5-autonomic-eyeball! Flashcards
what is accomodation
focusing of the eye
what does morphine do to pupil
miosis
what does organophostate poisoning do to pupil
miosis
what does cocaine do to pupil
mydriasis
what does amphetamine do to pupil
mydriases
what is mydriasis
dilation of pupil
what is miosis
constriction of pupil
what causes mydriases
increase in sympathetic outflow
what is the role of the pupillary dilator muscle
cause mydriasis with alpha adrenoceptor stimulation
what is another name for the pupillary dilator muscle
iris radial muscle
what is another name for the iris radial muscle
pupillary dilator muscle
what does alpha stimulation do to the pupillary dilator muscle
mydriases
what does alpha stimulation do to the iris radial muscle
mydriases
what is another name for the circular pupillary constrictor muscle
iris sphincter
what is another name for the iris sphincter
circular pupillary constrictor muscle
what kind of receptor stimulation happens with the iris sphincter
muscarinic
what kind of receptor stimulation happens with the circular pupillary constrictor muscle
muscarinic
what kind of receptor stimulation happens with the circular pupillary dilator muscle
alpha
what kind of receptor stimulation happens with the iris radial muscle
alpha
what kind of activation do ciliary muscles require
muscarinic
what does muscarinic activation do to ciliary muscles
contraction
what kind of vision does ciliary muscles help with
myopia (near vision)
what does the trabecular meshwork do
moves do that fluid can leave through the canal of schlemm
what does the canal of schlemm do
let fluid leave the eye
what causes the trabecular meshwork to move
ciliary muscle activation
how do ciliary muscles help with removing aqueous humor
puts tension on trabecular meshwork which opens pores to let outflow of aqueous humor in canal of schlemm
what does the ciliary epithelium do
produces the aqueous humor
what kind of receptors stimulate the ciliary epithelium
beta
how do beta blockers reduce IOP
reduces aqueous humor release from the ciliary epithelium (ciliary epithelium has beta adrenergic receptors)
how do muscarinic agonists reduce IOP
because it activates ciliary muscles which activates trabecular meshwork to open pores and let aqueous humor out into the canal of schlemm
what is galucoma and what can it cause
elevated IOP and it can cause optic nerve damage and blindness
what are the two types of glaucoma
open angle and angle closure glaucoma
what is open angle glaucoma
high pressure between cornea and iris
how common is open angle glaucoma and how easily is it treated
common and easily treated
what is angle closure glaucoma
high pressure between ciliary body and iris
how common is angle closure glaucoma and how easily is it treated
not as common and doesnt respond as well to drugs :(
what is the course of treatment for open angle glaucoma (4)
- beta blocker (stop ciliary body secretion)
- cholinergic agonist/cholinesterase inhibitor (preserve sympathetic tone)
- add adrenaline or apraclonidine (with b blocker still)(reduces blood flow to ciliary body)
- carbonic anhydrase inhibitor (affects ciliary body secretion)
why is it safe to take glaucoma meds if you have systemic circulation issues
the eye drops have very poor access to systemic circulation
what is Timolol (drug class)
betablocker
what is the difference with timolol and propranolol
timolol has no anesthetic effects (dont want that in the eye)
what does Timolol do
reduces secretion of aqueous humor from ciliary body and lower IOP
what is pilocarpine (drug class)
muscarinic agonist
what does pilocarpine do
cause ciliary muscle contraction
increase outflow of aqueous humor into circulation, reduce IOP
what are the untoward effects of pilocarpine
miosis (by iris sphincter)
myopia (by ciliary muscle)
what is physostigmine
anticholinesterase
what does physostigmine do to eye
ciliary muscle contraction, increase outflow of aqueous humor, reduce IOP
what does apraclonidine do
vasoconstrict, reduce blood flow to ciliary body, less aqueous humor secreted, IOP decreased
what do cannabinoids do to eye
lower IOP likely by relaxing the trabecular network
what is anandamide
endogenous ligand of the CB1 and CB2 receptors
what do CB1 receptors do (g protein)
Gi which reduces NT release by activating Ca2+ and GIRK channels
what direction does GIRK channels go
releases K+ from nerve terminal!
what does atropine do to the eye
dilate pupil for ocular examination
what kind of drug is atropine
muscarinic antagonist
why does atropine cause mydriasis
muscarinic antagonist, meaning it removes the parasympathetic tone to cause dilation (mydriasis)
what causes Horner’s syndrome
head trauma or stroke in brainstem
even if the damage is unilateral
can damage to sympathetic nerves cause horners syndrome
yes thats what it is about
can damage to parasympathetic nerves cause horners syndrome
no
what characterizes horners syndrome
interruption of oculosympathetic pathway somewhere between hypothalamus and eye
what are the 3 neurons that could be damaged to cause horners syndrome
1-hypothalamus to spinal cord
2-sympathetic preganglionic neuron
3-sympathetic ganglion neuron
what would you expect cocaine to do to the pupil
cause dilation
if cocaine doesn’t cause pupil dilation, where would the lesion be
neurons 1 2 or 3
how can you use amphetamines to test for horners syndrome
test neuron 3
-if it is intact, the pupil will dilate (it releases NA REGARDLESS of the condition of neuron 1 and 2 or sympathetic outflow to neuron 3)
in summary, what do alpha adreoceptor agonists do to eye
lowers IOP (decrease flow to ciliary body) mydriases (increase pupil size from pupillary dilator/iris radial muscle)
in summary, what do muscarinic agonists do to eye
miosis (pupillary constrictor/iris sphincter) myopia (ciliary muscle contraction, accomodation for near vision) lower IOP (contract ciliary muscle - tension on trabecular meshwork - aqueous humor squeezed out into circulation)
in summary, what do beta adreoceptor antagonists do to eye
lower IOP (blocks humor production by ciliary body)
why can atropine be bad for glaucoma
antimuscarinic (stops parasympathetic tone)
it can relax the ciliary muscle
