2. Neurones & glia Flashcards Preview

ESA 4- Nervous system > 2. Neurones & glia > Flashcards

Flashcards in 2. Neurones & glia Deck (18):

name the 3 types of glial cells and their general function

1. astrocytes (most abundant type) - supporters
2. oligodendrocytes - insulators
3. microglia - immune response


name 5 functions of astrocytes

1. structural support
2. help provide nutrition for neurones: glucose-lactate shuttle
3. remove neurotransmitters (uptake): control NT conc. (esp. important for toxic glutamate)
4. maintain ionic environment: K+ buffering
5. help to form BBB


describe the energy supply to neurones

Neurones don't store or produce glycogen.
- glucose enters interstitial space from blood via GLUT1 and then enters neurone via GLUT3
- glucose supply can be supplemented by astrocytes via glucose-lactate shuttle: take up glucose (GLUT1) and store as glycogen (enough for 10-15min). Can then be broken down to lactate which can be taken up by neurones and converted to pyruvate


how is NT response at pre-synaptic terminal ended and spread of NTs in brain prevented

astrocytes keep NT conc. low: have transporters for NT uptake (e.g. glutamate) and recycling


how do astrocytes buffer brain ECF [K+] when high neuronal activity

astrocytes have very negative resting MP allowing K+ uptake through several channels/transporters:
- K+ channel
- Na/K ATPase
- NKCC2 transporter


name 3 structures that form the BBB

1. tight junctions between brain capillary endothelial cells
2. basement membrane surrounding capillary
3. end feet of astrocyte processes (promote formation of tight junctions)


explain why the CNS is described as 'immune privileged'

- Immune response is present: microglia act as phagocytes and APCs, and T cells can enter CNS

- but inflammatory response is limited as rigid skull will not tolerate volume expansion (would lead to raised ICP) - CNS inhibits initiation of pro-inflammatory T cell resp.


name the 3 classes of neurotransmitter in the CNS

1. amino acids
2. biogenic amines - ACh, noradrenaline, dopamine, serotonin, histamine
3. peptides - somatostatin, neuropeptide Y, substance P


name the main excitatory amino acid NT and describe its MOA

glutamate: causes excitatory post-synaptic potential (increased neuronal firing) by binding to Na/K ligand-gated channels


describe the generation of initial fast depolarisation at CNS excitatory synapses

i. pre-synaptic terminal releases glutamate which diffuses across cleft...
ii. binds to AMPA Rs (Na+/K+ channels) causing them to open...
iii. Na+ influx and membrane depolarisation


describe the role of glutamate Rs in learning and memory

i. strong, high frequency stimulation/glutamate release at synapse...
ii. activation of NMDA Rs (Na+/K+ and Ca2+ channel) allows Ca2+ entry...
iii. up-regulates AMPA Rs - LONG TERM POTENTIATION (LTP)


why can excess glutamate cause neurone damage

too much glutamate... too much Ca2+ entry through NMDA Rs... excitotoxicity


name the 2 main inhibitory amino acid NTs in the CNS - how do these act?

1. GABA - acts in brain
2. Glycine - acts in brainstem and spinal cord

GABA and glycine Rs have integral Cl- channels: opening of channel... Cl- influx... hyperpolarisation - inhibtiory post-synaptic potential decreases AP firing


how do barbiturates and benzodiazepines act in the CNS

Both bind to GABA Rs and enhance response to GABA - anxiolytic and sedative actions by decreasing neuronal activity

1. barbiturates: sometimes used as anti-epileptic drugs
2. benzodiazepines: used to treat anxiety, insomnia and epilepsy


what is the role of glycine in the patellar reflex

i. sensory neurones from quadriceps spindle Rs synapse with interneurones in spinal cord...
ii. interneurone synapses with motor neurone to reciprocal muscle (hamstrings) - releases glycine to inhibit APs


degeneration of which neurones in which brain region is associated with Alzheimer's - how does this affect therapy

- degeneration of cholinergic neurones (ACh) in nucleus basalis
- therapy: ACh esterase inhibitors


degeneration of which neurones in which brain region is associated with Parkinson's

- degeneration of dopaminergic neurones in substantia nigra
- therapy: levodopa - converted to dopamine by DOPA decarboxylase (AADC)


why must carbidopa be given in combination with levodopa

carbidopa (cannot cross BBB) inhibits aromatic amino acid decarboxylase (AADC) in the periphery... inhibits peripheral metabolism of levodopa, allowing it to cross BBB for CNS function