Cholinergic Transmission and Parasympathomimetics
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Questions and Answers

What is the reason Acetylcholine is not therapeutically useful?

  • It only stimulates the muscarinic receptors
  • It has only nicotinic activity
  • It has a multiplicity of actions and is rapidly inactivated by cholinesterase enzyme (correct)
  • It is only found in the sympathetic nervous system

    • What type of receptors does Pilocarpine bind to?

  • Muscarinic acetylcholine receptors (mAChR) (correct)
  • Adrenergic receptors
  • Dopaminergic receptors
  • Nicotinic acetylcholine receptors (nAChR)

    • What is the effect of Acetylcholine on the heart rate?

  • Increases heart rate
  • Can either increase or decrease heart rate
  • Has no effect on heart rate
  • Decreases heart rate (correct)

    • Which of the following is an indirectly acting cholinergic agonist?

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

    What is the effect of Acetylcholine on the salivary secretion?

    <p>Increases salivary secretion</p> Signup and view all the answers

    How do directly acting cholinergic agonists work?

    <p>By binding directly to cholinoreceptors</p> Signup and view all the answers

    What is the effect of Acetylcholine on the tone of urinary bladder muscles?

    <p>Increases the tone of urinary bladder muscles</p> Signup and view all the answers

    What type of receptors does Nicotine bind to?

    <p>Nicotinic acetylcholine receptors (nAChR)</p> Signup and view all the answers

    What is the effect of atropine on the pupil?

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

    What is the therapeutic application of atropine in ophthalmology?

    <p>To measure refractive errors of the eye</p> Signup and view all the answers

    What is the effect of atropine on heart rate at low doses?

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

    What is the use of atropine as an antidote?

    <p>For overdose of cholinergic agonists</p> Signup and view all the answers

    What is the effect of atropine on intraocular pressure (IOP) in patients with glaucoma?

    <p>Increases IOP</p> Signup and view all the answers

    What is the source of atropine?

    <p>Atropa belladonna</p> Signup and view all the answers

    What is the historical use of atropine?

    <p>To dilate pupils for cosmetic reasons</p> Signup and view all the answers

    What is the meaning of 'belladonna'?

    <p>Beautiful lady</p> Signup and view all the answers

    What is the primary mechanism of action of anticholinesterases?

    <p>Increasing the levels of acetylcholine at the neuromuscular junction</p> Signup and view all the answers

    What is the primary use of pilocarpine in ophthalmology?

    <p>To lower intraocular pressure in emergency situations</p> Signup and view all the answers

    What is the primary cause of myasthenia gravis?

    <p>Autoimmune disorder</p> Signup and view all the answers

    What is the purpose of the edrophonium test in diagnosing myasthenia gravis?

    <p>To temporarily increase the levels of acetylcholine at the neuromuscular junction</p> Signup and view all the answers

    What is a common adverse effect of pilocarpine?

    <p>Stimulation of profuse sweating and salivation</p> Signup and view all the answers

    What is the name of the disease characterized by fluctuating weakness and fatigability?

    <p>Myasthenia gravis</p> Signup and view all the answers

    What is a treatment option for myasthenia gravis?

    <p>Cholinesterase inhibitors</p> Signup and view all the answers

    What is the duration of action of pilocarpine when applied topically to the cornea?

    <p>About one day</p> Signup and view all the answers

    Study Notes

    Cholinergic Transmission

    Parasympathomimetics

    • Parasympathomimetics can be classified into directly and indirectly acting cholinergic agonists.
    • Directly acting cholinergic agonists mimic the effect of acetylcholine (ACh) by binding directly to cholinoreceptors.
    • Examples of directly acting cholinergic agonists include:
      • Acetylcholine (ACh)
      • Pilocarpine
    • ACh has both nicotinic and muscarinic activity, but it is therapeutically of no importance due to its multiplicity of actions and rapid inactivation by cholinesterase enzyme.
    • Actions of ACh:
      • Heart rate: decreased
      • Blood pressure: decreased
      • Salivary secretion: increased
      • GIT secretion and motility: increased
      • Bronchial secretion: increased
      • Tone of urinary bladder muscles: increased
      • Pupil sphincter muscle: contracted
      • Ciliary muscle: contracted

    Adverse Effects of Cholinergic Drugs

    • Cholinergic drugs can cause adverse effects such as:
      • Increased salivation
      • Increased sweating
      • Nausea and vomiting
      • Abdominal cramps
      • Diarrhea

    Cholinergic Antagonists

    Anti-Muscarinic Agents

    • Examples of anti-muscarinic agents include:
      • Atropine
      • Scopolamine
      • Ipratropium
    • Atropine:
      • Isolated from Atropa belladonna
      • Has muscarinic activity
      • Actions:
        • Eye: mydriasis, unresponsiveness to light, cycloplegia, increased IOP in patients with glaucoma
        • CVS: bradycardia at low doses, modest tachycardia at high doses
      • Therapeutic applications:
        • Ophthalmic: mydriatic and cycloplegic effect
        • Antisecretory: blocks respiratory secretions prior to surgery
        • Antidote: for overdose of cholinergic agonists

    Indirectly Acting Cholinergic Agonists (Anticholinesterases)

    • Examples of anticholinesterases include:
      • Neostigmine (Prostigmine)
      • Edrophonium
    • Uses:
      • To stimulate bladder and GIT contraction
      • To treat myasthenia gravis

    Myasthenia Gravis

    • Myasthenia gravis is a neuromuscular disease characterized by fluctuating weakness and fatigability.
    • It is an autoimmune disorder caused by circulating antibodies that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting ACh.
    • Diagnosis: Edrophonium test
    • Treatment:
      • Cholinesterase inhibitors to directly improve muscle function
      • Immunosuppressant drugs to reduce the autoimmune process

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    Related Documents

    2 Cholinergic Transmission.ppt

    Description

    Learn about cholinergic transmission, parasympathomimetics, and their classification into directly and indirectly acting cholinergic agonists. Understand the actions and therapeutic uses of Acetylcholine and Pilocarpine.

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