Glia form and function Flashcards
What are glia?
non-excitable, axon myelinating cells
How do you identify glial cells?
-not seen by electrophysiological techniques can be identified through: -morphology -expression specific markers -immunohistochemical identification
What does the brain contain?
neurones and glia
what are the types of macroglia?
- schwann cells
- oligodendrocytes
- ependymal cells
- astrocytes
What are the myelin forming cells
- schwann cells (periphery)
- oligodendocytes
Apart from their locations, what is the difference between Schwann cells and oligodendrocytes?
Oligodendrocytes can myelinated multiple axons
What are Schwann Cells?
Myelinating cells in the PNS
What are oligodendrocytes?
Myelinating cells in the CNS
Can regeneration occur in the PNS?
- yes
- schwann cells and endoneurial tube surround the axon encourage growth
Can regeneration occur in the CNS?
- no
- no endoneurial tube
- actively prevented by signalling in CNS (prevent wonky connections being made)
What is the role of ependymal cells?
- form the walls of the ventricles in the brain and the central canal of the spinal cord
- involved in the production of cerebrospinal fluid
- ciliated so help circulate CSF
What is the largest and most numerous glial cell type?
astrocytes
What is the structure of astrocytes?
- stellate morphology
- processes can be long
- can look like dendrites
What is a marker for astrocytes?
GFAP
What is the role of astrocytes?
- neuronal guidance during development
- form the architecture of the brain and spinal cord
- astroglia stem cells (can differentiate into nerve cell or a glial cell)
What are the homeostatic mechanisms that astrocytes carry out?
- Homeostatic mechanisms:
- controlling the synapse
- neurovascular coupling
- responding to insult
How are astrocytes involved in neurovascular coupling?
- provide energy to neurone
- important for highly active neurones
- astrocyte may modulate cerebral mood flow
- indirect measure of neuronal activity measured
How do astrocytes respond to insult?
- damaged cells release ATP and glutamate this causes astrocyte hypertrophy and proliferation which is called reactive astrogliosis
- from glial scars around the injured CNS and produce inhibitory molecules that inhibit growth of damaged or severed axons
What are the resident immune competent cells in the CNS?
microglia
Where do microglia arise from?
Bone marrow monocytes
Where do microglia migrate to during development?
nervous sytem
How do microglia respond to danger?
- motile processes monitor the environment
- danger signals (disease) or injury trigger transformation
- in the activated state genes get turned on to deal with injury defence/repair
- they can also differentiate into phagocytes
How do astrocytes prevent K ion build up from high frequency neurone firing?
Expresses K transporters to take up K ions and buffer then within the ECF
What is the role of the astrocytes in controlling the synapse?
- express neurotransmitter transporters
* prevent diffusion of the neurotransmitter outside of synapse
what is the role of the astrocytes in protecting the synapse?
- express various transporters
- prevent entry from outside synapse
- protect synapse fro ECF
- maintain synaptic microenvironment
