Neurones And Glia Flashcards
What do glia do?
Support, nourish and insulate neurones
Remove waste
Name the types of glia
Astrocytes
Oligodendrocytes
Microglia
Which is the most abundant those of glia cell
Astrocytes
Functions of astrocytes?
Structural support
Provide nutrition for neurones via glucose-lactose shuttle
Remove neurotransmitters
Maintain ionic environment by buffering K+
Form part of blood brain barrier
How is the supply of glucose to neurones supplemented?
Astrocytes produce lactate which is transferred to neurones via the glucose-lactate shuttle (because neurones cannot store or produce glycogen)
Describe how the glucose lactate shuttle works
Glucose taken into the astrocyte from the bloodstream via GLUT1
Glucose -> glycogen -> pyruvate -> lactate
Lactate transported to interstitial pace via MTC1 along with H+
Transported into the neurone via MCT2 along with H+ where it is metabolised
When is the glucose-lactate shuttle used?
When there is high demand/very active - only supplies glucose for about 5 mins
How do astrocytes remove neurotransmitters?
Have transporters for transmitters to keep the extracellular concentration low
Why do astrocytes need to buffer potassium and how?
Potassium is released into the extracellular space by neurones and can cause depolarisation of a neurone if it builds up
Taken up by astrocytes via
🔹Na-K-ATPase
🔹Na-K-2Cl
🔹Potassium channels
What is oligodendrocytes do?
Myelinate axons in the CNS - the equivalent of Schwann cells in the PNS
What is the role of microglia?
Immunocompetent cells
- recognise foreign material and are activated
- dendritic processes swell so they can phagocytose foreign material
- brain’s main defence system
Which embryonic tissue is the CNS derived from?
Endoderm
Which embryonic tissue are microglia derived from?
Mesoderm
Functions of the blood brain barrier?
Limit diffusion of substances from the blood to the extracellular fluid
Maintain the correct environment for neurones
What makes up the blood brain barrier?
Tight junctions between endothelial cells of capillaries
Basement membrane surrounding the capillary
Foot processes of astrocytes
What are some substances that can be transported across the blood brain barrier?
Glucose
Amino acids
Potassium
Which molecules can diffuse freely across the blood brain barrier?
Gaseous molecules and water
Lipophilic molecules
What is meant by saying the CNS is immune privileged?
Has a specialised immune function
T-cells can enter the CNS but their inflammatory response is limited
Any inflammatory expansion in the CNS would not be tolerated due to rigidity of the skull
What is the axonal hillock?
Where the action potential is generated to pass along the axon
Connects the cell body to the axon
Name the different categories and types of neurotransmitters
Amino acids
- glutamate
- GABA
- glycine
Biogenic amines
- NA
- dopamine
- serotonin
- histamine
- ACh
Peptides
- dyphorin
- enkephalins
- substance P
- somatostatin
- CCK
- neuropeptide P
Which are the main neurotransmitters to cause an excitatory response?
The amino acids - glutamate
What are the two main types of glutamate receptors?
Inonotrophic - integral ion channel which increases the Na and K permeability, and sometimes Ca
Metabotrophic - a GPCR which allows changes in IP3 or (decreased) cAMP levels
What are the main ionotrophic receptors and what do they do?
AMPA: increase Na and K permeability
NMDA: increase Na, K and Ca permeability
Kainate receptors
What does it mean if a receptor is excitatory?
Will cause depolarisation and subsequently allow more action potentials to fire
(Excitatory Post-Synaptic Potential - EPSP)
