

Melanin Melanocytes