Flashcards in Neurones And Glia Deck (41):
What do glia do?
Support, nourish and insulate neurones
Name the types of glia
Which is the most abundant those of glia cell
Functions of astrocytes?
Provide nutrition for neurones via glucose-lactose shuttle
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
What is oligodendrocytes do?
Myelinate axons in the CNS - the equivalent of Schwann cells in the PNS
What is the role of microglia?
-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?
Which embryonic tissue are microglia derived from?
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?
Which molecules can diffuse freely across the blood brain barrier?
Gaseous molecules and water
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
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
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)
How are glutamate receptors thought to have memory?
Activation of NMDA and mGluRs can lead to upregulation of AMPA receptors
How can excessive amounts of glutamate cause cell death?
Can get too much entry of calcium due to activation of NMDA receptors so that intracellular concentration of calcium becomes too high
Which are the two main inhibitory neurotransmitters and where do they act?
GABA in the brain
Glycine in the brainstem and spinal cord
How do GABA(A) and glycine receptors inhibit action potentials?
They are integral Cl ion channels
Opening of the channels results in hyperpolarisation and this results in decreased action potential firing
(Inhibitory Post-Synaptic Potential - IPSP)
Which drugs bind to GABA receptors and what is their effect?
Cause sedation and anti-anxiety
Which neurotransmitters act as neuromodulators?
Biogenic amines and ACh
(Regulate a diverse population of neurones)
What is the role of ACh in the CNS?
Acts as an excitatory neurone on nicotinic and muscarinic receptors
On receptors present on pre-synaptic terminals to enhance the release of other neurotransmitters
What is the effect of ACh in the brain?
What is the degeneration of cholinergic neurones associated with?
In the nucleus basalis of Meynert - Alzheimer's disease
What is the distribution of cholinergic neurones?
Distributed widely through the CNS
Originate in the basal forebrain and brainstem
Have diffuse projections to many parts of the cortex and hippocampus
What functions are dopamine receptors involved in?
Where are noradrenaline receptors found?
On post-ganglionic effectors synapses in the SNS
In the CNS - operate as a GPCR in the cortex, hypothalamus, amygdala and cerebellum
What increases the release of noradrenaline and dopamine?
What is a decrease in noradrenaline associated with?
What are peptide neurotransmitters often involved in?
What are the three dopamine pathways in the brain and what are they involved in?
Nigrostriatal: motor control
Mesocortical and mesolimbic: mood, arousal and reward