MCQ Quiz: Pharmacology of the Sympathetic System

Welcome, PharmD students, to this MCQ quiz on the Pharmacology of the Sympathetic Nervous System! The sympathetic ‘fight or flight’ system plays a critical role in regulating cardiovascular function, respiratory activity, and metabolic processes. Drugs that mimic or block the actions of endogenous catecholamines like norepinephrine and epinephrine are essential in treating a wide array of conditions. This quiz will test your understanding of adrenergic receptors, and the mechanisms, therapeutic applications, and adverse effects of sympathomimetic and sympatholytic agents. Let’s dive in!

1. The primary neurotransmitter released by most postganglionic sympathetic neurons is:

• a) Acetylcholine (ACh)
• b) Serotonin
• c) Norepinephrine (NE)
• d) Gamma-aminobutyric acid (GABA)

Answer: c) Norepinephrine (NE)

2. Stimulation of Alpha-1 (α1) adrenergic receptors typically leads to:

• a) Bronchodilation.
• b) Vasoconstriction of peripheral blood vessels, increased blood pressure, and mydriasis.
• c) Decreased heart rate and contractility.
• d) Inhibition of norepinephrine release.

Answer: b) Vasoconstriction of peripheral blood vessels, increased blood pressure, and mydriasis.

3. Beta-1 (β1) adrenergic receptors are predominantly located in the:

• a) Bronchial smooth muscle and skeletal muscle vasculature.
• b) Heart (increasing heart rate and contractility) and kidney (stimulating renin release).
• c) Presynaptic nerve terminals.
• d) Uterine smooth muscle.

Answer: b) Heart (increasing heart rate and contractility) and kidney (stimulating renin release).

4. Stimulation of Beta-2 (β2) adrenergic receptors results in:

• a) Vasoconstriction and bronchoconstriction.
• b) Bronchodilation, vasodilation in skeletal muscle beds, and uterine relaxation.
• c) Increased heart rate only.
• d) Lipolysis in adipose tissue.

Answer: b) Bronchodilation, vasodilation in skeletal muscle beds, and uterine relaxation.

5. Phenylephrine is a sympathomimetic drug that acts primarily as a selective agonist at which receptors?

• a) Beta-1 adrenergic receptors
• b) Beta-2 adrenergic receptors
• c) Alpha-1 adrenergic receptors
• d) Alpha-2 adrenergic receptors

Answer: c) Alpha-1 adrenergic receptors

6. Clonidine lowers blood pressure by acting as an agonist at _______ receptors in the brainstem, which reduces sympathetic outflow.

• a) Alpha-1 adrenergic
• b) Central Alpha-2 adrenergic
• c) Beta-1 adrenergic
• d) Dopamine D1

Answer: b) Central Alpha-2 adrenergic

7. Albuterol is a commonly used bronchodilator that selectively stimulates which receptors in the lungs?

• a) Alpha-1 adrenergic receptors
• b) Beta-1 adrenergic receptors
• c) Beta-2 adrenergic receptors
• d) Muscarinic M3 receptors

Answer: c) Beta-2 adrenergic receptors

8. Dobutamine is an adrenergic agonist primarily used in acute heart failure for its relatively selective agonist activity at:

• a) Alpha-1 receptors, causing vasoconstriction.
• b) Beta-1 receptors, increasing myocardial contractility with less effect on heart rate than isoproterenol.
• c) Beta-2 receptors, causing bronchodilation.
• d) Dopamine receptors, causing renal vasodilation.

Answer: b) Beta-1 receptors, increasing myocardial contractility with less effect on heart rate than isoproterenol.

9. Epinephrine is a potent, non-selective adrenergic agonist. Its effects include:

• a) Only vasodilation.
• b) Increased heart rate and contractility (β1), bronchodilation (β2), and vasoconstriction in many vascular beds (α1).
• c) Only decreased heart rate.
• d) Only pupillary constriction.

Answer: b) Increased heart rate and contractility (β1), bronchodilation (β2), and vasoconstriction in many vascular beds (α1).

