36. Drugs and Synaptic Transmission

Question 1

Describe the steps in synaptic transmission? (5pts)

Answer 1

1. Synthesis
2. Storage
3. Release
4. Inactivation
5. Reuptake

Question 2

Describe the steps in synaptic transmission?

Answer 2

1. Precursor is taken up into the cell
2. The precursor is the converted to create the transmitter in the cytoplasm.
3. Transmitters are stored in the cytoplasm
4. The transmitters are broken down into other components by various enzymes within the nerve terminal.
5. Depolarisation due to the entry of sodium ion channels occurs. The influx of sodium ions down the nerve cell causes the excitation to hit the nerve terminal.
6. The further depolarisation of the membrane will cause calcium ions channels to open causing an influx of calcium ion
7. This causes the vesicle to fuse with the cell membrane releasing its contents
8. The transmitter will bind to its receptor
9. Termination of the response occurs- there is reuptake into the nerve terminal or transmitter is broken down rapidly by enzymes within the synaptic cleft.

Question 3

Describe sodium channel blockers?

Answer 3

Block the sodium channels which does not allow sodium influx e.g lignocaine

Question 4

Describe calcium channel blockers?

Answer 4

Block calcium ions. used for migraines e.g conotoxin

Question 5

Describe cholinergic neurones?

Answer 5

• Cholinergic neurones synthesise and store acetyl choline

1. Choline is taken up by a transmitter
2. Choline is converted to acetylcholine via choline acteyl transferase
3. Acetylcholine is then taken up by the vesicle and stored
4. The enzyme esterase breaks down acetylcholine into its constituent component choline.

• Acetylcholine is always being metabolised
• Acetylcholine responses are brief due to acetycholine esterases.

Question 6

What does VMAT do?

Answer 6

VMAT transports the noradrenaline into the vesicle where it is stored with chemicals such as ATP

Question 7

How is noradrenaline made? (9pts)

Answer 7

1. Tryosine is converted to DOPA via tyrosine hydroxylase.
2. DOPA is converted to dopamine via DOPA decarboylase.
3. Dopamine is packaged into synaptic vesicle where dopamine B hydroxylase converts it into noraadrenaline
4. Noraadrenaline is then stored in the vesicle and can be released.
5. Noradrenaline can then be converted in the adrenal cells to adrenaline.
6. Noradrenaline is metabolised into inactive components via monamine oxidase and catechol-o-methyl transferase.
7. Calcium ions are released from calcium ion channels
8. Noradrenaline binds to the adrenergic receptors
9. Noradrenaline is taken up metabolised

Question 8

Summary of synaptic transmission? (3pts)

Answer 8

1. Transmitters are packaged into vesicles e.g dopamine
2. Upon the influx of calcium these vesicles release neurotransmitters across the synaptic cleft.
3. Neurotransmitters bind to receptors on the post synaptic neurone.

Question 9

How are vesicles recycled? (4pts)

Answer 9

1. Entry of calcium ions cause the formation of a snare complex which drags the vesicle to the membrane.
2. The lipid of the vesicle then fuses with the lipid of the cell membrane
3. Neurotransmitter is released
4. Vesicles is recycled

Question 10

Describe how a V-snare is formed? (7pts)

Answer 10

1. Synaptotagmin has a calcium binding domain
2. Calcium ions are raised. They bind to Synaptotagmin which increases the affinity of the protein for membrane phospholipids
3. Synaptotagim interacts with the membrane phospholipids which causes membrane defamation
4. This brings the vesicle closer so the v snares and the t snares can interact. Interaction of synaptobrevin and synaxin occurs.
5. This drags the vesicle fully onto the membrane
6. A snare pin is formed
7. Vesicle fusion of the membrane occurs

Question 11

Describe Botulism? (5pts)

Answer 11

1. Botulinium toxin is produced by the anaerobic bactyerium closterium botolinum
2. The minimum lethal dose in mice is 10-12g
3. Simliar to diperthia and tetanus toxins
4. 2 subunits
5. The toxin is destroyed by heating to 85 degrees.