Synapses and neurotransmitters 2 Flashcards

1
Q

What is the criteria for a neurotransmitter?

A

Present in synaptic vesicles
Released in response to stimulation
Act on the post synaptic neuron

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2
Q

What does blocking the neurotransmitter prevent?

A

Synaptic transmission

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3
Q

What are 3 classes of neurotransmitter?

A

Amino acids
Amines
Peptides

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4
Q

What do peptide releasing hormones also sometimes release?

A

A small molecule transmitter called a ‘co-transmitter’

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5
Q

What can amino acids and amine neurotransmitters bind to?

A

Ligand gated ion channels
G protein coupled receptors

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6
Q

What can peptide neurotransmitters bind to?

A

G protein coupled receptors

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7
Q

Where are amino acids and amine neurotransmitters stored?

A

In synaptic vesicles

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8
Q

Where are peptide neurotransmitters stored?

A

Secretory granules

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9
Q

What is a ionotropic receptor?

A

Ligand gated ion channels that directly depolarise or hyperpolarise the postsynaptic cell

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10
Q

What is a metabotropic receptor?

A

G protein coupled receptor which can produce second messengers and cause biochemical changes throughout the cell

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11
Q

Is glutamate an excitatory or inhibitory neurotransmitter?

A

An excitatory

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12
Q

Where is Glutamate found?

A

In CNS, in all neurons

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13
Q

How is glutamate action terminated?

A

Selective reuptake into presynaptic terminals and glia

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14
Q

What are the 3 ionotropic receptors glutamate can act on?

A

AMPA
NMDA
Kainate

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15
Q

What does glutamate binding to AMPA receptors trigger?

A

Na+ and K+ currents, resulting in an EPSP

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16
Q

What do NMDA receptors often co exist with?

A

AMPA receptors

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17
Q

When do NMDA receptors open?

A

When the cell is already depolarised
- due to voltage dependent Mg2+ block

18
Q

What ion is NMDA permeable to ?

A

Ca2+ ions

19
Q

What is a coincidence factor?

A

A neuron that is activated right after a previous activation

20
Q

What is the mechanism for a metabotropic glutamate receptors?

A

Activates G proteins which triggers a downstream signalling cascade

21
Q

What is the consequence of mGluRs?

A

Allow glutamate to be inhibitory once G proteins are activated

22
Q

Glutamic acid + Glutamic acid decarboxylase -> ?

A

Glutamate

23
Q

How is GABA action terminated?

A

Selective uptake into presynaptic terminals and glia

24
Q

What is the most common inhibitory transmitter in CNS?

A

GABA

25
Q

What will GABA produce if the membrane potential is above chloride’s Nernst potential?

A

IPSPs via GABA A receptors

26
Q

What would occur in the event of too little GABA inhibition?

A

Seizures

27
Q

What would occur in the even of too much GABA inhibition?

A

Come or loss of consiousness

28
Q

What are the downstream effects of GABA + GABA receptor?

A

Chloride channels open
Membrane potential gets closer to chloride Nernst potential

29
Q

What is an allosteric drug?

A

A drug which has no effect without binding

30
Q

Name 4 allosteric drugs which modulate GABA A receptors

A

Ethanol
Benzodiazepine
Barbiturates
Neurosteroids

31
Q

Describe the function of GABA B receptor.

A

Open K+ channels
Close Ca2+ channels
Trigger other second messengers (cAMP)

32
Q

Function of glycine?

A

Inhibits neurons via glycine gated chloride channels
Binds NDMA to glutamate receptors

33
Q

Describe dendritic integration

A

Neurons receive inhibitory or excitatory signals on dendrites ->
EPSP is produced and propagates along the dendrite and arrive at the soma ->
Axon initial segment initiates the ap ->
The ap is actively regenerated and sent down the axon

34
Q

When wont GABA A produce a IPSP?

A

If Vm is near the chloride Nernst potential

35
Q

If GABA A receptors cant produce an IPSP, how do they act?

A

Via shunting inhibition

36
Q

What is shunting inhibition?

A

Opening chloride conductance which decreases the membrane and the current is able to leak out

37
Q

Describe presynaptic inhibition

A

Action potential arrives at the presynaptic terminal ->
At the same time, an ap arrives at presynaptic terminal of GABAergic neuron. GABA released onto neuron activates GABA B receptors which inactivated calcium channels ->
Less calcium binding means less neurotransmitter released ->
Causes a reduced effect on the postsynaptic neuron

38
Q

What is the purpose of inhibition?

A

Organisation of neurons

39
Q

If AMPA receptors are permeable to both Na+ and K+, why does activating them cause depolarisation?

A

Na+ flow into the cell whereas only a few K+ leave the neuron, causing an overall depolarisation.

40
Q

What would happen if GABA open GABA A receptors and the membrane potential is below chloride’s Nernst potential?

A

The membrane would depolarisation
- Net outflow of chloride ions