10. Prazosin, doxazosin, and terazosin are drugs that selectively block which adrenergic receptors, leading to vasodilation and relaxation of smooth muscle in the bladder neck and prostate?

• a) Alpha-2 adrenergic receptors
• b) Beta-1 adrenergic receptors
• c) Beta-2 adrenergic receptors
• d) Alpha-1 adrenergic receptors

Answer: d) Alpha-1 adrenergic receptors

11. Propranolol is a non-selective beta-blocker. This means it blocks:

• a) Only Beta-1 receptors.
• b) Only Beta-2 receptors.
• c) Both Beta-1 and Beta-2 receptors.
• d) Alpha-1 and Beta-1 receptors.

Answer: c) Both Beta-1 and Beta-2 receptors.

12. A potential adverse effect of using a non-selective beta-blocker like propranolol in a patient with asthma is:

• a) Tachycardia
• b) Bronchodilation
• c) Bronchoconstriction (due to β2 blockade)
• d) Hypertension

Answer: c) Bronchoconstriction (due to β2 blockade)

13. Metoprolol and atenolol are examples of _______ beta-blockers, meaning they have a greater affinity for β1 receptors than β2 receptors at therapeutic doses.

• a) Non-selective
• b) Cardioselective
• c) Alpha-1 selective
• d) Mixed alpha and beta

Answer: b) Cardioselective

14. Labetalol and carvedilol are unique beta-blockers because they also possess blocking activity at which other adrenergic receptor?

• a) Alpha-2 receptors
• b) Beta-2 receptors only
• c) Alpha-1 receptors, contributing to their vasodilating effects.
• d) Dopamine receptors

Answer: c) Alpha-1 receptors, contributing to their vasodilating effects.

15. Amphetamine and tyramine exert their sympathomimetic effects primarily by:

• a) Directly agonizing adrenergic receptors.
• b) Inhibiting acetylcholinesterase.
• c) Promoting the release of stored norepinephrine from sympathetic nerve terminals.
• d) Blocking muscarinic receptors.

Answer: c) Promoting the release of stored norepinephrine from sympathetic nerve terminals.

16. Cocaine is an indirect-acting sympathomimetic that blocks the reuptake of which neurotransmitters into presynaptic neurons?

• a) Only acetylcholine.
• b) Norepinephrine, dopamine, and serotonin.
• c) Only GABA.
• d) Only histamine.

Answer: b) Norepinephrine, dopamine, and serotonin.

17. Ephedrine and pseudoephedrine are considered mixed-acting sympathomimetics because they:

• a) Only block adrenergic receptors.
• b) Directly stimulate adrenergic receptors and also cause the release of endogenous norepinephrine.
• c) Only inhibit MAO.
• d) Only stimulate cholinergic receptors.

Answer: b) Directly stimulate adrenergic receptors and also cause the release of endogenous norepinephrine.

18. The enzyme primarily responsible for the metabolic breakdown of norepinephrine within the sympathetic nerve terminal is:

• a) Catechol-O-methyltransferase (COMT)
• b) Monoamine Oxidase (MAO)
• c) Acetylcholinesterase
• d) Tyrosine hydroxylase

Answer: b) Monoamine Oxidase (MAO)

19. Catechol-O-methyltransferase (COMT) is an enzyme involved in the metabolism of catecholamines (like NE and Epi) primarily in the:

• a) Presynaptic nerve terminal.
• b) Synaptic cleft and extraneuronal tissues (e.g., liver, kidney).
• c) Adrenal medulla only.
• d) Brain only.

Answer: b) Synaptic cleft and extraneuronal tissues (e.g., liver, kidney).

20. The “first-dose phenomenon,” characterized by marked postural hypotension and syncope, is a potential adverse effect associated with the initiation of therapy with:

• a) Beta-2 agonists
• b) Alpha-1 selective antagonists (e.g., prazosin)
• c) Non-selective beta-blockers
• d) Muscarinic agonists

Answer: b) Alpha-1 selective antagonists (e.g., prazosin)

21. Mirabegron is a newer drug used for overactive bladder that acts as a selective agonist at which receptor, leading to detrusor muscle relaxation?

