Sympathomimetics Classification and Actions

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Questions and Answers

Which type of adrenoceptors are primarily responsible for the fight-or-flight response in the sympathetic nervous system?

  • Beta-2
  • Alpha-1 (correct)
  • Beta-1
  • Alpha-2

What is the main endogenous ligand for the adrenoceptors in the human body?

  • Dopamine
  • Acetylcholine
  • Noradrenaline (correct)
  • Adrenaline

Which class of drugs directly activate adrenoceptors, leading to physiological responses similar to those of the sympathetic nervous system?

  • Sympathomimetics (correct)
  • Parasympathomimetics
  • Cholinesterase Inhibitors
  • Anticholinergics

Which neurotransmitter is primarily associated with dopaminergic receptors in the brain and peripheral nervous system?

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

What is the primary mechanism of action for sympathomimetic drugs acting indirectly?

<p>Preventing reuptake of neurotransmitters (D)</p> Signup and view all the answers

Which of the following drugs is classified as a non-selective α1, α2, β1, and β2 agonist?

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

Which of the following is a potential side effect of β2-selective sympathomimetic drugs like salbutamol?

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

Which of the following drugs is classified as a selective α2 agonist?

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

Which of the following neurotransmitters is classified as a D1, D2, and β1 agonist?

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

Which of the following drugs is classified as a selective β1 agonist?

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

Which of the following is a potential side effect of α1-selective sympathomimetic drugs like phenylephrine?

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

Which adrenergic receptor is adrenaline (epinephrine) NOT an agonist on?

<p>D2 (A)</p> Signup and view all the answers

What is a potential severe adverse effect of adrenaline (epinephrine) administration?

<p>Cerebral hemorrhage (A)</p> Signup and view all the answers

Which medication is used for the treatment of anaphylactic shock through local vasoconstriction?

<p>Adrenaline (epinephrine) (A)</p> Signup and view all the answers

Which neurotransmitter acts as a precursor for adrenaline and noradrenaline?

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

What is a potential adverse effect associated with prolonged infusion of dopamine?

<p>Gangrene of fingers/toes (D)</p> Signup and view all the answers

Which adrenergic receptor is not directly activated by Noradrenaline (Norepinephrine)?

<p>β2 (C)</p> Signup and view all the answers

In addition to its cardiovascular effects, what other effect is produced by Noradrenaline (Norepinephrine)?

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

What is the primary effect of Dobutamine on the cardiovascular system?

<ul> <li>Inotropy, + Dromotropy, + Chronotropy, + Bathmotropy (A)</li> </ul> Signup and view all the answers

Which of the following effects is not associated with Salbutamol?

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

What type of drug inhibits the reuptake of norepinephrine and dopamine?

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

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Study Notes

Introduction to Sympathetic Nervous System (SNS)

  • The sympathetic nervous system (SNS) is a part of the autonomic nervous system (ANS)
  • The SNS is responsible for the "fight or flight" response
  • The SNS is controlled by adrenergic receptors (adrenoceptors)

Adrenergic Receptors (Adrenoceptors)

  • Adrenoceptors are G-protein coupled receptors (GPCR)
  • There are two main types of adrenoceptors: alpha (α) and beta (β)
  • Alpha receptors are further divided into α1 and α2, while beta receptors are divided into β1, β2, and β3
  • Dopamine receptors are also involved in the SNS and are divided into D1 and D2

Sympathomimetics: Direct Acting

  • Sympathomimetics are drugs that mimic the effects of endogenous ligands on the SNS
  • Direct acting sympathomimetics are classified into non-selective, selective, and mixed acting
  • Non-selective sympathomimetics include adrenaline (α1, α2, β1, β2), noradrenaline (α1, α2, β1), and dopamine (D1, D2, β1)
  • Selective sympathomimetics include phenylephrine (α1), clonidine (α2), dobutamine (β1), and salbutamol (β2)

Sympathomimetics: Indirect Acting

  • Indirect acting sympathomimetics include releasing agents, catecholamine reuptake inhibitors, and MAO/COMT inhibitors
  • Releasing agents, such as amphetamine, stimulate the release of catecholamines from storage vesicles
  • Catecholamine reuptake inhibitors, such as amitriptyline, block the reuptake of noradrenaline from the synapse
  • MAO/COMT inhibitors, such as phenelzine and selegiline, inhibit the metabolism of catecholamines

Sympathomimetics: Mixed Acting

  • Mixed acting sympathomimetics, such as ephedrine, indirectly release noradrenaline and directly activate adrenoceptors (α1, α2, β1, β2)
  • Ephedrine is absorbed well orally and has a long duration of action
  • Ephedrine is excreted unchanged in the urine

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