Parasympathetic Nervous System Flashcards
why are nicotinic receptors in muscle and autonomic ganglia different?
because they are made up of different subunits
what are muscle nicotinic receptors blocked by?
tubocurarine
what are ganglion nicotinic receptors blocked by?
hexamethonium (and tubocurarine at high doses)
what are all muscarinic receptors blocked by?
atropine
what do muscarinic receptors control in the eye?
control pupil size and accommodation
pupils constrict (miosis)
ciliary muscle contracts, releasing the lens, which releases it into a “fat” shape, good for near vision (accommodation)
what do muscarinic receptors do in the heart?
reduce heart rate
the parasympathetic system (via vagus nerves) innervates mostly the sinoatrial and atrioventricular nodes and thr atria
muscarinic receptor activation slows heart rate by slowing the spontaneous depolarisation of pacemaker cells
what does pupillary constriction lead to?
reduction of intraocular pressure
which drug can be used for reduction of intraocular pressure in glaucoma?
pilocarpine
which drug can be used to relive dry mouth?
pilocarpine
what effect does muscarinic antagonism have on the eye?
pupillary dilatation (mydriasis) because of block of parasympathetic influence on sphincter pupillae mydriasis interferes with drainage via canal of schlemm and thus raises intraocular pressure
cycloplegia (ciliary muscle paralysis) hence paralysis of accommodation
what are the side effects of atropine at high doses?
restlessness, disorientation, hallucinations
confusion
what is the action of hyoscine (scopolamine)?
is a powerful CNS depressant, causing sleep and amnesia. it also has an anti-emetic effect - sea sickness pill
how can atropine like drugs (benzatropine) help in Parkinsons?
supress the tremor of Parkinsons disease, by blocking cholinergic transmission in the basal ganglia
which common drugs can block muscarinic receptors?
antipsychotics, antidepressants, antihistamines
