The Role Of Neurones And Glia Flashcards
What do neurones do?
Sense changes and communicate with other neurones
What do glial cells do?
Support, nourish and insulate neurones and remove ‘waste’. We have around 10^12 glia
What are the types of glial cells?
Astrocytes (several types) - most abundant, supporters
Oligodendrocytes - insulators
Microglia - immune response
What do astrocytes do?
Structural support
Provide nutrition - via glucose-lactate shuttle
Remove neurotransmitters - control concentration of neurotransmitters (especially important for glutamate as this is toxic)
Maintain ionic environment - K+ buffering
Help form blood-brain barrier
How do astrocytes hep to provide energy for neurones?
Neurones do not store or produce glycogen.
Astrocytes produce lactate which can be transferred to neurones via the glucose-lactate shuttle to supplement the supply of glucose
How do astrocytes help to remove neurotransmitters?
Re-uptake
Astrocytes have transporters for transmitters such as glutamate.
This helps to keep the extracellular concentration of glutamate low.
How do astrocytes help to buffer K+ in the brain?
Astrocytes take up K+ to prevent a rise of K+ in the brain as a result of high levels of neuronal activity.
What are the role of Microglia?
Macrophage of the brain.
Immunocompetant cells.
Recognise foreign material -activated
Phagocytosis to remove debris and foreign material
Brains main defence system.
What is the role of the blood brain barrier?
Limits the diffusion of substances from the blood to the brain extracellular fluid.
Maintains the correct environment for neurones.
Brain capillaries have:
- Tight junctions between endothelial cells
- Basement membrane surrounding capillary
- End feet of astrocyte processes
What substances are allowed to cross the blood brain barrier?
Substances such as glucose, amino acids and potassium are transported across the BBB.
This allows the concentration to be controlled.
How is the immune system different in the CNS?
Does not undergo rapid rejection of allografts.
Rigid skull will not tolerate volume expansion -too much inflammatory response would be harmful.
Microglial can act as antigen presenting cells.
T-cells can enter the CNS.
CNS inhibits the initiation of the pro-inflammatory T-cell response.
Immune privilege is not immune isolation, rather specialisation.
What are three different ways neurones can communicate?
Fast excitatory neurotransmission.
Fast inhibitory neurotransmission.
Modulatory response.
What are the four main sections of a nerve?
Cell soma
Dendrites
Axon
Terminals
What happens at a synapse in the brain?
Depolarisation in the terminal opens VGCC (voltage gated calcium channels). Ca2+ enter the terminal.
Vesicles fuse and release neurotransmitter.
Neurotransmitter diffuses across the synaptic cleft and binds to receptors in postsynaptic membrane.
What does the post synaptic response depend on?
Nature of transmitter.
Nature of receptor -ligand gated or GPCR.
What are some neurotransmitters in the CNS?
Over 30 neurotransmitters have been identified int he CNS. They can be divided into three chemical classes:
Amino acids
Biogenic amines
Peptides