M&R ANS Flashcards
What are the neurotransmitters in the SNS?
Short pre-ganglionic neurones are cholinergic (Ach)
Long post-ganglionic neurones are noradrenergic (NA)
2 exceptions - perspiration and ejaculation pathways are cholinergic
What are the neurotransmitters in the PNS?
Long pre-ganglionic neurones are cholinergic (Ach)
Short post-ganglionic neurones are also cholinergic (muscarine)
How is acetylcholine synthesised?
Ach is synthesised by choline acetyltransferase from choline and acetyl-CoA in the cytoplasm of cholinergic terminals.
How is acetylcholine broken down?
It is broken down in the synaptic cleft by acetylcholinesterase and there is a choline transporter which captures most of the choline and recycles it. The acetate is broken down
What enzyme is noradrenaline synthesised from?
Tyrosine
Describe the conversion of tyrosine to noradrenaline
Tyrosine -> dopa -> dopamine -> noradrenaline
in chromaffin cells there is an extra step from NA -> adrenaline
What is “uptake 1” and “uptake 2” wrt noradrenaline?
Uptake 1 is a Na+ dependent high affinity reuptake system which rapidly removes NA from the synaptic cleft back into the presynaptic terminal
Uptake 2 is a lower affinity reuptake system which removes any NA remaining
List the classes of drugs acting on the ANS?
- nicotinic cholinoceptor antagonists
- muscarinic cholinoceptor agonists
- muscarinic cholinoceptor antagonists
- cholinesterase inhibitors
Give an example of a nicotinic cholinoceptor antagonist and describe its action
Tubocurarine
Paralyses muscles during anaesthesia
Give an example of a muscarinic cholinoceptor agonist and describe its action
Pilocarpine- Treatment of glaucoma (administered locally)
Give an example of a muscarinic cholinoceptor antagonist and describe its action
Tolterodine - used to treat overactive bladder
Tropicamide
Pupillary dilation and paralysis
Give an example of an acetylcholinesterase inhibitor and describe its action
(act to enhance the actions of released Ach)
Donepezil - treatment of Alzheimer’s
Pyridostigmine - treatment of myasthenia gravis
Give an example of:
- a selective B1 agonist
- a selective B2 agonist
- a B antagonist
Selective B1 agonist = dobutamine. Has +ve inotropic effects
Selective B2 agonist = salbutamol. Bronchodilation
B antagonist = propanolol. -ve intotropic effects, unwanted bronchoconstriction
Give an example of:
- a selective a1 agonist
- a selective a2 agonist
- an a antagonist
- selective a1 antagonist
Selective a1 agonist = adrenaline/ phenylephrine. Local vasoconstrictor vs nasal decongestant
Selective a2 agonist = clonidine. Anti hypertensive - acts on presynaptic receptors to reduce NA release
alpha antagonist = phentolamine. Peripheral vasodilator to treat peripheral vascular disease (not used to treat hypertension as they cause postural hypotension)
Selective a1 antagonist = Prazosin. Used to treat hypertension
