Neurones and Glia Flashcards
What are the types of glial cells and their functions?
Astrocytes - support
Oligodendrocytes- insulation
Microglia- immune function
How do astrocytes support neurones?
4 ways
1. Provide nutrition (glucose-lactate shuttle) 2. Remove neurotransmitters 3. Maintain ionic gradient 4. Help form the BBB
True or false: neurones store and produce their own glycogen
FALSE! Neurones do not store or produce glycogen
Which neurotransmitter is particularly toxic to neurones?
Glutamate
How is glutamate removed by astrocytes in order to protect neurones?
Glutamate is converted to glutamine and transported in vesicles to be recycled
High levels of neuronal activity could lead to a rise in extracellular concentration of which ion?
K+
How do astrocytes buffer this excess K+?
They take up K+ via various transporters and channels to ensure that neurones are not firing inappropriate action potentials as a result of the high K+
What is the primary role of oligodendrocytes?
To myelinated axons in the CNS
What are the cells called that are responsible for myelination of the PNS?
Schwann cells
How do microglia help to defend the brain against infection?
Phagocytose foreign material and debris
Act as APCs to T cells
Microglia are derived from which embryonic tissue type?
Mesoderm
What is the role of the BBB?
To limit diffusion of substances from the blood into brain ECF
Brain capillaries have which three features to help to control the environment for the neurones?
Tight junctions in-between endothelial cells
Basement membrane around capillaries
End feet of astrocyte processes
Which substances are able to diffuse across the BBB?
Water
CO2
Lipophilic substances
Which substances are transported across the BBB as they are unable to diffuse across?
Glucose
AAs
Potassium
The CNS is described as having what kind of immune protection?
Immune privilege
In which three ways do neurones communicate?
Fast excitatory neurotransmission
Fast inhibitory neurotransmission
Modulatory responses
Way are the four main sections of a neurone?
Cell soma
Dendrites
Axon
Terminals
The main neurotransmitters in the CNS are what type of molecule?
Amino acids
Microglia can act as which specialised type of immune cell?
Antigen Presenting Cells
What does the CNS inhibit in order to make it “immune privileged”?
Inhibits the pro-inflammatory T cell response
Explain how neurotransmitters are released at the synapse upon arrival of the action potential.
AP arrives Depolarisation opens voltage-gated Ca2+ channels Ca2+ enters the terminal Vesicles fuse with the membrane Neurotransmitter is released
The postsynaptic response to neurotransmitter depends on what 2 things?
The nature of the transmitter
The nature of the receptor
What are the three chemical classes of neurotransmitter in the CNS?
Give some examples of each
Amino acids e.g. glutamate, GABA, glycine
Biogenic amines e.g. Ach, NA, dopamine, serotonin, histamine
Peptides e.g. CCK, somatostatin, dynorphin
Name the main excitatory amino acid neurotransmitter(s).
Glutamate
Name the inhibitory amino acid neurotransmitter(s).
Which is the main one in the brain?
GABA- main one in brain
Glycine
What are the two general types of neurotransmitter receptor?
Ligand-gated ion channels
IONOTROPIC
G protein-coupled receptors
METABOTROPIC
Name two types of ionotropic glutamate receptors.
What ions are they each permeable to?
AMPA- Na+/K+
NMDA- Na+/K+ and Ca2+
AMPA receptors mediate which kind of response?
Initial, fast depolarisation
NMDA receptors require glutamate and what other factor to allow ion flow through the channel?
The cell to be depolarised
Calcium ion entry through NMDA receptors is important for the induction of what?
Long term potentiation
Excitotoxicity can be caused by what?
Too much Ca2+ entry through NMDA
Too much glutamate
GABA and glycine receptors have integral _____ channels.
Cl-
How do GABA and glycine receptors elicit their inhibitory effects?
Cl- channels open
Cell becomes hyper-polarised
Inhibitory post-synaptic potential
Decreased AP firing
Which drugs bind to GABAa receptors to enhance the response to GABA?
What are these drugs used to treat clinically?
Barbiturates - epilepsy
Benzodiazepines- anxiety, insomnia, epilepsy
Where is glycine present in high concentrations?
Spinal cord
Brainstem
The synapse on which type of neurones release glycine?
What is the effect of the glycine?
Interneurones
Inhibit action potentials e.g.hamstring in patellar reflex
Each acts on which two receptors in the brain?
Nicotinic
Muscarinic
Where to cholinergic neurones originate in the brain?
Basal Forebrain
Brainstem
Where to the cholinergic pathways project to?
Many parts of the cortex and hippocampus
Where might you find cholinergic interneurones?
Corpus striatum
What kinds of cognitive function do cholinergic pathways have in the CNS?
Arousal
Learning & memory
Motor control
Memory
Degeneration of cholinergic neurones in the basal forebrain is associated with what disease?
What drugs can be used to alleviate symptoms of such?
Alzheimer’s disease
Cholinesterase inhibitors
Which dopaminergic pathway in the CNS is involved in motor control?
In which disease is this pathway effected?
Nigrostriatal pathway
Parkinson’s disease
Which dopaminergic pathway in the CNS is involved in mood, arousal and reward?
Mesolimbic pathway
How is Parkinson’s disease treated pharmacologically?
How does it work?
Levodopa
Converted to dopamine once it passes through the BBB
When using Levopoda, how do we prevent peripheral dopamine levels getting too high and causing the need for high levels of therapeutic L-dopa?
Give Carbidopa with L-DOPA inhibit its conversion into dopamine in the periphery but not in the brain as it cannot cross the BBB
Noradrenaline acts through which receptors in the brain and the periphery?
G protein couple alpha- and beta-adrenoceptors
Where are noradrenergic pathways generally found in the brain?
Where do they project to?
In the brainstem
Throughout the cortex, hypothalamus, amygdala and cerebellum
Where, specifically, does most of the noradrenaline come from?
A group of neurones in the LOCUS CERULEUS
When are the neurones of locus ceruleus at their least active?
When are they increasingly active?
Least- during sleep (inactive)
Increasing during behavioural arousal
Which neuronal pathways have a similar distribution to noradrenergic neurones?
Serotonin (5-HT)
What are the functions of serotonin?
Sleep/wakefullness
Mood
