Neurotransmitters 1

Question 1

3 steps of neurotransmission at a synapse?

Answer 1

Transmitter released from presynaptic neurone
Neurotransmitter binds to receptor on postsynaptic neurone
Signal is integrated and conducted by 2nd cell

Question 2

3 components of the synapse?

Answer 2

Presynaptic nerve ending/terminal
Synaptic gap (cleft)
Postsynaptic region/neurone

Question 3

Synapse symmetrical or asymmetric and why?

Answer 3

Asymmetric - Post synaptic membrane is very dense and is known as the post-synaptic density

Question 4

Is the nerve terminal specialised or general and what are its main features?

Answer 4

Very specialised
High numbers of synaptic vesicles
High numbers of mitochondria

Question 5

Why are mitochondria needed in presynaptic terminal?

Answer 5

Synthesis and release of neurotransmitter

- Exocytosis requires oxidative metabolism (ATP)

Question 6

What are synaptic vesicles filled with?

Answer 6

Contain approx. 5000 molecules of neurotransmitter

Question 7

3 stages of synaptic transmission?

Answer 7

Biosynthesis, packaging and release of the neurotransmitter
Receptor action
Transmitter Inactivation

Question 8

The 3 types of molecule for neurotransmitters?

Answer 8

Amino acids
Amines
Neuropeptides

Question 9

2 examples of amino acid neurotransmitter?

Answer 9

Glutamate

GABA (gamma aminobutyric acid)

Question 10

2 examples of amine neurotransmitter?

Answer 10

Noradrenaline

Dopamine

Question 11

Example of neuropeptide neurotransmitter?

Answer 11

Opioid peptides

Question 12

What is the role of the action potential in initiating synapse activation?

Answer 12

Depolarisation phase of action potential leads to opening of voltage-gated Ca2+ channels
Ca2+ influx into presynaptic terminal stimulates movement of synaptic vesicles towards the presynaptic membrane

Question 13

After the influx of Ca2+, what is the process of depolarising the postsynaptic membrane?

Answer 13

Ca2+ influx causes synaptic vesicles to fuse with presynaptic membrane
Neurotransmitter molecules released into synaptic cleft
Neurotransmitters binds to receptors on postsynaptic membrane causing influx of Na+ into post-synaptic region
This depolarises the post-synaptic terminal

Question 14

What happens after depolarisation of the postsynaptic membrane?

Answer 14

Neurotransmitter is broken down and taken back up into pre-synaptic terminal by active transport

Question 15

How fast is synaptic transmission and what ion does it rely on?

Answer 15

Very fast - 200microseconds

Ca2+ dependent - needs influx

Question 16

6 steps in activation and release of the neurotransmitter?

Answer 16

Membrane depolarisation
Ca2+ channels open
Ca2+ influx
Vesicle fusion
Vesicle exocytosis
Transmitter release

Question 17

How are neurotransmitter molecules taken back up into presynaptic terminal?

Answer 17

Vesicle recycling

Effectively endocytosis, using ATP they’re repackaged in synaptic vesicles

Question 18

4 examples of neurotoxins that target vesicle proteins?

Answer 18

Zn2+ dependent endopeptides
Alpha latrotoxin
Tetanus toxin
Botulinum toxin

Question 19

How do Zn2+ dependent endopeptides and alpha latrotoxin cause problems?

Answer 19

Endopeptides degrade the vesicle proteins and therefore inhibit neurotransmitter release
Alpha latrotoxin stimulates neurotransmitter release leading to depletion of source

Question 20

Role of vesicle proteins in neurotransmitter release?

Answer 20

Vesicles are primed and docked in the synaptic zone, as close as possible to pre-synaptic membrane ready for exocytosis
Ca2+ entry triggers rapid protein complex formation between vesicle, presynaptic membrane and cytoplasmic proteins leading to a fast exocytosis response to Ca2+ influx