3 Neurones and Glia Flashcards
What are the functions of glia? (CNS)
Support, nourish and insulate neurones and remove waste
Give some different types of glia. (CNS)
- Astrocytes
- Oligodendrocytes
- Microglia
What are the functions of astrocytes? (5)
- Structural support
- Provide some nutrition for neurones (glucose-lactate shuttle)
- Remove neurotransmitters (uptake) (esp glutamate)
- Maintain ionic environment (K+ buffering)
- Help form blood brain barrier
Explain how astrocytes help to provide energy for neurones. (neurones do not store or produce glycogen)
Supplements their supply of glucose- when neurones very active
- Astrocytes produce lactate
- Lactate transferred to neurones
Glucose lactate shuttle
What is excitotoxicity?
- pathological process
- neurons are damaged and killed
- due to overactivations of receptors for the excitatory neurotransmitter glutamate (too much glutamate)
- eg NMDA receptor and AMPA receptor
Too much Ca2+ entry through NMDA receptors
Too much glutamate= excitotoxicity
How do astrocytes help to remove neurotransmitters?
Astrocytes have transporters for transmitters eg glutamate
Helps to keep extracellular conc low
Why is it important that the astrocytes buffer K+ in the brain ECF.
High level of neuronal activity can lead to rise in K+ in brain ECF
Astrocytes take up K+ to prevent this
What is the function of oligodendrocytes?
Myelinating axons in CNS
What is the function of microglial cells and how do they carry out this function?
Immunocompentent cells- brains main defence system
- Activated- recognise foreign material
- Phagocytose- remove debris and foreign material
What is the role of the blood brain barrier?
Limits diffusion of substances from blood to brain ECF
–> maintain correct environment for neurones
What structures form the blood brain barrier? (3)
Ie what structures can be found on end of brain capillaries
- Tight junctions between endothelial cells
- Basement membrane surrounding capillary
- End feet of astrocyte processes
Give some examples of substances that can be transported across the blood brain barrier (ie can’t readily diffuse).
- Glucose
- Amino acids
- Potassium
How does the immune response of the brain (CNS) differ from the rest of the body (‘immune privilage’)? (4)
Fill in the missing labels:
The neurotransmitters in the CNS can be divded into 3 chemical classes. What are these 3 chemical classes and give an example of a neurotransmitter in each.
What is the main excitatory amino acid and what is the main inhibitory amino acid and where do they act??
Excitatory:
- glutamate
Inhibitory:
- GABA
- Glycine
What are the 2 types of glutamate receptors? Differentiate between them.
- Ionotropic
- Metabotropic
How do fast excitatory responses occur?
- Excitatory transmitters-
- -cause depolarisation-
- -act on ligand gated ion channels
Explain glutamate receptors role in learning and memory. (ie how receptors work)
-
NMDA receptors (and mGluRs) activated
- Up-regulate AMPA receptors
- Calcium entry through NMDA receptors
- Strong high frequency stimulation- Long Term Potentiation (LTP)
How do GABA and glycine receptors decrease action potential firing?
- Integrated Cl- channels
- Hyperpolarisation
- IPSP- inhibitory post-synaptic potential
Name 2 drugs that work to enhance the response of GABA and what are they used to treat? (bind to GABAA receptors)
-
Barbituates
- Antiepileptic drug
- Anxiolytic and sedative effects
- risk of fatal overdose & dependence and tolerance
- Anxiolytic and sedative effects
- Antiepileptic drug
-
Benzodiazepines
- Anxiety, insominia and epilepsy
- Sedative and anxiolytic effects
- Anxiety, insominia and epilepsy
Name the 4 main neurotransmitters that act as modulators in the CNS. ( Biogenic amines)
- Acetylcholine
- Dopamine
- Seratonin (5-HT)
- Noradrenaline
Acetylcholine is important as a neurotransmitter in the PNS. Outline its role in the PNS.
Cholinergic neurones are the first to die off in Alzheimer’s disease (in nucleus basalis) . What treatment is used to help this (alleviate symptoms)?
Cholinesterase inhibitors
What functions are cholinergic pathways of the CNS involved in? (3)
- Arousal
- Learning and memory
- Motor control
Outline the cholinergic pathways in the CNS.
Fill in the missing labels for the dopaminergic pathways in the CNS.
Identify 2 conditions which are associated with dopamine dysfunction.
- Parkinson’s disease
- loss of dopaminergic neurones
- substantia nigra input to corpus striatum
- Levodopa- drug used to treat
- Schizophrenia
- release of too much dopamine?
- Antipsychotic drugs= antagonists at dopamine D2 receptors
- release of too much dopamine?
How do the receptors to noradrenaline in the brain compare to those in the PNS?
They are the same (alpha and beta adrenoreceptors)- G protein-coupled adrenoreceptors
Outline the noradrenergic pathways in the CNS.
What are the functions of the serotonergic pathways in the CNS?
- Sleep/wakefulness
- Mood
What are SSRIs used to treat? (selective seratonin reuptake inhibitors)
Depression and anxiety disorders
Explain how amphetamines increase wakefullness (with relation to noradrenaline).
Most noradrenaline in brain comes from locus ceruleus
Locus ceruleus= inactive during sleep
Locus ceruleus- activity increases during behavioural arousal
Amphetamines increase release of noradrenaline and dopamine from locus cereuleus
(depression may be associated with deficiency in noradrenaline)
