Neurochemisty (cells of NS) Flashcards

1
Q

What is the other name for ionotropic receptors?

A

Ligand gated ion channels

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2
Q

What is the structure of ionotropic receptors like?

A
  • Transmembrane ion channel
  • Made up of 3, 4, or 5 subunits (form a channel w a hole)
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3
Q

What makes ionotropic receptors open?

A

Opens in repsonse to bidning of the specific NT on its extracellular side

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4
Q

What do ionotropic receptors allow to pass through?

A

Allows ions e.g. Na+, Ca2+ and Cl- to pass across the membrane

Results in membrane depolarisation or hyperpolarisation

Rapid response

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5
Q

Which of; depolarisation and hyperpolarisation is inhibitory and which is excitatory?

A

Depolarisation = excitatory

Hyperpolarisation = inhibitory

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6
Q

What is the other name for metabotropic receptors?

A

G protein receptors

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7
Q

What are metabotropic receptors made up of?

A

7 transmembrane domains

Receptors is not an ion channel but is indirectly associated w ion channels via a G protein via a series of intracellular events using second messengers = opening of channel

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8
Q

What are the types of G proteins?

A

Gi - inhibitory
Gs = stimulatory
Gq = stimulatory

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9
Q

Which responds faster; ionotropic or metabotropic?

A

Ionotropic

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10
Q

What are the 4 umbrella groupd of NTs?

A
  • Animo acids (non-essential)
  • Amines
  • Purines
  • Neuropeptides
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11
Q

What are the amino acid NTs?

A
  • Glutamate
  • GABA
  • Glycine
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12
Q

What are the Amine NTs?

A

Monoamines:
- ACh
- Serotonin
- Histamine

Catecholamines
- Dopamine
- Noradrenaline
- Adrenaline

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13
Q

What are the purine NTs?

A
  • Adenosine
  • ATP
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14
Q

What are the neuropeptides NTs?

A

Huge class of them

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15
Q

What is the process of the formation of amino acid glycine?

A

Glucose –> Pyruvate –> Serine –> Glycine

Glycine Hydroymethyl Transferase is used between serine & glycine

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16
Q

What is the process of the formation of amino acid GABA?

A

Glucose –> Pyruvate –> Acetyl CoA –> TCA cycle –> alpha-ketoglutarate –> glutamate –> GABA

Glutamate dehydrogenase between ak and glutamate

Glutamic acid decarboxylase between glutamate & GABA

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17
Q

What is the most commone excitatory NT in the brain?

A

Glutamate

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18
Q

What % of neurones use glutamate as a NT?

A

90%

80-90% of synapses are glutamate

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19
Q

What can glutamate not pass?

A

The blood brain barrier (BBB) –> it is synthesised in the presynaptic terminal

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20
Q

What is glutamate uptake & recycling called and what does it involve?

A

Glutamate-glutamine cycle

It involves astrocytes = GLT

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21
Q

What are the types of glutamate receptors?

A

Ionotropic glutamate receptors (IGluR)
- NMDA
- AMPA
- Kainate

Metabotropic glutamate receptors (mGluR)
- Group I
- Group II
- Group III

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22
Q

What is excitotoxictiy?

A

Overactivation of glutamate receptors (NMDA) –> induces neuronal cell death

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23
Q

What are the mechanisms in place to control excitotoxictiy?

A
  • When glutamate binds, causes morphological change, we don’t want too much so there is an additional magnesium block
  • Magnesium in centre doesn’t allow ions to pass through, needs to be removed
  • Glutamate binds to AMPA receptors first, causes depolarisation & removal of magnesium block
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24
Q

What is the most common inhibitory NT?

