56 Year 3: Basic Pharmacology II exam questions on Basic Pharmacology - Study Guide for medical students. Includes MCQs, answers, explanations and written quest
This MCQ set contains 56 questions on Basic Pharmacology - Study Guide in the Year 3: Basic Pharmacology II unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.
Correct answer: A – Mechanisms of drug action
Pharmacodynamics specifically studies the mechanisms of drug action and the biochemical and physiological effects of drugs on the body. Options B, C, and D describe pharmacokinetic processes (what the body does to the drug), while pharmacodynamics describes what the drug does to the body. ---
Correct answer: C – Decreased efficiency in drug biotransformation
Elderly patients experience decreased hepatic enzyme activity and reduced liver blood flow, leading to decreased drug biotransformation. This results in prolonged drug half-life and increased drug accumulation, necessitating dose reduction to prevent toxicity. ---
Correct answer: B – A measure of how tightly a drug binds to a receptor
Affinity refers to the strength of the interaction between a drug and its receptor. High affinity means the drug binds strongly to the receptor, requiring lower concentrations to achieve binding. This is distinct from efficacy, which describes the ability to produce an effect once bound. ---
Correct answer: D – Binds to the receptors without directly altering their function
An antagonist binds to a receptor but does not activate it. Instead, it blocks the receptor site, preventing endogenous ligands or agonists from binding and producing their effects. Antagonists have affinity but no intrinsic activity (efficacy). ---
Correct answer: B – Covalent bond
Irreversible inhibition occurs through covalent bond formation between the drug and its target. Covalent bonds are very strong and permanent, making the inhibition essentially irreversible. The effect only diminishes when new enzymes or receptors are synthesized. ---
Correct answer: D – Efficacy
Efficacy refers to the maximum response a drug can produce, regardless of dose. It indicates the drug's ability to produce the desired therapeutic effect. Potency refers to the dose required to produce a given effect, while efficacy describes the magnitude of that effect. ---
Correct answer: D – Plasma membranes and intracellular structures
Drug receptors are located on plasma membranes (G-protein coupled receptors, ion channels, enzyme-linked receptors) and intracellularly (nuclear receptors for steroid hormones, thyroid hormones). This allows drugs to interact with various cellular components to produce therapeutic effects. --- AUTONOMIC NERVOUS SYSTEM
Correct answer: A – Bronchial smooth muscle
Bronchial smooth muscle contains muscarinic receptors (M3), not nicotinic receptors. Nicotinic receptors are found at neuromuscular junctions (skeletal muscle), autonomic ganglia (both sympathetic and parasympathetic), and adrenal medulla. ---
Correct answer: A – Acetylcholine
When blood pressure increases, baroreceptors activate parasympathetic (vagal) output to the heart. The vagus nerve releases acetylcholine at the SA node, which binds to M2 muscarinic receptors, causing bradycardia and reduced cardiac output to lower blood pressure. ---
Correct answer: C – Amphetamine
Amphetamine is an indirect sympathomimetic that enters adrenergic nerve terminals and displaces stored norepinephrine, causing its release into the synaptic cleft. This mechanism is responsible for amphetamine's stimulant effects. Reserpine, in contrast, depletes catecholamine stores. ---
Correct answer: C – Decreased renal blood flow
During sympathetic activation, blood is redirected from non-essential organs (including kidneys and GI tract) to skeletal muscles, heart, and brain. This causes decreased renal blood flow. Other sympathetic effects include bronchodilation, decreased GI motility, mydriasis (pupil dilation), and tachycardia. ---
Correct answer: D – Diarrhea
Pyridostigmine and neostigmine are acetylcholinesterase inhibitors that increase acetylcholine levels at all cholinergic sites, including the GI tract. This leads to increased GI motility and secretions, causing diarrhea. Other cholinergic effects include bronchoconstriction, increased secretions, and bradycardia. ---
Correct answer: B – Tachycardia
