2) Roles of Neurones and Glia Flashcards
What are the 3 types of Glial Cells in CNS ?
> Astrocytes
Microglial Cells
Oligodendrocytes
What functions do Astrocytes have ?
> Structural Support
Help provide nutrition for the neurones
Remove Neurotransmitters (Uptake) - Especially important for Glutamate as it is toxic
Maintain ionic Environment - K+ Buffering
Help forms blood brain barrier
Why does Astrocytes need to provide Nutritional Support
Neurones don’t store or produce Glycogen
How do Astrocytes provide Nutritional Support
They produce Lactate which can be transferred to neurones via the Glucose - Lactate Shuttle.
- > Neurones uptake glucose and break it down into lactate to store. When needed it is converted into pyruvate which then used
- > Other wise glucose can also be directly taken up by neurones
How is the Blood Brain Barrier Formed ?
Formed by tight junctions between:
1) Capillary Endothelial Cells
2) Basement Membrane around the Capillary
3) Astrocytes (Foot Processes)
What is Permitted pass through the BBB ?
<> Water <> Carbon Dioxide <> Lipophillic substances <> Nutrients - Glucose - AA - Potassium
Describe the role of Oligodendrocytes ?
They Myelinate Multiple axons in the CNS
Describe the role of Microglia
Resident Macrophage (Smallest of the 3)
> These are required because a normal inflammatory response would be harmful as skin would prevent volume expansion
> Can act as antigen presenting cells
Describe the release of Neurotransmitter at a synapse
1) DP in the pre-synaptic bulb opens Ca2+ Channels
2) Ca2+ causes vesicles full of NTs to move and fuse with the Pre-Synaptic Membrane -> Releasing NTs into the synaptic cleft
3) NTs diffuse across and bind to receptors on the Post - Synaptic Membrane
What 3 classes can NTs be split into ?
1) Amino Acids
> Glutamate
> GABA
> Glycine
2) Biogenic Amines > Acetylcholine > Noradrenaline > Dopamine > Serotonin > Histamine
3) Peptides
> Somatostatin
> Neuropeptide y
What kind of Neurotransmitter is Glutamate ?
Excitatory, therefore causes an Excitatory Postsynaptic Potential
DP causes more AP
List the different types of Glutamate
Ionotropic
> AMPA (Na/K)
> Kainate (Na/K)
> NMDA (Na/K and Ca2+)
Metabotropic
> mGluR1-7
What happens at Glutamatergic Synapses ?
Both AMPA and NMDA receptors are present
> AMPA mediate the initial fast Depolarisation - Influx of Na+
> NMDA receptors allow ions to flow through once DP occurs, when glutamate is bound NMDA allows Ca2+ through
How is Glutamate Receptors important for leaning and memory ?
> Activation of NMDA receptors can up regulate AMPA receptors
Strong, high frequency stimulation cause Long Term Potentiation
-> Ca2+ entry is important for the induction of LTP
What happens if there is too much Glutamate ?
Too much influx of Ca2+ => Excitotoxicity
How can stroke patients suffer excitotoxicity ?
When cells die they release K+ calling DP activating NMDA receptors
What type of Neurotransmitters are GABA and Glycine ?
They are Inhibitory NT, therefore causes inhibitory post synaptic potential
Decreases Action Potential
How do GABA and Glycine Receptors do its job ?
Have Cl- Receptors, so binding lead to hyper-polarisation
What two types of drug can be used to bind to GABA receptors and what effect do they have ?
Barbiturates and Benzodiazepines
They bind to GABA receptors to enhance their effect so they decrease the activity of neurones
This is good for
> Epilepsy
> Anxiety
> Insomnia
How is Glycine relevant in reflexes ?
Inhibits counter acting muscles reflexes.
E.g. in Patella Reflex, glycine is released by interneurones to inhibit Hamstrings
Where is ACh is released ?
Released Diffusely from the Nucleus Basalis into the Cortex and Hippocampus
What is ACh involved in ?
> Arousal
Learning & Memory
Motor Control
How is Alzheimer’s related to the loss of ACh ?
In Alzhemier’s the first neurones to die are found in the Nucleus Basalis
> Thus a lack of ACh -> Memory Loss and Loss motor Control
Use Cholinesterase Inhibitors to help with symptoms
What are the 3 Pathway in which Dopamine is released ?
1) Mesocortical
2) Mesolimbic
They are involved in Mood and Arousal
3) Nigrostriatal
Involved in Motor Control
In the mid brain, Substantia Nigra
