Adrenergic receptors — especially beta adrenergic receptors — are central to cardiovascular, respiratory, and metabolic pharmacology. This concise introduction reviews beta receptor subtypes (β1, β2, β3), their Gs-coupled signal transduction, physiological actions like increased heart rate, bronchodilation, and lipolysis, and key drug classes such as selective agonists, nonselective and β1-selective blockers, and long-acting beta agonists. Designed for B. Pharm students, these MCQs emphasize receptor pharmacodynamics, binding affinity, partial agonism, intrinsic sympathomimetic activity, desensitization and clinical applications including hypertension, asthma, and heart failure. Clear explanations will strengthen exam preparation and practical understanding. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which subtypes are classified as beta adrenergic receptors?
- β1 only
- β2 only
- β3 only
- β1, β2 and β3
Correct Answer: β1, β2 and β3
Q2. Which G-protein is predominantly coupled to beta adrenergic receptors?
- Gi
- Gs
- Gq
- G12/13
Correct Answer: Gs
Q3. Activation of β1 receptors in the heart primarily causes:
- Bronchodilation
- Decreased heart rate
- Increased heart rate and contractility
- Vasoconstriction in skeletal muscle
Correct Answer: Increased heart rate and contractility
Q4. Which clinical drug is a selective β1 agonist commonly used in cardiogenic shock?
- Isoproterenol
- Dobutamine
- Salbutamol
- Propranolol
Correct Answer: Dobutamine
Q5. Salbutamol (albuterol) primarily targets which beta receptor subtype to relieve bronchospasm?
- β1
- β2
- β3
- α1
Correct Answer: β2
Q6. Mirabegron is a therapeutic agonist for which beta receptor subtype used to treat overactive bladder?
- β1
- β2
- β3
- β4
Correct Answer: β3
Q7. Chronic agonist exposure of beta receptors typically leads to:
- Up-regulation of receptor numbers
- Down-regulation and desensitization
- No change in receptor density
- Conversion to alpha receptors
Correct Answer: Down-regulation and desensitization
Q8. Which cellular proteins phosphorylate activated beta receptors to initiate desensitization?
- Protein tyrosine kinases (PTKs)
- G protein-coupled receptor kinases (GRKs)
- MAP kinases
- Phospholipase C
Correct Answer: G protein-coupled receptor kinases (GRKs)
Q9. Recruitment of which protein leads to receptor internalization after GRK phosphorylation?
- Arrestin
- Calmodulin
- CREB
- Phosphodiesterase
Correct Answer: Arrestin
Q10. Beta receptor activation leads to increased intracellular cAMP via stimulation of:
- Adenylyl cyclase
- Guanylyl cyclase
- Phospholipase C
- Tyrosine kinase
Correct Answer: Adenylyl cyclase
Q11. Which effect is mediated mainly by β2 receptor activation in skeletal muscle vasculature?
- Vasoconstriction
- Vasodilation
- Platelet aggregation
- Renin inhibition
Correct Answer: Vasodilation
Q12. A nonselective beta blocker that crosses the blood–brain barrier due to high lipophilicity is:
- Atenolol
- Nadolol
- Propranolol
- Sotalol
Correct Answer: Propranolol
Q13. Which beta blocker is β1-selective and hydrophilic, commonly used with lower CNS penetration?
- Propranolol
- Atenolol
- Metoprolol (lipophilic)
- Carvedilol
Correct Answer: Atenolol
Q14. Intrinsic sympathomimetic activity (ISA) of some beta blockers results in:
- Pure antagonism with no activity
- Partial agonist activity at beta receptors
- Strong inverse agonism only
- Alpha-1 receptor blockade
Correct Answer: Partial agonist activity at beta receptors
Q15. Which of the following drugs exhibits ISA?
- Pindolol
- Propranolol
- Atenolol
- Bisoprolol
Correct Answer: Pindolol
Q16. Beta-adrenergic stimulation of juxtaglomerular cells primarily increases:
- ADH release
- Renin release
- Aldosterone breakdown
- ANP secretion
Correct Answer: Renin release
Q17. Long-acting β2 agonists (LABAs) like salmeterol are mainly used for:
- Acute asthma attacks only
- Maintenance therapy and prevention of bronchospasm
- Hypertension emergency
- Cardiac arrest resuscitation
Correct Answer: Maintenance therapy and prevention of bronchospasm
Q18. Which mechanism explains bronchodilation on β2 receptor activation?
