CNS cell types

Question 1

Name the three main glial cells in the CNS

Answer 1

• Oligodendrocytes
• Microglia
• Astrocytes

Question 2

Describe upper motor neurons

Answer 2

• large
• Excitatory
• Glutamatergic
• Long projection pyramidal cells

Question 3

Describe striatal interneurons

Answer 3

• Small
• Inhibitory
• GABAergic

Question 4

Describe Oligodendrocytes

Answer 4

• Myelinating cells of the CNS
• Unique to vertebrates
• Provide metabolic support for axon and enable rapid nerve conduction
• Demyelinating diseases e.g. multiple sclerosis

Question 5

describe the myelin sheath

Answer 5

• formed by wrapping of axons by oligodendroctye processes
• highly compared (70% lipid, 30% protein)
• myelin specific proteins (MBP, MAG, MOG, PLP, PMP22) involved in compaction - excellent markers

Question 6

Describe microglia

Answer 6

• Resident immune cells of the CNS
• resting state, highly ramified, motile processes survey environment
• upon activation (ATP) retract processes, become amoeboid and motile
• proliferate at sites of injury (phagocytic)

Question 7

Functions of microglia

Answer 7

• Immune surveillance
• phagocytosis (debris/microbes)
• synaptic plasticity - pruning
• process dynamics

Question 8

Describe astrocytes

Answer 8

• Star-like cells
• Highly heterogeneous
• most numerous glial cells in the CNS
• common marker GFAP

Question 9

Types of astrocyte

Answer 9

Fibrous - white matter, less elaborate, contacts with blood vessels, pia surface and nodes of ranvier
Protoplasmic - grey matter, extremely elaborate, processes contact blood vessels and pia surface

Question 10

Astrocyte functions

Answer 10

• developmental (radial glia)
• structural (define brain micro-architecture)
• envelope synapses (tripartite synpase)
• homeostatic (buffer K+, glutamate etc.)
• support neurons (glutamate-glutamine shuttle, lactate shuttle)
• neurovascular coupling (basis of fMRI)
• disease (gliosis/astrocytosis)

Question 11

Specialised astrocytes

Answer 11

• Radial glia (stem-like progenitor cells, developmental)
• Muller glia (specialised radial glia of the retina)
• Bergmann glia (cerebellum, extremely elaborate, purkinje cell dendrites and synapses)

Question 12

CNS terminology

Answer 12

• abundance of neuronal cell bodies in nuclei
• axons gathered into tracts
• tracts that cross midline = commissures
• grey matter contains neural cell bodies and processes
• neuropil contains few cell bodies
• white matter contains abundance of myelinated tracts and commissures

Question 13

PNS terminology

Answer 13

• cell bodies and supporting cells located in ganglia
• axons bundled into nerves
• many PNS axons are enveloped by Schwaan cells (myelinating cells of the PNS)

Question 14

What is the BBB formed by

Answer 14

• endothelial tight junctions
• pericytes
• astrocyte end feet
• continuous basement membrane

Question 15

What is the BBB sensitive to

Answer 15

• inflammation
• hypertension
• trauma
• ischaemia

Question 16

Describe ependymal cells

Answer 16

• epithelial-like, line ventricles and central canal of spinal cord
• CSF production, flow and absorption
• ciliated - facilitates flow
• allow solute exchange between nervous tissue and CSF

Question 17

Describe the choroid plexus

Answer 17

• frond-like projections
• formed from modified ependymal cells, villa form around network of capillaries, large surface area
• main site CSF production by plasma filtration
• tight gap junctions between cells form blood-CSF barrier