Autonomic Nervous System PDF

AUTONOMIC NERVOUS SYSTEM (ANS) Contents… Comparison  Comparison Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia.  Central Control of ANS C...

AUTONOMIC NERVOUS SYSTEM (ANS) Contents… Comparison  Comparison Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia.  Central Control of ANS Cerebral cortex through the hypothalamus and reticular formation Brain stem - reflexes for heart rate and BP Spinal cord - reflexes for urination, defecation and erection Taylor EW, Jordan D, Coote JH: Central control of the cardiovascular and respiratory systems and their interactions in vertebrates. Physiol Rev 79:855,  Autonomic Visceral Reflex Arc Taylor EW, Jordan D, Coote JH: Central control of the cardiovascular and respiratory systems and their interactions in vertebrates. Physiol Rev 79:855, 1999. Comparison … Two divisions: Sympathetic and Parasympathetic Usually two systems work together to maintain a balanced state or homeostasis in the body Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia. Sympathetic and Parasympathetic ‘tone’  SYMPATHETIC NERVOUS SYSTEM Acts in times of emergency such as ‘FRIGHT’ or ‘FLIGHT’ Prepares the body to act Increases heart rate and respiration Raises blood pressure Slows activity in the digestive tract Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia. PARASYMPATHETIC NERVOUS SYSTEM Counteracts the actions of the sympathetic after the emergency Dominates in quite and relaxed conditions ‘House keeping functions’ – digestion and micturition Slows the heart rate and respiration Lowers the blood pressure Two Cell Motor Pathway The first is the preganglionic neuron, whose cell body is located in the brain or spinal cord – In the sympathetic division, the cell body is located in the lateral grey horns (thoraco-lumbar) – In the parasympathetic division, the cell body is located in various nuclei of brain stem or in the lateral grey horns (sacral) Two Cell Motor Pathway The second is the postganglionic neuron, whose cell body is in an autonomic ganglion -The postganglionic fiber sends impulses to a target organ -The effects at the target organ are due to type of neurotransmitter and specific cell surface receptors on the effector cells  Two Cell Motor Pathway Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia.  SYMPATHETIC PARASYMPATHETIC PREGANGLIONIC FIBRES THORACOLUMBAR DIVISION CRANIOSACRAL DIVISION LENGTH OF PREGANGLIONIC SHORT LONG AXONS PREGANGLIONIC FIBRES TRAVEL VENTRAL ROOT OFA SPINAL CRANIAL NERVE OR VENTRAL IN NERVE ROOT OFA SPINAL NERVE PARAVERTEBRAL GANGLIONAND GANGLION TERMINAL GANGLION PREVERTEBRAL GANGLION THE PREGANGLIONIC AXON A LARGE NUMBER OF A SMALL NUMBER OF SYNAPSES WITH: POSTGANGLIONIC NEURONS POSTGANGLIONIC NEURONS EFFECTS WIDESPREAD NARROW LENGTH OF POSTGANGLIONIC LONG SHORT AXONS GENERAL DESCRIPTION OF "FIGHT-OR FLIGHT" RESPONSE "HOUSEKEEPING" EFFECTS MOST BODY STRUCTURES SWEAT GLANDS, ARRECTOR PILI RECEIVE DUAL INNERVATION, BUT MUSCLES, FAT CELLS, CUTANEOUS LACRIMAL (TEAR) GLANDS A FEW ARE INNERVATED BY ONE BLOOD VESSELS DIVISION ONLY Sympathetic Division ‘Thoracolumbar’  The Sympathetic Division Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy  The Sympathetic Ganglion Paravertebral ganglion – Located parallel to spinal cord on either side – Connected to the spinal nerve through the grey and white rami Prevertebral Gangliaon – Lie anterior to the vertebral column – Occur only in abdomen and pelvis – Unpaired, not segmentally arranged – Also called collateral  Postganglionic Neurons 3 types of postganglionic fibres – Which enter the spinal nerve through the grey ramus – Which travel along the blood vessels to supply head & neck – From collateral ganglia which travel short distance to innervate visceral organs The Sympathetic Ganglion Sympathetic Pathways