SNS Flashcards
What is the SNS response?
Mydriasis
Decreased salivation
Increased HR, SV
Vasoconstriction
Bronchodilation and decreased lung secretions
Reduced GI motility and secretions
Inhibition of bladder contraction
Glycogenolysis
Which are the Adrenergic Receptors
Alpha: a1 and a1
Beta: B1, B2, B3
In which 2 places do the SNS neurons behave differently
Adrenal medulla: where NE–>E by Phenylethanolamine N methyl transferase
Sweat glands: ACh is neurotransmitter
Which enzymes metabolise NE and E
COMT: catechol-o-methyl transferase
MAO: monoamine oxidases
Steps in NE neurotransmission
- Hydroxylation of tyrosine
- Dopamine enters vesicle and is converted to NE
- Influx of Ca causes release of NE via exocytosis
- Binding of NE to postsynaptic receptor activates the receptor
- Released NE is rapidly taken into neuron.
- NE is metabolised by MAO and COMT
What inhibits re-uptake of NE?
Cocaine and Imipramine
NE acts on which receptors
a1, a2, B2 and its direct acting
E acts on which receptors
a1,a2,B1,B2 and its direct acting
Ephedrine acts on which receptors
its acts on all adrenergic receptors both direct and indirect acting by weakly stimulating the release of NE and E from nerve endings in SNS
Amphetamine causes…
strong NE and E release indirectly
Cocaine causes
Directly inhibits NE and Dopamine re-uptake
a1 receptors are located…
on post synaptic membrane
a1 receptors are specific to
vascular smooth muscle
Eye
a2 receptors are located…
Presynaptic nerve endings
a2 receptors are specific to
GIT, pancreas and platelets
They inhibit release of NE
Which alpha receptors is stimulatory and which is inhibitory
a1: stimulatory
a2: inhibitory
B1 receptor is specific to
Cardiac tissue
B2 receptor is specific to
Respiratory, uterus, Liver, VSM
B3 receptors are specific to
Detrusor muscle of bladder
are involved in Lipolysis
Adrenergic receptors have affinity for which neurotransmitter
a1: NE > E
a2: E > NE
B1: NE=E
B2: E»NE
Response of a1 stimulation
Vasoconstriction
Incr. Peripheral Resistance
Incr. BP
Mydriasis
Incr closure of bladder sphincter
Response of a2 stimulation
Inhibits NE release
Incr. Acetylcholine release
Inhibition of insulin release
Response of B1 stimulation
Incr HR
Incr. Lipolysis
Incr. Myocardial contractility
Incr. Renin
Response of B2 stimulation
Vasodilation
Decr. Peripheral Resistance
Bronchodilation
Incr. Glycogenolysis
Incr. Glucagon release
Relaxes uterine smooth muscle
Indications of Adrenaline
Drug of choice in Anaphylaxis
Combined with LA=incr. DOA
During cardiac arrest
CI of Adrenaline
Tachyarrythmias
Pheochromocytoma
Administration of Adrenaline
IM,SC
IV in severe cases
A/E of adrenaline
peripheral vasoconstriction: prolonged use can cause necrosis/gangrene
Angina
hypertension
Tachycardia
Ventricular arrythmias
MOA of Adrenaline
Potent stimulant of a and B adrenoreceptors
Potent vasoconstrictor and cardiac stimulant
+ve inotropic & chronotropic actions on heart ( β1)
vasoconstriction in vascular beds (α)
Also activates β2 receptors in skeletal muscles vasodilation
Respiratory : bronchodilation (β2)
Hyperglycemia : increased glycogenolysis in liver (β2) decreased
release of insulin (α2)
Phenylephrine is a
A1 agonist
MOA of Phenylephrine
Vasoconstrictor= Incr BP
Causes mydriasis
Vasoconstriction of nasal mucosa= decreased nasal secretions
Indications of Phenylephrine
Nasal decongestant
Hypotension
Mydriatic in Eye exams
Administration of Phenylephrine
Oral, topical
IV
Eye drops
A/E of Phenylephrine
Nausea
Hypertension
Oxymetazoline and Xylometazoline are
Alpha adrenergic agonists
Administration of Oxymetazoline and Xylometazoline
Topical nasal sprays
MOA of Oxymetazoline and Xylometazoline
Vasoconstrict nasal mucosa and conjunctiva
Indications of Oxymetazoline and Xylometazoline
Nasal decongestant
How long can Oxymetazoline and Xylometazoline be used
Max. 5 days
>5 days: Rebound congestions
Clonidine is
a2 adrenoreceptor in CNS
Indications of Clonidine
Migraine prophylaxis
a-metyldopa is
a2 agonist in brain
MOA of a-methyldopa
decr. sympathetic outflow= decr HR, decr. CO and TPR= Decr. BP