Cellular Physiology Of The Brain Flashcards
List 4 roles of Astrocytes
- Help to provide nutrition for neurones via Glucose-lactate shuttle
- Uptake of neurotransmitter to keep concentration low
- Maintain ionic environment via K+ buffering
- Help to form blood brain barrier
Can neurones store or produce glycogen?
No
How do astrocytes provide nutrition to neurones
- Produce lactate from blood glucose (which is 1st converted to Glycogen and Pyruate in the cell)
- Lactate transported to neuron via Glucose-lactate shuttle
- Lactate converted to Pyruvate in neurone and used to make ATP
Name a toxic neurotransmitter that can be taken up by astrocytes
Glutamate
List the features of K+ buffering by Astrocytes
- Astrocytes have a RMP even more (-ve) than that of neurones
- Na-K ATPase and NKCC2 channels involved
- Astrocytes are connected to each other, so ions can move between them
Compare Microglia in resting and activated phases
These cells can act as APCs
Resting: Dendritic with long projections
Activated/ Phagocytic: Compact with disappearance of dendrites
Describe 3 structural features of the Blood Brain Barrier
- Tight junctions between endothelial cells of capillaries
- Basement membrane around capillaries
- End feet of astrocyte processes surrounding capillaries
Describe the meaning of the CNS being immune privileged
- No inflammation tolerated due to rigidity of skull (would lead to damage/ compression of vessels -> neuron damage)
- Microglia act as Antigen Presenting Cells to T cells
- T cells enter CNS through Blood Brain barrier
List the 4 main sections of a neurone
- Cell soma
- Axon
Dendrites and Terminals, which often synapse with each other
Describe neurotransmitter release briefly
- Depolarisation causes opening of VGCCs
- Ca diffuses in and causes release of vesicles containing neurotransmitter
List the 3 chemical classes of neurotransmitters in the CNS
- Amino acids
- Biogenic amines
- Peptides (Encephalin, Dynorphin, Somatostatin, CCK, Neuropeptide Y)
Which chemical class do the following neurotransmitters belong to?
- Glutamate
- GABA
- Glycine
Are they inhibitory or excitatory?
All are amino acid neurotransmitters
Glutamate- Excitatory
GABA and Glycine- Inhibitory
List 5 Biogenic Amines
- ACh
- Dopamine
- NA
- Histamine
- Serotonin (5-HT)
Over 70% of CNS synapses involve the use of which neurotransmitter?
Glutamate (The major excitatory neurotransmitter)
Compare the 2 classes of Glutamate receptors
Ionotropic: Contain an integral ion channel that opens upon activation, leading to depolarisation
Metabotropic: a GPCR linked to either;
- Changes in IP3 and Ca mobilisation
OR
- Adenylyl Cyclase inhibition and reduced cAMP levels
Compare the 3 types of Ionotropic Glutamate receptors
AMPA Receptors: Permeable to Na and K ions
Kainate receptors: Permeable to Na and K ions
NMDA receptors: Permeable to Na, K and CA ions
Describe the role of the 2 types of Ionotropic Glutamate receptors present in Glutamatergic synapses
- AMPA receptros mediate the initial depolarization
- NMDA receptors are permeable to Ca
In order for Ca to flow through NMDA receptors what are 2 things required?
What chemical acts on these receptors as a co-agonist?
- Cell must be depolarised
- Glutamate must bind
Glycine
Glutamate receptors have a role in learning and memory.
What can NMDA receptor activation cause?
What does strong, high frequency stimulation cause?
Up-regulation of AMPA receptors
Long Term Potentiation, LTP (Ca entry through NMDA receptors is important for this)
What can excess Ca entry through NMDA receptors cause?
Excitotoxicity (too much glutamate) as Ca is toxic in high Intracellular concentrations
Name the main inhibitory neurotransmitters in the;
- Brain
- Brainstem
- Spinal Cord
Brain: GABA
Brainstem and Spinal Cord: Glycine
Describe briefly how binding to GABAa and Glycine receptors cause Hyper-polarisation leading to an IPSP
- Both receptors have integral Cl- channels
- These channels open and Cl- diffuses in
- Inside of neuron is now more negative-> reduced firing of APs
Compare GABAa and GABAb receptors
GABAa: Ligand gated receptors
GABAb: GPCRs, have a modulatory role
Name 2 types of drugs that act on GABAa receptors
How do they affect the receptors?
- Barbiturates
- Benzodiazepines
Enhance the response of the receptors to binding by GABA
DO NOT BIND TO THE RECEPTORS THEMSELVES