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Neuroscience and Mental health > 8. Neurotransmitters > Flashcards

8. Neurotransmitters Flashcards

1
Q

5 key features for effective synaptic transmission

A 
Rapid timescale 
Diversity
Adaptability
Plasticity
Learning and memory
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2
Q

Where is the signal received?

A

At dendritic spines

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3
Q

Where does integration of the signals coming down the dendrites occur?

A

Soma

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4
Q

What is the width of a synaptic cleft? What does this represent and what is the consequence of this?

A

20-100 nm
Represents high resistance to transfer of electrical charge
This is why chemical transmission is required

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5
Q

Why are there many mitochondria in the presynaptic nerve terminal?

A

Neurotransmission is a highly energy dependent process

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6
Q

3 steps of synaptic transmission

A
  1. Biosynthesis, packaging and release of neurotransmitter
  2. Receptor action
  3. Inactivation
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7
Q

What are the 3 classes of neurotransmitter? Give an example of each

A

Amino acids e.g. gamma amino butyric acid (GABA)
Amines e.g. noradrenaline
Neuropeptides e.g. Opioid peptides

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8
Q

Diversity of neurotransmitters

A

May mediate rapid (μs - ms) or slower effects (ms)

Vary in abundance from mM to nM CNS tissue concentrations

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9
Q

Which type of neurotransmitter is most prevalent in the CNS? Give 2 examples

A

Amino acid neurotransmitters
Glutamate: key excitatory transmitter
GABA: Key inhibitory transmitter

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10
Q

Describe the activation of a CNS synapse

A

AP depolarises cell, causes Na+ influx
AP triggers Ca2+ entry required for neurotransmitter release
Neurotransmitter vesicle fuses with membrane
Neurotransmitter is released by exocytosis
Neurotransmitter acts on receptor
Neurotransmitter removed to stop action on synapse by transporter

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11
Q

What are the 4 essential components to synaptic transmission?

A 
Restricted to specialised structures: the SYNAPSE 
Fast ~ within ms (200 μs) 
Calcium: transmitter release requires an increase in intracellular Ca2+ (200 μM) 
Synaptic vesicles (SVs) provide the source of neurotransmitter
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12
Q

How can rapid release occur?

A

Synaptic vesicles filled with neurotransmitter and docked in the synaptic zone, strong association with proteins, form a complex “primed”: ready for action
Ca2+ entry activates a Ca2+ sensor in the protein-vesicle complex, changing conformation: promotes fusion with membrane and opening of a pore to release transmitter
Interaction between synaptic vesicle and synaptic membrane proteins allows rapid response

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13
Q

List 3 neurotoxins that target vesicular proteins

A

Tetanus toxin: Paralysis (zinc dependent endopeptidases inhibit transmitter release)
Botulinum toxin: Flaccid paralysis
Alpha Latrotoxin: prevents recycling of the vesicles and hence releases the transmitter to total depletion

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14
Q

What does transmitter release require?

A

Transmitter containing vesicles to be docked on the presynaptic membrane
Protein complex formation between vesicle, membrane and cytoplasmic proteins to enable both vesicle docking and a rapid response to Ca2+ entry leading to membrane fusion and exocytosis.
ATP and vesicle recycling

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15
Q

What are the 2 types of receptor and what is the most important difference in their properties?

A

Ion Channel Receptor: FAST (u-msec)

G-protein linked receptor: SLOW (s-minutes)

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16
Q

What may the effectors of G-protein linked receptors be?

A

Enzymes or channels

17
Q

What is the effect of glutamate on the post-synaptic membrane?

A

Glutamate is excitatory: causes influx of Na+

18
Q

What is the effect of GABA on the post-synaptic membrane?

A

GABA is inhibitory: causes influx of Cl-

19
Q

What are the 2 main types of glutamate receptor? State some properties.

A

AMPA: rapid acting: causes depolarisation, only operates on cell that’s already been depolarised, majority of fast excitatory synapses, rapid onset, offset and desensitisation
NMDA: slower acting (despite still being excitatory and fast), serve as coincidence detectors which underlie learning mechanism, requires 2 conditions for activation = depolarisation of membrane + glutamate binding, NMDA lets in Na+ and Ca2+

20
Q

Where is glutamate formed?

A

Glutamate is a product of intermediary metabolism

e.g. glycolysis and TCA cycle

21
Q

Which transporter actively takes glutamate up into glial cells on the pre-synaptic membrane?

A

Excitatory Amino Acid Transporter (EAAT)

22
Q

How is glutamate inactivated in the glial cells?

A

Glutamate is converted to glutamine by GLUTAMINE SYNTHETASE

23
Q

What causes epileptic seizures?

A

Increased release of glutamate, causing hyperexcitability

24
Q

What is epilepsy characterised by?

A

Recurrent seizures due to abnormal neuronal excitability

25
Q

Describe the structure of GABA and state how it is produced.

A

GABA has the same structure as Glutamate but with the carboxyl group removed.
GABA is produced from glutamate by the action of GLUTAMIC ACID DECARBOXYLASE (GAD).

26
Q

What transporter takes GABA up into the glial cells?

A

GABA Transporter (GAT)

27
Q

Describe the inactivation of GABA in the glial cells.

A

GABA is converted to SUCCINATE SEMIALDEHYDE by GABA Transaminase (GABA-T)

28
Q

Describe how the GABA receptor can be manipulated to create treatments for epilepsy.

A

Binding sites on the pentameric GABA receptor for benzodiazepines, steroids, barbiturates etc.
These sites can be manipulated to facilitate the activity of GABA and produce anti-epileptic drugs.

29
Q

GABA receptor important because of inhibitory action it has. Drugs have been developed to enhance GABA transmission as anti-anxiety and anti-epilepsy treatment. List 4 types of drug that facilitate GABA transmission

A

Antiepileptic
Anxiolytic
Sedative
Muscle relaxant

30
Q

What is the consequence of GABA hyper polarising the membrane?

A

Threshold is increased for cell firing

31
Q

Give 2 examples of neurotransmitters in CNS and 1 example in NMJ that act on ion channel receptors

A

CNS: Glutamate, GABA
NMJ: ACh at nicotinic receptors

32
Q

Give 3 examples of neurotransmitters in CNS and PNS that act on G-protein coupled receptors

A

ACh at muscarinic receptors
Dopamine (DA)
Noradrenaline (NA)

33
Q

What do GLUR, GABAR and GlyR receptors do?

A

GLUR: causes excitation as opens Na+ channel and depolarises membrane.
GABAR: on dendritic spines. Receptor is inhibitory, allows Cl- entry causes hyperpolarisation
GlyR: on Soma. Causes increase in Cl- conductance

Neuroscience and Mental health (11 decks)

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