to Periphery The Adrenal Medulla Parasympathetic Division ‘Craniosacral’  The Parasympathetic Division Preganglionic neurons originate in the brainstem and the lateral horn of the spina cord in sacral region Pass through cranial nerves III, VII, IX, X and S2-4 Extend some distance, synapse in terminal ganglia, and release Ach  Postganglionic neurons originate in the terminal ganglia, pass a short distance and then release Ach  Cranial Outflow Origin of Location of Nerve preganglionic Effector organ terminal ganglia fibers Eyes (smooth Occulomotor nerve Midbrain Cilliary ganglion muscle in iris & (III) nerve cilliary body ) Pterygopalatine & Lacrimal, Salivary Facial (VII) nerve Pons submandibular & mucous glands ganglia Glossopharyngeal Medulla oblongata Otic ganglion Parotid gland (IX) nerve Heart, lungs, GI Vagus (X) nerve Medulla oblongata Terminal ganglia tract, liver, pancreas Parasympathetic innervations  Sacral Outflow Emerges from S2-S4 Form splanchnic nerves Innervates lower half of large intestine, rectum, urinary bladder, reproductive organs Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia.  ANS Dual Innervations Divisions of the ANS innervate many of the same organs -Different effects are due to specific different neurotransmitters and receptor types of effectors Guyton and Hall , Textbook Of Medical Physiology, 11th edition; 2006; Elsevier Inc.1600 John F. Kennedy Blvd., Suite 1800 Philadelphia. Target Parasymp.Symp (Eye (Iris.Myosis.Mydriasis (Eye (Ciliary ms.Contraction.No innervation Salivary Gland.Watery sec.Mucous sec Sweat Glands No innervation sweating ++ Target Parasymp. Symp Organ Heart - - - HR. ++ HR & force VC coronary VD Lungs Bronchoconst. Bronchodilation GIT ++ peristalsis, -- peristalsis, secretion & bile. secretion. UB& rectum Urination & Retension. defecation Genetalia Erection Ejaculation. Target Organ Parasympathetic Sympathetic Effects Effects Endocrine Pancreas Stimulates insulin Inhibits insulin secretion. secretion. Blood Vessels Little effect. Constricts most blood vessels and increases BP. Exception – dilates blood vessels serving skeletal muscle fibers (cholinergic).  Neural Communication ▪ Neurotransmitters ▪ Chemical messengers that traverse the synaptic gaps between neurons ▪ When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, and thereby bring about effect K D Tripathi, Essentials of Medical Pharmacology,6th edition,2008 Jaypee brothers medical publishers,Delhi Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.  Neurotransmitters SOMATIC NERVOUS SYSTEM ACh Striated muscle AUTONOMIC NERVOUS SYSTEM Sympathetic Heart ACh NE Sm. mus. Glands Sweat ACh ACh glands ACh Ad. M. → E, → NE Parasympathetic Heart ACh ACh Sm. mus. Glands  Cholinergic Receptors Muscarinic Receptors Nicotinic Receptors (Peripheral Cholinergic ) (Central Cholinergic) R.) Strong affinity to muscarine Weak affinity to muscarine Weak affinity to nicotine Strong affinity to nicotine -Parasympathetic supplying -Autonomic ganglia (Nn) effector organs - Adrenal Medulla (Nn) -Sweat gland - Neuromuscular junction (Nm) - CNS -CNS (Nn) Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.  Muscarinic Receptors M1 (Neural) M2 (Cardiac) M3 (Glandular) -CNS Presynaptically -Exocrine gland - CNS - Atria and conducting -Smooth muscles - Gastric parietal cells tissue -Vascular endothelium Atropine Atropine Atropine Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.  Adrenergic Adrenergic Adrenergic Adrenergic Receptors Receptors Receptors Receptors αα Subtype Subtype ββSubtype Subtype α1 α2 β1, β2 & β3 - Presynaptic adrenergic smooth muscles β1 (heart) nerve terminal β2 (smooth muscles) CNS- β3 (lipocytes) β cells of pancreas- Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. ) Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.