L8: drugs affecting neuromuscular junction

Question 1

How many processes can drug affect to modify chemical synaptic transmission?

Answer 1

5

Question 2

What processes pre-synaptically can affect the synaptic transmission?

Answer 2

• Synthesis
• Storage
• Release
  of the neurotransmitter

Question 3

What processes post-synaptically can affect the synaptic transmission?

Answer 3

• Receptors
• Removal mechanism
  for the neurotransmitter

Question 4

First stage of events in pre-synaptic ‘cholinergic’ transmission

Answer 4

Acetylcholine is synthesised from choline + acetylcoenzyme A by action of enzyme Choline Acetyl Transferase (CAT)

Question 5

Second stage of events in pre-synaptic ‘cholinergic’ transmission

Answer 5

Choline is taken into nerve terminal by a transporter protein

Question 6

Synthesis

What does Hemicholinium block the uptake of?

Answer 6

Uptake of choline into nerve terminal

Question 7

Storage

What does **AH5184 **block the uptake of?

Answer 7

Uptake of ACh into synaptic vesicle

Question 8

Release

What does **Conotoxins **block?

Answer 8

Blocks voltage-gated Ca2+ channels

Question 9

Release

What does Botulinum block?

Answer 9

Blocks process of exocytosis

Question 10

Third stage of events in pre-synaptic ‘cholinergic’ transmission

Answer 10

ACh is stored by synaptic vesicles that are released by exocytosis

Question 11

First stage of post-synaptic events in cholinergic transmission

Answer 11

After being released, ACh diffuses across synaptic gap & activates receptors on post-synaptic membrane

Question 12

Two types of ACh receptors

Answer 12

1) Nicotinic Receptors
2) Muscarinic Receptors

Question 13

What are nicotinic receptors activated by?

Answer 13

Nicotine from tobacco plant

Question 14

What are muscarinic receptors activated by?

Answer 14

Muscarine from poisonous Fly Agaric mushroom

Question 15

What is ACh broken down by during the removal from the synapse?

Answer 15

Enzyme acetylcholinesterase (AChE), found in the synaptic gap

Question 16

Name the enzyme involved in the synthesis of acetylcholine (ACh)

Answer 16

Choline Acetyl Transferase (CAT)

Question 17

Name the enzyme involved in the destruction of ACh

Answer 17

Acetylcholinesterase (AChE)

Question 18

What happens to the choline produced following the destruction of ACh?

Answer 18

Being recycled, taken back into nerve terminal for synthesis of new ACh

Question 19

What are the FIVE key processes that drugs can interfere with at any chemical synapse

Answer 19

1) Synthesis
2) Removal
3) Release
4) Receptors
5) Removal

Question 20

What is the motor unit?

Answer 20

Motor nerve + muscle fibre it controls

Question 21

Why is the muscle membrane thrown into folds?

Answer 21

Increasing SA

Question 22

What is the specialised area of the muscle membrane called?

Answer 22

Muscle “end plate”

Question 23

What is the neurotransmitter released in skeletal neuromuscular junction?

Answer 23

Acetylcholine

Question 24

What is the receptor present on the muscle in skeletal neuromuscular junction?

Answer 24

Nicotinic acetylcholine receptors

Question 25

Define agonist

Answer 25

Substance that mimics the actions of a neurotransmitter to produce a response when it binds to a specific receptor

Question 26

How many protein subunits form the nicotinic ACh receptor?

Answer 26

5

Question 27

Structure of nicotinic ACh receptor

Answer 27

5 protein subunit surrounding a non-selective cation channel which is permeable to Na+ & K+

Question 28

When does the non-selective cation channel on the nicotinic ACh receptor open?

Answer 28

2 molecules of ACh bind to the protein complex, 1 to each alpha-subunit

Question 29

What does opening of the channel of nicotinic ACh receptor leads?

Answer 29

Leads to depolarisation of the end-plate region of muscle membrane

Question 30

Where is botulinum toxin found?

Answer 30

Uncooked foods

Question 32

What is blepharospasm?

Answer 32

Involuntary tight closure of eyelids

Question 33

What does botulin target in blepharospasm?

Answer 33

Inappropriate contraction of the skeletal muscle

Question 34

Does botulinum toxin given locally or systemically?

Answer 34

Locally

Question 35

Role of botulin in presynaptic transmission

Answer 35

Inhibits the release of ACh

Question 36

Define antagonist

Answer 36

Substance that stops the action/effect of another substance

Question 37

What are at the nicotinic ACh receptor to post- synaptically inhibit neuromuscular transmission?

Answer 37

Reversible competitive antagonists

Question 38

Are reversible competitive antagonists GENERAL ANAESTHETICS?

Answer 38

NOOO, used alongside to stop contraction

Question 39

How can effects of muscle relaxants during surgery be reversed?

Answer 39

Acetylcholinesterase inhibitor, neostigmine