Pharmacology: Autonomic Nervous System. Questions and answers.
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1. List the types of cholinergic drugs and their classifications.
● Answer:
○ Cholinergic Agonists: Directly interact with cholinergic receptors.
■ Choline Esters:
■ Acetylcholine
■ Methacholine
■ Carbachol
■ Bethanechol
■ Alkaloids:
■ Muscarine
■ Pilocarpine
■ Arecoline
○ Anticholinesterases: Increase availability of ACh at cholinergic receptors.
2. Describe the muscarinic actions of acetylcholine (ACh).
○ Answer:
■ Heart: ACh hyperpolarizes SA nodal cells, decreasing impulse generation
(bradycardia). It also slows conduction through the AV node and His-
Purkinje fibers, potentially leading to A-V block.
■ Blood Vessels: ACh causes vasodilation via M3 receptors on endothelial
cells, releasing nitric oxide (NO). This results in a decrease in blood
pressure and flushing.
■ Smooth Muscle: ACh contracts smooth muscles in various organs,
increasing gastrointestinal motility, bladder contraction, and bronchial
constriction.
■ Glands: ACh stimulates secretion from parasympathetically innervated
glands, leading to increased sweating, salivation, and gastrointestinal
secretions.
■ Eye: ACh causes miosis through contraction of the circular muscle of the
iris and increases aqueous humor outflow, reducing intraocular pressure.
3. Outline the nicotinic actions of acetylcholine (ACh).
○ Answer:
■ Autonomic Ganglia: ACh stimulates both sympathetic and
parasympathetic ganglia, leading to increased heart rate and blood
pressure at higher doses.
■ Skeletal Muscles: ACh applied to muscle endplates causes contraction.
High doses can induce twitching and fasciculations but are rapidly
hydrolyzed in circulation.
,4. Describe the central nervous system (CNS) actions of acetylcholine.
○ Answer:
ACh does not penetrate the blood-brain barrier when injected intravenously, thus
lacking central effects. However, direct injection into the brain can produce
arousal followed by depression. Cholinergic drugs that enter the brain can result
in complex behavioral and neurological effects.
5. List the uses of cholinergic drugs.
○ Answer:
■ Bethanechol: Used to treat postoperative or postpartum nonobstructive
urinary retention and neurogenic bladder.
■ Methacholine: Previously used to terminate paroxysmal supraventricular
tachycardia but is now obsolete.
■ Pilocarpine: Used as an eye drop for open-angle glaucoma and to
counteract mydriatics.
■ Arecoline: Investigated for cognitive enhancement in dementia but found
to have no therapeutic use.
6. Describe the effects and side effects of pilocarpine.
○ Answer:
■ Effects: Pilocarpine stimulates muscarinic receptors, leading to increased
sweating, salivation, and other secretions. It causes miosis and reduces
intraocular pressure when applied to the eye.
■ Side Effects: Common side effects include an initial stinging sensation in
the eye, painful spasm of accommodation, and cardiovascular effects such
as hypotension at low doses and possible tachycardia at high doses.
7. Outline the toxicological significance of muscarine and the types of mushroom
poisoning.
○ Answer:
■ Muscarine: Found in certain poisonous mushrooms, it has muscarinic
actions but is not used therapeutically.
■ Types of Mushroom Poisoning:
■ Muscarine Type: Causes early symptoms of muscarinic actions,
reversed by atropine.
■ Hallucinogenic Type: Caused by compounds like muscimol,
leading to central symptoms; atropine is contraindicated.
■ Phalloidin Type: Causes late symptoms due to liver and kidney
damage; supportive treatment is required.
8. Describe the properties and actions of arecoline.
○ Answer:
Arecoline, found in betel nut, exhibits both muscarinic and nicotinic actions,
influencing skeletal muscle endplates. It has CNS effects and has been tried as a
cognitive enhancer in dementia but has not demonstrated therapeutic efficacy.
9. Outline the classification of anticholinesterases (anti-ChEs). Answer: Anticholinesterases
are classified into two main categories:
Skeletal muscle effects: Increased contraction force, potential blockade at high doses.
Central nervous system effects: Alertness, potential cognitive improvements, and
adverse effects like confusion and convulsions.
11. Compare and contrast reversible and irreversible anticholinesterases in terms of their
mechanism and effects.
Answer:
12. Describe the therapeutic uses of anticholinesterases.
Answer:
Anticholinesterases are used for:
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