Sympathetic Nervous System Overview
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Questions and Answers

What is the primary action of the presynaptic α2 receptor concerning Ca2+ influx?

  • Stimulates the synthesis of norepinephrine
  • Modifies the action of neurotransmitters in the synapse
  • Inhibits Ca2+ influx through voltage-dependent channels (correct)
  • Enhances Ca2+ influx through voltage-dependent channels
  • Which of the following is not a direct action of norepinephrine (NE) in the sympathetic nervous system?

  • Reuptake into pre-synaptic neurons
  • Release into the synapse
  • Synthesis from tyrosine (correct)
  • Activation of postsynaptic receptors
  • What is the function of metyrosine in the synthesis of norepinephrine?

  • Increases the production of dopamine
  • Inhibits the conversion of tyrosine to dopa (correct)
  • Stimulates the activity of presynaptic adrenoceptors
  • Enhances vesicular storage of norepinephrine
  • Which drug is known to block the vesicular storage of dopamine and norepinephrine?

    <p>Reserpine</p> Signup and view all the answers

    What effect does cocaine have on norepinephrine following its release?

    <p>Inhibits the neuronal reuptake of norepinephrine</p> Signup and view all the answers

    Which process is involved in increasing the transport of norepinephrine into the synapse?

    <p>Amphetamine action</p> Signup and view all the answers

    How does the presynaptic α2 receptor affect sympathetic neurotransmission?

    <p>Inhibits calcium influx, reducing norepinephrine release</p> Signup and view all the answers

    Which component is NOT a part of the norepinephrine synthesis pathway?

    <p>Acetylcholine</p> Signup and view all the answers

    What is the primary action of reserpine in relation to noradrenaline?

    <p>It blocks the vesicular monoamine transporter (VMAT), preventing noradrenaline storage.</p> Signup and view all the answers

    What adverse effect is NOT typically associated with reserpine use?

    <p>Increased serotonin levels</p> Signup and view all the answers

    How do indirect-acting sympathomimetic drugs primarily enhance noradrenaline action?

    <p>By reducing noradrenaline reuptake and facilitating its release.</p> Signup and view all the answers

    What pathway allows drug molecules to displace noradrenaline within the neuron?

    <p>Via the norepinephrine transporter (NET) into the presynaptic neuron.</p> Signup and view all the answers

    Which neurotransmitter is NOT mentioned as being depleted by reserpine?

    <p>Glutamate</p> Signup and view all the answers

    What happens to noradrenaline (NA) when reserpine blocks the VMAT?

    <p>NA accumulates in the cytoplasm and is degraded.</p> Signup and view all the answers

    What additional effect does reserpine have beyond noradrenaline depletion?

    <p>It depletes serotonin and dopamine from neurons in the brain.</p> Signup and view all the answers

    Which mechanism describes how amphetamine indirectly acts as a sympathomimetic drug?

    <p>It enters the neuron, exchanging with noradrenaline stored in vesicles.</p> Signup and view all the answers

    What is the primary focus of the video on adrenergic antagonists?

    <p>Illustrating noradrenergic neuro transmission</p> Signup and view all the answers

    Which drugs are covered in the video regarding psychomotor stimulants?

    <p>Amphetamines, methylphenidate, and cocaine</p> Signup and view all the answers

    What additional information does the video on monoamine oxidase inhibitors provide?

    <p>Further details about MAO inhibitors</p> Signup and view all the answers

    Which chapters from Rang and Dale’s Pharmacology focus on neurodegenerative diseases?

    <p>Chapter 40 and Chapter 48</p> Signup and view all the answers

    What is a potential negative consequence discussed in the video on psychomotor stimulants?

    <p>Drug abuse factors related to stimulants</p> Signup and view all the answers

    What is the primary role of COMT inhibitors in the treatment of Parkinson's disease?

    <p>To prevent the metabolism of dopamine in the brain and periphery</p> Signup and view all the answers

    Which COMT inhibitor acts in the brain?

    <p>Tolcapone</p> Signup and view all the answers

    What is the effect of MAO-B inhibitors in the context of Parkinson's disease?

    <p>They prevent inactivation of dopamine in the brain</p> Signup and view all the answers

    Which of the following drugs acts directly on striatal dopamine receptors in Parkinson's treatment?

    <p>Dopamine agonists</p> Signup and view all the answers

    What is a common indication for using methyldopa?

    <p>Hypertension treatment</p> Signup and view all the answers

    In the context of adrenergic drug action, what does MAO stand for?

    <p>Monoamine oxidase</p> Signup and view all the answers

    What is the effect of drugs that inhibit norepinephrine reuptake?