- Decreased cAMP in airway smooth muscle
- Increased cAMP leading to smooth muscle relaxation
- Opening of voltage-gated calcium channels
- Increased phospholipase C activity
Correct Answer: Increased cAMP leading to smooth muscle relaxation
Q19. Which property determines a drug’s ability to occupy receptors at low concentration?
- Efficacy
- Potency (affinity)
- Intrinsic activity
- Bioavailability
Correct Answer: Potency (affinity)
Q20. A partial agonist at beta receptors has which profile compared with a full agonist?
- Higher maximal response
- Lower efficacy but can antagonize full agonists
- No receptor binding
- Identical efficacy at all concentrations
Correct Answer: Lower efficacy but can antagonize full agonists
Q21. Which beta blocker also blocks α1 receptors and is used for hypertension with added vasodilation?
- Propranolol
- Carvedilol
- Pindolol
- Acebutolol
Correct Answer: Carvedilol
Q22. Which laboratory measure would most directly reflect increased β1 receptor activation in the heart?
- Decrease in plasma renin activity
- Increase in heart rate and contractility
- Bronchoconstriction
- Decreased lipolysis
Correct Answer: Increase in heart rate and contractility
Q23. Which β2-selective agonist has a rapid onset and is used for acute bronchospasm?
- Salmeterol
- Formoterol
- Salbutamol (albuterol)
- Mirabegron
Correct Answer: Salbutamol (albuterol)
Q24. Beta-3 receptor activation in adipose tissue primarily increases:
- Glycogen synthesis
- Lipolysis and thermogenesis
- Smooth muscle contraction
- Platelet aggregation
Correct Answer: Lipolysis and thermogenesis
Q25. Which pharmacodynamic term describes the maximal effect a drug can produce?
- Potency
- Efficacy
- Affinity
- Selectivity
Correct Answer: Efficacy
Q26. Beta blockers are relatively contraindicated in which condition due to risk of bronchospasm?
- Stable angina
- Asthma and reactive airway disease
- Hypertension with tachycardia
- Essential tremor
Correct Answer: Asthma and reactive airway disease
Q27. Which effect is a common adverse effect of nonselective beta blockade?
- Hyperglycemia in type 1 diabetics
- Bronchospasm
- Tachycardia
- Excessive sweating
Correct Answer: Bronchospasm
Q28. Which measurement assesses drug binding affinity to the receptor in vitro?
- EC50
- KD
- Emax
- Half-life
Correct Answer: KD
Q29. Isoproterenol is best described as:
- Selective β1 antagonist
- Nonselective beta agonist
- Selective β2 antagonist
- α1 agonist
Correct Answer: Nonselective beta agonist
Q30. Beta receptor blockade reduces blood pressure partly by decreasing:
- Cardiac output and renin release
- Peripheral insulin sensitivity
- Bronchodilation
- Hematocrit
Correct Answer: Cardiac output and renin release
Q31. Which of the following is a long-acting β2 agonist with faster onset suitable for maintenance therapy?
- Salmeterol
- Formoterol
- Terbutaline
- Propranolol
Correct Answer: Formoterol
Q32. The primary intracellular effector activated by cAMP in beta receptor signaling is:
- Protein kinase A (PKA)
- Protein kinase C (PKC)
- Calcium/calmodulin kinase II
- Tyrosine kinase
Correct Answer: Protein kinase A (PKA)
Q33. Use of a nonselective beta blocker in pheochromocytoma without prior alpha blockade can cause:
- Severe hypertension due to unopposed alpha stimulation
- Marked hypotension
- Bronchodilation
- Hypoglycemia
Correct Answer: Severe hypertension due to unopposed alpha stimulation
Q34. Which beta blocker is known for combined alpha-1 blockade and antioxidant properties used in heart failure?
