Autonomic nervous system and cholinomimetics
- 1. Autonomic nervous system and cholinomimetics By Dr Kumar Gourav PG resident, pharmacology
- 3. Peripheral nervous system ï‚— The peripheral nervous system (PNS) is the division of the nervous system containing all the nerves that lie outside of the central nervous system (CNS).
- 4. Peripheral nervous system ï‚— Somatic nervous systen the part of the peripheral nervous system responsible for carrying sensory and motor information to and from the central nervous system. ï‚— Autonomic nervous system is the part of the peripheral nervous system responsible for regulating involuntary body functions, such as blood flow, heartbeat,
- 6. Autonomic nervous system ï‚— It is further divided into two branches: 1. sympathetic system regulates the flight or fight responses 2. parasympathetic system helps maintain normal body functions and conserves physical resources.
- 10. Cholinergic system  Neurotransmitters – acetylcholine Acetylcholine: It is hydrolysed by enzyme cholinesterases. cholinesterases true cholinesterases pseudocholinesterases
- 12. Cholinergic receptors • Present in heart, smooth muscle, exocrine glands and CNS Muscarinic (M) • Located in neuromuscular junction(NMJ), autonomic ganglia and adrenal medulla Nicotinic (N)
- 13. Classification
- 14. Muscarinic actions 1. Cardiovascular system a. Heart : bradycardia conduction is slowed force of contraction reduced b. Blood vessels: vasodilation decreased BP
- 15. Muscarinic actions 2. Smooth muscle: a. Gastrointestinal tract: increases tone of the gut peristaltic movements increases GI secretion relaxes the sphincter(defecation)
- 16. Muscarinic actions b. Urinary bladder: contracts detrusor muscle relaxes the trigonal sphincter (urination)
- 17. Muscarinic actions c. Bronchi : Contracts bronchial smooth muscle (Bronchospasm) Inc tracheobronchial secretion Hence contraindicated in bronchial asthma
- 18. Muscarinic actions 3. Exocrine glands: increases all secretion like salivary, lacrimation, sweat, bronchial, gastric etc. 4. Eye : does not produce any effect on topical application because of its poor penetration through tissues.
- 19. Nicotinic actions ï‚— To elicit nicotinic actions, larger doses of Ach is required 1. Autonomic ganglia: tachycardia, hypertension 2. Skeletal muscle: twitching, fasciculation, paralysis 3. CNS: No effect. (does not cross BBB)
- 20. USES  Pilocarpine is used only in the eye as 0.5– 4% drops.  It is a third-line drug in open angle glaucoma.  It facilitates drainage of aqueous humour and reduces the intraocular pressure (IOP)
- 21. Anticholinesterases ï‚— Anticholinesterases (anti-ChEs) are agents which inhibit Cholinesterases and protect ACh from hydrolysis. ï‚— Hence Ach gets accumulates in muscarinic and nicotinic sites producing cholinergic effects. ï‚— Hence it is called indirectly acting cholinergic drugs
- 23. uses 1. As miotic in glaucoma 2. Myasthenia gravis 3. Postoperative paralytic ileus / urinary retention 4. Curare poisoning 5. Belladona poisoning 6. Alzheimer’s disease
- 24. Myasthenia gravis ï‚— An autoimmune disorder ï‚— Development of antibodies against nicotinic receptors (NR) at the muscle endplate ï‚— Weakness and easy fatigability on repeated activity ï‚— Recovery after rest.
- 25. Treatment  Neostigmine/pyridostigmine – allow ACh released from prejunctional endings to accumulate and act on the receptors .  Corticosteroids afford considerable improvement by their immunosuppressant action.
- 26. Treatment ï‚— Other immunosuppressants like azathioprine and cyclosporine ï‚— Edrophonium aggravates MG
- 27. OP poisoning ï‚— Signs and symptoms 1. Muscarinic effects: Irritation of eye, lacrimation, salivation, sweating, copious tracheo-bronchial secretions, miosis, blurring of vision, bronchospasm, breathlessness, colic, involuntary defecation and urination.
- 28. OP poisoning 2. Nicotinic effects: Muscular fasciculations, weakness, respiratory paralysis (central as well as peripheral). 3. Central effects: Irritability, disorientation, unsteadiness, tremor, ataxia, convulsions, coma and death. • Death is generally due to respiratory failure.
- 29. Treatment 1. Termination of further exposure to the poison— fresh air, wash the skin and mucous membranes with soap and water, 2. gastric lavage according to need. 3. Maintain patent airway, 4. positive pressure respiration if it is
- 30. OP poisoning treatment 5.Supportive measures — maintain BP, hydration, control of convulsions with judicious use of diazepam. 6. Specific antidotes— (a) Atropine (b) Cholinesterase reactivators like pralidoxime