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Sem 5 - The Nervous System > 3. The Role Of Neurones And Glia > Flashcards

3. The Role Of Neurones And Glia Flashcards

1
Q

What is the basic role of neurones?

A

To communicate with each other and sense changes

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2
Q

What is the basic role of glia?

A

Support, nourish, and insulate neurones, and remove waste

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3
Q

What are the 3 types of glial cells?

A

Astrocytes
Oligodendrocytes
Microglia

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4
Q

Which type of glia are the most abundant?

A

Astrocytes

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5
Q

What is the role of astrocytes?

A

Support

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6
Q

Which type of glial cells are responsible for insulation?

A

Oligodendrocytes

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7
Q

What do microglia do?

A

Immune response within the CNS

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8
Q

Which cells help form the blood-brain barrier?

A

Astrocytes

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9
Q

How do astrocytes “support” the CNS?

A

Structural support
Provide nutrition
Remove neurotransmitters
Buffer electrolytes

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10
Q

How are neurones supplied with glucose?

A

Glucose-lactate shuttle in astrocytes

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11
Q

Why do astrocytes need to provide the lactate to the CNS?

A

Neurones do not store or produce glycogen themselves, so the glucose that crosses the BBB is supplemented by lactate from astrocytes

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12
Q

When are astrocytes most important wrt energy supply?

A

When blood glucose is low

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13
Q

Describe the mechanism by which astrocytes supplement neuronal glucose supplies.

A

Glucose crosses BBB via GLUT 1 transporter into the astrocyte, where it is stored as glycogen. This can be converted into pyruvate then lactate when needed. Lactate is transported with H+ via MCT1&2 transporters where it is converted to pyruvate for ATP.

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14
Q

Why is it important for astrocytes to remove neurotransmitter?

A

Without reuptake/control by astrocytes, build up can cause toxicity.

Also allows neurones to reset and refire

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15
Q

Give an example of a neurotransmitter that can become toxic if it builds up.

A

Glutamate

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16
Q

What ion is chiefly buffered by astrocytes in the brain?

A

K+

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17
Q

What can cause excess K+ in the brain ECF?

A

Neuronal activity increase causes release of K+ into ecf

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18
Q

How many pathways do astrocytes use to mop up excess K+?

A

3

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19
Q

By what 3 mechanisms do astrocytes mop up K+?

A
  • Na+K+ATPase
  • Na+K+2Cl- cotransporters
  • K+ and Cl- move into glial cells via channels together due to very negative MP of glial cells
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20
Q

What do oligodendrocytes myelinate?

A

Neurone axons

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21
Q

How many axons does one oligodendrocyte myelinate?

A

Multiple

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22
Q

When are microglia activated?

A

When they recognise foreign material

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23
Q

How do microglia remove debris/foreign material?

A

By phagocytosis

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24
Q

What is the main function of the BBB?

A

Limit diffusion of substances from blood to brain to maintain the correct environment for neurones

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25
Q

Describe the structure of the BBB.

A

Capillaries in the brain have tight junctions between the endothelial cells of the vessels, the BM surrounding the capillary, and the end of the feet of the astrocyte processes. Microglia also surround these junctions.

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26
Q

What are some of the important substances that the BBB regulates (from the very long list)?

A

Glucose
Na+
K+
Amino acids

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27
Q

What is special about the immune system of the CNS?

A

It does not undergo rapid rejection of allografts, unlike the rest of the body as too much inflammation will be harmful as rigid skull will not tolerate volume expansion.

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28
Q

How do microglia act to trigger an immune response in the CNS if necessary?

A

Act as antigen presenting cells so T cells can enter the CNS

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29
Q

What kinds of signals can occur at the synapse?

A

Fast excitatory
Fast inhibitory
Modulatory

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30
Q

How does neurotransmitter release occur?

A
  • Terminal depolarises
  • Opens VG Ca2+ channels -> Ca2+ influx
  • Vesicles of neurotransmitter respond to increase in Ca2+
  • Vesicles fuse with end plate and release transmitter
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31
Q

What does the post-synaptic response to a neurotransmitter depend on?

A

Nature of the transmitter

Nature of the receptor

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32
Q

What 3 broad categories can neurotransmitters be divided into?

A

Amino acids
Biogenic amines
Peptides

33
Q

What amino acids can commonly act as CNS neurotransmitters?

A

Glutamate
GABA
Glycine

34
Q

What are some of the biogenic amines that act as CNS neurotransmitters?

A 
ACh
NA
Dopamine
Serotonin
Histamine
35
Q

What are some of the peptides that act as CNS neurotransmitters?

A 
Dynorphin
Encephalins
Substance P
Somatostatin
Cholecystokinin
Neuropeptide Y
36
Q

Which amino acid is the most common neurotransmitter?

