Cholinomimetics Flashcards
(46 cards)
Muscarinic vs nicotinic effects
Muscarinic effects are those that can be replicated by muscarine, and can be abolished by low doses of the antagonist atropine
Muscarinic actions correspond to those of parasympathetic stimulation
After atropine blockade of muscarinic actions larger doses of acetylcholine can induce effects similar to those caused by nicotine
which neurons are cholinergic?
motor neurons
what receptors are in all autonomic ganglia?
nicotinic
where are muscarinic receptors found?
PNS on effector organ
SNS on effector organ on sweat glands
what are the 3 main muscarinic receptors subtypes
M1
M2
M3
M1 receptor examples
M1: Salivary glands
Stomach
CNS
M2 receptor examples
M2: Heart
decreases heart rate
M3 receptor examples
M3: Salivary glands
bronchial/visceral SM
Sweat glands
Eye
Which receptors are Gq and which ones are Gi
M1, M3 & M5 Gq: stimulates PLC (phospholipase C) to increase production of IP3 and DAG
M2 & M4 Gi reduces the production of cAMP
odds= Gq
Evens =Gi
where are M4 and M5
in the CNS
Muscarinic receptors are generally excitatory, exception?
M2 on the heart are inhibitory
what are all muscarinic receptors
type 2 receptors- G protein coupled
what type of receptors are nicotinic receptors
ligand gated ion channels
what subunits make up the nicotinic receptors
5 subunits: α β γ δ ε
subunit combination determines?
the ligand binding properties of the receptor
what do muscle types have?
Muscle type: 2α β δ ε
what do ganglion types have?
Ganglion type: 2α 3β (CNS - similar)
which receptor is acetylcholine weaker in?
Effects of ACh weaker in nicotinic compared to muscarinic
what are the three main muscarinic effects on the eye?
Contraction of the ciliary muscle: accommodation for near vision
Contraction of the sphincter pupillae (circular muscle of the iris): Constricts pupil (miosis) and improves drainage of intraocular fluid
Lacrimation (tears)
what is glaucoma?
increase in intraocular pressure- this can cause damage to the optic nerves and retina and lead to blindness
what is aqueous humour and what is it used for?
Aqueous humour is generated by the capillaries of the ciliary body • The aqueous humour is generated and it flows into the anterior chamber of the eye • Its role is to supply oxygen and nutrients to the lens and cornea because they don’t have a blood supply • The aqueous humour diffuses forwards across the lens, then across the cornea and it drains through the canals of Schlemm back into the venous system
what happens in angle-closure glaucoma?
the angle between cornea and the iris becomes narrowed
this narrowing reduces the drainage of intraocular fluid via the canals of schlemm
what happens when you give a patient with angle-closure glaucoma a muscarinic agonist?
Contraction of sphincter pupillae opens pathway for aqueous humour, allowing drainage via the canals of Schlemm and reducing intra-ocular pressure
what are the muscarinic effects on the heart?
M2 receptors are inhibitory, and found in atria and both nodes
- decreases cAMP
- decreased calcium entry = decreased cardiac output
- increased potassium efflux = decreased heart rate