Eye drugs Flashcards
(20 cards)
what is the ANS split into?
parasympathetic and sympathetic
what are the main three muscles in the eye?
circular, ciliary, radial
what are each of the three eye muscles controlled by (neurotransmitter) and what nervous system response do they provide?
circular and ciliary - acetylcholine and parasympathetic
radial - noradrenaline and sympathetic
name 4 eye drugs and the type of drug they are
phenylephrine - alpha-adrenoceptor agonist
tropicamide - non-selective muscarinic receptor antagonist
pilocarpine - muscarinic 3 receptor agonist
tetracaine - local anaesthetic
what happens to the pupil when the circular muscle contracts?
the pupil constricts
what happens to the pupil when the radial muscle contracts?
the pupil dilates
describe the mechanism of accommodation
the ciliary muscle will contract to round the lens for close vision
the ciliary muscle will relax to flatten the lens for distant vision.
what happens to the eye in low light and bright light?
low light:
activation of SNS, constriction of radial muscle, dilation of the pupil
bright light:
activation of PNS
contraction of the circular (constrictor) muscle
constriction of the pupil
describe the mechanism between white sclera and red sclera
white:
direct activation of blood vessel alpha 1 adrenergic receptors which causes contraction of vascular smooth muscle (vasoconstriction) and causes reduced blood flow
red:
direct activation of endothelial via muscarinic receptors which release nitric oxide causing relaxation of vascular smooth muscle and increased blood flow (vasodilation)
what effect on the eye will muscarinic agonists have?
contraction of circular muscle fibres
miosis (pupil constriction)
improved drainage due to opening of Canal of Schlemm
what effect on the eye will muscarinic antagonists have?
prevent circular muscle contraction
mydriasis (pupil dilation due to active opposing action of SNS on radial muscle)
closure of Canal of Schlemm (increases intraocular pressure and can cause glaucoma)
cycloplegia
temporary paralysis of the ciliary muscle causing disturbance in ability for accommodation
what type of drug specifically is tetracaine?
voltage gated sodium channel blocker
what G protein is tropicamide linked to? can you describe the mechanism of action?
Gq - inhibits activation of PLC which decreases intracellular calcium as a result
AND
Gi - inhibits adenylyl cyclase
blocks binding of ACh causing relaxation of the circular muscle causing pupil dilation (mydriasis) and cycloplegia
which G protein is phenylephrine linked to? can you describe the mechanism of action?
Gq - PLC - IP3 and DAG - increase Ca2+ release from ER causing contraction of radial muscles causing pupil dilation (mydriasis) and vasoconstriction of the smooth muscle
which G protein is pilocarpine linked to? can you describe the mechanism of action?
Gq - PLC - IP3 and DAG - release of Ca2+ release from ER causing contraction of circular muscle and vascular smooth muscle causing pupil constriction and whitening of sclera
name some clinical uses for muscarinic antagonists clinically
ophthalmology
enhancement of gastrointestinal and bladder tone
treatment of Alzheimer’s disease
describe closed angle glaucoma
blocked canal of Schlemm
accumulation of aqueous humour will increase pressure on the back of the eye
can cause damage on the retina and cause blindness
pilocarpine and carbochol can treat this
pilocarpine will cause constriction of the pupil to open the angle to allow drainage
tropicamide clinical uses
ophthalmology (mydriasis and cycloplegia)
what does DAG and IP3 stand for?
diacylglycerol and inositol trisphosphate
