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The Patient - pharmacology (Y2-1) > Cholinergic receptors > Flashcards

Cholinergic receptors Flashcards

1
Q

Acetylcholine has a permanent positive charge. True or false?

A

True

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2
Q

What is acetylcholine broken down into and what facilitates this?

A

Acetate and choline

Acetylcholinesterase

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3
Q

What happens to choline when ACh is broken down?

A

Gets recycled - taken back to presynaptic nerve terminal

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4
Q

Describe the series of events in cholinergic transmission

A

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

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5
Q

Where does synthesis of ACh take place?

A

presynaptic nerve terminal

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6
Q

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

A

True

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7
Q

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

A

True

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8
Q

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

A

False - muscarinic and nicotinic are found in CNS

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9
Q

Where are muscarinic receptors found?

A

CNS
Parasympathetic
Sympathetic (less)

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10
Q

Where are nicotinic receptors found?

A

CNS
NMJ
Autonomic ganglia

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11
Q

Describe the structure of nicotinic receptors

A

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

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12
Q

Name two nicotinic receptor agonists.

A

Nicotine

Suxamethonium

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13
Q

Name three nicotinic receptor antagonists

A

Atracurium
Tubocurarine
alpha bungarotoxin

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14
Q

What is the structural difference of a foetal nicotinic receptor?

A

Instead of epsilon, gamma

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15
Q

Describe the structure of a muscarinic receptor.

A 
Monomeric
M1-5 subtypes 
5 receptor types
Binding site for G protein
1 ACh binding site per subunit 
Response is slower than nicotinic
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16
Q

Name two muscarinic receptor agonists

A

Muscarine

Pilocarpine

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17
Q

Name two muscarinic receptor antagonists

A

Atropine

Hyoscine

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18
Q

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

A

Muscarinic

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19
Q

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

A

True

20
Q

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

A

Muscarinic

21
Q

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

A

Nicotinic receptors

Muscarinic receptors

22
Q

Botox works on release of acetylcholine. True or false?

A

True

23
Q

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

A

True

24
Q

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

A

False - act on AChE (ACh metabolism)

25
Q

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

A

Competitive antagonists - produce flaccid paralysis in patients

26
Q

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

A

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

27
Q

How do polarising blockers work at nAChRs?

A

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

28
Q

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

A

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

29
Q

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

A

False - makes situation worse as they add agonist

30
Q

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

A

Suxamethonium

31
Q

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

A

Atracurium
Rocuronium
Pancuronium

32
Q

Atracurium breaks down spontaneously. True or false?

A

True

33
Q

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

A

True

34
Q

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

A

pilocarpine in glaucoma

bethanechol in bladder disorders

35
Q

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

A

True

36
Q

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

A

False - tachycardia

37
Q

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

A

Prevent bronchial secretions during surgery

38
Q

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

A

False - muscarinic antagonists

39
Q

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

A

True

40
Q

How does the botulinum toxin block the release of ACh?

A

Breaking down snare proteins

41
Q

Irreversible AChE jnhibitors are used therapeutically. True or false?

A

False

42
Q

Sarin is a reversible AChE inhibitor. True or false?

A

False - irreversible

43
Q

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

A

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

44
Q

Describe the molecular mechanism of sarin

A

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

45
Q

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

A

Atropine (muscarinic antagonist)

The Patient - pharmacology (Y2-1) (18 decks)

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