    <p>Enhance the effect of norepinephrine at receptor sites</p> Signup and view all the answers

    Which of these drugs primarily displaces norepinephrine from the presynaptic neuron?

    <p>Amphetamines</p> Signup and view all the answers

    What is the primary effect of sympathomimetic drugs on the sympathetic nervous system?

    <p>They enhance the sympathetic response.</p> Signup and view all the answers

    Which of the following drug classes inhibits the reuptake of noradrenaline?

    <p>Antidepressants</p> Signup and view all the answers

    What term is used for drugs that block the sympathetic nervous system's response?

    <p>Sympatholytic</p> Signup and view all the answers

    Which mechanism do drugs like reserpine utilize to affect noradrenaline?

    <p>They displace NA from presynaptic storage sites.</p> Signup and view all the answers

    Amphetamines primarily function by which of the following actions?

    <p>Displacing NA from storage</p> Signup and view all the answers

    Which of these substances is known to inhibit the metabolism of noradrenaline?

    <p>Cocaine</p> Signup and view all the answers

    What is a significant characteristic of direct-acting sympathetic drugs?

    <p>They mimic the action of neurotransmitters.</p> Signup and view all the answers

    Which of the following outcomes is expected when sympatholytic drugs are administered?

    <p>Decreased blood pressure</p> Signup and view all the answers

    What is the role of drugs that inhibit norepinephrine reuptake in the nervous system?

    <p>They enhance the synaptic effect of norepinephrine.</p> Signup and view all the answers

    Which of the following accurately describes the effect of sympathomimetic and sympatholytic drugs?

    <p>Sympathomimetics mimic noradrenaline while sympatholytics block its effects.</p> Signup and view all the answers

    Methyldopa is known to primarily act on which aspect of noradrenergic neurotransmission?

    <p>Inhibiting the synthesis of norepinephrine</p> Signup and view all the answers

    What type of effects would you expect from a drug that enhances norepinephrine activity?

    <p>Increased alertness</p> Signup and view all the answers

    Sympathomimetics may have various clinical uses due to their action on which systems?

    <p>The adrenergic nervous system</p> Signup and view all the answers

    Which factor is critical to understanding the role of sympatholytic drugs?

    <p>They decrease sympathetic activity.</p> Signup and view all the answers

    What effect will a drug that blocks the sympathetic division have on the parasympathetic response?

    <p>It will increase the parasympathetic response.</p> Signup and view all the answers

    Which receptors are involved in the inhibitory feedback mechanism that affects the release of norepinephrine?

    <p>α2 receptors</p> Signup and view all the answers

    Which component is inhibited by the activation of presynaptic α2 receptors?

    <p>Release of norepinephrine</p> Signup and view all the answers

    What type of drug, such as pseudoephedrine, has both direct and indirect actions?

    <p>Mixed-acting agonists</p> Signup and view all the answers

    Activation of which protein diminishes the action of adenylyl cyclase when α2 receptors are activated?

    <p>Gi protein</p> Signup and view all the answers

    What is a consequence of reserpine's action on noradrenaline storage within neurons?

    <p>Decrease in tissue noradrenaline content</p> Signup and view all the answers

    Which mechanism does amphetamine use to enhance noradrenaline action?

    <p>Displacement of noradrenaline into the cytoplasm</p> Signup and view all the answers

    What is a significant adverse effect of reserpine?

    <p>Depression</p> Signup and view all the answers

    How does reserpine affect serotonin levels in the brain?

    <p>Depletes serotonin levels</p> Signup and view all the answers

    Which of the following statements about the action of indirect-acting sympathomimetics is correct?

    <p>They reduce norepinephrine reuptake via NET.</p> Signup and view all the answers

    What role does the vesicular monoamine transporter (VMAT) play regarding noradrenaline?

    <p>Transports noradrenaline into storage vesicles</p> Signup and view all the answers

    What happens to noradrenaline once it accumulates in the cytoplasm due to reserpine action?

    <p>It is degraded by monoamine oxidase (MAO).</p> Signup and view all the answers

    What is the primary effect of blocking vesicular monoamine transporter (VMAT) with reserpine?

    <p>Decreased release of noradrenaline</p> Signup and view all the answers

    What is the role of βγ subunits of the G protein associated with presynaptic α2 receptors?

    <p>They inhibit Ca2+ influx.</p> Signup and view all the answers

    Which of the following pathways correctly describes the conversion of tyrosine to norepinephrine?

    <p>Tyrosine → Dopa → Dopamine → Norepinephrine</p> Signup and view all the answers

    What effect does the drug bretylium have on norepinephrine release?