• a) Beta-1 adrenergic receptor
• b) Beta-2 adrenergic receptor
• c) Beta-3 adrenergic receptor
• d) Alpha-1 adrenergic receptor

Answer: c) Beta-3 adrenergic receptor

22. Dopamine, when administered at low doses (e.g., 1-2 mcg/kg/min IV), primarily stimulates D1 receptors in the renal vasculature, leading to:

• a) Renal vasoconstriction.
• b) Renal vasodilation and increased renal blood flow.
• c) No effect on renal blood flow.
• d) Systemic hypertension.

Answer: b) Renal vasodilation and increased renal blood flow.

23. Phentolamine is a non-selective alpha-adrenergic antagonist that blocks both α1 and α2 receptors. It is sometimes used in the management of:

• a) Asthma
• b) Hypertensive emergencies due to catecholamine excess (e.g., pheochromocytoma).
• c) Bradycardia
• d) Motion sickness

Answer: b) Hypertensive emergencies due to catecholamine excess (e.g., pheochromocytoma).

24. Phenoxybenzamine is an irreversible, non-selective alpha-adrenergic antagonist primarily used in the preoperative management of:

• a) Acute myocardial infarction.
• b) Pheochromocytoma to control hypertension and prevent catecholamine-induced hypertensive crises.
• c) Glaucoma.
• d) Asthma.

Answer: b) Pheochromocytoma to control hypertension and prevent catecholamine-induced hypertensive crises.

25. Beta-blockers are contraindicated or should be used with extreme caution in patients with:

• a) Hypertension.
• b) Angina pectoris.
• c) Severe bradycardia, second- or third-degree heart block (without a pacemaker), or decompensated heart failure.
• d) Migraine headaches.

Answer: c) Severe bradycardia, second- or third-degree heart block (without a pacemaker), or decompensated heart failure.

26. The therapeutic effect of alpha-2 agonists like clonidine in treating hypertension is often limited by side effects such as:

• a) Tachycardia and agitation.
• b) Sedation, dry mouth, and potential for rebound hypertension upon abrupt withdrawal.
• c) Bronchoconstriction.
• d) Severe peripheral edema.

Answer: b) Sedation, dry mouth, and potential for rebound hypertension upon abrupt withdrawal.

27. Which of the following is a primary therapeutic use for selective alpha-1 adrenergic agonists like phenylephrine?

• a) Treatment of asthma.
• b) As a nasal decongestant (topical/oral) or to increase blood pressure in certain hypotensive states.
• c) Management of benign prostatic hyperplasia.
• d) Treatment of glaucoma.

Answer: b) As a nasal decongestant (topical/oral) or to increase blood pressure in certain hypotensive states.

28. The synthesis of norepinephrine begins with which amino acid precursor?

• a) Tryptophan
• b) Tyrosine
• c) Phenylalanine
• d) Methionine

Answer: b) Tyrosine (Tyrosine -> DOPA -> Dopamine -> Norepinephrine)

29. Nebivolol is a cardioselective beta-blocker that also has vasodilating properties, believed to be mediated by:

• a) Alpha-1 blockade.
• b) Stimulation of nitric oxide (NO) release from endothelial cells.
• c) Beta-2 agonism.
• d) Calcium channel blockade.

Answer: b) Stimulation of nitric oxide (NO) release from endothelial cells.

30. “Intrinsic Sympathomimetic Activity” (ISA) found in some beta-blockers like pindolol means these drugs act as:

• a) Full agonists at beta receptors.
• b) Irreversible antagonists at beta receptors.
• c) Partial agonists at beta receptors, causing some receptor activation while also blocking endogenous catecholamines.
• d) Pure alpha receptor antagonists.

Answer: c) Partial agonists at beta receptors, causing some receptor activation while also blocking endogenous catecholamines.

