ANS introduction Dr sachin
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The document provides a comprehensive overview of the autonomic nervous system (ANS), detailing its division into sympathetic and parasympathetic systems, their functions, and neurochemical transmissions. It emphasizes the subconscious regulation of vital bodily functions that occur without conscious awareness, highlighting neurotransmitter roles like acetylcholine and norepinephrine. Additionally, the enteric nervous system is discussed as the third division of the ANS, with its own functional autonomy in the gastrointestinal tract.
ANS introduction Dr sachin
- 1. INTRODUCTION TO ANS Dr. Sachin Gupta Department Of Pharmacology UCMS
- 2. NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM Processes, interprets, stores information Issues orders to muscles, glands organs BRAIN SPINAL CORD Bridge between Brain & Peripheral nerves PERIPHERAL NERVOUS SYSTEM Transmits information to & from CNS
- 3. PERIPHERAL NERVOUS SYSTEM EFFERENT DIVISION AUTONOMIC SYSTEM Regulates glands, blood vessels, internal organs SYMPATHETIC Mobilizes body for action energy output PARASYMPATHETIC Conserves energy, maintains quiet state ENTERIC AFFERENT DIVISION SOMATIC SYSTEM Controls skeletal muscles
- 4. Autonomic Nervous System • Sympathetic System prepares an individual to ‘fight, flight or fright’ • Parasympathetic System aims at ‘conserving & restoring energy’
- 5. Autonomic Nervous System • Autonomic Nervous System is composed of Efferent neurons that innervates- • Smooth muscles of viscera • Cardiac muscle • Vasculature & • Exocrine glands. • Thereby controlling---- digestion, cardiac output, blood flow & glandular secretions. • The Autonomic system regulates the everyday requirements of vital bodily functions without the conscious participation of the mind.
- 6. Autonomic Nervous System • Make adjustments to ensure optimal support for body activities • Operate via subconscious control • Have viscera as most of their effectors
- 8. PREDOMINANTLY SYMPATHETIC INNERVATION- • Radial muscle of iris • Smooth muscles of eyelids • Pilomotor muscle • Ventricular myocardium • Bladder neck (trigone) • Seminal vesicles • Vas deferens PREDOMINANTLY PARASYMPATHETIC INNERVATION- • Circular muscle of iris • Ciliary muscle • Lacrimal glands • Mucous membrane of git & bronchial tree • Pancreatic exocrine glands • Detrusor muscle of bladder • Erectile tissue of penis
- 10. Role of the Parasympathetic Division • Concerned with keeping body energy use low • Involves the D activities – digestion, defecation, and diuresis
- 11. PARASYMPATHETIC NERVOUS SYSTEM • Preganglionic parasympathetic axons travel a long distance before eventually reaching their target ganglia which are located close to or even within the target end organs. • The Parasympathetic postganglionic fibers---shorter than preganglionic fibers. • Preganglionic fibers--- Myelinated • Postganglionic fibers---Non-myelinated (except--- ciliary Parasympathetic postganglionic fibers--- Myelinated)
- 14. PARASYMPATHETIC NERVOUS SYSTEM • Also called the CRANIOSACRAL system because all its preganglionic neurons are located in the nuclei of brain stem or sacral levels of the spinal cord. • Cranial nerves III,VII, IX and X • In lateral horn of gray matter from S2-S4 • Distribution of Parasympathetic fibers is wholly visceral • Acetylcholine is neurotransmitter at end organ as well as at preganglionic synapse: “cholinergic”
- 15. SYMPATHETIC NERVOUS SYSTEM • “Fight or flight’’ response • Release adrenaline and noradrenaline • Increases heart rate and blood pressure • Increases blood flow to skeletal muscles • Inhibits digestive functions
- 16. SYMPATHETIC NERVOUS SYSTEM • The preganglionic neurons of Sympathetic Nervous System have their cell bodies in lateral horn of grey matter of Thoracic & Lumbar regions (T1-L2/3) of Spinal cord • Thoracolumbar outflow • The preganglionic neurons are short in comparison to postganglionic neuron. • Preganglionic sympathetic fibers tend to synapse with a large no of Postganglionic fibers which in turn have a more diffused ramification at Neuroeffector junction (NEJ)
- 17. SYMPATHETIC NERVOUS SYSTEM • Immediately after the spinal nerve leaves the spinal canal, the preganglionic sympathetic fibers leave the spinal nerve & pass through a white ramus into paravertebral sympathetic chain of 22 sympathetic ganglia, which lie bilaterally on either side of the spinal column.
- 18. SYMPATHETIC NERVOUS SYSTEM • The postganglionic sympathetic neurons thus originate either in one of the Sympathetic chain ganglia or in one of the peripheral sympathetic ganglia. • From either of these two sources, the postganglionic fibers then travel to their destinations in the various organs.
- 19. Neurochemical Transmission • Cholinergic Transmission • Adrenergic Transmission
- 20. CHOLINERGIC TRANSMISSION • ACh- Neurotransmitter in • All Autonomic Ganglion Synapses (Sympathetic / Parasympathetic) • All Postganglionic parasympathetic neurons • Sympathetic neurons innervating sweat glands • The nerve endings supplying Adrenal medulla • Most enteric nervous system neurons • The somatic motor nerve endings supplying skeletal muscles • Effects of Ach are mediated by NICOTINIC and MUSCARNIC receptors
- 22. Nicotinic Receptors • Bind- • ACh • Nicotine • Muscarine (weak affinity) • Composed of 5 subunits • Functions as Ligand-gated ion channel • When bound to ACh, these receptors undergo conformational change that allows entry of Na+ ions, resulting in depolarization of the effector cell.
