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231 > Lecture 6: Synaptic Transmission || (Neurotransmitters and Receptors) > Flashcards

Lecture 6: Synaptic Transmission || (Neurotransmitters and Receptors) Flashcards

1
Q

The excitability of neurons conferred by the expressions of ______ that allow ________ when activated

A

channels

depolarisation

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2
Q

If local potentials reach ________ for voltage-gated ______ channels, an _________ _________ is initiated

A

threshold
Na+
action potential

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3
Q

A local potential can be both _________ and _________

A

excitatory

inhibitory

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4
Q

_______ allows saltatory conduction along the axon

A

myelination

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5
Q

What are the three different types of neurotransmitters?

A

small molecules
neuropeptides
gaseous transmitters

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6
Q

Give two examples of small molecule neurotransmitters involved in classical neurotransmitters, and state whether they are excitatory or inhibitory

A
  • glutamate: excitatory

- GABA: inhibitory

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7
Q

Most neurons in the brain have which types of neurotransmitters?

A

both neuropeptide neurotransmitters and small molecule neurotransmitters

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8
Q

ACh is a class of which type of neurotransmitter?

A

small molecule

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9
Q

What are some sites of action for ACh? (5)

A

brain, NMJ, autonomic endings, basal ganglia, GI tract

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10
Q

Amino acids are a class of which type of neurotransmitter?

A

small molceule

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11
Q

Give 3 examples of amino acid neurotransmitters

A

glutamate
GABA
glycine

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12
Q

What are three sites of action for amino acid neurotransmitters?

A

brain, spinal cord, retina

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13
Q

Biogenic amines are a class of what type of neurotransmitter?

A

small molecule

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14
Q

What are 3 examples of biogenic amine neurotransmitters?

A

adrenaline
noradrenaline
dopamine

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15
Q

What are three sites of action for amino acid neurotransmitters?

A

brain, spinal cord, sympathetic endings

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16
Q

Purines are a class of what types of neurotransmitter?

A

small molecule

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17
Q

What are two examples of purines as neurotransmitters?

A

ATP

Adenosine

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18
Q

What are two sites of action for purine neurotransmitters?

A

brain

autonomic ganglia

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19
Q

Peptides are a class of what type of neurotransmitter?

A

neuropeptides

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20
Q

What are three sites of action for neuropeptide transmitters?

A

brain, spinal cord, pituitary gland

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21
Q

Gasses are a class of what type of neurotransmitters?

A

gaseous neurotransmitters

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22
Q

Give two examples of gaseous neurotransmitters

A

Nitric oxide

carbon monoxide

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23
Q

What is the most common excitatory neurotransmitter in the brain?

A

glutamate

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24
Q

Do glial cells participate in synaptic transmission?

A

yes, astrocytes are active participants in synaptic transmission and are active in communication between neurons and the brain

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25
Q

How is glutamate synthesised in the pre-synaptic neuron?

A

glutamine is converted to glutamate via the enzyme glutaminase

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26
Q

What are the four stages of glutamatergic synapses?

A
  1. synthesis of glutamate
  2. packaging of glutamate
  3. exocytosis of glutamate
  4. recycling
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27
Q

Describe the packaging process of glutamate during glutamatergic synapses

A

the packaging of glutamate is energy dependent so it requires the activity of ATPase to power the vesicular glutamate transporter (vGLUT) glutamate to pump glutamate up its conc gradient into the vesicles (thus requiring the energy from ATPase to break down ATP)

28
Q

Describe the process of exocytosis of glutamate during glutamatergic synapses

A

The action potential arrives, voltage gated Ca2+ open, Ca2+ influx which triggers vesicle fusion. This releases glutamate into the synaptic cleft. There is diffusion across the synaptic cleft to activate glutamate receptors on the post-synaptic cell

29
Q

Describe the process of recycling of glutamate during glutamatergic synapses

A

The glial cells expresses excitatory amino acid transporters (EAAT) 1 and 2 which mops up any of the extra glutamate that gets released. This is converted back to glutamine via glutamine synthase and then pumped out of the astrocyte and back into the axon terminal by EAAT5

30
Q

Describe the roll of EAATs

A

They pump glutamine of glutamate against their concentration gradient into astrocytes or neurons. This requires energy

31
Q

Pumping glutamine or glutamate up their concentration gradient into astrocytes or neurons requires energy. Where does this energy come from?

