3. The Role of Neurones and Glia

Question 1

What are the general functions of glial cells?

Answer 1

Support, nourish, insulate, and remove waste of neurones.

Question 2

What are the three main types of glial cells?

Answer 2

Astrocytes, oligodendrocytes, and microglia.

Question 3

What are the functions of astrocytes?

Answer 3

Provide structural support, provide nutrition for neurone, remove neurotransmitters, maintain an ionic environment, help form BBB.

Question 4

Why do astrocytes need to provide neurones with nutrition?

Answer 4

Neurones can’t store or produce glycogen so need a direct source of glucose or lactose.

Question 5

What is the direct path of nutrition to neurones?

Answer 5

From endothelium to neurone.

Question 6

How do areas of the brain with high energy consumption receive adequate additional energy?

Answer 6

Via glucose-lactate shuttle from astrocytes to neurone.

Question 7

How do astrocytes deal with neurotransmitters following an AP?

Answer 7

Specific transporters to remove the neurotransmitter, so extracellular concentration remains low. The NT then is recycled back via the astrocytes by convering them to glutamine.

Question 8

Why is it important that excess NT are removed by astrocytes?

Answer 8

Keeps glutamine concentration low as it’s toxic at high concentration.

Question 9

Why do astrocytes remove K+ from extracellular fluid?

Answer 9

High concentration causes depolarisation in neurones.

Question 10

What is the role of oligodendrocytes?

Answer 10

Myelination of the neurones within the CNS.

Question 11

What is the origin of microglia cells?

Answer 11

Mesodermal origin.

Question 12

What are the roles of microglia?

Answer 12

Immunocompetent cells and phagocytic so form basis of brains’ defence system - recognise foreign material and phagocytose to remove debris and foreign material.

Question 13

What is the role of the BBB?

Answer 13

Limit diffusion of substances from blood to extracellular substances of brain. Maintains correct environment for neurones to be produced.

Question 14

What forms the BBB?

Answer 14

Tight junctions between endothelial cells, basement membrane surrounding the capillaries and foot processes of astrocytes.

Question 15

How is movement of needed molecules across the BBB allowed?

Answer 15

Specialised transporters.

Question 16

What can move freely across the BBB?

Answer 16

Gaseous molecules, H2O and lipophilic molecules.

Question 17

What is meant by the CNS being immune privileged?

Answer 17

It has a specialised immune function. It has a regulated inflammatory response, where T-cell response is significantly limited.

Question 18

Why does the CNS need a regulated inflammatory response?

Answer 18

Any inflammatory expansion in the CNS would not be tolerated due to rigidity of the skull.

Question 19

What are the main three categories of neurotransmitter?

Answer 19

Amino acids, biogenic amines, peptides.

Question 20

What are the main neurotransmitters and the receptors causing excitation in the CNS?

Answer 20

Amino acids, receptors for glutamate.

Question 21

What is the difference between ionotrophic and metabotrophic glutamate receptors?

Answer 21

Ionotrophic - integral ion channel, increasing Na+ and K+ permeability. Metabotrophic - GPCR allowing changes in IP3 or cAMP levels.

Question 22

What are the three main types of ionotrophic receptors and their roles?

Answer 22

AMPA increase K+ and Na+ permeability. NMDA increase Na+, K+, and Ca+ permeability. Kainate receptors.

Question 23

What is the overall role of ionotrophic glutamate receptors?

Answer 23

Cause depolarisation so more APs fire.

Question 24

How can Ca2+ entry through NMDA cause cell damage?

Answer 24

If intracellular levels get too high so too much glutamate can cause excitotoxicty.

Question 25

What is the main inhibitory neurotransmitter in the brain?

Answer 25

GABA.

Question 26

What does glycine act as in the brainstem and spinal cord?

Answer 26

Inhibitory neurotransmitter.

Question 27

What types of channels are glycine and GABA receptors?

Answer 27

Cl-

Question 28

What is the result of opening GABA and glycine receptors?

Answer 28

Hyperpolarisation so decreased APs.

Question 29

What effect do barbiturates and benzodiazepines have and how?

Answer 29

Bind GABA receptors so cause sedation and anti-anxiety through hyperpolarisation.

Question 30

What are neuromodulators?

Answer 30

Regulate diverse population of neurones.

Question 31

What are the roles of ACh?

Answer 31

Acts at NMJ, ganglionic synapse of ANS, and postganglionic neurone for PNS, and central neurotransmitter. Excitatory on nicotinic and muscarinic receptors.

Question 32

What is degeneration of cholinergic neurones in the nucleus basalis of Meynert associated with?

Answer 32

Alzheimer’s disease.

Question 33

Where do ACh neurones originate and project to?

Answer 33

From basal forebrain and brainstem and project to many parts of the cortex and hippocampus.

Question 34

Where are dopamine receptors found?

Answer 34

In regions for motor control.

Question 35

What are dopamine receptors involved in?

Answer 35

Mood, arousal, and reward.

Question 36

What is loss of dopamine receptors associated with?

Answer 36

Parkinson’s disease.

Question 37

What is too much dopamine associated with?

Answer 37

Schizophrenia.

Question 38

Where are NA receptors found?

Answer 38

Postganglionic effector synapses on the SNS and in the CNS. Throughout cortex, hypothalamus, amygdala and cerebellum.