A

Glutamate

37
Q

Is glutamate an excitatory or inhibitory neurotransmitter?

A

Excitatory

38
Q

Which amino acid neurotransmitters are inhibitory?

A

GABA

Glycine

39
Q

What % of all CNS synapses are glutamatergic?

A

70%, evenly distributed throughout CNS

40
Q

What are the 3 types of ionotropic glutamate receptors?

A

AMPA. Kainate, and NMDA receptors

41
Q

What is EPSP?

A

Excitatory post-synaptic potential i.e. depolarisation causes more APs to be generated

42
Q

What receptor do glutamatergic synapse have?

A

AMPA and NMDA

43
Q

What do these 2 types of receptor do within the glutamatergic synapse?

A

AMPA mediate initial fast depolarisation, and NMDA are Ca2+ permeable so mediate long term potentiation of APs.

44
Q

Which neurotransmitter receptors have a very important role in learning and memory?

A

Glutamate receptors

45
Q

How are glutamate receptors involved in learning and memory?

A

NMDA receptors activated can upregulate AMPA receptors. If stimulation is strong, high, and regular, there is long term potentiation.

46
Q

With glutamate receptors, what can cause excitotoxicity?

A

Too much Ca2+ or too much glutamate

47
Q

What is the main inhibitory a.a. in the CNS?

A

GABA

48
Q

What kind of ion channels are GABA and glyceine receptors?

A

Cl-

49
Q

What does a Cl- influx cause?

A

IPSP - inhibitory post synaptic potential

50
Q

How can we utilise GABA in a clinical setting?

A

With GABA agonists for anxiolytic effect and sedative action

51
Q

Name the GABA agonists we use.

A

Barbiturates and Benzodiazepines

52
Q

Where is glyceine present most?

A

Brainstem and spinal cord (released by inhibitory neurones e.g. in knee jerk to inhibit knee flexor contracting)

53
Q

Where are biogenic amines used?

A

In specific pathways in the CNS

54
Q

Where does ACh act?

A

NM junction, ganglion synapse in ANS, postganglionic in PSNS, and centrally also.

55
Q

What receptors does ACh act on?

A

Nicotinic and Muscarinic receptors

56
Q

Is ACh ususally excitatory or inhibitory?

A

Excitatory

57
Q

Where in the brain do the main cholinergic pathways originate from?

A

Basal forebrain and brainstem

58
Q

Where do the cholinergic pathways spread to?

A

Many parts of the cortex and hippocampus

59
Q

Where are there local cholinergic neurones?

A

In a few places e.g. the corpus striatum. These are interneurones.

60
Q

What are the cholinergic pathways involved in?

A

Arousal, learning, memory, and motor control.

61
Q

What is degeneration of cholinergic pathways associated with?

A

Alzheimers disease

62
Q

What can we use to alleviate the symptoms of Alzheimers disease?

A

Cholinesterase inhibitors

63
Q

What is the nigrostriatal pathway involved in?

A

Motor control

64
Q

Which pathways are involed in mood, arousal, and reward?

A

Mesocortical and mesolimbic

65
Q

What are the main conditions associated with dopamine dysfunction?

A

Parkinson’s disease and Schizophrenia

66
Q

Tell me about Parkinson’s disease.

A

Associated with loss of dopaminergic neurones in the substantia nigra, which means corpus striatum is less stimulated.

67
Q

What can we treat the symptoms of Parkinson’s with?

A

Levodopa which is converted to dopamine

68
Q

What converts Levodopa to dopamine?

A

DOPA decarboxylase

69
Q

Tell me about Schizophrenia.

A

May be due to too much dopamine, therefore treated partially with D2 antagonists.

70
Q

Which drugs can cause schizophrenic-like behaviour, and how does it work?

A

Amphetamines - cause dopamine and NA release

71
Q

What is the problem with giving levodopa?

A

Not all the dopamine gets to the CNS as much of it is converted in the periphery. Carbidopa should be given alongside levodopa to inhibit AADC converting levodopa to dopamine in the periphery

72
Q

What is AADC?

A

Aromatic amino acid decarboxylase

73
Q

Where does most of the NA in the brain come from?

A

It is produced by a group of neurones in the locus ceruleus

74
Q

When is the locus ceruleus inactive?

A

In sleep

75
Q

When does NA release increase?

A

Behavioural arousal and wakefulness

76
Q

What do amphetamines do in the brain?

A

Increase NA and dopamine release

77
Q

Where is NA released throughout the brain?

A

Diffuse release throughout the cortex, hypothalamus, amygdulla, and cerebellum.

78
Q

Where are serotonergic neurones distributed?

A

Diffusely throughout the cortex, hypothalamus, amygdulla, and cerebellum.

79
Q

What functions do serotonergic neurones have?

A

Role in sleep/wakefullness, and mood.

Sem 5 - The Nervous System (4 decks)

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