Autonomic Nervous System & Anti-Dysrhythmic Drugs
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Questions and Answers

Which type of receptor is primarily responsible for smooth muscle contraction in visceral organs?

  • α1 (correct)
  • β2
  • Nicotinic AChR
  • β1

    • What is the primary function of the postganglionic neuron in the sympathetic nervous system?

  • Release of Noradrenaline (NA) (correct)
  • Release of IP3/DAG
  • Release of ACH
  • Preganglionic stimulation

    • Which receptor is associated with vasodilation in skeletal muscle?

  • β1
  • α1
  • Nicotinic AChR
  • β2 (correct)

    • What is the effect of sympathetic nervous system stimulation on the heart?

    <p>Increased frequency and contractile force</p> Signup and view all the answers

    Which of the following is NOT a function of the sympathetic nervous system?

    <p>Renal excretion</p> Signup and view all the answers

    What is the primary neurotransmitter released by the preganglionic neuron?

    <p>Acetylcholine (ACh)</p> Signup and view all the answers

    Which nerve is responsible for ciliary muscle contraction and accommodation?

    <p>N.VII</p> Signup and view all the answers

    What is the effect of muscarinic receptors on the heart rate?

    <p>Decreased heart rate</p> Signup and view all the answers

    Which of the following is NOT a function of the muscarinic receptor subtype M1?

    <p>Cardiac muscle function</p> Signup and view all the answers

    What is the effect of muscarinic receptors on the liver?

    <p>Decreased glycogenolysis</p> Signup and view all the answers

    What is the effect of muscarinic receptors on the stomach and intestines?

    <p>Increased motility and secretions</p> Signup and view all the answers

    Which of the following is a function of the muscarinic receptor subtype M2?

    <p>Heart function</p> Signup and view all the answers

    What is the effect of muscarinic receptors on blood pressure?

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

    What is the effect of muscarinic receptors on the trachea and bronchi?

    <p>Constriction of the trachea and bronchi</p> Signup and view all the answers

    What type of receptors are present in sweat glands, despite being innervated by the sympathetic nervous system?

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

    What is the effect of a muscarinic agonist on vessels?

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

    What is the result of blocking the parasympathetic nervous system with a muscarinic antagonist, such as atropine?

    <p>Anticholinergic effects</p> Signup and view all the answers

    What is the equation used to describe the relationship between ion distribution and membrane potential?

    <p>Goldman-Katz equation</p> Signup and view all the answers

    What is the characteristic of the cardiac action potential in ventricular myocytes?

    <p>Low resting potential</p> Signup and view all the answers

    What is the difference between cardiac action potential in ventricular myocytes and pacemaker cells?

    <p>Pacemaker cells lack a resting potential</p> Signup and view all the answers

    What is the result of muscarinic effects on the eye?

    <p>Blurred vision</p> Signup and view all the answers

    What is the term for anti-muscarinic effects?

    <p>Anticholinergic effects</p> Signup and view all the answers

    What is the effect of digitalis on calcium exchange?

    <p>Decrease calcium exchange</p> Signup and view all the answers

    What is the result of increased [Ca++]i in the heart?

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

    What is the mechanism by which digitalis increases vagal tone?

    <p>Unknown mechanism</p> Signup and view all the answers

    What is the effect of atropine on the heart rate?

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

    Which of the following drugs has negative chronotropic side effects?

    <p>Beta-blockers</p> Signup and view all the answers

    What is the effect of digitalis on the effective refractory period (ERP)?

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

    Which of the following drugs acts on voltage-gated calcium channels?

    <p>Calcium channel blockers</p> Signup and view all the answers

    How do you treat bradycardia?

    <p>With atropine</p> Signup and view all the answers

    What is the primary mechanism behind the slow depolarization from -60 mV (pacemaker potential)?

    <p>An If current through a 'funny' Na+ channel</p> Signup and view all the answers

    What is the name of the channel responsible for the If current?

    <p>HCN channel</p> Signup and view all the answers

    What is the primary action of Class I anti-dysrhythmic drugs?

    <p>Blocking voltage-sensitive sodium channels</p> Signup and view all the answers

    What is the characteristic of Class Ib anti-dysrhythmic drugs?

    <p>High frequency dependence and specificity for voltage-gated Na channels</p> Signup and view all the answers

    What is the effect of Class I drugs on pacemaker potentials?

    <p>Decreasing conduction velocity</p> Signup and view all the answers

    What is a common side effect of Class I anti-dysrhythmic drugs?