31. One reason why cardioselective beta-blockers are generally preferred over non-selective beta-blockers in patients with asthma or COPD is that they:

• a) Cause more potent bronchodilation.
• b) Have less of an inhibitory effect on β2 receptors in the lungs, reducing the risk of bronchoconstriction.
• c) Are always more effective at lowering blood pressure.
• d) Have no effect on heart rate.

Answer: b) Have less of an inhibitory effect on β2 receptors in the lungs, reducing the risk of bronchoconstriction.

32. A significant drug interaction can occur between MAO inhibitors and indirect-acting sympathomimetics (like tyramine in foods) because MAO inhibitors:

• a) Increase the reuptake of norepinephrine.
• b) Prevent the breakdown of norepinephrine and tyramine, leading to an exaggerated release of NE and potentially a hypertensive crisis.
• c) Directly block adrenergic receptors.
• d) Enhance the metabolism of sympathomimetics.

Answer: b) Prevent the breakdown of norepinephrine and tyramine, leading to an exaggerated release of NE and potentially a hypertensive crisis.

33. The pharmacological effects of stimulating β3-adrenergic receptors include:

• a) Bronchoconstriction.
• b) Increased heart rate.
• c) Lipolysis in adipose tissue and relaxation of the detrusor muscle of the bladder.
• d) Vasoconstriction.

Answer: c) Lipolysis in adipose tissue and relaxation of the detrusor muscle of the bladder.

34. What is the primary mechanism by which norepinephrine’s action is terminated in the synaptic cleft?

• a) Enzymatic degradation by acetylcholinesterase.
• b) Reuptake into the presynaptic neuron via the norepinephrine transporter (NET).
• c) Diffusion away from the cleft and uptake by extraneuronal tissues.
• d) Binding to muscarinic receptors.

Answer: b) Reuptake into the presynaptic neuron via the norepinephrine transporter (NET).

35. Which adrenergic agonist is the drug of choice for treating anaphylactic shock due to its potent α1, β1, and β2 effects?

• a) Phenylephrine
• b) Albuterol
• c) Epinephrine
• d) Clonidine

Answer: c) Epinephrine

36. Reflex tachycardia can be a compensatory response seen after administration of drugs that cause significant:

• a) Bradycardia.
• b) Vasodilation and a drop in blood pressure (e.g., some alpha-1 blockers or direct vasodilators).
• c) Bronchoconstriction.
• d) Increased heart rate directly.

Answer: b) Vasodilation and a drop in blood pressure (e.g., some alpha-1 blockers or direct vasodilators).

37. Tamsulosin is an alpha-1 antagonist that is more selective for α1A receptors, which are predominantly found in the:

• a) Heart
• b) Bronchial smooth muscle
• c) Prostate and bladder neck
• d) Vascular smooth muscle throughout the body

Answer: c) Prostate and bladder neck (This contributes to its greater uroselectivity for BPH).

38. The “fight or flight” response initiated by the sympathetic nervous system includes all of the following physiological changes EXCEPT:

• a) Increased heart rate and blood pressure.
• b) Dilation of pupils (mydriasis).
• c) Increased gastrointestinal motility and secretion.
• d) Bronchodilation and mobilization of glucose.

Answer: c) Increased gastrointestinal motility and secretion. (Sympathetic system generally inhibits GI activity).

39. Abrupt withdrawal of clonidine therapy can lead to rebound hypertension. This is thought to be due to:

• a) Downregulation of alpha-2 receptors during treatment.
• b) Upregulation of sympathetic activity or receptor sensitivity when the inhibitory effect of clonidine is suddenly removed.
• c) Accumulation of clonidine metabolites.
• d) Permanent damage to baroreceptors.

Answer: b) Upregulation of sympathetic activity or receptor sensitivity when the inhibitory effect of clonidine is suddenly removed.

40. Which beta-blocker is very short-acting (half-life of minutes) and administered intravenously, often used for rapid control of ventricular rate in atrial fibrillation or for perioperative hypertension?

• a) Propranolol
• b) Atenolol
• c) Esmolol
• d) Nadolol

Answer: c) Esmolol (Metabolized by red blood cell esterases).