    <p>It inhibits norepinephrine release.</p> Signup and view all the answers

    Which drug increases the transport of norepinephrine into the synapse by indirect action?

    <p>Amphetamine</p> Signup and view all the answers

    Which mechanism describes how neuronal reuptake of norepinephrine is affected?

    <p>Inhibited by cocaine</p> Signup and view all the answers

    What is the effect of reserpine on neurotransmitters?

    <p>It depletes dopamine and norepinephrine.</p> Signup and view all the answers

    Which dietary source is rich in tyrosine, crucial for norepinephrine synthesis?

    <p>High-protein food products</p> Signup and view all the answers

    What would be the expected effect of sympathomimetic drugs?

    <p>Enhancement of sympathetic nervous system activity</p> Signup and view all the answers

    What is a central action of amphetamine as an indirect sympathomimetic drug?

    <p>Appetite suppression</p> Signup and view all the answers

    Which of the following effects is NOT caused by indirect-acting sympathomimetic drugs like amphetamine?

    <p>Peripheral vasodilation</p> Signup and view all the answers

    How does amphetamine primarily enhance the action of norepinephrine?

    <p>By displacing NA from vesicles</p> Signup and view all the answers

    What is a primary therapeutic use for methylphenidate, another indirect sympathomimetic drug?

    <p>Treating ADHD</p> Signup and view all the answers

    Which receptor types are activated by the norepinephrine displaced by amphetamine?

    <p>Both alpha and beta receptors</p> Signup and view all the answers

    What potential negative effect is associated with the use of amphetamine?

    <p>Significant potential for abuse</p> Signup and view all the answers

    What happens to norepinephrine during the action of amphetamine in the nerve terminal?

    <p>NA is displaced into the synaptic cleft</p> Signup and view all the answers

    What overall effect do indirect-acting sympathomimetic drugs have on the cardiovascular system?

    <p>They can raise arterial pressure and heart rate.</p> Signup and view all the answers

    What is the primary action of sympathomimetic drugs?

    <p>They mimic the action of norepinephrine.</p> Signup and view all the answers

    Which class of drugs is specifically known to inhibit the reuptake of norepinephrine?

    <p>Antidepressants</p> Signup and view all the answers

    Which effect is associated with the use of sympatholytic drugs?

    <p>Decreased blood pressure</p> Signup and view all the answers

    What is the main mechanism through which amphetamines enhance the action of norepinephrine?

    <p>By displacing norepinephrine from presynaptic neurons</p> Signup and view all the answers

    Which drug is known for its ability to block the vesicular storage of norepinephrine?

    <p>Reserpine</p> Signup and view all the answers

    In the context of noradrenergic neurotransmission, what do the terms sympathomimetic and sympatholytic signify?

    <p>Drugs that respectively enhance and inhibit sympathetic responses.</p> Signup and view all the answers

    What adverse effect is commonly associated with drugs that inhibit norepinephrine reuptake?

    <p>Insomnia</p> Signup and view all the answers

    Methyldopa is primarily used to treat which condition?

    <p>Hypertension</p> Signup and view all the answers

    Which process does reserpine influence regarding norepinephrine?

    <p>Storage</p> Signup and view all the answers

    What effect does cocaine have on norepinephrine levels?

    <p>Inhibits its reuptake</p> Signup and view all the answers

    Which of the following characteristics identifies direct-acting sympathomimetic drugs?

    <p>They directly stimulate adrenergic receptors.</p> Signup and view all the answers

    How do drugs that inhibit the metabolism of norepinephrine affect its levels?

    <p>Increase norepinephrine levels</p> Signup and view all the answers

    What is a key effect of sympathomimetics on the parasympathetic response?

    <p>Decreases parasympathetic activity</p> Signup and view all the answers

    Study Notes

    Sympathetic Nervous System and Noradrenergic Transmission

    • Sympathomimetic drugs increase the sympathetic response, while sympatholytic drugs block the sympathetic response. This means that sympathomimetic drugs inhibit the parasympathetic response and vice versa.
    • Direct-acting sympathetic drugs mimic the action of norepinephrine (NA), while indirect-acting sympathetic drugs influence the release or termination of NA.
    • The sympathetic nervous system is responsible for the "fight or flight" response, preparing the body for stressful situations.
    • The presynaptic α2 receptor in the sympathetic nervous system inhibits Ca2+ influx, leading to a decrease in norepinephrine release.

    Noradrenaline (NA) Synthesis, Storage, Release, and Termination

    • NA synthesis: Tyrosine is converted to dopamine, which is then converted to NA.
    • NA storage: NA is stored in synaptic vesicles.
    • NA release: NA is released into the synapse in response to nerve stimulation.
    • NA termination: NA is terminated through reuptake into the presynaptic neuron and metabolism by enzymes like Monoamine Oxidase (MAO) and Catechol-O-methyl transferase (COMT).

