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Semester 5 - CNS > Session 2 - The Environment of the Brain > Flashcards

Session 2 - The Environment of the Brain Flashcards

1
Q

What are the two main consitutients of the CNS?

A

Neruones and Glial cells

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2
Q

What are the two main roles of neurones?

A

Sense changes

Communicate with other neurones

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3
Q

Give the five roles of glial cells

A

Support
Nourish
Insulate neurones
Remove waste

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4
Q

What are the three main types of glial cell?

A

Astrocytes
Oligodendrocytes
Microglia

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5
Q

What are the four main roles of astrocytes?

A

Offer structural support
Help to provide nutrition for neurones
Help to remove neurotransmitters
Help to buffer K+ in brain ECF

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6
Q

Why is it necessary that astrocytes provide nutrition for neurones?

A

Neurones cannot store glycogen, and thus get most of their glucose from blood. This causes issues when they need a LARGER supply of energy

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7
Q

How do astrocytes provide nutrition for neurones?

A

Act as a store of glycogen

Produce lactate, which can be transferred to neurones to supplement their supply of glucose

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8
Q

How do astrocytes help to remove neurotransmitters?

A

Uptake spare neurotransmitters from synaptic cleft, removing them from functional circulation.

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9
Q

Why is it important astrocytes remove neurotransmitters?

A
  • Helps to stop transmitter spilling over to neighbouring cells
  • helps terminate the synaptic response
  • Helps to recycle transmitters or breakdown product back to terminal
  • Also keeps glutamate levels down, as too much is toxic to neurones
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10
Q

HOw is glutmate toxic to neurones?

A

Causes opening of NMDA receptors, leading to calcium entry - excessive glutamate causes excessive opening and excessive activation

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11
Q

How do astrocytes help to buffer K+ in the brain?

A

K+ ions move out of neurones during repolarisation after an action potential, an event which occurs a huge amount in the brain.
Astrocytes take up K+ via action of Na-K-ATPase

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12
Q

What is the role of oligodendrocytes?

A

Responsible for myelination of axons in the CNS

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13
Q

What do microglia do?

A

o The macrophages of the brain - immunocompetent cells, which recognise foreign material. When activated they phagocytose foreign material and debris.
o Can also act as an antigen presenting cell to T cells.

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14
Q

What is the blood brain barrier?

A

A theoretical dividing walls which exists to maintain the environment of the brain in a steady state, protecting it from extracelluar ion changes, peripheral hormones and drugs. Also prevents circulation neurotransmittes from entering CNS.

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15
Q

Outline the structure of th eblood brain barrier

A

o Endothelial cells of cerebral capillaries have very high resistance tight junctions between them
 Even small ions cannot permeate between the cells
 Also basement membrane of capillaries
o Astrocytes have foot processes that adhere to the capillary endothelial cells, so they are entirely enclosed.
 Also secrete factors that help to maintain the endothelial cell tight junctions

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16
Q

What molecules can simply diffuse across the BBB?

A

Water and lipid soluble molecules can diffuse across

Sustances such as glucose, amino acids and potassium are transported across (conc can be controlled)

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17
Q

What is mean by stating that the CNS is immunopriveledged?

A

Less vulnerable to the vagaries of the immune system

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18
Q

Why does the CNS have to be immune privileged?

A

Rigid skull will not tolerate volume expansion, so too mcuh inflammatory response would be harmful

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19
Q

How do immune reactions occur in the CNS?

A

o Microglia act as antigen presenting cells to T cells, which can enter the CNS via post-capillary venules
o CNS inhibits the initiation of the pro-inflammatory T-cell response

20
Q

Give four main structural features of a neurone

A

o Cell body (Soma)
o Dendrites
o Axon
o Terminals

21
Q

Outline the course of neurotransmitter release

A

Opening of Voltage gated Ca2+ channels
The action potential arrives at the presynaptic membrane. This causes the opening of voltage-gated Ca2+ channels and the subsequent influx of calcium ions down their concentration gradient.

Formation of Snare Complex and Neurotransmitter Release
This increase in intracellular calcium concentration leads to Ca2+ binding to Synaptotagmin, leading to the formation of the Snare Complex and Ach release.

