SNS Agonists Flashcards
(71 cards)
1
Q
Neurotransmitter of SNS preganglionic fibres
A
ACh
2
Q
Neurotransmitter of SNS postganglionic fibres Exception?
A
NA. Exception sweat glands - ACh, and adrenal medulla - NA and A
3
Q
Type of adrenoceptor involved in glycolysis
A
B3
4
Q
MOA of A1 adrenoceptor
A
PLC –> IP3 and DAG
5
Q
MOA of A2 adrenoceptor
A
decreases cAMP
6
Q
MOA of B1 adrenoceptor
A
Increases cAMP
7
Q
Which adrenoceptor increases cAMP
A
B1 and B2
8
Q
MOA of B2 adrenoceptor
A
Increases cAMP
9
Q
Which adrenoceptor decreases cAMP
A
A2
10
Q
Which adrenoceptor converts PLC to IP3 and DAG
A
A1
11
Q
What is a directly acting sympathomimetic
A
mimic the actions of adrenaline and noradrenaline by stimulating adrenoceptors
12
Q
What type of adrenoceptor controls aqueous humour production of ciliary body
A
B
13
Q
What type of adrenoceptor dilates trachea and bronchioles
A
B2
14
Q
What type of adrenoceptor controls glycogenolysis and gluconeogenesis
A
A1 and B2
15
Q
What type of adrenoceptor lipolysis
A
A1 and B1
16
Q
What type of adrenoceptor increases renin secretion
A
B1
17
Q
What type of adrenoceptor found in salivary glands
A
A and B
18
Q
What type of adrenoceptor in the skin
A
A1
19
Q
What type of adrenoceptor in the heart
A
B1
20
Q
What type of adrenoceptor in the GIT
A
A and B
21
Q
Why must you be careful prescribing a beta blocker for diabetes
A
As beta receptors cause break down glycogen
22
Q
What type of adrenoceptor is found in skeletal blood vessels
A
B2
23
Q
B2 effect on skeletal blood vessels
A
Dilation
24
Q
What type of adrenoceptor visceral blood vessels
A
A1
25
NA vs A more selective for A receptors?
NA
26
NA vs A more selective for B receptors?
A
27
Which endogenous catecholamine is more selective for A receptors
NA
28
Which endogenous catecholamine is more selective for B receptors
A
29
NA synthesis, excretion and metabolism?
* Tyrosine is converted to DOPA by tyrosine hydroxylase in the nerve endings.
* DOPA is then converted to dopamine and the dopamine is converted to noradrenaline in the vesicles by the action of dopamine B-hydroxylase.
* Upon an AP, there is an influx of Ca2+ and the vesicles migrate to the nerve ending, emerge out and release the NT into the synapse.
* Deactivation is via reuptake into the nerve terminal itself to be reused or into extraneuronal tissue
30
What amino acid is used to make DOPA and ultimately NA
Tyrosine
31
What enzyme is the rate-limiting step for the synthesis of NA
Tyrosine hydroxylase
32
What enzyme converts tyrosine to DOPA
Tyrosine hydroxylase
33
What converts DOPA to dopamine
DOPA decarboxylase
34
What converts dopamine to NA
Dopamine B-hydroxylase
35
What does DOPA decarboxylase do
Covert DOPA to dopamine
36
What can mediate NA synthesis and release
Presynaptic A2 receptors
37
5 SNS agonists?
adrenaline, phenylephrine, clonidine, dobutamine and salbutamol
38
A1 selective drug?
Phenylephrine
39
A2 selective drug?
Clonidine
40
B1 selective drug?
Dobutamine
41
B2 selective drug?
Salbutamol
42
What does Phenylephrine act on?
A1
43
What does Clonidine act on?
A2
44
What does Dobutamine act on?
B1
45
What does Salbutamol act on?
