Question 1

Which of the following statements best describes the mechanism of action of depolarising muscle relaxants such as suxamethonium?

Accepted Answer

They act as agonists at nicotinic acetylcholine receptors, causing persistent depolarisation and subsequent muscle paralysis.

Question 2

Which muscarinic receptor subtype is primarily responsible for increasing heart rate and force of contraction?

Accepted Answer

$$M_2$$

Question 3

A patient presents with muscle weakness, drooping eyelids, and difficulty swallowing. Laboratory tests reveal antibodies against nicotinic acetylcholine receptors. What is the most likely diagnosis?

Accepted Answer

Myasthenia gravis

Question 4

Which of the following drugs is used as a short-acting muscle relaxant during procedures such as bronchoscopy and acts by causing persistent depolarisation at the neuromuscular junction?

Accepted Answer

Suxamethonium

Question 5

Which of the following is a non-depolarising muscle relaxant that acts as a competitive antagonist at the nicotinic acetylcholine receptor at the motor endplate?

Accepted Answer

Tubocurarine

Question 6

Which of the following equations correctly represents the hydrolysis of acetylcholine by acetylcholinesterase?

Accepted Answer

$$\mathrm{ACh} + \mathrm{H_2O} \rightarrow \mathrm{Choline} + \mathrm{Acetate}$$

Question 7

Which of the following drugs is used to treat organophosphate poisoning due to its ability to block muscarinic receptors?

Accepted Answer

Atropine

Question 8

Which of the following is a reversible anticholinesterase agent that is effective in treating glaucoma due to its ability to cross the blood-brain barrier?

Accepted Answer

Physostigmine

Question 9

A farmer exposed to organophosphate pesticides develops respiratory paralysis and difficulty swallowing. What is the underlying mechanism of toxicity?

Accepted Answer

Irreversible covalent binding to acetylcholinesterase, leading to persistent depolarisation at the neuromuscular junction

Question 10

Which of the following drugs is used to reverse muscle paralysis caused by non-depolarising muscle relaxants at the end of surgery?

Accepted Answer

Neostigmine

Question 11

Which muscarinic antagonist is commonly used as an adjunct in anesthesia to decrease secretions and also to treat organophosphate poisoning?

Accepted Answer

Atropine

Question 12

Which of the following statements about ganglion-blocking drugs is correct?

Accepted Answer

They decrease acetylcholine release and cause loss of cardiovascular reflexes.

Question 13

Which of the following is a direct muscarinic agonist used to treat paralytic ileus and atony of the bladder?

Accepted Answer

Bethanechol

Question 14

Which of the following drugs is used as a mydriatic agent for eye examination by blocking muscarinic receptors?

Accepted Answer

Tropicamide

Question 15

Which of the following is a characteristic effect of non-depolarising muscle relaxants at the neuromuscular junction?

Accepted Answer

Competitive antagonism at nicotinic acetylcholine receptors

Question 16

Which of the following is a clinical use of reversible anticholinesterase agents?

Accepted Answer

Treatment of myasthenia gravis

Question 17

Which of the following muscarinic antagonists is used for the treatment of asthma by inhalation?

Accepted Answer

Ipratropium

Question 18

Which of the following statements best explains why organophosphate poisoning affects both muscarinic and nicotinic receptors?

Accepted Answer

Organophosphates irreversibly inhibit acetylcholinesterase, increasing acetylcholine at both muscarinic and nicotinic synapses.

Question 19

Which of the following drugs is used to treat peptic ulcer by decreasing gastric acid secretion through action on $$M_1$$ receptors or ganglion cells?

Accepted Answer

Pirenzepine

Pharmacological Modification of Chemical Transmission: Cholinergic Transmission and Muscle Relaxants

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