L8: Parasympathetic system

1. Q: Where are nicotinic receptors located?

Parasympathetic and sympathetic ganglion, skeletal neuromuscular junction, and brain.

2. Q: What are the features of nicotinic receptors?

Consist of 3 subunits: α, β, δ; Different selectively and response to pharmacological agents; Ligand-gated ion channel; Stimulation leads to increased cation permeability; Stimulated by acetylcholine and nicotine.

3. Q: Where is the M1 muscarinic receptor located?

CNS and salivary gland.

4. Q: What are the effects of stimulating the M1 muscarinic receptor?

CNS excitation, memory enhancement, and increased salivary excretion.

5. Q: Where is the M2 muscarinic receptor located?

Heart.

6. Q: What are the effects of stimulating the M2 muscarinic receptor?

Decreased heart rate, contractility, and AV conduction.

7. Q: Where is the M3 muscarinic receptor located?

Smooth muscle, exocrine glands, and eye.

8. Q: What are the effects of stimulating the M3 muscarinic receptor?

Contracts all smooth muscles (except blood vessels); Increases glandular secretion; Allows ocular accommodation.

9. Q: What are the two regions of acetylcholinesterase (ACE)?

Anionic site and esteratic site.

10. Q: What is the function of acetylcholinesterase (ACE)?

Rapidly hydrolyzes acetylcholine.

11. Q: What is the turnover rate of acetylcholinesterase (ACE)?

High turnover rate.

12. Q: What are the effects of nicotinic receptor agonists?

Enhance neurotransmission in both the parasympathetic and sympathetic systems; Effects may predominate in some sympathetic sites and parasympathetic sites; Higher dosage can affect neuromuscular junction and brain.

13. Q: Name some examples of nicotinic receptor agonists.

Nicotine, lobeline, and epibatidine.

14. Q: What is the mechanism of anticholinesterase drugs?

They inhibit ACE to increase ACh activity at all cholinergic postganglionic synapses.

15. Q: Name some examples of anticholinesterase drugs.

Neostigmine and pyridostigmine.

16. Q: What is the clinical use of neostigmine and pyridostigmine?

They are used to treat myasthenia gravis.

17. Q: What is the antidote for anticholinesterase poisoning?

Pralidoxime.

18. Q: How does pralidoxime work as an antidote for anticholinesterase poisoning?

It lures the phosphate group away from the esteratic site of ACE.

19. Q: What are the effects of muscarinic receptor agonists?

Reduce heart rate and decrease contractility; Contraction of all smooth muscles (except blood vessels); Increase exocrine gland secretion; Constriction of pupils, ciliary muscle contraction, and improved drainage of aqueous humor.

20. Q: Name some examples of muscarinic receptor agonists.

Bethanechol, pilocarpine, and cevimeline.

21. Q: What is the effect of nicotinic receptor antagonists?

They inhibit sympathetic and parasympathetic systems, neuromuscular junction, and brain.

22. Q: Name some examples of nicotinic receptor antagonists.

Botulinum toxin and β-bungarotoxin.

23. Q: What are the effects of muscarinic receptor antagonists?

Increased heart rate and contractility; Contraction of all smooth muscles (except blood vessels); Inhibition of exocrine gland secretion; Pupil dilation, relaxation of ciliary muscle, and increased intraocular pressure.

24. Q: Name some examples of muscarinic receptor antagonists.

Atropine, hyoscine, tropicamide, ipratropium, and darifenacin.

25. Q: What is the clinical use of darifenacin?

It is used to treat urinary incontinence due to overactive bladder.

Q: What is the clinical use of neostigmine and pyridostigmine?

They are used to treat myasthenia gravis and to reverse the effects of non-depolarizing neuromuscular blocking agents.