Cholinergic Agonists and Antagonists Quiz

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Questions and Answers

What is the primary action of cholinergic agonists on the parasympathetic nervous system?

  • They inhibit the action of acetylcholine.
  • They mimic the effects of acetylcholine. (correct)
  • They decrease the production of acetylcholine.
  • They block the receptors for acetylcholine.

Which type of cholinergic receptor is primarily responsible for stimulating smooth muscle and slowing the heart rate?

  • Beta receptors
  • Muscarinic receptors (correct)
  • Nicotinic receptors
  • Alpha receptors

What is the primary function of cholinesterase in the nervous system?

  • To synthesize acetylcholine.
  • To break down acetylcholine. (correct)
  • To bind to acetylcholine receptors.
  • To stimulate the release of acetylcholine.

What is the primary mechanism of action of indirect-acting cholinergic agonists?

<p>They inhibit the breakdown of acetylcholine. (C)</p> Signup and view all the answers

Which of the following is NOT a common response to the administration of cholinergic agonists?

<p>Increased heart rate (D)</p> Signup and view all the answers

Which of the following pairs of cholinergic receptors are found in the skeletal muscles?

<p>Nicotinic and Muscarinic (C)</p> Signup and view all the answers

What is the difference between reversible and irreversible cholinesterase inhibitors?

<p>Reversible inhibitors have a shorter duration of action than irreversible inhibitors (C)</p> Signup and view all the answers

What is the primary clinical application of cholinesterase inhibitors?

<p>Treatment of Alzheimer's disease. (B)</p> Signup and view all the answers

What are the two main categories of adrenergic antagonists based on receptor selectivity?

<p>Alpha and beta (D)</p> Signup and view all the answers

How do alpha-blocking agents work?

<p>They directly block alpha receptors. (B)</p> Signup and view all the answers

What is a key difference between selective and nonselective alpha blockers?

<p>Selective alpha blockers only block alpha1 receptors, while nonselective block both alpha1 and alpha2 receptors. (A)</p> Signup and view all the answers

What is a potential adverse effect of nonselective beta blockers?

<p>Bronchoconstriction (B)</p> Signup and view all the answers

Which of the following is a clinical use of adrenergic neuron blockers?

<p>Treatment of hypertension (D)</p> Signup and view all the answers

What is the mechanism by which beta blockers decrease heart rate?

<p>They block beta receptors, preventing the effects of neurotransmitters. (A)</p> Signup and view all the answers

What is a potential consequence of abruptly discontinuing beta blockers?

<p>Tachycardia (C)</p> Signup and view all the answers

Why is the use of nonselective beta blockers contraindicated in patients with asthma?

<p>Nonselective beta blockers cause bronchoconstriction, worsening asthma symptoms. (D)</p> Signup and view all the answers

What is the primary use of irreversible cholinesterase inhibitors?

<p>Treatment of glaucoma (D)</p> Signup and view all the answers

What is the primary clinical indication for reversible cholinesterase inhibitors?

<p>Treatment of myasthenia gravis (A)</p> Signup and view all the answers

What is the mechanism of action of cholinergic antagonists?

<p>They occupy acetylcholine receptors, blocking acetylcholine binding (C)</p> Signup and view all the answers

What is the main effect of anticholinergics on the heart?

<p>Increased heart rate (B)</p> Signup and view all the answers

What is the main effect of anticholinergics on the gastrointestinal tract?

<p>Decreased motility (A)</p> Signup and view all the answers

Which of the following is NOT a common effect of anticholinergics?

<p>Increased bladder contraction (D)</p> Signup and view all the answers

Which type of cholinergic receptor is primarily involved in the effects of anticholinergics?

<p>Muscarinic receptors (B)</p> Signup and view all the answers

What is the primary effect of anticholinergics on the central nervous system (CNS)?

<p>Suppression of tremors and muscular rigidity associated with Parkinsonism (D)</p> Signup and view all the answers

What is the mechanism by which direct-acting sympathomimetics exert their effect?

<p>They directly stimulate adrenergic receptors (B)</p> Signup and view all the answers

Which of the following is NOT an endogenous catecholamine?

<p>Isoproterenol (C)</p> Signup and view all the answers

What is the main effect of stimulating alpha1-adrenergic receptors?

<p>Vasoconstriction (C)</p> Signup and view all the answers

Which of the following enzymes is responsible for the inactivation of norepinephrine inside the neuron?

<p>Monoamine oxidase (MAO) (D)</p> Signup and view all the answers

What is the mechanism of action of alpha2-adrenergic agonists?

<p>Indirect stimulation of alpha2-adrenergic receptors by inhibiting the release of norepinephrine (D)</p> Signup and view all the answers

What is the term for drugs that block the effects of adrenergic neurotransmitters?

<p>Adrenergic antagonists (D)</p> Signup and view all the answers

Flashcards

Cholinergic Agonists

Drugs that stimulate the parasympathetic nervous system by mimicking acetylcholine.

Cholinergic Antagonists

Drugs that block the action of acetylcholine in the parasympathetic nervous system.

Muscarinic Receptors

Cholinergic receptors that stimulate smooth muscle and slow heart rate.

Nicotinic Receptors

Cholinergic receptors affecting skeletal muscles.

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Direct-Acting Agonists

Cholinergic agonists that activate receptors directly for a tissue response.

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Cholinesterase Inhibitors

Drugs that inhibit the enzyme cholinesterase, allowing acetylcholine to accumulate.

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Reversible Inhibitors

Cholinesterase inhibitors that bind the enzyme for minutes to hours.

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Irreversible Inhibitors

Cholinesterase inhibitors that permanently bind to the enzyme.

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Reversible cholinesterase inhibitors

Drugs used to treat myasthenia gravis and Alzheimer's disease.

