Understanding the structure and function of the parasympathetic nervous system is essential for B. Pharm students studying pharmacology and therapeutics. This craniosacral division of the autonomic nervous system uses acetylcholine at pre- and postganglionic synapses, acting on nicotinic (Nn/Nm) and muscarinic (M1–M5) receptors to regulate heart rate, glandular secretion, smooth muscle motility, and ocular responses. Key topics include ganglionic architecture, vagus nerve pathways, receptor subtypes, cholinergic transmission, acetylcholinesterase activity, and pharmacologic modulators such as muscarinic agonists/antagonists and cholinesterase inhibitors. Clinical correlations—bradycardia, bronchospasm, miosis, urinary retention—illustrate therapeutic and toxicologic implications. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which anatomical origin best describes the parasympathetic nervous system outflow?
- Thoracolumbar outflow (T1–L2)
- Craniosacral outflow (brainstem nuclei and S2–S4)
- Only cranial nerves III and VII
- Only sacral plexus
Correct Answer: Craniosacral outflow (brainstem nuclei and S2–S4)
Q2. What is the primary neurotransmitter released by preganglionic parasympathetic neurons?
- Norepinephrine
- Dopamine
- Acetylcholine
- Serotonin
Correct Answer: Acetylcholine
Q3. Which receptor subtype is predominantly found at autonomic ganglia and is activated by acetylcholine from preganglionic fibers?
- Muscarinic M2
- Nicotinic Nn (neuronal)
- Nicotinic Nm (muscle)
- Beta-2 adrenergic
Correct Answer: Nicotinic Nn (neuronal)
Q4. Which muscarinic receptor subtype mediates decreased heart rate via inhibition of adenylyl cyclase in the sinoatrial node?
- M1
- M2
- M3
- M5
Correct Answer: M2
Q5. Muscarinic M3 receptors primarily couple to which G-protein and signaling pathway?
- Gs — increase cAMP
- Gi — decrease cAMP
- Gq — activate phospholipase C and increase IP3/DAG
- Tyrosine kinase receptor pathway
Correct Answer: Gq — activate phospholipase C and increase IP3/DAG
Q6. Which drug is a reversible acetylcholinesterase inhibitor used to treat myasthenia gravis and has limited CNS penetration?
- Physostigmine
- Neostigmine
- Organophosphate (e.g., parathion)
- Atropine
Correct Answer: Neostigmine
Q7. Which clinical effect is characteristic of parasympathetic activation in the eye?
- Mydriasis (pupil dilation) and cycloplegia
- Miosis (pupil constriction) and accommodation (near vision)
- Loss of corneal reflex
- Increased intraocular pressure due to aqueous production
Correct Answer: Miosis (pupil constriction) and accommodation (near vision)
Q8. Bethanechol is a muscarinic agonist used clinically to treat postoperative urinary retention; what property makes it suitable?
- Strong nicotinic receptor activity
- Resistance to acetylcholinesterase degradation
- Irreversible binding to muscarinic receptors
- High lipid solubility allowing CNS penetration
Correct Answer: Resistance to acetylcholinesterase degradation
Q9. Which drug is a muscarinic antagonist used to treat organophosphate poisoning by reversing muscarinic symptoms and crosses the blood–brain barrier?
- Pralidoxime (2-PAM)
- Neostigmine
- Atropine
- Pilocarpine
Correct Answer: Atropine
Q10. Organophosphate poisoning causes accumulation of acetylcholine by irreversibly inhibiting which enzyme?
- Monoamine oxidase
- Butyrylcholinesterase only
- Acetylcholinesterase
- Choline acetyltransferase
Correct Answer: Acetylcholinesterase
Q11. Which autonomic effector shows an exception where sympathetic neurons use acetylcholine rather than norepinephrine?
- Cardiac muscle
- Sweat glands (thermoregulatory)
- Bronchial smooth muscle
- Adrenal medulla
Correct Answer: Sweat glands (thermoregulatory)
Q12. Hexamethonium is a historical ganglionic blocker; what receptor does it block to inhibit autonomic ganglia?
- Muscarinic M3
- Nicotinic Nn
- Nicotinic Nm
- Beta-1 adrenergic
Correct Answer: Nicotinic Nn
Q13. Which muscarinic antagonist is commonly used topically in the eye to induce mydriasis for fundoscopy?
- Pilocarpine
- Bethanechol
- Tropicamide
- Neostigmine
Correct Answer: Tropicamide
Q14. Activation of parasympathetic pathways to the bronchial tree produces which effect relevant to asthma?
- Bronchodilation mediated by beta-2 receptors
- Bronchoconstriction and increased bronchial secretions
- Decreased mucous production
- No direct effect; only sympathetic controls airways
Correct Answer: Bronchoconstriction and increased bronchial secretions
Q15. Which co-transmitter or modulatory substance is often released with acetylcholine from parasympathetic nerves and contributes to vasodilation?
- Norepinephrine
- Nitric oxide (NO)
- Dopamine
- Bradykinin
Correct Answer: Nitric oxide (NO)
Q16. Pilocarpine is a muscarinic agonist used in glaucoma; its mechanism reduces intraocular pressure primarily by:
- Decreasing aqueous humor production via ciliary epithelium inhibition
- Increasing trabecular outflow through contraction of the ciliary muscle
- Blocking beta receptors in the eye
- Increasing episcleral venous pressure
Correct Answer: Increasing trabecular outflow through contraction of the ciliary muscle
Q17. Which statement correctly contrasts preganglionic and postganglionic parasympathetic neurons?
