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Neurology > S1: Central Neurotransmitters > Flashcards

S1: Central Neurotransmitters Flashcards

1
Q

What are autoreceptors?

A

They are pre-synaptic receptors which are involved with controlling release of NT
They are inhibitory

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2
Q

Explain synaptic transmission

A
  • AP travels down axon and arrives at synaptic bouton
  • When it reaches synapse, VGCCs open Ca2+ ions enter the presynaptic terminal
  • The Ca2+ ions cause the synaptic vesicles to fuse with synaptic membrane
  • NT are released into synapse
  • NTs activate postsynaptic receptors or ion channels
  • Some NTs diffuse out of the synapse, some are taken up by reuptake sites, some are metabolised
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3
Q

What do vesicles contain NT have in their membranes?

A
    • Pump and Exchangers are found in the vesicle membrane that pump neurotransmitters from the cytosol where they are synthesised into the vesicle
  • Calcium sensitive proteins on membrane of vesicle waiting for AP to arrive
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4
Q

What is clathrin?

A

Clathrin is a protein that reforms the vesicles and recycles the important proteins in the vesicle membrane by endocytosis
- It itself then dissociates from the vesicle and is reused

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5
Q

What are the 2 main types of synaptic receptors?

A
  1. Ionotropic
    - Ligand gated ion channels
    - Fast synaptic transmission
  2. Metabotropic
    - GPCR : G protein coupled receptors (mostly)
    - Slow signal modulation
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6
Q

How is synaptic transmission terminated?

A

Neurotransmitter is removed.
This can be by:

  • Diffusion (all NT)
  • Enzymatic Breakdown
  • Specific re-uptake sites
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7
Q

How are post synaptic potentials determined?

A

By adding up EPSPs and IPSPs

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8
Q

List some different types of NT

A
  • Excitatory amino acids e.g. glutamate
  • Inhibitory amino acids e.g. GABA and glycine
  • Monoaminese.g. dopamine, NA, 5-HT
  • Neuropeptides e.g. Substace P, CCK
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9
Q

What is the molecular weight of small and large CNS neurotransmitters?

A

Small (MW < 500)

Large (MW > 500)

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10
Q

Where are small NT synthesised?

A

Small molecular weight NTs are synthesised and stored in nerve terminals

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11
Q

Where are peptide NT synthesised (large)?

A

Peptide NTs are synthesised in neuronal cell bodies and transported down the axon to the nerve terminals.

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12
Q

Give examples of small CNS transmitters

A
  • Ach
  • Monoamines (NA, DA, 5-HT)
  • Histamine
  • AAs (Glutamic acid, aspartic acid, GABA, glycine)
  • Nucleotides and nucleosides (adenosine, ATP)
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13
Q

Give examples of small CNS transmitters

A
  • Hormones

- Opioid peptides

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14
Q

Give an example of an excitatory amino acid NT

A

Glutamate

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15
Q

How is glutamate synthesised?

A

Glutamine—->Glutamate

Phosphate activated glutaminase

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16
Q

Where is glutamate synthesised?

A

In nerve terminals

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17
Q

How is glutamate transported into vesicles?

A

VGLUT (vesicular glutamate transporters)

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18
Q

What receptors does glutamate act on?

A

Ionotropic receptors that are mainly found post synaptically

Metabotropic receptors (mGlu 1 - 8)

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19
Q

What are the 3 groups of mGlu receptors and where are they found?

How are they grouped?

A

Group 1: mglu 1,5 are found post-synaptically
Group 2: mglu 2,3 are found pre-synaptically
Group 3: mglu 4,6,7,8 are found pre-synaptically

Receptor types are grouped based on receptor structure and physiological activity

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20
Q

How is the synaptic transmission of glutamate terminated?

A

This is via EAAT

Excitatory amino acid transporter

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21
Q

What disorders is glutamate probably involved in?

A

Glutamate is probably involved in schizophrenia (NMDA receptor hypofunction) , epilepsy, after stroke (through neurotoxicity, causing apoptosis) and maybe some types of depression.

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22
Q

Give 2 examples of an inhibitory amino acid NT

A

GABA and Glycine

23
Q

How is GABA synthesised?

A

It is synthesised from glutamate!

Glutamate ----> GABA
   Glutamate decarboxylase (GAD) and vitamin B6 (co-factor)

It is synthesised in nerve terminals

24
Q

How is glycine synthesised?

A

Serine ——-> Glycine
Serine Hydroxymethyltransferase

Threonine ———>Glycine
Theronine Aldolase

It is synthesised in nerve terminals

25
Q

How are GABA and Glycine transported into vesicles?

