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Autonomic Nervous System Introduction
The document provides an overview of the autonomic nervous system. It describes the distribution and function of cholinergic and adrenergic receptors. Cholinergic receptors include muscarinic M1-M5 receptors and nicotinic receptors. Adrenergic receptors include alpha-1, alpha-2, beta-1, beta-2, and beta-3 receptors. The effects of the sympathetic and parasympathetic nervous systems on various organ systems are explained based on the receptors involved. These include effects on the heart, blood vessels, smooth muscle, glands, eyes, autonomic ganglia and skeletal muscle. The conclusion summarizes the key receptor types and notes that sympathetic and parasympathetic effects
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Autonomic Nervous System Introduction
- 1. Autonomic Nervous System: Introduction Dr.Pravin Prasad M.B.B.S., MD Clinical Pharmacology Lecturer, Lumbini Medical College & TH 6 February 2019 (23 Magh 2075), Wednesday
- 2.
- 3. A Case Scenario DECERASEDHEART RATE
- 4.
- 5. By the endof this class, MBBS Sem I students will be able to: ➢Describe the distribution and function of: ✓Cholinergic receptors ✓Adrenergic receptors ➢Explain the effect (and the basis) of autonomic nervous system on various organ system
- 6. Pre-Test: Label thestructures
- 7. Pre-Test: Structural andFunctional Organization of Nervous System
- 8.
- 9. Receptors: Cholinergic ➢Muscarinic receptor(G-protein coupled) ➢Selective agonist: Muscarine ➢Selective antagonist: Atropine ➢Subtypes: M1-M5 ✓M1, M3, M5: excitatory (Gq coupled) ✓M2, M4: inhibitory (Gi/Go coupled) β Gα Gγ
- 10. Receptors: Cholinergic ➢Nicotinic receptors(Ion channel receptor) ➢Selective agonist: Nicotine ➢Selective antagonist: d-tubocurarine ➢Subtypes: NN, NM ✓Usually excitatory α
- 11. Cholinergic effect onorgan system Organ Receptor Involved Mechanism Effect Heart M2 • Hyperpolarization of SA Node • Increased Refractory Period at AV node and His-Purkinje Fibres Bradycardia, cardiac arrest, Delayed conduction, Prolonged P-R interval, Heart Block BloodVessels Nitric Oxide(NO) release (endothelium): Vasodilation Fall in BP, flushing M3 Vasoconstriction (smooth muscle of vessels) NO – dilatation of cavernous sinus Erection of penis
- 12. Cholinergic effect onorgan system Organ Receptor Involved Mechanism Effects SmoothMuscle M3 Increased tone and peristalsis of GIT, sphincters relaxed Abdominal cramps, evacuation of bowels Increased peristalsis in ureters, detrusor contracts, trigone & sphincter relaxes Voiding of bladder Constriction of bronchial muscles Bronchospasm, dyspnoea, asthmatic attack
- 13. Cholinergic effect onorgan system Organ Receptor Involved Mechanism Effects Glands M3 + M2 Increased secretion Salivation, sweating, lacrimation, increased tracheobronchial and gastric secretions Eyes M3 Contraction of circular muscle of iris Miosis Contraction of ciliary muscle Blurring of near vision, increased aqueous outflow, decreased intra ocular pressure in glaucomatous eye
- 14. Cholinergic effect onorgan system Organ Receptor Involved Mechanism & Effects Autonomic Ganglia NN • Stimulation at higher doses Skeletal Muscles NM • Contraction of muscle fibres • Intra-arterial injection: twitching and fasciculations
- 15.
- 16. Receptors: Adrenergic Alpha (α)receptors Beta(β) receptors Relative potency of agonists Adrenaline (Adr) ≥ Noradrenaline (NA )> Isoprenaline (Iso) Iso > Adr > NA Antagonists Phenoxybenzamine Propanolol Coupling Protein Go/Gq/Gi Gs βGα Gγ
- 17. Receptors: Adrenergic α1 α2 LocationPost-junctional on effector organs Pre-junctional: nerve ending Post-junctional: brain, pancreatic β cells Extra-junctional: some vessels, platelets G-protein coupling Gq Go/Gi Selective agonist Phenylephrine, Methoxamine Clonidine Selective antagonist Prazosin Yohimbiine, Rauwolscine
- 18. Receptors: Adrenergic β1 β2β3 Location Heart, JG cells in kidney Bronchi, blood vessels, uterus, liver, g.i.t, urinary tract, eye Adipose tissue Selective agonist Dobutamine Salbutamol, terbutaline BRL 37344 Selective antagonist Metoprolol, Atenolol ICI 118551, α- methyl propranolol CGP 20712A
- 19. Adrenergic Effects onorgan system Alpha (α) receptors Beta (β) receptors Rise in BP Fall in BP Little action on heart, arrhythmia at high doses ↑ rate, force and conduction velocity of heart - Bronchodilation Mydriasis, decreased aqueous secretion No effect on iris, relaxation of ciliary muscles, enhanced aqueous secretion
- 20. Adrenergic Effects onorgan system Alpha (α) receptors Beta (β) receptors Intestinal relaxation, contraction of sphincters Intestinal relaxation Bladder trigone contraction Detrusor relaxation Uterus contraction Relaxation Splenic capsule contraction Relaxation
- 21. Adrenergic Effects onorgan system Alpha (α) receptors Beta (β) receptors NM transmission facilitated Active state abbreviated in slow contracting fibres Incomplete fusion of responses Enhanced firing of muscle spindles Decreased insulin secretion Augmented insulin and glucagon secretion Glycogenolysis Glycogenolysis (liver, muscle)
- 22. Conclusion ➢Cholinergic receptors: M1-M5,NN and NM ➢Adrenergic receptors: α1 and α2, β1- β3 ➢M, α and β receptors: GPCRs ➢Nicotinic receptors: Ion channel receptors ➢Effects of sympathetic and parasympathetic systems are not always opposite to each other ✓Can be explained on the basis of receptor involved
- 23. Thank you… ➢Any queries? ➢Nextclass: ✓Friday ✓Cholinomimetic agents ➢Please read and come!