pharmocology Flashcards
(24 cards)
What is the function of the autonomic nervous system (ANS)?
The ANS controls smooth muscle and involuntary functions of internal organs. It consists of two major systems: the parasympathetic system and the sympathetic system
What neurotransmitters are involved in the ANS?
Acetylcholine (ACh) is the main neurotransmitter for cholinergic (parasympathetic) fibers.
Noradrenaline (norepinephrine) is the main neurotransmitter for adrenergic (sympathetic) fibers.
What is the role of acetylcholine in the parasympathetic system?
: Acetylcholine acts on muscarinic receptors at the neuro-effector junction to mediate parasympathetic effects such as accommodation (focus adjustment) and miosis (pupil constriction).
What is the role of noradrenaline in the sympathetic system?
Noradrenaline acts on adrenergic receptors (mainly alpha-1) at the dilator muscle to mediate sympathetic effects like mydriasis (pupil dilation) and vasoconstriction in the eye.
What is the difference between agonists and antagonists in pharmacology?
Agonists: Drugs that bind to a receptor and activate it, mimicking the natural neurotransmitter’s effect.
Antagonists: Drugs that bind to a receptor but do not activate it, blocking the effect of the natural neurotransmitter.
What is the key-lock system in receptor pharmacology?
The key-lock system describes how drugs (keys) bind to receptors (locks) to alter the receptor’s shape and induce a biological response.
Agonists: Have both affinity (binding strength) and efficacy (ability to produce a response).
Antagonists: Have affinity but no efficacy (do not produce a biological response).
What are the main receptors involved in ocular pharmacology?
Muscarinic receptors: Found in the ciliary muscle and sphincter muscle of the pupil.
Alpha-1 adrenergic receptors: Found in the dilator muscle and superficial conjunctival vasculature.
What is the effect of acetylcholine on the ciliary muscle?
Acetylcholine, acting on muscarinic receptors, promotes accommodation (focus adjustment) in the eye, which is the ability to focus on near objects.
What is the effect of acetylcholine on the sphincter muscle of the pupil?
Acetylcholine, acting on muscarinic receptors, causes miosis (constriction of the pupil) by stimulating the sphincter muscle.
How do sympathomimetic drugs work in optometry?
Sympathomimetic drugs mimic the effects of the sympathetic nervous system, causing mydriasis (pupil dilation) by acting on alpha-1 adrenergic receptors in the dilator muscle.
What is the action of phenylephrine in the eye?
Phenylephrine, a sympathomimetic drug, acts on alpha-1 adrenergic receptors to cause mydriasis (pupil dilation) and widening and whitening of the eye.
What are parasympathomimetics, and how do they affect the eye?
Parasympathomimetics are drugs that simulate the action of acetylcholine and promote effects like accommodation and miosis (pupil constriction). Example: Pilocarpine.
What are anticholinesterases, and how do they affect the eye?
Anticholinesterases inhibit the enzyme acetylcholinesterase, leading to increased acetylcholine levels and promoting accommodation and miosis (pupil constriction). Examples: Physostigmine (reversible), Ecothiophate (irreversible).
What are antimuscarinics, and how do they affect the eye?
Antimuscarinics are drugs that block muscarinic receptors and inhibit the effects of acetylcholine. This results in cycloplegia (paralysis of accommodation) and mydriasis (pupil dilation). Examples:
Natural: Atropine
Synthetic: Cyclopentolate, Tropicamide, Homatropine
What are sympathomimetics used for in optometry?
Sympathomimetics (e.g., Phenylephrine, Naphazoline) are used to cause mydriasis (pupil dilation) and are used in ocular decongestion.
What are adrenergic blockers, and how do they affect the eye?
Adrenergic blockers block adrenergic receptors and reduce sympathetic effects, leading to miosis, ptosis, and conjunctival injection. Examples: Thymoxamine, Dapiprazole.
What is the effect of alpha-1 adrenergic receptor activation on the eye?
Activation of alpha-1 adrenergic receptors causes mydriasis (pupil dilation) by stimulating the dilator muscle in the iris.
How do adrenergic blockers affect the pupil?
Adrenergic blockers block the effects of noradrenaline at alpha-1 adrenergic receptors, leading to miosis (pupil constriction), ptosis (drooping eyelids), and conjunctival redness.
What is the role of cholinomimetic esters in optometry?
Cholinomimetic esters (e.g., Pilocarpine) mimic acetylcholine, causing accommodation and miosis. These are used for treating conditions like glaucoma by reducing intraocular pressure.
How do cholinomimetic alkaloids affect the eye?
Cholinomimetic alkaloids (e.g., Pilocarpine) stimulate muscarinic receptors, leading to accommodation and miosis by enhancing the action of acetylcholine.
What is the difference between reversible and irreversible anticholinesterases?
Reversible anticholinesterases (e.g., Physostigmine) temporarily inhibit acetylcholinesterase, increasing acetylcholine levels.
Irreversible anticholinesterases (e.g., Ecothiophate) permanently inhibit acetylcholinesterase, and their effects last longer.
What is the purpose of cycloplegia in optometry?
Cycloplegia is the paralysis of accommodation, which is useful in measuring refractive error without the interference of accommodation, often induced by antimuscarinic drugs like Cyclopentolate or Atropine.
What action would a Parasympathomimetic drug have on the eye?
this would cause accommodation and miosis as they mimic the parasympathetic system utilises the meurotransmitter acetylcholine which only bind to muscarinic receptors, these receptors are present on both the sphincter muscle and ciliary muscle. the sphincter muscle cause pupil miosis and the ciliary muscle is responsible for accommodation
what is the name of the neurotransmitter that leads to adrenergic innervation??
noradrenaline
