Cells of the CNS & Development Flashcards
What are ependymal cells?
Low columnar or cuboidal cells that line the central canal of the spinal cord and the ventricle within the brain
- DO NOT have basal lamina/basement membrane
Describe a neuron
Contains a soma (metabolic centre of the cell) with dendrites (receive information) and axons (conducting unit for carrying signals to other cells)
What are astrocytes and what is their passive function?
A type of glial cell.
Passive functions include neurotransmitter uptake and degradation (glutamate uptake), K+ homeostasis, neuronal energy supply, maintenance of the BBB, injury response and recovery
What are the active functions of astrocytes?
They are excitable and show exocytosis (gliotransmitters), modulate neuronal function, modulate blood flow
What are the similarities and differences between Schwann cells and Oligodendrocytes?
Both produce myelin, providing electrical insulation for neurons which speeds up condution.
Each oligodendrocyte extends processes that wrap around parts of several axons in the CNS.
Schwann cells wrap around ONE axon in the PNS
What is the immune system of the CNS?
The CNS is immune privileged, and microglia are the local defence cells. They resemble macrophages - phagocytic
What are ganglia?
Aggregations of cell bodies of neurons outside the CNS.
Sensory ganglia house the cell bodies of sensory neurons
Autonomic ganglia house the cell bodies of post-ganglionic neurons
How are cells added to the cortex in development?
Cells are added from to the outside from within - neuroepithelium adds layers to generate cortex (all new neurons are born at the ventricular surface which contains stem cells)
- radial glia are radially arrayed, neurons can follow them, take them up to directly where they need to form a new layer
How is the spinal cord developed?
The notochord releases molecules (sonic hedgehog) which acts on the floor plate –> causes the floor plate to start producing sonic hedgehog too, acts as an inductive element so that it turns the cells around them into motor neurons
- interneurons appear just dorsal to motor neurons, they are induced by motor neurons releasing motor neuron factor
What is central tolerance?
Occurs in the primary lymphoid tissue as development is occurring
- trying to get rid of any autoreactive lymphocytes before they get out into the tissues
What are the 4 mechanisms used to induce tolerance?
Deletion - checkpoint against which lymphocytes are measured and if they have receptors they are killed off
Anergize - turn off the capacity to respond
Ignore - ignore the trigger
Regulate - active process, where an autoreactive response may be initiated but then the response is dampened down
What is a mechanism of B cell peripheral tolerance?
Ignorance/anergy/death
- lack of co-stimulation/T cell help
- lifespan is short in the absence of T cell help & low affinity
What is positive selection in regards to T cell development?
Thymocytes that express TCRs capable of recognising self-MHC are selected to survive
What is negative selection in regards to T cell development?
Removal of immature lymphocytes that have strong reactivity to self peptide
What is AIRE?
Autoimmune regulator of expression
- results in ectopic expression of peripheral tissue proteins in thymic medulla –> testing
- defects in AIRE lead to failure of negative selection for some antigens and result in autoimmunity