41. One of the therapeutic uses of beta-blockers in patients with ischemic heart disease (e.g., post-myocardial infarction) is to:

• a) Increase myocardial oxygen demand.
• b) Decrease myocardial oxygen demand by reducing heart rate, contractility, and blood pressure.
• c) Cause coronary vasodilation directly.
• d) Prevent platelet aggregation.

Answer: b) Decrease myocardial oxygen demand by reducing heart rate, contractility, and blood pressure.

42. The pharmacology of midodrine, an alpha-1 agonist, makes it useful for treating:

• a) Asthma
• b) Symptomatic orthostatic hypotension
• c) Pheochromocytoma
• d) Acute heart failure

Answer: b) Symptomatic orthostatic hypotension

43. Yohimbine is an older drug that acts as an alpha-2 antagonist. Its effect would be to:

• a) Decrease sympathetic outflow.
• b) Increase sympathetic outflow and norepinephrine release (by blocking presynaptic autoreceptors).
• c) Stimulate beta-1 receptors.
• d) Block alpha-1 receptors.

Answer: b) Increase sympathetic outflow and norepinephrine release (by blocking presynaptic autoreceptors).

44. A common adverse effect of beta-blockers related to their CNS penetration (especially lipophilic ones like propranolol) can be:

• a) Euphoria and agitation.
• b) Fatigue, lethargy, and sleep disturbances.
• c) Enhanced cognitive function.
• d) Severe psychosis.

Answer: b) Fatigue, lethargy, and sleep disturbances.

45. The primary reason beta-blockers can mask some symptoms of hypoglycemia in diabetic patients is that they:

• a) Increase blood glucose levels.
• b) Block the sympathoadrenal response (e.g., tachycardia, tremors) that often signals hypoglycemia.
• c) Enhance insulin secretion.
• d) Cause rapid glucose uptake into cells.

Answer: b) Block the sympathoadrenal response (e.g., tachycardia, tremors) that often signals hypoglycemia. (Sweating may still occur).

46. Tyrosine hydroxylase is the rate-limiting enzyme in the synthesis of:

• a) Acetylcholine
• b) Serotonin
• c) Catecholamines (dopamine, norepinephrine, epinephrine)
• d) Histamine

Answer: c) Catecholamines (dopamine, norepinephrine, epinephrine)

47. Drugs like labetalol and carvedilol are beneficial in certain cardiovascular conditions due to their combined pharmacological actions of:

• a) Beta-1 agonism and alpha-1 agonism.
• b) Beta-blockade (reducing cardiac work) and alpha-1 blockade (causing vasodilation, reducing afterload).
• c) Muscarinic agonism and nicotinic antagonism.
• d) Beta-2 antagonism and alpha-2 agonism.

Answer: b) Beta-blockade (reducing cardiac work) and alpha-1 blockade (causing vasodilation, reducing afterload).

48. The choice between a selective and non-selective beta-blocker often depends on:

• a) The cost of the medication only.
• b) Patient comorbidities, such as asthma or peripheral vascular disease, where β2 blockade could be detrimental.
• c) The color of the tablet.
• d) The pharmacist’s personal preference.

Answer: b) Patient comorbidities, such as asthma or peripheral vascular disease, where β2 blockade could be detrimental.

49. Oxymetazoline is a long-acting alpha-1 agonist found in OTC nasal decongestant sprays. Prolonged use (e.g., >3-5 days) can lead to:

• a) Systemic hypertension.
• b) Rhinitis medicamentosa (rebound nasal congestion).
• c) Severe bradycardia.
• d) Bronchodilation.

Answer: b) Rhinitis medicamentosa (rebound nasal congestion).

50. Understanding the pharmacology of the sympathetic system is crucial for pharmacists to:

• a) Synthesize catecholamines.
• b) Optimize drug therapy, predict and manage adverse effects, identify drug interactions, and counsel patients effectively on medications affecting this system.
• c) Perform autonomic function tests.
• d) Only dispense beta-blockers.

Answer: b) Optimize drug therapy, predict and manage adverse effects, identify drug interactions, and counsel patients effectively on medications affecting this system.