Glia - form and function Flashcards
How many more glia are there than neurones in a human brain?
10x more glia
What do glia offer?
Physical support
Metabolic support
Electrical insulation
Guiding connections
How are glia noticeable?
They cannot be seen by electrophysiological techniques
Morphology
Expression specific markers
Immunohistochemical identification
What are the two divisions of glia?
Macroglia
Microglia
Name the 4 types of macroglia
Schwann cells
Oligodendrocytes
Ependymal cells
Astrocytes
Which two cells form myelin?
Schwann cells
Oligodendrocytes
What are the differences between Schwann cells and oligodendrocytes?
Schwann cells are in the peripheral nervous system
Oligodendrocytes are in the central nervous system
Schwann cells myelinate one axon
Oligodendrocytes myelinate many axons (up to 30)
What does myelination promote?
Regeneration
Can axen regeneration occur in the PNS or CNS?
PNS = yes CNS = no
What allows axon regeneration in the PNS?
Schwann cells and endoneurial tube surrounding the axon encourage growth
What stops axon regeneration in the CNS?
No endoneurial tube
Prevented by signalling in CNS
What is the role of an ependymal cell?
Form the walls of the ventricles in the brain and central canal of the spinal cord
Produce cerebrospinal fluid
What structural adaptations do ependymal cells have?
They are ciliated
Helps circulate the cerebrospinal fluid
Describe an astrocyte
Largest glial cell
Most numerous glial cell
What is the function of an astrocyte?
Neuronal guidance during development
Form architecture of brain and spinal cord
What are astroglia stem cells responsible for?
Adult neurogenesis
Gliogenesis
What role do astrocytes play in homeostasis?
K+ buffering in extracellular fluid
How do astrocytes buffer K+
They have express transporters to take up K+ ions
Why do astrocytes buffer K+
Prevent accumulation of K+ as a result of neuron firing
How do astrocytes work alongside synapses?
They express neurotransmitter transporters
Prevent diffusion outside of the synapse
How do the astrocytes protect the synapse?
They express various transporters
Prevent entry from outside of the synapse
Protect synapse from extracellular fluid
What do astrocytes create at the synaptic junction?
A synaptic microenvironment
Explain neurovascular coupling
The ‘foot’ of the astrocyte envelops the capillaries and neurons
Provides energy to the neurons
Essential in highly active neurons
What can the astrocyte modulate?
Cerebral blood flow
What is cerebral blood flow and indirect measure of?
Neuronal activity
What does a damaged astrocyte release?
ATP and glutamate
How does the astrocyte cell respond to damage?
Hypertrophy
Proliferation
What is the name given to the proliferation of astrocytes in response to damage?
Reactive astrogliosis
What do astrocytes form in the CNS when damaged?
Glial scars
What does an astrocyte produce when an axon is damaged?
Inhibitory molecules to prevent growth
Describe a microglia
Smallest glial cell
10% of glial cells
What is the role of microglia?
Immune cell of the CNS
Where do microglia originate from?
Bone marrow monocytes
When do microglia migrate to the nervous system?
During development
How does a microglia work?
Motile processes monitor environment
Signals of disease or injury trigger transformation into phagocytic cell
What is reactive microgliosis?
The activation of microglia into phagocytic cells
CNS immune system and injury repair is carried out by which glial cell?
Microglia
