From poisons to surgery Part 1

Question 1

from what plants do curare alkaloids come from

Answer 1

condo-dendron tomentosum plants

Question 2

What are curare alkaloids?

Answer 2

a group of highly effective arrow poisons

Question 3

What type of poison are curare alkaloids and how does this affect the body

Answer 3

• muscle relaxant poison
• stops your from being able to move

Question 4

what type of antagonist is D-tubocurarine at nicotinic acetylcholine receptors

Answer 4

It is a reversible competitive antagonist
at nicotinic acetylcholine receptors

Question 5

what is D-Tubocurarine sometimes called

Answer 5

• a non-depolarising neuromuscular blocking agent

Question 6

what happens at the synapse between the neuron and muscle (Somatic nervous system)

Answer 6

• acetylcholine is released and combines with nicotinic acetylcholine receptors

Question 7

how many nanometres is the gap between the presynaptic membrane and acetylcholine receptors?

Answer 7

50nm

Question 8

Explain how neuromuscular synapses work in reference to acetylcholine (ACh) molecules

Answer 8

1. ACh molecules are stored in vesicles in presynaptic terminal
2. incoming action potential causes vesicles to fuse with the cell membrane and release ACh
3. ACh molecules bind to nicotinic receptors on post-synaptic cells

Question 9

what type of ion channels are nicotinic acetylcholine receptors?

Answer 9

ligand gated ion channels

Question 10

Describe the steps for skeletal muscle contraction starting with ACh

Answer 10

1. ACh binds to nicotinic acetylcholine receptors
2. influx of sodium ions
3. depolarisation (an increase in membrane potential)
4. this ultimately leads to muscular contraction

Question 11

describe the 4 steps for the termination of action potential response

Answer 11

1. ACh is broken down by acetylcholinesterase (AChE)
2. ACh becomes just acetyl and Choline, terminating the action of acetylcholine
3. Choline is transported ack into the presynaptic terminal
4. Choline is combined with Acetyl-CoA to form acetylcholine again inside the presynaptic neurone.

Question 12

what 2 things does activation of nicotinic receptors lead to?

Answer 12

• Depolarisation of membrane
• activation/opening of voltage-gated sodium channels

Question 13

Outline the 2 step effect of an antagonist (eg: curare) on membrane potential

Answer 13

1. motor nerve stimulated with ACh released, leading to short depolarisation
2. amplitude pf depolarisation would be reduced by curare

Question 14

what does washing out curare eventually lead to for motor nerve stimulation

Answer 14

• eventually leads to recovery of nerve, so depolarisation can occur again

Question 15

• what is the clincal issue with tubocurarine that means it is superseded by other drugs

Answer 15

• slow to recover and has adverse effects

Question 16

what are the 3 reversible competitive antagonists at nACh receptors?

Answer 16

• Atracurium
• pancuronium
• rocuronium

Question 17

what are 2 features of Atracurium

Answer 17

• short-acting (15-30 mins)
• can be given by infusion for longer term effects

Question 18

what are 2 features of Pancuronium

Answer 18

• longer duration (60-120 mins)
• used for longer term action in intensive care

Question 19

what are 2 features of rocuronium

Answer 19

• faster onset (within 2 mins)
• intermediate duration (30-40 mins)

Question 20

What are 3 clincal uses for atracurium, Pancuronium and Rocuronium

Answer 20

• Muscle relaxant
• due to muscle relaxation, ligher anaethesias can be used
• relaxs vocal cords for tracheal intubation or mechanical ventilation

Question 21

what 2 things are important to realise when using muscle relaxants clinically

Answer 21

• respiration must be assisted/controlled until patient recovers
• patient must receive sufficient anaesthetic or sedation to prevent awareness