Pharmacology Autonomic Nervous System Pharmacology 5

Question 1

Physostigmine crosses the blood-brain barrier while neostigmine does not. The structural reason is:

Accepted Answer

Physostigmine is a tertiary amine; neostigmine is a quaternary ammonium compound

Answer

Tertiary amines (physostigmine) are lipid-soluble and cross the BBB, while quaternary ammonium compounds (neostigmine) are permanently charged and cannot.

Question 2

Mirabegron is a newer drug for overactive bladder. Its mechanism differs from oxybutynin because it:

Accepted Answer

Is a beta-3 adrenergic agonist that relaxes the detrusor

Answer

Mirabegron activates beta-3 receptors on bladder detrusor muscle, promoting relaxation and increasing bladder capacity without anticholinergic side effects.

Question 3

Labetalol is useful in hypertensive emergencies in pregnancy because it:

Accepted Answer

Blocks both alpha-1 and beta receptors, lowering BP without causing reflex tachycardia

Answer

Labetalol's combined alpha-1 and non-selective beta blockade reduces peripheral resistance and prevents reflex tachycardia, making it effective and relatively safe in pregnancy.

Question 4

Methacholine challenge testing is used to diagnose asthma. Methacholine acts by:

Accepted Answer

Directly stimulating muscarinic receptors causing bronchoconstriction

Answer

Methacholine is a synthetic muscarinic agonist that causes bronchoconstriction; asthmatic airways are hyperresponsive and show a ≥20% drop in FEV1 at low doses.

Question 5

Reserpine depletes catecholamine stores by:

Accepted Answer

Inhibiting the vesicular monoamine transporter (VMAT), preventing storage of catecholamines

Answer

Reserpine irreversibly inhibits VMAT, so newly synthesized catecholamines cannot be packaged into vesicles and are degraded intraneuronally.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Autonomic Nervous System Pharmacology 5