A

GABA –> 1/3 of neurones use GABA as a NT

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25
Where is GABA synthesised?
In the presynaptic terminal
26
Where does GABA uptake happen?
In the presynaptic terminal & astrocytes --> GAT
27
What are the types of GABA receptors?
GABAA --> ligand-gates ion channel GABAB --> G protein-coupled receptor GABAC -->Ligand-gated ion channel
28
What is GABA a target for?
Benzodiazepines
29
Where is glycine most commonly found?
Most commone inhibitory NT in the spinal cord & brain stem Expressed by interneurones in the spinal cord
30
Where is glycine synthesised?
In the presynaptic terminal
31
Where does glycine uptake happen?
In the presynaptic terminal --> GlyT a glycine specific transporter
32
What is the ionotropic receptor for glycine called?
GlyR --> receptor that binds to the NT glycine Is an inhibitory receptor - dysfuntion linked to autism
33
What is glycine a co-agonist with?
Glutamate NMDA recpetors = work together to regulate the activity of neurones in the brain
34
Where is ACh found?
Widely distributed around the CNS
35
What is ACh used for?
- Arousal - Attention - Memory - Motivation
36
What neurodegenerative disease is linked to ACh?
Alzheimer's --> as ACh is important for learning and memory
37
What is ACh important for as the primary NT of the PNS?
- Vasodilation of vasculature - Contraction of smooth muscle e.g. iris & lens ciliary muscle of eye - Secretion of body fluids e.g. tears, saliva & sweat - Slows HR - Inc GI tone & secretions
38
Which NT is the primary NT at junctions?
ACh - at choliergic synapses
39
What are the stages of producing Acetlycholine?
Glucose --> Pyruvate --> Acetly CoA --> Aceytl (CoA lost) --> choline added = Acetyl choline
40
How is ACh broken down?
By an enzyme acetlycholinesterase (AChE) Broken down into choline & acetate --> choline taken back up to make more ACh
41
What are the 2 types of ACh receptors?
- Nicotinic receptors (nAChR) - Muscarinic receptors (mAChR)
42
What are nicotinic receptors?
Type of ionotropic receptoractivated by ACh & nicotine Found on cell bodies & dendrites of postganglionic neurones - cause wave of deoplarisation in postganglionic neurone if they allow an influx of +ive ions
43
What is the antagonist for nicotinic receptors?
Bungarotoxin: Able to act on these receptors, inhibits action = no contraction of muscles, causes paralysis - this is used in snake venom
44
What is the agonist for muscarinic receptors?
Muscarine
45
What is the antagonist for muscarinic receptors?
Atropine Commonly used for ppl with heart conditions --> specifically w low HR
46
What is a muscarinic receptor?
A type of metabotropic receptor activated by ACh & muscarine Found oneffector organs that are innervated by the PNS Involved in learning, memory, attention & regulation of mood
47
What is the agonist for nicotinic receptors?
Nicotine
48
What inhibits the reuptake of serotonin?
SSRIs e.g. fluoxetine
49
Where are cell bodies of serotonergic neurones found?
In the raphe nucleus of the brain stem Their axons project to nearly every part of the brain (only used about 1% of the time)
50
What are the functions of serotonin?
Mood, sleep ad appetite
51
What is serotonin synthesised from?
The amino acid tryptophan
52
Why shouldn't you eat cheese before bed?
Cheese (specifically cheddar) has high amounts of Tryptophan which forms serotonin & causes funny dreams
53
What are the receptors for serotonin called?
5-HT receptors - they perform differet physiological processes based on where they're found in the body
54
Where are histaminergic neurones found?
Cell bodies of histaminergic neurones found in the tuberomamillary nucleus of the posterior hypothalamus Their axons project to nearly every part of the brain & spinal cord
55
What is a prominet role of histamines?
Promoting wakefulness By binding to H1 histamine receptors on wake promoting neurones, they are taken back up by H3 histamine receptors on the presynaptic neurone
56
Where are histamines synthesised?
Synthesised by neurones from non-essential amino acid histidine
57
What are the effects of histamines mediated by?
GPCRs : H1R - H3R
58
How is histamine formed?
- Formed from the amino acids histadine through a process called decarboxylation --> removes carboxyl group form the histidien molecules - Process is catalysed by an enzyme called histidine decarboxylase - Once formed it is stored in vesicles in the cell until it released in response to a stimulus
59
What are the 4 main dopamine pathways in the brain?
- Mesolimbic pathway - Mesocortical pathway - Nigrostriatal pathway - Tuberoinfundibular pathway
60
What is the mesolibic pathway for?
Major reward pathway
61
What is the mesocortical pathway for?
Executive functions
62
What is the nigrostraital pathway for?
Movement Loss of dopamine neurones in substantial nigra = Parkinson's disease
63
What is the tuberoinfundibular pathway for?
Prolactin secretion from pituitary gland Prolactin plays important role in stimulating production of milk after birth
64
Where does dopamine uptake happen?
In the presynaptic terminal via DAT
65
What are the metabotropic receptors for dopamine?
D1-like receptors & D2-like receptors
66
Dopamine synthesis
Pls refer to notes
67
Where are cell bodies of noradrenic neuones?
In the locus coerulus of the brain stem Thier axons project to nearly every part of the brain and spinal cord
68
What does noradrenaline do?
Alertness, arousal, attention
69
What is the primary NT in the sympathetic NS?
Noradrenaline Used in the fight or flight response
70
Where is noradrenaline synthesised?
In neurones
71
Where doe noradrenaline uptake happen?
Into presynaptic terminal = NET
72
What are the metabotropic receptors for noradrenaline?
Alpha and beta
73
How can noradrenaline receptors be used to treat medical conditions?
Beta blockers --> used for heart conditions Beta agonists e.g. salbutamol --> asthma treatment
74
Where are cell bodies of adrenergic neurones found?
In the medulla of the brain stem Their axons project to the thalamus, hypothalamus & spinal cord
75
What triggers the release of adrenaline?
The sympathetic nervous system triggers its release from adrenal glands Fight or flight response
76
Where is adrenaline synthesised?
In neurons only in the medulla oblongata of the brain stem
77
Where does adrenaline uptake happen?
In the presynaptic terminal
78
What does adrenaline bind to?
Noradrenaline metabotropic receptors --> alpha and beta
79
What is a purine NT?
An excitatory cotransmitter in the autonomic NS Inhibitory BT in the enteric NS
80
What is purine a cotransmitter with?
Various other NTs in the brian e.g. glutamate, dopamine, serotonin
81
Descibe the action of purines
- ATP present in vesicles & when released acts directly on receptors & broken down to adenosine by extracellular ATPase - Adenosine can then act on receptors and is taken back up into the neuron for ATP resynthesis - Adenosine metabotropic receptors = P1 - ATP ionotropic receptors = P2X - ATP metabotropic receptors = P2Y - Sympathetic nervous system triggers its release from adrenal glands
82
What are neuropeptides?
Chemical messengers made up of small chains of amino acids --> 3 to 36 amino acids long Coexist in neurones w one or more NT
83
Where are neuropeptides synthesised?
In cell body of neurones from large presursor proteins Packaged into large dense core vesicles
84
What are neuropeptides released in response to?
In response to repetivite AP firing
85
What are neuropeptides generally like?
- No reuptake in the neurone - Response = slow & prolonged - Tend to act viametabotropic receptors - Over 100 known neuropeptides - Various roles
86
Give an example of a neuropeptide w various roles
Neuropeptide Y - Sympathetic NS = vasoconstrictor - Hypothalamus = food intake