CHOLINORECEPTORS

Question 1

Acetylcholine has a permanent positive charge. True or false?

Answer 1

True

Question 2

What is acetylcholine broken down into and what facilitates this?

Answer 2

Acetate and choline

Acetylcholinesterase

Question 3

What happens to choline when ACh is broken down?

Answer 3

Gets recycled - taken back to presynaptic nerve terminal

Question 4

Describe the series of events in cholinergic transmission

Answer 4

AP comes down neuron and depolarises the nerve terminal
depolarisation activates voltage sensitive calcium channels
Ca2+ enter the presynaptic nerve terminal and cause vesicles that contain ACh to fuse with the membrane, releasing contents into synapse
ACh interacts with the receptor and has an effect on target organ
ACh broken down by AChE into acetate and choline

Question 5

Where does synthesis of ACh take place?

Answer 5

presynaptic nerve terminal

Question 6

Muscarinic receptors are GPCRs and are slower than nicotinic receptors. True or false?

Answer 6

True

Question 7

Nicotinic receptors are ligand-gated ion channels. True or false?

Answer 7

True

Question 8

Only muscarinic receptors are found in the CNS. True or false?

Answer 8

False - muscarinic and nicotinic are found in CNS

Question 9

Where are muscarinic receptors found?

Answer 9

CNS
Parasympathetic
Sympathetic (less)

Question 10

Where are nicotinic receptors found?

Answer 10

CNS
NMJ
Autonomic ganglia

Question 11

Describe the structure of nicotinic receptors

Answer 11

Have a pentameric structure - 2 a, B, delta and epsilon
18 subunits
at least 2 ACh binding sites (on a)
quick response

Question 12

Name two nicotinic receptor agonists.

Answer 12

Nicotine

Suxamethonium

Question 13

Name three nicotinic receptor antagonists

Answer 13

Atracurium
Tubocurarine
alpha bungarotoxin

Question 14

What is the structural difference of a foetal nicotinic receptor?

Answer 14

Instead of epsilon, gamma

Question 15

Describe the structure of a muscarinic receptor.

Answer 15

Monomeric
M1-5 subtypes 
5 receptor types
Binding site for G protein
1 ACh binding site per subunit 
Response is slower than nicotinic

Question 16

Name two muscarinic receptor agonists

Answer 16

Muscarine

Pilocarpine

Question 17

Name two muscarinic receptor antagonists

Answer 17

Atropine

Hyoscine

Question 18

Which receptors do anti-emetic and anti-asthma drugs work on?

Answer 18

Muscarinic

Question 19

Paralysing agents in surgery work on nicotinic receptors. True or false?

Answer 19

True

Question 20

Drugs used in eye exams and to treat glaucoma work on which receptors?

Answer 20

Muscarinic

Question 21

ACh receptors are divided into two types. What are they?

Answer 21

Nicotinic receptors

Muscarinic receptors

Question 22

Botox works on release of acetylcholine. True or false?

Answer 22

True

Question 23

Drugs that treat myasthenia gravis act on AChE. True or false?

Answer 23

True

Question 24

Drugs that treat Alzheimer’s disease act on ACh release. True or false?

Answer 24

False - act on AChE (ACh metabolism)

Question 25

How do non-depolarising blockers at nAChRs block neuromuscular transmission?

Answer 25

Competitive antagonists - produce flaccid paralysis in patients

Question 26

How can effects of non-depolarising blockers at nAChR be reversed?

Answer 26

Give drug that increases conc of ACh (i.e. inhibitor of AChE)

Question 27

How do polarising blockers work at nAChRs?

Answer 27

They are agonists, not broken down by AChE. Patients experience a muscle twitch before flaccid paralysis

Question 28

Why doesn't a patient that's taking a depolarising blocker experience tetany?

Answer 28

Because depolarisation is sustained as a result of activation of the receptor and this leads to desensitisation to electrical activity.

Question 29

The effects of depolarising blockers can be reversed by AChE inhibitors. True or false?

Answer 29

False - makes situation worse as they add agonist

Question 30

Which is the only depolarising blocker that is currently clinically used?

Answer 30

Suxamethonium

Question 31

What are examples of non-depolarising blockers used in surgery?

Answer 31

Atracurium Rocuronium Pancuronium

Question 32

Atracurium breaks down spontaneously. True or false?

Answer 32

True

Question 33

Pancuronium has a long duration of action and is used in euthanasia. True or false?

Answer 33

True

Question 34

Muscarinic agonists are not widely used. What are the two examples in which they are used?

Answer 34

pilocarpine in glaucoma | bethanechol in bladder disorders

Question 35

Muscarinic antagonists are widely used because muscarinic receptors are widespread throughout parasympathetic and CNS. True or false?

Answer 35

True

Question 36

Muscarinic antagonists block parasympathetic nervous system, leading to bradycardia. True or false?

Answer 36

False - tachycardia

Question 37

Atropine is a muscarinic antagonist. What is its use in surgery?

Answer 37

Prevent bronchial secretions during surgery

Question 38

Tiotropium and ipratropium are muscarinic agonists used as second line bronchodilators in asthma. True or false?

Answer 38

False - muscarinic antagonists

Question 39

Systemic effects of botulinum toxin can lead to death. True or false?

Answer 39

True

Question 40

How does the botulinum toxin block the release of ACh?

Answer 40

Breaking down snare proteins

Question 41

Irreversible AChE jnhibitors are used therapeutically. True or false?

Answer 41

False

Question 42

Sarin is a reversible AChE inhibitor. True or false?

Answer 42

False - irreversible

Question 43

Irreversible AChE inhibitors cause muscle paralysis, although they result in uncontrollable amount of ACh in synapse which should lead to contraction. Why?

Answer 43

Because nAChR can exist in an open state, closed state and a desensitised state. After a few contractions, due to ACh being present, the muscle becomes flaccid. This is because the desensitised state is switched on when the receptor is exposed to ACh for a prolonged period of time - ACh still binds but the channel closes Also, if nAChRs are open continuously, they will be continuously depolarised and so no further APs take place Net effect of these factors result in no muscle contraction

Question 44

Describe the molecular mechanism of sarin

Answer 44

Serine is important in the function of AChE as it accepts the acetate group that is released from Ach breakdown Acetyl-serine residue is broken down to recycle the active site back it its starting form Sarin attaches to serine Sarin-serine bond too strong to be broken down and the enzyme is not recycled = dead

Question 45

Which drug is injected I.M to save the life of someone that has been exposed to sarin?

Answer 45

Atropine (muscarinic antagonist)