3 Neurones and Glia

Question 1

What are the functions of glia? (CNS)

Answer 1

Support, nourish and insulate neurones and remove waste

Question 2

Give some different types of glia. (CNS)

Answer 2

• Astrocytes
• Oligodendrocytes
• Microglia

Question 3

What are the functions of astrocytes? (5)

Answer 3

1. Structural support
2. Provide some nutrition for neurones (glucose-lactate shuttle)
3. Remove neurotransmitters (uptake) (esp glutamate)
4. Maintain ionic environment (K⁺ buffering)
5. Help form blood brain barrier

Question 4

Explain how astrocytes help to provide energy for neurones. (neurones do not store or produce glycogen)

Answer 4

Supplements their supply of glucose- when neurones very active

1. Astrocytes produce lactate
2. Lactate transferred to neurones

Glucose lactate shuttle

Question 5

What is excitotoxicity?

Answer 5

• 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

Question 6

How do astrocytes help to remove neurotransmitters?

Answer 6

Astrocytes have transporters for transmitters eg glutamate

Helps to keep extracellular conc low

Question 7

Why is it important that the astrocytes buffer K⁺ in the brain ECF.

Answer 7

High level of neuronal activity can lead to rise in K⁺ in brain ECF

Astrocytes take up K⁺ to prevent this

Question 8

What is the function of oligodendrocytes?

Answer 8

Myelinating axons in CNS

Question 9

What is the function of microglial cells and how do they carry out this function?

Answer 9

Immunocompentent cells- brains main defence system

1. Activated- recognise foreign material
2. Phagocytose- remove debris and foreign material

Question 10

What is the role of the blood brain barrier?

Answer 10

Limits diffusion of substances from blood to brain ECF

–> maintain correct environment for neurones

Question 11

What structures form the blood brain barrier? (3)

Ie what structures can be found on end of brain capillaries

Answer 11

1. Tight junctions between endothelial cells
2. Basement membrane surrounding capillary
3. End feet of astrocyte processes

Question 12

Give some examples of substances that can be transported across the blood brain barrier (ie can’t readily diffuse).

Answer 12

• Glucose
• Amino acids
• Potassium

Question 13

How does the immune response of the brain (CNS) differ from the rest of the body (‘immune privilage’)? (4)

Answer 13

Question 14

Fill in the missing labels:

Answer 14

Question 15

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.

Answer 15

Question 16

What is the main excitatory amino acid and what is the main inhibitory amino acid and where do they act??

Answer 16

Excitatory:

• glutamate

Inhibitory:

• GABA
• Glycine

Question 17

What are the 2 types of glutamate receptors? Differentiate between them.

Answer 17

1. Ionotropic
2. Metabotropic

Question 18

How do fast excitatory responses occur?

Answer 18

1. Excitatory transmitters-
2. -cause depolarisation-
3. -act on ligand gated ion channels

Question 19

Explain glutamate receptors role in learning and memory. (ie how receptors work)

Answer 19

• NMDA receptors (and mGluRs) activated
  
  • Up-regulate AMPA receptors
  • Calcium entry through NMDA receptors ​
    
    • ​Strong high frequency stimulation- Long Term Potentiation (LTP)

Question 20

How do GABA and glycine receptors decrease action potential firing?

Answer 20

• Integrated Cl^- channels
• Hyperpolarisation
• IPSP- inhibitory post-synaptic potential

Question 21

Name 2 drugs that work to enhance the response of GABA and what are they used to treat? (bind to GABA_A receptors)

Answer 21

• Barbituates
  
  • Antiepileptic drug
    
    • Anxiolytic and sedative effects
      
      • risk of fatal overdose & dependence and tolerance
• Benzodiazepines
  
  • Anxiety, insominia and epilepsy
    
    • Sedative and anxiolytic effects

Question 22

Name the 4 main neurotransmitters that act as modulators in the CNS. ( Biogenic amines)

Answer 22

1. Acetylcholine
2. Dopamine
3. Seratonin (5-HT)
4. Noradrenaline

Question 23

Acetylcholine is important as a neurotransmitter in the PNS. Outline its role in the PNS.

Answer 23

Question 24

Cholinergic neurones are the first to die off in Alzheimer’s disease (in nucleus basalis) . What treatment is used to help this (alleviate symptoms)?

Answer 24

Cholinesterase inhibitors

Question 25

What functions are cholinergic pathways of the CNS involved in? (3)

Answer 25

1. Arousal 2. Learning and memory 3. Motor control

Question 26

Outline the cholinergic pathways in the CNS.

Answer 26

Question 27

Fill in the missing labels for the dopaminergic pathways in the CNS.

Answer 27

Question 28

Identify 2 conditions which are associated with dopamine dysfunction.

Answer 28

* 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

Question 29

How do the receptors to noradrenaline in the brain compare to those in the PNS?

Answer 29

They are the same (alpha and beta adrenoreceptors)- G protein-coupled adrenoreceptors

Question 30

Outline the noradrenergic pathways in the CNS.

Answer 30

Question 31

What are the functions of the serotonergic pathways in the CNS?

Answer 31

* Sleep/wakefulness * Mood

Question 32

What are SSRIs used to treat? (selective seratonin reuptake inhibitors)

Answer 32

Depression and anxiety disorders

Question 33

Explain how amphetamines increase wakefullness (with relation to noradrenaline).

Answer 33

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)