The Parasympathetic Nervous System and Muscarinic Receptors Flashcards
mAChR vs. nAChR.. ligand gated or GPCR?
mAChR : GPCR
nAChR: ligand gated
Where are nAChRs found?
In NMJ, Ganglia, Adrenal gland
Main antagonizer of mAChR?
Atropine
What is the difference between stimulation effects of ACh on mAChR and nAChR? wHY ?
In low doses, ACh will stimulate mAChR. Higher doses are needed to stimulate nAChR because they are located within the ganglia.
Describe the 5 points of Dale’s experiment
- When given ACh low dose, it acts on mAChR for vasodilation.
- Atropine administration blocks this action
- Larger dose of ACh will stimulate ganglia and cause sympathetic effects with atropine administration.
- ACh also affects adrenal medulla to activate sympathetic nevous system.
- Hexamethonium blocks all ganglia effects nAChR and also in PNS.
What type of antagonist is atropine?
Competitive antagonist
How does vasodilation occur in genitalia?
Through externally applied agonists
Are there mAChR in the adrenal glands and what is its effect?
Yes there are long lasting duration mAChR effects to cause depolarisation.
How does parasympathetic system affect the eye?
It will constrict pupils due to the circular muscle. It also contracts ciliary muscle to release the lens and make it into a fat shape for near vision accomodation
What are the 2 main ways of stimulating parasympathetic nerves?
Stimulating the muscarinic receptors and inhibiting cholinesterase
Why is ACh not appropriate for clinical use?
It is too short acting because it is quickly hydrolyzed by cholinesterase
What drugs are used for open angle glaucoma?
Dipivefrine
What drugs are used to relieve dry mouth?
Pilocarpine
What muscarinic drug is used to stimulate GI motility?
Oral Bethanechol
What muscarinic drug is used for urinary retention?
Bethanecol although catheterisation is more common