    Indirect-Acting Sympathetic Drugs: Displacers of NA

    • Reserpine blocks the vesicular monoamine transporter (VMAT), which prevents the transport of NA into storage vesicles. This leads to a decrease in available NA, blocking sympathetic transmission, and potentially causing depression and parkinsonism.
    • Amphetamines enter the presynaptic neuron and displace NA from storage vesicles, increasing NA release. They also inhibit NA reuptake.

    Catechol-O-Methyl Transferase (COMT) Inhibitors

    • COMT inhibitors prevent the metabolism of dopamine, primarily used in the treatment of Parkinson's disease due to dopamine deficiency in the basal ganglia.
    • Tolcapone and entacapone are examples of COMT inhibitors.
    • Some COMT inhibitors act in the periphery (tolcapone, entacapone), while others act in the brain (tolcapone).

    Sites of Action of Drugs Affecting Noradrenergic Neurotransmission

    • Presynaptic neuron: Drugs can act on the synthesis, storage, release, and reuptake of NA.
    • Postsynaptic receptor: Drugs can either activate or block the NA receptors.

    Resources for Learning

    • Osmosis videos: Consider utilizing "Adrenergic antagonists: presynaptic antagonists," "Monoamine oxidase inhibitors," and "Psychomotor stimulants" videos to supplement your understanding.

    Noradrenergic Transmission and Indirect-Acting Sympathetic Drugs

    • Indirect-acting sympathetic drugs affect the sympathetic nervous system by acting inside the post-ganglionic neuron.
    • These drugs enhance or inhibit the sympathetic nervous system by affecting the synthesis, storage, release, re-uptake or binding of NA to its target receptors.

    Drug Classes Affecting Noradrenergic Neurotransmission

    • Drugs that affect NA storage: These drugs displace NA from the presynaptic neuron, including methyldopa, reserpine, amphetamines.
    • Drugs that affect NA reuptake: These drugs inhibit NA reuptake into the presynaptic neuron, including cocaine and antidepressants.
    • Drugs that affect NA metabolism: These drugs inhibit the metabolism of NA.

    Presynaptic Feedback Control of the Sympathetic Nervous System

    • The inhibitory feedback mechanism is mediated through the α2 receptors.
    • Activation of presynaptic α2 receptors activates Gi protein, which inhibits adenylyl cyclase.
    • This inhibition prevents the opening of calcium channels, decreasing exocytosis and inhibiting the release of NA.

    Reserpine

    • Reserpine blocks the vesicular monoamine transporter (VMAT), preventing the transport of noradrenaline and other amines into storage vesicles.
    • This leads to an accumulation of NA in the cytoplasm, where it is degraded by monoamine oxidase (MAO).
    • Reserpine depletes NA, serotonin (5-HT), and dopamine from neurons in the brain.
    • Adverse effects: depression, parkinsonism, gynaecomastia.

    Indirect-Acting Sympathomimetic Drugs

    • Displacers of NA: These drugs are structurally similar to NA and are taken up into the presynaptic neuron by the NA transporter (NET).
    • Once inside, they displace NA from storage vesicles, leading to an increase in NA concentration in the synapse.
    • They also reduce NA reuptake via NET, enhancing the action of the released NA.
    • Examples include amphetamine, methylphenidate, and atomoxetine.

    Clinical Uses of Displacers of NA

    • Amphetamine: Narcolepsy, ADHD.
    • Methylphenidate: ADD, ADHD.
    • Atomoxetine: ADHD.

    Widespread Effects of Indirect-Acting Sympathomimetic Drugs

    • They increase NA levels in the synapse, activating all adrenergic receptors (α and β).
    • This results in various effects throughout the body:
      • Bronchodilation
      • Raised arterial pressure
      • Peripheral vasoconstriction
      • Increased heart rate and force of myocardial contraction
      • Inhibition of gut motility.

    Central Effects of Displacers of NA

    • They have significant central effects:
      • Appetite suppression
      • CNS stimulant effects
      • Potential for abuse.

    Therapeutic Uses of Indirect-Acting Sympathomimetic Drugs

    • They have limited therapeutic uses due to their widespread and significant effects.

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    Description

    This quiz covers the fundamental concepts of the sympathetic nervous system and noradrenergic transmission. You will learn about the roles of sympathomimetic and sympatholytic drugs, the mechanisms of norepinephrine synthesis, and its impacts on the body's fight or flight response.

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