- Preganglionic fibers are short; postganglionic are long
- Preganglionic release norepinephrine; postganglionic release acetylcholine
- Preganglionic are long and project to terminal ganglia near effector organs; postganglionic are short
- Both pre- and postganglionic fibers synapse in the spinal cord
Correct Answer: Preganglionic are long and project to terminal ganglia near effector organs; postganglionic are short
Q18. Which clinical sign is NOT typical of acute muscarinic overstimulation (cholinergic crisis)?
- Bradycardia
- Miosis and blurred vision
- Dry skin and reduced sweating
- Bronchorrhea and bronchospasm
Correct Answer: Dry skin and reduced sweating
Q19. What is the primary action of pralidoxime (2-PAM) in organophosphate poisoning management?
- Block muscarinic receptors centrally
- Reactivate phosphorylated acetylcholinesterase if given early
- Irreversibly inhibit acetylcholinesterase
- Serve as a muscarinic agonist to compete with excess ACh
Correct Answer: Reactivate phosphorylated acetylcholinesterase if given early
Q20. Which pharmacologic agent would increase salivary secretion through muscarinic receptor activation?
- Atropine
- Suxamethonium (succinylcholine)
- Pilocarpine
- Propranolol
Correct Answer: Pilocarpine
Q21. Which receptor subtype predominates at the neuromuscular junction of skeletal muscle and is the target for succinylcholine?
- Nicotinic Nn
- Nicotinic Nm
- Muscarinic M2
- Mitochondrial acetylcholine receptor
Correct Answer: Nicotinic Nm
Q22. A drug that selectively blocks M3 receptors would most likely produce which effect?
- Increased heart rate through SA node M2 blockade
- Reduced glandular secretions and decreased smooth muscle contraction (e.g., bronchodilation)
- Neuromuscular blockade of skeletal muscle
- Selective vasodilation via endothelial M1 receptors
Correct Answer: Reduced glandular secretions and decreased smooth muscle contraction (e.g., bronchodilation)
Q23. Which enzyme synthesizes acetylcholine in cholinergic neurons?
- Acetylcholinesterase
- Choline acetyltransferase (ChAT)
- Tyrosine hydroxylase
- Choline esterase
Correct Answer: Choline acetyltransferase (ChAT)
Q24. Which autonomic function is mainly mediated by the vagus nerve (cranial nerve X) parasympathetic output?
- Vasoconstriction of peripheral arterioles
- Increased heart rate and contractility
- Slowing heart rate, increased GI motility, and bronchoconstriction
- Pupil dilation and eyelid elevation
Correct Answer: Slowing heart rate, increased GI motility, and bronchoconstriction
Q25. Which class of drugs would antagonize the effects of pilocarpine on the eye?
- Beta blockers (e.g., timolol)
- Alpha-1 agonists (e.g., phenylephrine)
- Muscarinic antagonists (e.g., tropicamide)
- Acetylcholinesterase inhibitors (e.g., physostigmine)
Correct Answer: Muscarinic antagonists (e.g., tropicamide)
Q26. Which feature differentiates physostigmine from neostigmine in clinical use?
- Physostigmine is charged and does not cross the BBB; neostigmine crosses readily
- Physostigmine crosses the blood–brain barrier and treats central anticholinergic toxicity; neostigmine does not
- Both are irreversible organophosphates
- Neostigmine is used to produce miosis in glaucoma emergency
Correct Answer: Physostigmine crosses the blood–brain barrier and treats central anticholinergic toxicity; neostigmine does not
Q27. Which clinical test assesses parasympathetic integrity of the heart by evaluating vagal tone?
- Cold pressor test
- Valsalva maneuver and heart rate variability analysis
- Forced expiratory volume (FEV1)
- Orthostatic blood pressure alone
Correct Answer: Valsalva maneuver and heart rate variability analysis
Q28. In the gastrointestinal tract, parasympathetic stimulation primarily causes which of the following?
- Decreased peristalsis and decreased secretions
- Increased peristalsis and increased secretions
- Sphincter contraction and decreased motility
- Complete relaxation of smooth muscle tone
Correct Answer: Increased peristalsis and increased secretions
Q29. Chronic inhibition of acetylcholinesterase would cause receptor regulation changes; which is most likely at muscarinic receptors?
- Upregulation (increased receptor density)
- No change in receptor number
- Downregulation (decreased receptor density) due to sustained agonist exposure
- Conversion of muscarinic to nicotinic receptors
Correct Answer: Downregulation (decreased receptor density) due to sustained agonist exposure
Q30. Which statement best describes the pharmacologic rationale for using antimuscarinic agents in COPD exacerbations?
- Antimuscarinics stimulate M3 receptors to increase bronchial secretions
- Antimuscarinics block muscarinic-mediated bronchoconstriction and reduce secretions
- They increase acetylcholine release from parasympathetic terminals
- They inhibit beta-2 receptors to produce bronchodilation
Correct Answer: Antimuscarinics block muscarinic-mediated bronchoconstriction and reduce secretions
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com