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Flashcards in Trachte Deck (20):
1

mydriasis

pupil dilation

caused by sympathetic innervation

3 muscles: pupillary dilator (alpha1 receptor) constriction and superior tarsal constriction; ciliary muscle (beta2  receptor) relaxation

 

2

miosis

pupil constriction

parasympathetic response

2 muscles: ciliary muscle contractionpupillary sphincter contraction

All work through muscarinic receptors

(also...Enhance drainage of aqueous humor (trabecular meshwork & canal of Schlemm))

3

agonist

An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response.

Whereas an agonist causes an action, an antagonist blocks the action of the agonist and an inverse agonist causes an action opposite to that of the agonist.

4

antagonist

. Whereas an agonist causes an action, an antagonist blocks the action of the agonist (and an inverse agonist causes an action opposite to that of the agonist.)

5

aqueous humor production

Sympathetic

Enhance aqueous humor formation (ß receptors)
Inhibit aqueous humor formation (alpha2 receptors)

Parasympathetic 

Enhance drainage of aqueous humor (trabecular meshwork & canal of Schlemm) via muscarinic receptors

6

Drugs promoting mydriasis

A. sympathetic activation or B. inhibition of the parasympathetic pathway!!

A = phenylephrine, epinephrineamphetamine (promotes NE release from postganglionic cell) or cocaine (blocks Na+ dependent NE reuptake transporter)

B= Inhibitors of parasympathetic nervous system (Atropine—muscarinic antagonist. Literally translates as “pretty women”)

7

alpha1 adrenergic stimulants

mydriatics 

PHENYLEPHRINE (selective) (mydrifrin) is a drug used in eye drops to dilate pupil. Also reverses ptosis in Horner’s Syndrome.

Epinephrine (Epitrate) 0.5 to 2% solution to treat glaucoma (nonselective!!!)-- promotes humor outflow and inhibits formation

8

No eye response to cocaine or amphetamine means what?

postganglionic Horner’s Syndrome

9

Agents releaseing NE

nicotine 

amphetamine -- reverses axoplasmic pump

hydroxyamphetamine (0.1% solution) used to diagnose post-ganglionic nerve damage vs. a defect prior to the postganglionic nerve

no reaction means postganglionic nerve defect

response to amphetamine indicates normal post-ganglionic nerve

10

If eye responds to pilocarpine with miosis, then problem...

is with the nerve (third nerve palsy)

pilocarpine is a muscarinic agonist

11

If eye does not respond to pilocarpine, then problem...

is with the eye itself (Atropinic mydriasis)

pilocarpine is a muscarinic agonist

12

Drugs producing miosis 

Nicotine activates parasympathetic nerves

Muscarinic agonists such as Pilocarpine (Pilocar), acetylcholine (Miochol)

Pilocarpine used as 2% solution
1% solution to differentiate IIIrd nerve palsy from “Atropinic” mydriasis

If pilocarpine is active (produces miosis) then the defect must be in the nerve.

13

Agents preventing acetylcholine degradation...

increase in ACh will cause miosis... pupil constriction... via parasympathetic activation (sort of)

Physostigmine (Isopto eserine), Ecothiophate (phospholine iodide), demecarium (Humorsol), isofluorophate (floropryl)

14

Norepinephrine depleting agents...

cause miosis

NE release from postganglionic terminal on smooth muscle prevented

Reserpine -- not normally used for eye treatment, but can have ocular side effects. 

15

Drugs for Treatment of Glaucoma

ß Blockers: Timolol (Timoptic); Betaxolol (Betoptic); Carteolol (Ocupress); Levobunolol (Betagan); Metipranolol (Optipranolol)- they decrease aqueous humor formation

Muscarinic Receptor Agonists-
Pilocarpine (Pilocar)- enhances aqueous humor drainage through trabecular meshwork & canal of Schlemm

Anticholinesterases-
Physostigmine (Isopto eserine), Ecothiophate (Phospholine iodide)- enhances aqueous humor drainage through trabecular meshwork & canal of Schlemm

16

Ptosis and treatment

drooping of the upper eyelid due to paralysis or disease, 

Characteristic of sympathetic nerve disruption;
Superior tarsalis muscle holds eyelid open

Myasthenia gravis
Botulinism
Occulomotor palsy
Muscular Dystrophy

treate wth botulinum toxin (inhibits acetylcholine release)

17

Summary

Mydriatic Agents

alpha1 agonist, Phenylephrine
Muscarinic antagonist, Atropine
Agents releasing norepinephine, Amphetamine
Agents preventing norepinephrine uptake into the nerve (Cocaine)

These can all precipitate closed angle gluacoma

18

Summary 

Miotic Agents

Muscarinic agonist (Pilocarpine, Acetylcholine)
a1 adrenergic antagonists (Terazosin)
Anticholinesterases (Physostigmine)
Nicotine

19

Treatments for Glaucoma

Agents enhancing aqueous humor outflow (by trabecular meshwork and Canal of Schlemm)
Muscarinic agonists (pilocarpine)
Prostaglandins (Latanaprost)
Epinephrine

Agents suppressing aqueous humor production (by ciliary processes)
ß adrenergic antagonists (Timolol)
a2 adrenergic agonists (Aproclonidine)
Carbonic anhydrase inhibitors (Acetazolamide)

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