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

    What is the characteristic of Class Ia anti-dysrhythmic drugs?

    <p>High frequency dependence and slow dissociation</p> Signup and view all the answers

    What is the primary indication for Class I anti-dysrhythmic drugs?

    <p>Ventricular and atrial tachyarrhythmias</p> Signup and view all the answers

    Study Notes

    Autonomic Nervous System Effects on Heart and Other Organs

    • The sympathetic nervous system has a preganglionic neuron that releases ACH, which acts on nicotinic ACH receptors.
    • The postganglionic neuron releases noradrenaline (NA), which acts on different adrenergic receptors (AR) at end organs.

    Adrenergic Receptors

    • α1 receptors: smooth muscle contraction, vasoconstriction in viscera, and GI motility.
    • β1 receptors: heart frequency, contractile force, and conduction at A-V node.
    • β2 receptors: smooth muscle relaxation, vasodilation in skeletal muscle, and bronchi dilation.

    Sympathetic Nervous System: Adrenergic Receptors

    • Preganglionic neurons release ACH, which acts on nicotinic ACH receptors.
    • Postganglionic neurons release NA, which acts on different AR at end organs.
    • Effects of sympathetic nervous system on different organs:
      • Eyes: pupillary dilation.
      • Heart: increased heart rate.
      • Lungs: bronchi dilation.
      • Liver: increased glycogenolysis.
      • Stomach and intestines: increased motility and secretions.
      • Arteries and veins: increased blood pressure and redistribution of blood flow away from GI tract.

    Muscarinic Acetylcholine Receptors

    • ACH release and breakdown by ACH esterase.
    • Muscarinic receptors:
      • M1: IP3/DAG signaling in CNS, glands, and smooth muscle.
      • M2: cAMP signaling in heart and CNS.
      • M3: IP3/DAG signaling in smooth muscle and glands.
      • M4: cAMP signaling in smooth muscle and glands.
      • M5: IP3/DAG signaling in smooth muscle and glands.
    • Effects of muscarinic receptors:
      • SLUDGE (Salivation, Lacrimation, Urination, Defecation, Gastrointestinal motility, and Emesis) or DUMBELS (Diarrhea, Urination, Miosis, Bronchorrhea, Bronchospasm, and Emesis).

    Anti-Dysrhythmic Drugs

    • Classification of anti-dysrhythmic drugs according to the Vaughan Williams system:
      • Class I: sodium channel blockers.
      • Class II: β-adrenoreceptor antagonists.
      • Class III: drugs that prolong the cardiac action potential.
      • Class IV: calcium channel antagonists.

    Class I – Na+ Channel Blockers

    • Mechanism of action: block voltage-sensitive sodium channels.
    • Effects: slow conduction velocity of pacemaker potentials throughout the heart and affect myocyte action potentials.
    • Used for: ventricular and atrial tachyarrhythmias.
    • Side effects: bradycardia and potential worsening of arrhythmias.
    • Subclasses:
      • Ia: dissociation within < 0.5 sec.
      • Ib: highly frequency-dependent, used for bradyarrhythmia (i.v.).

    Digitalis

    • Used for heart failure and some arrhythmias to increase ventricular output.
    • Mechanism of action:
      • Inhibition of NaK-ATPase, leading to increased [Na+]i and [Ca++]i.
      • Increased vagal tone, leading to cardiac slowing and reduced rate of conduction through AV node.
      • Increased [Ca++]i, leading to increased twitch tension and increased chance of afterdepolarisations and tachycardia.

    Muscarinic Antagonist Effects

    • Dry mouth and eyes.
    • Urinary retention.
    • Slowing of digestion.
    • Constipation.
    • Tachycardia.
    • Bronchodilation.
    • Less mucus production.
    • Less sweating.
    • Mydriasis.
    • Loss of accommodation, leading to blurred vision.

    Study Questions

    • Which anti-dysrhythmic drugs have negative chronotropic side effects?
    • Which drugs and drug classes act on:
      • Voltage-gated sodium channels.
      • Potassium channels.
      • Voltage-gated sodium channels.
      • Voltage-gated calcium channels.
    • How do you treat bradycardia?
    • What is the mechanism of action of these drugs?
    • How do sodium channel blockers target only the most active channels?

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    Description

    This quiz covers the effects of the autonomic nervous system on the heart and other organs, including the sympathetic ganglion and anti-dysrhythmic drugs. It also discusses the release of acetylcholine (ACh) and noradrenaline (NA) and their receptors.

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