- 24. NM NN LOCATION SKELETAL NEUROMUSCULAR JUNCTION (NMJ) postsynaptic AUTONOMIC GANGLIA ADRENAL MEDULLA CNS MEMBRANE RESPONSE • EXCITATORY • END PLATE DEPOLARIZATION • SKELETAL MUSCLE CONTRACTION • EXCITATORY • DEPOLARIZATION and FIRING OF POSTGANGLION NEURON • DEPOLARIZATION & SECRETION OF CATECHOLAMINES
- 25. MUSCRINIC RECEPTORS • Bind--- • ACh • Muscarine (alkaloid present in certain poisonous mushrooms. It was first isolated in Amanita muscaria) • Present at – • Smooth muscles • Glands • G- protein coupled receptors
- 28. M1 M2 M3 LOCATION • CNS(cortex & hippocampus) • AUTONOMIC GANGLIA • GASTRIC PARACRINE CELLS CARDIAC— SA node AV node Atrium Ventricle NEURAL- presynaptic terminals • EXOCRINE GLANDS • SMOOTH MUSCLES • VASCULAR ENDOTHELIUM FUNCTIONAL RESPONSE • EXCITATORY--- • Gastric acid secretion • GI motility • CNS excitation • INHIBITORY--- • SA node-rate of impulse generation • AV node- velocity of conduction • Atrium- • refractory period • contraction • Ventricle- contraction • Peripheral nerves- ganglionic transmission • EXCITATORY--- • Smooth muscle– contraction • Glands– secretion
- 29. ADRENERGIC TRANSMISSION • With exception of the sweat glands , Norepinephrine is the primary neurotransmitter in sympathetic ganglionic neurons • Epinephrine is released from chromaffin cells of adrenal medulla and acts as a circulating hormone • Norepinephrine & Epinephrine act via α & β receptors • Smooth muscle contraction – α1 receptors • Stimulation of heart – β1 receptors • Smooth muscle relaxation – β2 receptors • Lipolysis in brown fat – β3 receptors
- 31. RECEPTOR LOCATION G-PROTEIN SECOND MESSENGER α1 Postsynaptic Most smooth muscles, salivary glands, liver cells Gq IP3 DAG α2 Presynaptic on adrenergic or cholinergic nerve terminals; Postsynaptic in brain; β-Pancreatic cells Vascular smooth muscle (α ) Gi cAMP β1 Postsynaptic at cardiac muscle, Juxtaglomerular apparatus; Presynaptic at adrenergic & cholinergic nerve terminals Gs cAMP β2 Post- as well as Presynaptic in Bronchi, Coronary arteries, uterus & smooth muscles; also in myocardium Gs cAMP β3 Postsynaptic at adipocytes Gs cAMP
- 32. ENTERIC NERVOUS SYSTEM • The Enteric Nervous System, considered as the third division of the ANS, consists of highly organized neurons situated in the wall of GIT. • It includes the– • Myenteric plexus (Auerbach’s plexus) • Submucus plexus (Meissner’s plexus) • This network receives preganglionic fibers from the Parasympathetic & from the postganglionic Sympathetic neurons.
- 33. • Neurons-- • Sensory neurons- Receive information from sensory receptors • Motor neurons- control gi motility & secretions • Interneurons- integrate information from sensory neurons & provide it to enteric motor neurons • Neurotransmitters-- • Acetylcholine– Excitatory– • Smooth muscle contraction • Increase in intestinal secretions • Release of enteric hormones • Dilatation of blood vessels • Norepinephrine– Actions opposite that of Ach • Other neurotransmitters– Neuropeptide(NP), Substance P(SP), Serotonin (5HT), Dopamine(DA), Cholecystokinin(CCK)
- 34. • Enteric Nervous System - functions autonomously • “BRAIN OF THE GUT” • Sympathetic & Parasympathetic fibers---communication links between ANS & CNS • Sympathetic stimulation– • Inhibition of GI secretions & motor activities • Contraction of GI sphincters & blood vessels • Parasympathetic stimulation- • Increase motility of intestine • Relaxes the sphincters
- 35. CONCLUSION • The main function of ANS is to maintain the entire body and to also connect all the nerves • So basically, it maintains everything we do in our everyday life. • A thorough knowledge of the Anatomy and Physiology of Autonomic Nervous System is necessary for having a better understanding of Autonomic dysfunction & the role of overwhelming number of drugs having an affect on this system.
- 36. BIBLIOGRAPHY 1. Principles of pharmacology by HL Sharma and KK Sharma (2nd edition) 2. Basic and clinical pharmacology by Bertram G. Katzung (11th edition) 3. The pharmacological basis of therapeutics by Goodman and Gilman (11th edition) 4. Lippincott's illustrated reviews: pharmacology (5th edition) 5. Essentials of pharmacology by K D Tripathi (6th edition) 6. Review of Medical Physiology by William F. Ganong (23rd edition) 7. Grey’s Anatomy The anatomical basis of Clinical Practice(40th edition)
- 37. THANK YOU FOR YOUR TIME AND ATTENTION