- Atenolol
- Carvedilol
- Pindolol
- Propranolol
Correct Answer: Carvedilol
Q35. Tachyphylaxis to β2 agonists during repeated dosing is primarily due to:
- Enzyme induction
- Receptor desensitization and down-regulation
- Increased drug absorption
- Enhanced receptor synthesis
Correct Answer: Receptor desensitization and down-regulation
Q36. Which feature distinguishes a selective β1 blocker from a nonselective beta blocker?
- Blockade of bronchial β2 receptors
- Preferential cardiac receptor blockade at therapeutic doses
- Alpha receptor blockade
- Intrinsic sympathomimetic activity always present
Correct Answer: Preferential cardiac receptor blockade at therapeutic doses
Q37. Which pharmacokinetic property most influences how often a beta agonist inhaler must be dosed?
- First-pass hepatic metabolism
- Duration of action (half-life) and receptor residence time
- Plasma protein binding only
- Renal clearance solely
Correct Answer: Duration of action (half-life) and receptor residence time
Q38. A drug that decreases the constitutive activity of a receptor below basal level is called a:
- Partial agonist
- Inverse agonist
- Neutral antagonist
- Allosteric potentiator
Correct Answer: Inverse agonist
Q39. Which receptor subtype is primarily responsible for beta-mediated glycogenolysis in the liver?
- β1
- β2
- β3
- M2 muscarinic
Correct Answer: β2
Q40. When switching a patient from a beta blocker to withdrawal, abrupt cessation may cause:
- Improved tolerance without risks
- Rebound tachycardia and angina due to receptor up-regulation
- Permanent receptor loss
- Immediate enhancement of bronchodilation
Correct Answer: Rebound tachycardia and angina due to receptor up-regulation
Q41. Which assay parameter describes the concentration of agonist producing 50% of maximal effect?
- KD
- EC50
- Emax
- IC50
Correct Answer: EC50
Q42. Nebivolol is a β1-selective blocker with an additional vasodilatory effect mediated by:
- α2 blockade
- Endothelial nitric oxide release
- Direct calcium channel blockade
- β3 agonism in adipose tissue
Correct Answer: Endothelial nitric oxide release
Q43. Which clinical scenario would favor use of a β1-selective blocker over a nonselective agent?
- Patient with severe asthma
- Congestive heart failure requiring alpha blockade
- Hypertensive patient with severe peripheral vascular disease
- Hypoglycemic-prone diabetic where bronchoconstriction must be avoided
Correct Answer: Patient with severe asthma
Q44. Beta receptor coupling to Gs leads to which sequence?
- Gs → decreased adenylyl cyclase → decreased cAMP
- Gs → increased adenylyl cyclase → increased cAMP → PKA activation
- Gs → activation of phospholipase C → IP3/DAG
- Gs → direct opening of potassium channels only
Correct Answer: Gs → increased adenylyl cyclase → increased cAMP → PKA activation
Q45. Which beta receptor subtype is most implicated in uterine relaxation during pregnancy?
- β1
- β2
- β3
- α2
Correct Answer: β2
Q46. A neutral antagonist at beta receptors would be expected to:
- Reduce basal receptor activity below zero
- Block agonist binding without changing constitutive activity
- Act as a partial agonist
- Directly activate Gq signaling
Correct Answer: Block agonist binding without changing constitutive activity
Q47. Which clinical effect is expected when β2 receptors on skeletal muscle are activated?
- Bronchoconstriction
- Increased glycogenolysis and potassium uptake into muscle
- Decreased blood flow to skeletal muscle
- Reduced tremor
Correct Answer: Increased glycogenolysis and potassium uptake into muscle
Q48. The phenomenon where chronic blockade of receptors leads to increased receptor density is called:
- Down-regulation
- Up-regulation (supersensitivity)
- Desensitization
- Agonist tachyphylaxis
Correct Answer: Up-regulation (supersensitivity)
Q49. Which beta antagonist is commonly used for migraine prophylaxis due to central nervous system penetration?
- Atenolol
- Propranolol
- Nadolol (hydrophilic)
- Metoprolol (no CNS penetration)
Correct Answer: Propranolol
Q50. In receptor binding theory, a drug with high affinity and low intrinsic efficacy is best described as:
- Full agonist
- Partial agonist
- Inverse agonist
- Noncompetitive antagonist
Correct Answer: Partial agonist
