Neuroglia Cells Flashcards
In what year was it acknowledged that some nerves were surrounded by sheaths with nuclei?
1838
When was the term Neuroglia coined?
1856
In what year were neuroglia acknowledged as individual entities?
1888
When was it discovered that there were multiple types of glial cells?
Mid 1800’s to early 1900’s
When were glial cells proved to be more than just structural cells?
Late 1900’s
Where are neuroglia formed?
Neuroglia are formed in the gastrula.
Specifically:
Macroglia are formed in the ectoderm.
Schwann Cells are formed in the neural crest.
Microglia are formed in the mesoderm.
Describe the morphology of astrocytes.
They have a star-like morphology with processes ending in end-feet which contact blood vessels and neurones directly.
Where are fibrous astrocytes found?
Present in the white matter tracts of the brain and spinal cord (+optic nerve & nerve fiber layer of the retina.)
Describe the morphology of fibrous astrocytes.
Their short process contact blood vessels and axona at the nodes of ranvier. The soma is arranged in rows between axon bundles and there is plenty of overlap between processes.
Where are protoplasmic astrocytes found.
Present in the grey matter of the brain and spinal cord.
Describe the morphology of protoplasmic astrocytes.
Their many short processes contact blood vessels and neurones at the synapse and soma and as they form astrocytic domains there is very little overlap.
What is the function of protoplasmic astrocytes?
Their function is to regulate the activity of the synapses and recycle neurotransmitters.
Where are radial glial cells found?
Present in the developing brain, they disappear after maturation.
Describe the morphology and function of radial glial cells.
They have two main processes which connect the ventricle wall and the surface of the brain to act as scaffolding to assist with neuronal migration.
What are Bergmann Glia Cells?
Are a type of radial glial cell present in the cerebellum with the cell body located in the Purkinje cell layer.
What is the morphology of Bergmann Glia Cells?
They have few processes that extend to the surface of the cerebellum , and some also form contacts with synapses on the Purkinje neurone dendrites.
What are Muller Cells?
Type of radial glial cell present in the retina.
What are Muller Cells?
Type of radial glial cell present in the retina.
Describe the morphology of Muller Cells.
Has longitudinal processes that make contact with synapses and blood vessels similar to protoplasmic astrocytes.
What are Ependymal Cells?
Line the ventricles and form the choroid plexus, they produce and move cerebrospinal fluid.
What are Tanycytes?
Line the wall of the 3rd ventricle and have long processes that extend into the hypothalamus which make contact with neurones and blood vessels in order to regulate food intake.
What is the overall function of Astrocytes?
To maintain the homeostasis of the extracellular environment if the system to ensure optimum function of neurones.
List the specific functions of astrocytes (7)
- Uptake and buffering of extracellular K+
- Remove glutamate from the synapse
- Metabolic support for neurones
- Regulate blood flow according to neuronal activity
- Supply neurotransmitter precursors to neurones
- Protect neurones against toxic compounds
- Modulate neuronal activity.
What are Oligodendrocytes?
Their processes extend and wrap around an axon to produce myelin of the CNS. Each processes myelinates a single axon but different processes can originate from a single oligodendrocyte.
What are Microglia?
These are small cells present throughout the brain and are the resident immune cells of the CNS.
Describe Microglia at rest.
At rest they are highly ramified, microdomains that processes are sent out and retracted within for constant surveillance, they also express receptors for inflammatory molecules, pathogens and immune stimuli.
Describe Microglia when active.
When active they are ameboid, capable of phagocytosis and if they are M1 cells they are proinflammatory whereas M2 cells are anti-inflammatory.
What are Schwann Cells?
These myelinate\ensheath axons of peripheral nerves. Myelinating schwann cells wrap their entire cell around the axon.
What are Remak Cells?
Nonmyelinating schwann cells AKA Remak cells ensheath multiple axons into Remak fibres.
What factor determines if an axon is myelinated or ensheathed?
Diameter
