(2.1) Glial Cells, Blood Brain Barrier & Neurotransmission

Question 1

Describe 5 functions of Astrocytes.

Answer 1

• Structural supports of neurones
• Nutritional supplies to neurones: Glucose & Lactate (by anaerobic respiration & self-storage via glucose-lactate-shuttle)
• Recycle neurotransmitters: Glutamate Glutamine
• Maintain ionic environment: LOW in [K+]extra-cellular -> -ve membrane potential -> uneasy depolarisation
• Control expression of channels on Blood-Brain-Barrier -> movements of hydrophilic molecules

Question 2

What cells form the myelination in the CNS & what cells in the PNS?

Answer 2

• CNS by Oligodendrocytes

- PNS by Schwann cells

Question 3

What roles do Microglia perform?

Answer 3

• Phagocytosis

- Antigen-presenting

Question 4

From which embryological origins do each Glial cells arise?

Answer 4

• Astrocytes & Oligodendrocytes from Ectoderm

- Microglia from Mesoderm

Question 5

What form the layers of blood brain barrier?

Answer 5

• Endothelium of the brain
• Foot processes of Astrocytes
• Basement membrane of capillaries

Question 6

Describe the movements across blood brain barrier of:

• Glucose
• Amino Acid
• Potassium
• Lipophilic Molecules
• Gases

Answer 6

• Via transporters (modulated by Astrocytes): Glucose, Amino Acids, Potassium
• Freely: Lipophilic & Gaseous molecules

Question 7

What does in mean by the CNS is immune privileged?

Answer 7

T lymphocytes response limited -> inflammatory response limited

Question 8

Draw a simple diagram of a neurone, briefly describe the functions of each structure.

Answer 8

• Dendrites: projected from Soma, receiving info
• Soma: cell body, containing genetic info
• Axonal Hillock: axon projection nearest to Soma, generating action potential
• Axonal Terminals: extensions out of Soma, delivering info
• Myelination: insulation, provide saltatory conduction, faster info transmission

https://www.google.co.uk/search?q=neuron&espv=2&biw=1200&bih=717&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMI7uekiPS6yAIVhFgUCh0gjg1Y#imgrc=Fo8GI8TeeEitOM%3A

Question 9

Briefly draw out differences between Multipolar, Bipolar, Unipolar neurones. Give an example of each.

Answer 9

• Multipolar: lots dendrites + 1 axon e.g. Motor neurones
• Bipolar: 1 dendrite + 1 axon e.g. Interneurones
• Unipolar: no dendrites + 1 axon e.g. Sensory neurones

https://www.google.co.uk/search?espv=2&biw=1200&bih=717&tbm=isch&sa=1&q=neuron+types&oq=neuron+types&gs_l=img.3..0i19l2j0i8i30i19j0i5i30i19l5j0i8i30i19.140791.142057.0.142156.6.6.0.0.0.0.121.383.2j2.4.0….0…1c.1.64.img..2.4.381.gjBiOjerCQs#imgrc=ZRunNEhGGXuSEM%3A

Question 10

List some examples of neurotransmitters:

• Amino Acids x3
• Biogenic Amines x4
• Peptides x2

Answer 10

• Amino Acids: Glycine, Glutamate, GABA
• Biogenic Amines: Dopamine, Noradrenaline, Acetylcholine, Serotonin
• Peptides: Somatostatin, Cholecystokinin

Question 11

What is the most common type of receptor responsible for Fast-Excitatory Neurotransmission in the CNS?

Answer 11

Glutamate Receptor

Question 12

What is the most common type of receptor responsible for Fast-Inhibitory Neurotransmission in the CNS? How do they act inhibitory?

Answer 12

• GABA A in the brain
• Glycine in the brainstem & spinal cord
• Permeable to Cl- -> Hyperpolarisation

Question 13

Briefly describe the differences between the subtypes of Glutamate receptors. What roles do they perform?

Answer 13

• AMPA & Kainate: permeable to Na+ & K+
• NMDA: permeable to Na+ & K+ & Ca2+
• Metabotropic: GPCR for IP3 & cAMP
• Memory via Long-Term-Potentiation: activation of NMDA & mGluG upregulate AMPA expression

Question 14

Why may excessive Glutamate transmission be dangerous?

Answer 14

Activation of NMDA receptor -> Ca2+ influx -> Excitotoxicity

Question 15

Give two drugs used to treat anxiety and cause sedative effects. How do they work?

Answer 15

• Barbiturate
• Benzodiazepine
• GABA A agonists -> enhance Fast-Inhibitory-Neurotransmission in the CNS

Question 16

List and state where some Acetylcholine receptors can be found.

Answer 16

• Nicotinic Ach-R: in neuromuscular junction & pre-ganglionic fibres in both SNS & PSNS
• Muscurinic Ach-R: in post-ganglinonic fibres in Parasympathetic nervous system

Question 17

What response does Acetylcholine cause as neurotransmitter?

Answer 17

• Memory
• Learning
• Motor
• Arousal
• On presynaptic terminals to enhance the release of other neurotransmitters

Question 18

Briefly describe the underlying cause of Alzheimer’s Disease.

Answer 18

Loss of Acetylcholinergic neurones in Nucleus Basalis of Meynert

Question 19

Briefly describe the underlying cause of Parkinson’s Disease.

Answer 19

Degeneration of Dopamine-generating-cells in Substantia Nigra

Question 20

Which neurotransmitter is linked with Schizophrenia?

Answer 20

Excessive Dopamine

Question 21

What response does Dopamine cause as neurotransmitter?

Answer 21

• Arousal
• Motor
• Reward
• Mood

Question 22

Briefly describe the underlying cause of Multiple Sclerosis.

Answer 22

Loss of Oligodendrocytes -> loss of myelination in CNS

Question 23

Which ion blocks a subtype of Glutamate receptors during -ve or resting membrane potential? Which subtype is it?

Answer 23

• Mg2+

- NMDA-R

Question 24

Distinguish between spatial and temporal summation. What effect do they have on conducting action potential?

Answer 24

• Spatial Summation: a lot of stimuli at once
• Temporal Summation: single but continuous stimuli
• An electrical current diminishes the further it moves from the source, summation of stimuli lead to conduction of action potential

Question 25

Suggest some possible drug reactions with Benzodiazepines

Answer 25

- Addiction & tolerance - Withdrawal (insomnia, agitation) - Respiratory & CNS depression