A

Both are transported into vesicles by using vesicular inhibitory amino acid transporters (VIAAT)

26
Q

How is synaptic transmission of GABA terminated?

A

Using the enzyme GABA Transaminase

Using the reuptake transporter GAT - GABA transporter

27
Q

How is synaptic transmission of glycine terminated?

A

Using the enzyme glycine decarboxylase

Using the reuptake transporter GlyT - Glycine transporter

28
Q

How do GAT and GlyT terminate transmission?

A

They reuptake the two inhibitory neurotransmitters back into the presynaptic terminal to be packaged into vesicles by VIAAT

29
Q

What receptors does GABA act on?

A

Ionotropic receptors for GABA include GABA A (e.g. Cl-)

Metabotrophic receptors for GABA include GABA B

30
Q

What receptors does glycine act on?

A

Ionotropic receptors for glycine include Glycine (e.g. Cl-)

31
Q

What disorders is GABA involved in?

A

GABA excites GABA-A receptors which is an ion channel, probably involved in anxiety and epilepsy

32
Q

Why are disorders in animals in glycine associated with?

A

Startle goats have an glycine receptor deficiency so GABA A receptors are upregulated to compensate. When startles, there flight and flight system kicks in so rapidly it paralyses them.

33
Q

What are the three types of monoamine neurotransmitters?

A

Noradrenaline
Serotonin
Dopamine

34
Q

How is serotonin synthesised?

A

L-tryptophan ——*–>5-hydroxy-L-tryptophan —–**—> Serotonin (5-HT)

  • = Tryptophan hydroxylase
  • *= L-aromatic acid decarboxylase

It is synthesised in the nerve terminals

35
Q

How is noradrenaline, serotonin and dopamine transported into vesicles?

A

By VMAT (Vesicular monoamine transporters)

36
Q

What receptors does 5-HT bind to?

A

Ionotropic: 5-HT 3 (Na+/K+/Ca2+)
Metabotropic: 5-HT 1 - 5-HT 7

37
Q

What disorders is serotonin involved in?

A

These are involved in depression, anxiety, pain and feeding.

38
Q

How is synaptic transmission of 5-HT terminated?

A

Enzymes: Monoamine Oxidase (MAO)

Reuptake transporter: SERT - serotonin reuptake transporter

39
Q

How is dopamine synthesised?

A

Tyrosine –*–> DOPA –**—> Dopamine

  • = Tyrosine hydroxylase
  • *= DOPA decarboxylase

It is synthesised in the nerve terminals

40
Q

What receptors does dopamine act on?

A

Metabotropic : D1 - D5 (all GPCR)

41
Q

How is synaptic transmission of dopamine terminated?

A

Enzyme:
Monoamine Oxidase (MAO)
Catechol-O-methyl transferase (COMT)

Reuptake transporters: Dopamine transporter (DAT)

42
Q

What disorders is dopamine associated with?

A

It is involved in Parkinson’s disease, drug abuse, schizophrenia, ADHD and maybe depression.
In parkinsons disease there is a lack of dopamine, so DOPA is the treatment (dopamine cannot cross blood-brain barrier).

43
Q

How is noradrenaline synthesised?

A

Dopamine—->Noradrenaline

The enzyme Dopamine B-hydroxylase is used

It is synthesised in nerve terminals

44
Q

What receptors does noradrenaline act on?

A

Metabotropic - a1 a2 B1 B2

45
Q

How is the synaptic transmission of noradrenaline terminated?

A

Enzyme:
Monoamine Oxidase (MAO)
Catechol-O-methyl transferase (COMT)

Reuptake transporter:
NERT - Norepinephrine reuptake transporter

46
Q

What is NA associated with?

A
  • Fight or Flight

- Depression

47
Q

How is acetyl choline synthesised?

A

Choline + Acetyl Coenzyme A ——> Ach

The enzyme choline acetyl transferase is used

It is synthesised in nerve terminals

48
Q

How is acetyl choline transported into vesicles?

A

By VACht - Vesicular acetyl choline transporters

49
Q

What receptors does Ach act on?

A

Ionotrophic: Nicotinic (nAChR)
Metabotrophic: Muscarinic (mAChR)

50
Q

How is synaptic transmission of Ach terminated?

A

Acetylcholinesterases

51
Q

What does muscarinic antagonist do in the pupil?

A

Muscarinic antagonist contract muscles to dilate the pupil

52
Q

What is co-transmission?

A

Nerves can release more than on NT termed co-transmission.

One of the current theories is that, one type of nerve always releases the same set of NTs

53
Q

Where are neuropeptides synthesised?

A

They synthesised in the soma and transported to nerve terminals

Neurology (29 decks)

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