B2
46
What does the selectivity of a directly acting SNS agonist depend on?
concentration, high concentrations lose selectivity
47
Symptoms of hypersensitivity? (6...)
blood vessels move apart so you get a lot of fluid moving into the tissues
This leads to a fall in circulating fluid volume and hence a fall in blood pressure
Also contraction of bronchial smooth muscle and constriction of the muscles around the throat, causing respiratory distress
It can also constrict the smooth muscle in the GI tract causing vomiting and diarrhoea
48
why is A better than NA for anaphylaxis (4)
o Adrenaline acts more on the beta receptors than noradrenaline and this stimulates bronchodilation and relaxation of the throat muscles B2
o Adrenaline will also stimulate the heart so you get tachycardia, this will support the blood pressure B1
o Adrenaline also acts on alpha receptors and causes vasoconstriction A1
o Adrenaline also, via the beta 2 receptors, slows down the release of histamine from the mast cell
49
What to remember when thinking about NA vs A for anaphylaxis
BLS - ABC
50
What pulmonary conditions can A be used for and why can it be used for this (4 and 2)
Asthma, acute bronchospasm, chronic bronchitis, emphysema
It is used for these purposes because it causes B2 mediated bronchodilation and it also suppresses mediator release
51
How does adrenaline work for glaucoma
Adrenaline is good for glaucoma because it stimulates the alpha receptors in the vessels within the ciliary body causing vasoconstriction of these vessels. This means that less blood containing substrates will be delivered to the ciliary body and the production of aqueous humour is reduced. A2 also inhibit the production of aqueous humour
52
How is A used with local anaesthetic
causes A1 constriction of the blood vessels in the local area thus preventing the clearance of the anaesthetic from the area.
53
How is A used with spinal anaesthetics
If you give a little bit of adrenaline at the same time you can constrict the blood vessels so you can maintain the blood pressure
54
How is A used for cariogenic shock
Stimulates B1 receptor so heart starts pumping again
55
Unwanted effects of A (5+3)
| Why does this happen
```
Because A is non selective
• Secretions - reduced and thick
• CNS - minimal
• CVS Effects:
o Tachycardia, palpitations, arrhythmias
o Cold extremities, hypertension
o OVERDOSE - cerebral haemorrhage, pulmonary embolism
• GIT - minimal
• Skeletal muscle - tremor
```
56
which adrenoceptor is found in the presynaptic membrane?
A2
57
What effect does clonidine have on NA release and how
Clonidine will stimulate the pre-synaptic alpha 2 receptors - this has a negative effect on the synthesis and release of noradrenaline
58
How does clonidine lower blood pressure and TPR (2)
* Clonidine will stimulate the pre-synaptic alpha 2 receptors - this has a negative effect on the synthesis and release of noradrenaline
* If you release less NA then you are going to get less stimulation at the effector organ - this means you get less vasoconstriction hence a fall in TPR and blood pressure
o Within the brainstem it works on the baroreceptors reduces the sympathetic drive coming out of the brain
This reduces the TPR and it also reduces the amount of noradrenaline released at the nerve terminal thus reducing TPR further
Also less NA means less renin secretion and so less ATII so less vasoconstriction
59
What is clonidine used for
Hypertension, glaucoma and migraines
60
what is isoprenaline selective for
Beta receptors
61
what drug is beta selective
Isoprenaline
62
Metabolism of phenylephrine?
More resistant to COMT degradation but not MAO
63
Metabolism of isoprenaline? Half life?
Less susceptible to uptake 1 and MAO breakdown. This makes half-life much longer (2 hours)
64
Clinical uses of isoprenaline
Cariogenic shock, acute heart failure, myocardial infarction
65
What must you be cautious of when using isoprenaline?
it stimulates beta 2 receptors in the vasculature causing dilation which can mean blood pools so you get less venous return. This causes baroreceptors to fire and increase heart rate, but isoprenaline has already increased heart rate via b1 agonism, and this can lead to arrhythmias
66
Use of dobutamine
Cardiogenic shock
67
Plus side to dobutamines short half life?
You can stop administering it as soon as normal cardiac output is restored
68
Why is dobutamine preferred to isoprenaline for cariogenic shock
B1 selectivity
69
Metabolism of salbutamol?
Relatively resistant to COMT and MAO
70
Clinical uses of salbutamol? Why? Which adrenoceptor
B2 selective agonist. Used to treat asthma, b2 mediated bronchial smooth muscle dilation. inhibits bronchoconstricting substance degranulation from mast cells via b2.
Can also be used to relax uterine smooth muscle via B2 to prevent abortion.
71
Side effects of salbutamol?
Reflex tachycardia, tremor, blood sugar dysregulation
