2 - Cells of the CNS Flashcards
Immune cells of the CNS
Microglia
Number of layers of neurons in the cortex
Six (shallowest is one, deepest is six)
Ependymal cell location
Low columnar or cuboidal cells that line central canal of spinal cord and ventricles within brain .
Role of ependymal cells
Some have cilia to aid CSF flow.
Lack a basal lamina
Aspects of neurons that distinguish them from other cells 1 2 3 4
1) Specialised for signalling.
2) High levels of protein synthesis
3) Metabolically limited
4 Terminally differentiated
Golgi stain
A type of silver stain, used to visualise neurons
What regulates neuron morphology?
The cytoskeleton
Components of cytoskeleton
1
2
3
1) Actin
2) Intermediate filaments
3) Microtubules
Actin
Dynamic assembly/disassembly allows shape changes and movement (eg: spines and growth cones)
Intermediate filaments
In all processes.
Permanent.
Microtubules
Dynamic, composed of tubulin, involved in axon transport
Alternative name for neuron cell body
Soma
Why do neurons have high levels of protein production?
Protein required for ion channels, receptors, cytoskeleton
Nissl bodies
Rough ER, free ribosomes in the cytoplasm of neurons.
Astrocyte passive support functions (passive = respond to when neurons function) 1 2 3 4 5
1) Neurotransmitter uptake and degradation
2) K+ homeostasis
3) Neuronal energy supply
4) Maintenance of the BBB.
5) Injury response and recovery
Astrocyte active functions
1
2
1) Modulation of neuronal function
2) Modulation of blood flow
How do astrocytes supply glucose to neurons?
Wrap around blood vessels, take up glucose, deliver these to neurons
Two crucially-important neurotransmitters in the brain
Glutamate and GABA
How are glutamate and GABA removed from the brain?
Astrocytes have glutamate and GABA transporters, and remove neurotransmitters from synaptic cleft
How are glial cells stimulated? 1 2 3 4
1) Neurotransmitters (ATP, glutamate)
2) Trauma
3) Spontaneous
4) Inflammatory mediators
These stimulate Ca2+ waves in glia (increased Ca2+ levels)
How do glia communicate?
Glia contain synaptic vesicles and show exocytosis of gliotransmitters
What happens to neurons when there is a glial Ca2+ wave?
Inhibition of adjacent neurons
Effect of a Ca2+ wave in an astrocyte associated with a blood vessel
Leads to vasoconstriction OR vasodilation (depending on neural metabolic needs
Function of oligodendrocytes
Responsible for myelination of CNS neurons.
Predominant glial cell of the white matter
Structural difference between Schwann cells and oligodendrocytes
Oligodendrocytes extend processes that wrap around parts of several axons. Schwann cells wrap around one axon.
Where do microglia come from?
Bone marrow
Appearance of microglia
Large dendritic processes that extend from cell body
Roles of microglia 1 2 3 4
1) Constantly survey the CNS.
2) Change rapidly in response to inflammation or injury- upregulate cytokines/growth factors
3) May play a role in development and disease (lack of microglia alters mouse behaviour)
4) Phagocytic
Structure of peripheral nerves
1
2
3
1) One or more bundles (fascicles) or nerve fibres. Each nerve within these fascicles (plus surrounding Schwann cell) is surrounded by endoneurium.
2 Each fascicle is surrounded by collagenous tissue called perineurium.
3) If there is more than one fascicle, than there is further layer of collagenous tissue called epineurium.
Two types of ganglia
Sensory - House cell bodies of sensory neurons (EG dorsal root ganglia)
Autonomic - Hose the cell body of post-ganglionic neurons (parasympathetic, sympathetic neurons)
Ganglia
Aggregations of cell bodies of neurons outside the CNS
Contents of ganglia
Cell bodies, nerve fibres, satellite cells
