2) Roles of Neurones and Glia

Question 1

What are the 3 types of Glial Cells in CNS ?

Answer 1

> Astrocytes
Microglial Cells
Oligodendrocytes

Question 2

What functions do Astrocytes have ?

Answer 2

> Structural Support
Help provide nutrition for the neurones
Remove Neurotransmitters (Uptake) - Especially important for Glutamate as it is toxic
Maintain ionic Environment - K+ Buffering
Help forms blood brain barrier

Question 3

Why does Astrocytes need to provide Nutritional Support

Answer 3

Neurones don’t store or produce Glycogen

Question 4

How do Astrocytes provide Nutritional Support

Answer 4

They produce Lactate which can be transferred to neurones via the Glucose - Lactate Shuttle.

• > Neurones uptake glucose and break it down into lactate to store. When needed it is converted into pyruvate which then used
• > Other wise glucose can also be directly taken up by neurones

Question 5

How is the Blood Brain Barrier Formed ?

Answer 5

Formed by tight junctions between:

1) Capillary Endothelial Cells
2) Basement Membrane around the Capillary
3) Astrocytes (Foot Processes)

Question 6

What is Permitted pass through the BBB ?

Answer 6

<> Water 
<> Carbon Dioxide 
<> Lipophillic substances 
<> Nutrients 
- Glucose 
- AA
- Potassium

Question 7

Describe the role of Oligodendrocytes ?

Answer 7

They Myelinate Multiple axons in the CNS

Question 8

Describe the role of Microglia

Answer 8

Resident Macrophage (Smallest of the 3)
> These are required because a normal inflammatory response would be harmful as skin would prevent volume expansion
> Can act as antigen presenting cells

Question 9

Describe the release of Neurotransmitter at a synapse

Answer 9

1) DP in the pre-synaptic bulb opens Ca2+ Channels
2) Ca2+ causes vesicles full of NTs to move and fuse with the Pre-Synaptic Membrane -> Releasing NTs into the synaptic cleft
3) NTs diffuse across and bind to receptors on the Post - Synaptic Membrane

Question 10

What 3 classes can NTs be split into ?

Answer 10

1) Amino Acids
> Glutamate
> GABA
> Glycine

2) Biogenic Amines 
> Acetylcholine 
> Noradrenaline 
> Dopamine 
> Serotonin 
> Histamine 

3) Peptides
> Somatostatin
> Neuropeptide y

Question 11

What kind of Neurotransmitter is Glutamate ?

Answer 11

Excitatory, therefore causes an Excitatory Postsynaptic Potential
DP causes more AP

Question 12

List the different types of Glutamate

Answer 12

Ionotropic
> AMPA (Na/K)
> Kainate (Na/K)
> NMDA (Na/K and Ca2+)

Metabotropic
> mGluR1-7

Question 13

What happens at Glutamatergic Synapses ?

Answer 13

Both AMPA and NMDA receptors are present
> AMPA mediate the initial fast Depolarisation - Influx of Na+
> NMDA receptors allow ions to flow through once DP occurs, when glutamate is bound NMDA allows Ca2+ through

Question 14

How is Glutamate Receptors important for leaning and memory ?

Answer 14

> Activation of NMDA receptors can up regulate AMPA receptors
Strong, high frequency stimulation cause Long Term Potentiation
-> Ca2+ entry is important for the induction of LTP

Question 15

What happens if there is too much Glutamate ?

Answer 15

Too much influx of Ca2+ => Excitotoxicity

Question 16

How can stroke patients suffer excitotoxicity ?

Answer 16

When cells die they release K+ calling DP activating NMDA receptors

Question 17

What type of Neurotransmitters are GABA and Glycine ?

Answer 17

They are Inhibitory NT, therefore causes inhibitory post synaptic potential
Decreases Action Potential

Question 18

How do GABA and Glycine Receptors do its job ?

Answer 18

Have Cl- Receptors, so binding lead to hyper-polarisation

Question 19

What two types of drug can be used to bind to GABA receptors and what effect do they have ?

Answer 19

Barbiturates and Benzodiazepines
They bind to GABA receptors to enhance their effect so they decrease the activity of neurones

This is good for
> Epilepsy
> Anxiety
> Insomnia

Question 20

How is Glycine relevant in reflexes ?

Answer 20

Inhibits counter acting muscles reflexes.

E.g. in Patella Reflex, glycine is released by interneurones to inhibit Hamstrings

Question 21

Where is ACh is released ?

Answer 21

Released Diffusely from the Nucleus Basalis into the Cortex and Hippocampus

Question 22

What is ACh involved in ?

Answer 22

> Arousal
Learning & Memory
Motor Control

Question 23

How is Alzheimer’s related to the loss of ACh ?

Answer 23

In Alzhemier’s the first neurones to die are found in the Nucleus Basalis
> Thus a lack of ACh -> Memory Loss and Loss motor Control

Use Cholinesterase Inhibitors to help with symptoms

Question 24

What are the 3 Pathway in which Dopamine is released ?

Answer 24

1) Mesocortical
2) Mesolimbic
They are involved in Mood and Arousal
3) Nigrostriatal
Involved in Motor Control

In the mid brain, Substantia Nigra

Question 25

What are two conditions linked to Dopamine Dysfunction?

Answer 25

Parkinson’s Disease
> Nigrostriatal Pathway is first to go
> Treat with Levodopa

Schizophrenia
>Too much Dopamine Release
> Treat with Dopamine Receptor Antagonists

Question 26

How does L-DOPA work ?

Answer 26

Converted into Dopamine in the brain by AADC enzymes,
must be given along side Carbidopa so this inhibits Peripheral AADC enzymes so that it isn’t converted into dopamine too early as Dopamine cannot cross the BBB

Question 27

What is the difference in mechanism of action of Noradrenaline in the CNS compared to PNS

Answer 27

Operates through alpha and beta adrenoreceptors

Question 28

Where is NA released ?

Answer 28

Released from the Locus Coeruleus in the brainstem and diffuses throughout the Cortex, Hypothalamus and Cerebellum

Question 29

What role does NA have ?

Answer 29

• Mood
• Arousal (Not Sexual)
• Motor Tone

Question 30

What role does Serotonin have ?

Answer 30

Sleep and Mood

Question 31

How can you treat depression ?

Answer 31

Using SSRIs

Question 32

Where is serotonin released ?

Answer 32

Originates from Raphe Nuclei

Projects mostly Rostrally