Pharmacology Autonomic Nervous System Pharmacology 2

Question 1

A patient with pheochromocytoma requires surgical removal. Which alpha-blocker is used preoperatively to prevent hypertensive crisis?

Accepted Answer

Phenoxybenzamine

Answer

Phenoxybenzamine is a non-selective, irreversible alpha-blocker used preoperatively in pheochromocytoma to prevent catecholamine-induced hypertensive crises.

Question 2

Which muscarinic receptor subtype is primarily responsible for the decrease in heart rate caused by vagal stimulation?

Accepted Answer

M2

Answer

M2 receptors in the sinoatrial node mediate the negative chronotropic effect of acetylcholine released by vagal stimulation.

Question 3

Bethanechol is used to treat postoperative urinary retention. What is its mechanism of action?

Accepted Answer

Directly stimulates muscarinic receptors

Answer

Bethanechol is a direct-acting muscarinic agonist that stimulates bladder detrusor contraction without significant nicotinic activity.

Question 4

A patient takes a non-selective beta-blocker and later uses an epinephrine auto-injector. Which cardiovascular effect is most likely?

Accepted Answer

Severe hypertension with bradycardia

Answer

With beta-blockade, epinephrine's alpha-1 vasopressor effect is unopposed, causing severe hypertension; the reflex bradycardia is enhanced by beta-blockade.

Question 5

Which drug causes mydriasis and cycloplegia by blocking muscarinic receptors in the eye?

Accepted Answer

Atropine

Answer

Atropine blocks M3 receptors on the iris sphincter and ciliary muscle, causing pupil dilation (mydriasis) and loss of accommodation (cycloplegia).

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Autonomic Nervous System Pharmacology 2