Questions and Answers
Which pharmacological effect is associated with beta-2 (β2) adrenergic receptors?
What is a contraindication for the use of adrenaline?
Which of the following effects is a result of norepinephrine administration?
What is a common adverse effect of adrenaline?
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Which of the following uses of adrenaline is appropriate for a medical emergency?
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Which metabolic action is primarily associated with beta-3 (β3) adrenergic receptors?
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In which condition is norepinephrine primarily used?
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What is the main action of alpha-1 (α1) adrenergic receptors on blood vessels?
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What is the primary function of α1-adrenoceptors?
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Which of the following best describes the function of β1-adrenoceptors?
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What is a major effect of β2-adrenoceptors on the respiratory system?
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What is the primary mechanism that ends the action of norepinephrine in synaptic space?
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How does the stimulation of presynaptic α2-adrenoceptors affect norepinephrine release?
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Which adrenergic receptor subtype primarily facilitates lipolysis in adipose tissue?
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What is a characteristic of catecholamines compared to non-catecholamines?
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What physiological effect does stimulation of β2-adrenoceptors have on the gastrointestinal tract?
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Which sympathomimetic specifically stimulates alpha-1 adrenergic receptors?
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Which of the following actions is NOT associated with sympathetic stimulation?
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Which of the following is a feature of indirect-acting sympathomimetics?
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What is a common use of adrenaline in medical settings?
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What distinguishes mixed sympathomimetics from other types?
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Which of the following characteristics applies to non-catecholamines?
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Which sympathomimetic agent is categorized as dual acting?
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Which drug is known for its selective stimulation of beta-2 adrenergic receptors?
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What action is primarily associated with the β1 receptors when activated by isoprenaline?
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Which is NOT a therapeutic use of isoprenaline?
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What is a key effect of dopamine at low doses?
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Which condition is dobutamine primarily used to treat?
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The primary action of phenylephrine is:
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How does dopamine affect blood pressure at high doses?
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What is one contraindication for the use of isoprenaline?
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What is a common side effect associated with the use of phenylephrine?
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Which of the following is a selective b2 agonist used for bronchodilation in asthma and COPD?
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What is the primary therapeutic use of Ritodrine?
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Which of the following describes the action mechanism of Clonidine?
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Which of the following best describes the side effects of Amphetamine with long-term use?
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What is a primary function of Pseudoephedrine as a decongestant?
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What is the main characteristic of Ephedrine as a sympathomimetic agent?
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Which adrenergic stimulant is primarily used in glaucoma treatment?
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What type of drug is Terbutaline classified as?
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Study Notes
Adrenergic Transmission
- Norepinephrine synthesis involves the conversion of tyrosine in neurons.
- Norepinephrine is stored in vesicles until needed.
- Upon stimulation, norepinephrine is released into the synaptic cleft.
- It binds to postsynaptic adrenergic receptors to exert effects.
- Action is terminated by neuronal reuptake, MAO, and COMT.
Adrenergic Receptors
- α-adrenoceptors: Subtypes α1 (excitatory functions) and α2 (inhibitory functions).
- β-adrenoceptors: Subtypes β1 (excitatory in heart), β2 (inhibitory in smooth muscles), and β3 (lipolysis in adipose tissue).
- α1 and β1, β2, β3 receptors are located postsynaptically; α2 and β2 receptors are presynaptic.
α-Adrenoceptors
- α1 receptors are excitatory, causing vasoconstriction, mydriasis, and uterine contraction.
- α2 receptors inhibit norepinephrine release via negative feedback.
β-Adrenoceptors
- β1 receptors increase heart rate, force of contraction, and renin release.
- β2 receptors promote relaxation of various smooth muscles, including bronchodilation and intestinal relaxation.
- β3 receptors stimulate lipolysis in adipose tissue.
Actions of Sympathomimetics
- Common sympathetic actions: mydriasis, increased heart rate, bronchodilation, hyponatremia, among others.
- Medications can be classified as direct-acting, indirect-acting, or mixed-acting based on their mechanism.
Classification of Sympathomimetics
- Direct-acting: Stimulate adrenergic receptors directly (e.g., adrenaline, isoprenaline).
- Indirect-acting: Promote norepinephrine release or inhibit its uptake (e.g., amphetamines, cocaine).
- Mixed (Dual acting): Both direct and indirect action (e.g., ephedrine).
Chemical Classification
- Catecholamines: Water-soluble, act quickly, and not effective orally (metabolized by COMT & MAO). Examples: adrenaline, isoprenaline.
- Non-catecholamines: Lipid-soluble, effective orally, longer duration, less metabolized. Examples: ephedrine, amphetamine.
Non-selective Adrenergic Agonists
- Adrenaline acts on all receptor subtypes and is used for various severe clinical scenarios (e.g., anaphylaxis, cardiac arrest).
- Norepinephrine primarily targets α1 and β1 receptors; used in hypotensive states.
- Isoprenaline mainly affects β receptors; used in cardiac arrest and some asthma cases.
Selective Adrenergic Agonists
- Phenylephrine: Selective α1 agonist, used as a nasal decongestant and vasopressor.
- Dobutamine: Selective β1 agonist, increases myocardial contractility, used in heart failure.
- Salbutamol: Selective β2 agonist, used for bronchodilation in asthma.
Indirectly Acting Sympathomimetics
- Amphetamine and cocaine act by releasing or inhibiting reuptake of norepinephrine.
- Amphetamines have CNS stimulant effects, commonly lead to dependency.
Dual Acting Sympathomimetics
- Ephedrine has both direct receptor activation and promotes norepinephrine release, often used in respiratory distress.
- Pseudoephedrine is primarily used as a decongestant due to its vasoconstriction properties.
Therapeutic Uses and Adverse Effects
- Adrenaline: Used in anaphylaxis, cardiac arrest; can cause tachycardia, hypertension, tissue necrosis.
- Norepinephrine: Used in severe hypotension; can also lead to reflex bradycardia and peripheral ischemia.
- Isoprenaline: For cardiac situations but contraindicated in hyperthyroidism; side effects include increased heart rate.
- Dopamine: Varies in effect with dosage; critical in cardiogenic shock.
- Dobutamine: For short-term heart failure management; may cause tachycardia.
- Phenylephrine: Topical decongestant; potential for hypertension and reflex bradycardia.
Important Contraindications
- Caution in patients with coronary heart diseases, hypertension, or closed-angle glaucoma, due to the potential for exacerbating these conditions.
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Description
This quiz covers the key concepts of adrenergic transmission, including the synthesis, storage, and action of norepinephrine. Additionally, it delves into the various types of adrenergic receptors, their functions, and the physiological effects they mediate. Perfect for students studying neuropharmacology or physiology.