22
Q

Give three different classes of CNS neurotransmitters

A

Amino acids
Biogenic amines
Peptides

23
Q

Give an excitatory amino acid based neurotrasmitter

A

Glutamate

24
Q

Give an inhibitory amino acid neurotransmitter

A

GABA (brain) and glycine (Brainstem and Spinal Cord)

25
Q

Give three biogenic amines NTs

A

 Acetylcholine, Noradrenaline, Dopamine, Serotonin (5-HT), Histamine

26
Q

Give three pepitde NTs

A

 Dynorphin, enkephalins, Substance P, somatostatin, Cholecystokinin, Neuropeptide Y

27
Q

Give three glutamate receptors

A

o AMPA Receptor – Ion channel is Na+ and K+ permeable
o NMDA Receptor – Ion channel is Ca2+ permeable
o Kainate receptor

28
Q

What makes up 70% of CNS synapses?

A

o Over 70% of CNS synapses
o Have both AMPA and NMDA receptors
o NMDA receptors need glutamate to bind and the cell to be depolarised to allow Ca2+ entry (and subsequent neurotransmitter release)

29
Q

What is synaptic plasciticity?

A

Glutamate receptors are thought to have an important role in learning and memory
o Activation of NMDA receptors and mGluRs can lead to up regulation of AMPA
o Strong, high frequency stimulation can cause Long Term Potentiation (LTP)
 This is thought to be the basis of long time synapse strengthening and learning

30
Q

What is excitotoxicity?

A

o Ca2+ entry through NMDA receptors is important in Excitotoxicity.
o Too much Glutamate  Excitotoxicity
o Astrocytes take up glutamate from the synaptic cleft to prevent this (see above)

31
Q

What causes inhibition of GABA and glycine receptors?

A

have integral Cl- ion channels. The opening of these channels causes hyperpolarisation, decreasing action potential firing (inhibitory post-synaptic potential IPSP).
o GABAA is the main inhibitory neurotransmitter in the brain, and is bound by barbiturates, benzodiazepines. Both of these enhance channel response to GABA.
o Glycine is present in high concentrations in the spinal cord and brainstem

32
Q

Name four biogenic amines

A

o Acetylcholine, Noradrenaline, Dopamine, Serotonin (5-HT)

33
Q

What do biogenic amines do?

A

o Mostly act as neuromodulators

o Confined to specific pathways

34
Q

Give three places in which acetylcholine is a neurotransmitter

A

o Neurotransmitter at neuromuscular junction, ganglion synapse in autonomic nervous system, postganglionic in parasympathetic nervous system

35
Q

What does acetylcholine act on in the CNS?

A

o In CNS acts on both nicotinic and muscarinic receptors in the brain
 Mainly excitatory
 Receptors often on presynaptic terminals to enhance the release of other transmitters
 Main functions are arousal, learning and memory and motor control

36
Q

Where are the chlinergic pathways in the CNS located?

A

o Neurones originate in the basal forebrain and brainstem
o Diffuse projections to many parts of the cortex and hippocampus
o Also local cholinergic interneurons (e.g. corpus striatum)

37
Q

What is the pathology of alzhermiers disease?

A

o Degeneration of cholinergic neurones in the nucleus basalis of Meynert is associated with Alzheimer’s disease
o Cholinesterase inhibitors are used to alleviate symptoms of Alzheimer’s disease

38
Q

Give three pathways in brain involving dopamine

A

o Nigrostriatal Pathway
 Motor control
o Mesocortical and Mesolimbic Pathways
 Mood, arousal, reward

39
Q

What is parkinson’s disease associated with?

A

The loss of dopaminergic neurones in the substantia nigra

40
Q

How can parkinsons be treated?

A

With L-DOPA (converted to dopamine by DOPA decarboxylase)

41
Q

What is a possible aeitology of schizopherenia? Back up with example

A

May be due to release of too much dopamine

- Amphetamines release dopamine and noradrenaline, which produces a schizophrnic like behaviour

42
Q

What do anti-psychotic drugs target?

A

Dopa,mine D2 receptors

43
Q

Where does noradrenaline in the brain come from?

A

Lcus ceruleus

44
Q

When are locus ceruleus active (and not)?

A

 Locus Ceruleus neurones inactive during sleep
 Activity increases during behavioural arousal
- Amphetamines increase release of noradrenaline and dopamine and increase waefulness

45
Q

What is the relationship between mood and state of arousal?

A

Depression may be associated with a deficiency of NA

46
Q

What are the functions of serotnin?

A

o Functions include sleep/wakefulness, mood, vomiting centre in brainstem

47
Q

What do SSRIs do?

A

o Selective Serotonin Reuptake Inhibitors (SSRIs) increase the concentration of serotonin in synapses, treating depression and anxiety

Semester 5 - CNS (25 decks)

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