A

it comes from the co-transport with things going down their concentration gradient (usually Na+)

32
Q

Gaseous neurotransmitters act on receptors in the synaptic cleft BECAUSE gaseous neurotransmitters freely diffuse across the cell membrane

A

the first statement is false and the second statement is true

33
Q

Why are drugs of abuse bad?

A

because they interact with systems in the brain and cause physical changes in the brain

34
Q

Give an example of a drug of abuse and what it increases the levels of

A

methamphetamine

increases levels of noradrenaline, dopamine, serotonin

35
Q

Meth stimulates what responses?

A

it stimulates fight, flight or fright response and stimulates the reward centres

36
Q

Nicotine mimics the effect of which neurotransmitter?

A

ACh

37
Q

PCP and ketamine mimic the effects of which neurotransmitter?

A

glutamate

38
Q

Anti-anxiety drugs mimic the effect of which neurotransmitter?

A

GABA

39
Q

Meth mimics the effect of which neurotransmitter?

A

adrenaline

40
Q

Ecstasy mimics the effect of which neurotransmitter?

A

serotonin

41
Q

Heroin mimics the effect of which neurotransmitter?

A

opioids

42
Q

What are the two receptors in the post synaptic cells involved in classical neurotransmission?

A

ionotrophic and g-protein coupled receptors

43
Q

What is the main receptor involved in neurotransmision?

A

g protein-coupled receptors

44
Q

What are ionotrophic receptors?

A

they are the ones which are themselves an ion channel

the complex on which the transmitter binds is the same complex that has the channel within its structure

45
Q

What are G-protein coupled receptors?

A

a type of metabotrophic receptors (things that change molecular signalling)
the G-protein is the start of a second messenger system within the target cell

46
Q

What is the most common type of metabotrophic receptor?

A

G-protein coupled receptors

47
Q

Describe how metabotrophic receptors work

A

the neurotransmitter binds to the cell surface receptor
the G protein complex inside of the cell which is attached to the receptor, once activated by the transmitter, the α subunit dissociates which does something to another protein
this could be activated of an ion channel

48
Q

What three subunits make up the G protein complex inside the cell of a G protein coupled receptor?

A

α, β, gamma

49
Q

Describe the process of activation of an ion channel by a G-protein coupled receptor

A

the α subunit dissociates which does something to another protein and in this case, it is the opening of an ion channel. Ions cross the membrane which changes the membrane potential for the cell (depolarisation or hyperpolarisation - excitatory or inhibitory)

50
Q

What is the advantage of the second messenger system opening an ion channel?

A

you can have the same messenger which can have the opposite effect on the ion channel

51
Q

Describe an ionotrophic receptor

A

the transmitter binds to a receptor where the ion channel is an integral part of the receptor
when the neurotransmitter binds, the ion channel opens which causes ions to flow either in or out of the cell, depending on the electrochemical gradient

52
Q

Describe the glutamate receptor

A

is has three transmembrane domains and four subunits
depending on the combination of subunits, you can make different types of glutamate receptors as they confer different properties to the receptors

53
Q

Give three subtypes of glutamate receptors

A

NMDA, AMPA and kainate receptors

54
Q

What do the three subtypes of glutamate receptors have in common?

A

they all have the same ion channel so they are all excitatory

55
Q

What type of receptor is a glutamate receptor?

A

an ionotrophic receptor

56
Q

What are the types of ions what flow through glutamate receptors?

A

Na+, Ca2+

57
Q

Cys-loop receptors are what type of receptor?

A

ionotrophic receptor

58
Q

How many transmembrane domains are there in a cys-loop receptor?

A

4

59
Q

How many subunits does a cys-loop receptor have?

A

5

60
Q

Can you have different subclasses of cys-loop receptors by changing up the subunits involved?

A

yes

61
Q

What ions flow in and out of a cys-loop receptor?

A

K+ flows out

Na+, Ca2+ and Cl- can flow in

62
Q

How is NO produced in an axon terminal?

A

arginine is converted to citruline by nitric oxide synthase and NO is a byproduct

63
Q

How does NO get from the presynaptic cell to the post-synaptic cell?

A

it diffuses

64
Q

What is the effect of NO on the post0synaptic cell?

A

NO acts on soluble guanylyl cyclase which changes the activity of this enzyme to use energy to convert GTP to cGMP. This is a second messenger system

65
Q

Why can NO go anywhere and have an effect in lots of places?

A

because it is lipophilic which means that it can diffuse across any cell’s membrane

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