Atropine is an antimuscarinic that blocks parasympathetic effects. Overdose presents with "hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter." Tachycardia results from blockade of vagal (M2) receptors in the heart. Other signs include mydriasis, decreased secretions, and hyperthermia. ---
Correct answer: C – Hyperthermia
Hyperthermia is the most life-threatening effect in children because belladonna alkaloids (atropine) block sweat glands, preventing heat dissipation. Children have less efficient thermoregulation and higher metabolic rates, making them particularly vulnerable to dangerous temperature elevations. ---
Correct answer: C – Epinephrine
Epinephrine is the first-line treatment for anaphylaxis. It acts on α1 receptors (vasoconstriction to reverse hypotension), β1 receptors (increased cardiac output), and β2 receptors (bronchodilation). It also stabilizes mast cells, preventing further mediator release. Route: IM into anterolateral thigh. ---
Correct answer: E – Triglycerides in fat cells
Epinephrine stimulates β3 receptors in adipose tissue, activating hormone-sensitive lipase, which breaks down triglycerides into free fatty acids and glycerol. This lipolysis provides energy substrates during the fight-or-flight response. Epinephrine increases cAMP, glucose, lactate, and free fatty acids. ---
Correct answer: C – Phenylephrine
A transplanted heart is denervated (no sympathetic or parasympathetic innervation). It responds only to circulating catecholamines via direct receptor stimulation. Phenylephrine is a selective α1 agonist with no direct cardiac effects. Any heart rate changes would be indirect (reflex bradycardia from vasoconstriction), but reflexes are absent in denervated hearts. --- AUTACOIDS
Correct answer: C – L-histidine decarboxylase
L-histidine decarboxylase is the enzyme responsible for converting L-histidine to histamine by removing the carboxyl group. This occurs primarily in mast cells, basophils, and gastric enterochromaffin-like cells. Histamine is then stored in granules until released by various stimuli. ---
Correct answer: B – Cholinergic
First-generation antihistamines have anticholinergic (antimuscarinic) properties in addition to H₁ blockade. Blockade of muscarinic receptors in the bladder detrusor muscle and internal sphincter leads to urinary retention. Other anticholinergic effects include dry mouth, constipation, and blurred vision. ---
Correct answer: B – Choline acetyltransferase
Choline acetyltransferase (ChAT) catalyzes the synthesis of acetylcholine from acetyl-CoA and choline in the presynaptic nerve terminal. The reaction occurs in the cytoplasm, and acetylcholine is then transported into synaptic vesicles by vesicular acetylcholine transporter (VAChT). ---
Correct answer: C – Hemicholinium
Hemicholinium blocks the sodium-dependent high-affinity choline transporter at the presynaptic membrane, preventing choline uptake. This depletes the substrate needed for acetylcholine synthesis, ultimately leading to neuromuscular blockade. It's used experimentally but not clinically. ---
Correct answer: B – Diarrhoea
Carcinoid syndrome, caused by serotonin-secreting tumors, produces excessive 5-HT₃ and 5-HT₄ receptor stimulation in the GI tract. This increases intestinal secretions and motility, leading to chronic diarrhea. Other symptoms include flushing, bronchoconstriction, and right-sided valvular heart disease. ---
Correct answer: C – Serotonin
Serotonin (5-hydroxytryptamine, 5-HT) is synthesized from the amino acid tryptophan through hydroxylation and decarboxylation. It's an indole-ethylamine found in enterochromaffin cells (90%), platelets, and CNS neurons. It regulates mood, sleep, appetite, and GI motility. ---
Correct answer: D – All of the above
Serotonin has complex cardiovascular effects: (1) Vasodilation in skeletal muscle via 5-HT₇ receptors and NO release; (2) Reflex bradycardia from baroreceptor activation (Bezold-Jarisch reflex); (3) Vasoconstriction in splanchnic, renal, and pulmonary circulation via 5-HT₂ receptors. ---
Correct answer: D – None of the above
Bradykinin causes relaxation (not contraction) of vascular smooth muscle, leading to vasodilation and increased vascular permeability. It stimulates endothelial cells to release nitric oxide (NO) and prostacyclin (PGI₂), producing vasodilation. It also causes pain and is involved in inflammatory responses. --- ANTIMICROBIAL AGENTS