Pharmacology Autonomic Nervous System Pharmacology 4

Question 1

Succinylcholine produces initial muscle fasciculations followed by paralysis. This is because it is a:

Accepted Answer

Depolarizing neuromuscular blocking agent

Answer

Succinylcholine depolarizes the motor end plate continuously, causing initial fasciculations then flaccid paralysis as the membrane cannot repolarize.

Question 2

Vecuronium reverses neuromuscular blockade is achieved with neostigmine. What must be co-administered to prevent bradycardia?

Accepted Answer

Atropine or glycopyrrolate

Answer

Neostigmine inhibits acetylcholinesterase, increasing acetylcholine at all cholinergic synapses including the heart; atropine or glycopyrrolate is co-administered to block muscarinic bradycardia.

Question 3

Phenylephrine is used as a nasal decongestant. Its mechanism is:

Accepted Answer

Selective alpha-1 agonist causing vasoconstriction

Answer

Phenylephrine selectively activates alpha-1 receptors on nasal blood vessels, causing vasoconstriction and reduced mucosal edema.

Question 4

Which cholinergic drug is used to diagnose myasthenia gravis by briefly improving muscle strength?

Accepted Answer

Edrophonium

Answer

Edrophonium is an ultra-short-acting acetylcholinesterase inhibitor; transient improvement in muscle strength after injection confirms myasthenia gravis.

Question 5

Dopamine at low doses (1–3 mcg/kg/min) causes renal vasodilation primarily via:

Accepted Answer

Dopamine D1 receptor stimulation

Answer

At low doses, dopamine activates D1 receptors on renal vasculature, causing vasodilation and increased renal blood flow.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Autonomic Nervous System Pharmacology 4