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

Question 1

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

Answer 1

channels

depolarisation

Question 2

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

Answer 2

threshold
Na+
action potential

Question 3

A local potential can be both _________ and _________

Answer 3

excitatory

inhibitory

Question 4

_______ allows saltatory conduction along the axon

Answer 4

myelination

Question 5

What are the three different types of neurotransmitters?

Answer 5

small molecules
neuropeptides
gaseous transmitters

Question 6

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

Answer 6

• glutamate: excitatory

- GABA: inhibitory

Question 7

Most neurons in the brain have which types of neurotransmitters?

Answer 7

both neuropeptide neurotransmitters and small molecule neurotransmitters

Question 8

ACh is a class of which type of neurotransmitter?

Answer 8

small molecule

Question 9

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

Answer 9

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

Question 10

Amino acids are a class of which type of neurotransmitter?

Answer 10

small molceule

Question 11

Give 3 examples of amino acid neurotransmitters

Answer 11

glutamate
GABA
glycine

Question 12

What are three sites of action for amino acid neurotransmitters?

Answer 12

brain, spinal cord, retina

Question 13

Biogenic amines are a class of what type of neurotransmitter?

Answer 13

small molecule

Question 14

What are 3 examples of biogenic amine neurotransmitters?

Answer 14

adrenaline
noradrenaline
dopamine

Question 15

What are three sites of action for amino acid neurotransmitters?

Answer 15

brain, spinal cord, sympathetic endings

Question 16

Purines are a class of what types of neurotransmitter?

Answer 16

small molecule

Question 17

What are two examples of purines as neurotransmitters?

Answer 17

ATP

Adenosine

Question 18

What are two sites of action for purine neurotransmitters?

Answer 18

brain

autonomic ganglia

Question 19

Peptides are a class of what type of neurotransmitter?

Answer 19

neuropeptides

Question 20

What are three sites of action for neuropeptide transmitters?

Answer 20

brain, spinal cord, pituitary gland

Question 21

Gasses are a class of what type of neurotransmitters?

Answer 21

gaseous neurotransmitters

Question 22

Give two examples of gaseous neurotransmitters

Answer 22

Nitric oxide

carbon monoxide

Question 23

What is the most common excitatory neurotransmitter in the brain?

Answer 23

glutamate

Question 24

Do glial cells participate in synaptic transmission?

Answer 24

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

Question 25

How is glutamate synthesised in the pre-synaptic neuron?

Answer 25

glutamine is converted to glutamate via the enzyme glutaminase

Question 26

What are the four stages of glutamatergic synapses?

Answer 26

1. synthesis of glutamate 2. packaging of glutamate 3. exocytosis of glutamate 4. recycling

Question 27

Describe the packaging process of glutamate during glutamatergic synapses

Answer 27

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)

Question 28

Describe the process of exocytosis of glutamate during glutamatergic synapses

Answer 28

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

Question 29

Describe the process of recycling of glutamate during glutamatergic synapses

Answer 29

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

Question 30

Describe the roll of EAATs

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

the first statement is false and the second statement is true

Question 33

Why are drugs of abuse bad?

Answer 33

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

Question 34

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

Answer 34

methamphetamine | increases levels of noradrenaline, dopamine, serotonin

Question 35

Meth stimulates what responses?

Answer 35

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

Question 36

Nicotine mimics the effect of which neurotransmitter?

Answer 36

ACh

Question 37

PCP and ketamine mimic the effects of which neurotransmitter?

Answer 37

glutamate

Question 38

Anti-anxiety drugs mimic the effect of which neurotransmitter?

Answer 38

GABA

Question 39

Meth mimics the effect of which neurotransmitter?

Answer 39

adrenaline

Question 40

Ecstasy mimics the effect of which neurotransmitter?

Answer 40

serotonin

Question 41

Heroin mimics the effect of which neurotransmitter?

Answer 41

opioids

Question 42

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

Answer 42

ionotrophic and g-protein coupled receptors

Question 43

What is the main receptor involved in neurotransmision?

Answer 43

g protein-coupled receptors

Question 44

What are ionotrophic receptors?

Answer 44

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

Question 45

What are G-protein coupled receptors?

Answer 45

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

Question 46

What is the most common type of metabotrophic receptor?

Answer 46

G-protein coupled receptors

Question 47

Describe how metabotrophic receptors work

Answer 47

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

Question 48

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

Answer 48

α, β, gamma

Question 49

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

Answer 49

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)

Question 50

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

Answer 50

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

Question 51

Describe an ionotrophic receptor

Answer 51

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

Question 52

Describe the glutamate receptor

Answer 52

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

Question 53

Give three subtypes of glutamate receptors

Answer 53

NMDA, AMPA and kainate receptors

Question 54

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

Answer 54

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

Question 55

What type of receptor is a glutamate receptor?

Answer 55

an ionotrophic receptor

Question 56

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

Answer 56

Na+, Ca2+

Question 57

Cys-loop receptors are what type of receptor?

Answer 57

ionotrophic receptor

Question 58

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

Answer 58

4

Question 59

How many subunits does a cys-loop receptor have?

Answer 59

5

Question 60

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

Answer 60

yes

Question 61

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

Answer 61

K+ flows out | Na+, Ca2+ and Cl- can flow in

Question 62

How is NO produced in an axon terminal?

Answer 62

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

Question 63

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

Answer 63

it diffuses

Question 64

What is the effect of NO on the post0synaptic cell?

Answer 64

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

Question 65

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

Answer 65

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