pharmacology of the parasympathetic nervous system Flashcards
part of circulation and breathing module
what are three medicines/drugs which target the parasympathetic nervous system
- buscopan
- atropine
- urivoid
what is the mechanism of buscopan and its uses
- ibs relief and for stomach cramps/pain
- targets visceral smooth muscle
- muscarinic antagonist (prevents agonist binding to muscarinic receptors found on smooth muscle preventing smooth muscle contractions- part of parasympathetic NS)
what is the mechanism of atropine
- used to treat bradycardia and increase heart rate
- targets muscarinic receptors specifically M2 receptors in the heart
- muscarinic antagonists- prevent agonist binding and prevent a decrease I heart rate and parasympathetic stimulation
- can be used to also reduce saliva and urination during surgery
what is the mechanism of urivoid (bethanecol)
- muscarinic agonist (causes contraction of muscles e.g. in go tract which would help with urination)
- triggers urination and production of saliva which is needed after surgery
what are the two medicines used for asthma
- salbutamol
- ipratropium bromide
what is the mechanism behind salbutamol
- used as a bronchodilator for asthma- causes relaxation of smooth muscle in airways
- beta adrenergic agonist- stimulates the receptor and triggers muscle relaxation by mimicking adrenaline
what is the mechanism behind ipratropium
- muscarinic antagonist
- inhibition of parasympathetic nervous system by preventing contraction of muscle
- useful for asthma, copd
- can be used with salbutamol
what are the different types of muscarinic receptors
- 5 types from m1 to m5
- m135 couples to Gq
- M24 couples to Gi/o
- most important ones we need to know include M3 which is involved in contraction (lungs, go) and M2 found in heart for decreasing output
what are the effects of parasympathetic stimulation
- rest and digest
- includes increasing contraction e.g. in gi tract, more urination, saliva production, constriction of bronchioles resulting in slower breathing
- decreasing heart rate
what neurotransmitters does parasympathetic neuroses release and on what receptors
- pre ganglionic neurone release Ash on nicotinic choligernic receptors (ligand gated ion channel receptors)
- post ganglionic neurone release Ach on muscarinic receptors found on tissue
where does the pre ganglionic neurone tend to exit from the CNS for parasympathetic stimiulation
- bottom of spinal cord
- top of spinal cord (vagus nerve)
where is the parasympathetic ganglia located
close to or within target organ
how is acetylcholine made and broken down between two neurones
- made of acetyl coenzyme A and choline Catalysed by chAT (choline acetyltransferase)
- broken down by acetylcholinesterase in synaptic cleft and transported back to pre synaptic neurone (axon terminal)
what does NANC stand for and its meaning
-non adrenergic non cholinergic transmission
- alongside acetylcholine other molecules can be released from neurone to muscarinic receptor such as nitric oxide - for smooth muscle relaxation
- VIP can also be released for slower response
- both VIP and NO are usually co released with Ash not on their own
what are examples of muscarinic agonist (drugs)
- bethanechol (found in urivoid)
- muscarine=
- pilopcarpine (pilopine) = for mouth dryness
- methacholine= bronchoconstrictiong of lungs-asthma test