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Irreversible cholinesterase inhibitors

Potent agents primarily indicated for glaucoma treatment.

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Effects of anticholinergics

Decrease GI motility and salivation, cause mydriasis and increased heart rate.

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Mydriasis

Dilation of the pupils, often caused by anticholinergic drugs.

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Adrenergic agonists

Drugs that stimulate the sympathetic nervous system.

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Alpha1 receptors

Adrenergic receptors involved in vasoconstriction and increased blood return.

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Beta1 receptors

Adrenergic receptors increasing heart rate and myocardial contractility.

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Beta2 receptors

Adrenergic receptors that relax smooth muscles and decrease GI motility.

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Dopaminergic receptors

Receptors that dilate renal, mesenteric, coronary, and cerebral arteries.

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Monoamine oxidase (MAO)

An enzyme that inactivates norepinephrine inside the neuron.

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Sympathomimetic drugs

Drugs mimicking sympathetic nervous system responses, categorized into three types.

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Nonselective adrenergic drugs

Drugs that stimulate multiple adrenergic receptor sites.

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Adrenergic antagonists

Drugs that block alpha- and beta-receptors, inhibiting neurotransmitter effects.

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Alpha-adrenergic antagonists

Drugs that specifically block alpha receptors, can be selective or nonselective.

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Selective vs Nonselective alpha blockers

Selective blocks alpha1; nonselective blocks both alpha1 and alpha2.

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Beta blockers

Drugs that block beta receptors, reducing heart rate and lowering blood pressure.

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Intrinsic sympathomimetic activity (ISA)

Property of some beta blockers that partially activate beta receptors, preventing full activation.

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Effects of beta blockers

Useful for treating hypertension, angina, and myocardial infarction, but should not be stopped abruptly.

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Adrenergic neuron blockers

Drugs that inhibit norepinephrine release from sympathetic neurons, reducing blood pressure.

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Consequences of abrupt beta blocker cessation

Stopping suddenly can lead to tachycardia, hypertension, and increased risk of myocardial infarction.

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Study Notes

Cholinergic Agonists and Antagonists

  • Cholinergic agonists (parasympathomimetics) mimic acetylcholine, a parasympathetic neurotransmitter.
  • Cholinergic receptors include muscarinic (smooth muscle, heart rate) and nicotinic (skeletal muscle).
  • Cholinergic agonists are categorized as direct-acting (receptor activation) or indirect-acting (inhibiting cholinesterase).
  • Cholinesterase inhibitors (acetylcholinesterase inhibitors/anticholinesterases) prevent acetylcholine breakdown.
  • Reversible inhibitors bind cholinesterase temporarily (minutes to hours).
  • Irreversible inhibitors permanently bind cholinesterase.
  • Major cholinergic agonist responses: increased bladder/GI tone, miosis (pupil constriction), and increased neuromuscular transmission. Other effects include decreased heart rate/blood pressure and increased secretions.
  • Cholinesterase inhibitors treat myasthenia gravis and Alzheimer's disease.
  • Irreversible cholinesterase inhibitors primarily treat glaucoma.
  • Cholinergic antagonists (muscarinic antagonists/anticholinergics) block acetylcholine's actions at receptors.
  • Key organs affected by anticholinergics: heart, respiratory tract, GI tract, urinary bladder, eyes, and exocrine glands
  • Anticholinergics produce opposite effects to cholinergic agonists (decreased GI motility, salivation, increased pulse rate).
  • Anticholinergics block the parasympathetic system, allowing the sympathetic system to dominate.
  • Anticholinergics are used to lessen tremors and rigidity in parkinsonism.

Adrenergic Agonists and Antagonists

  • Adrenergic agonists (sympathomimetics) mimic the sympathetic neurotransmitters norepinephrine and epinephrine.
  • Adrenergic agonists act on several receptors in various tissues (e.g., heart, lungs, GI tract).
  • Key adrenergic receptors include alpha1, alpha2, beta1, beta2 (and dopaminergic).
  • Alpha1 receptors cause vasoconstriction.
  • Alpha2 receptors inhibit norepinephrine release, reducing vasoconstriction.
  • Beta1 receptors increase heart rate and contractility.
  • Beta2 receptors relax smooth muscles (lungs, GI tract).
  • Dopaminergic receptors cause vasodilation.
  • Neurotransmitter inactivation occurs through reuptake, enzymatic degradation (e.g., MAO, COMT), or diffusion.
  • Drugs can prolong neurotransmitter action by inhibiting reuptake or degradation.
  • Adrenergic agonists are classified as direct-acting, indirect-acting, or mixed-acting.
  • Catecholamines include epinephrine, norepinephrine, and dopamine (endogenous). Synthetic catecholamines include isoproterenol and dobutamine.
  • Epinephrine acts on multiple receptors (alpha1, beta1, beta2).
  • Nonselective drugs affect more than one receptor; selective drugs affect a specific receptor.
  • Alpha2 drugs reduce blood pressure centrally.
  • Adrenergic antagonists (sympatholytics) block adrenergic receptor sites, preventing neurotransmitter action.
  • Antagonists block alpha and beta receptors.
  • Alpha blockers (alpha1-blockers, nonselective alpha blockers) treat peripheral vascular disease and benign prostatic hyperplasia.
  • Beta blockers decrease heart rate which usually decreases blood pressure. Nonselective beta blockers block beta1 and beta2 (affect lungs).
  • Intrinsic sympathomimetic activity (ISA) describes the ability of certain beta blockers to partially activate receptors.
  • Beta blockers treat hypertension, angina, and myocardial infarction (MI)
  • Beta blockers should be tapered gradually.
  • Adrenergic neuron blockers decrease blood pressure by inhibiting norepinephrine release.

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