Autonomic Nervous System PDF

‫بسم هللا الرحمن الرحيم‬ ‫قالوا سبحانك ال علم لنا إال ما علمتنا‬ ‫إنك أنت العليم الحكيم‬ ‫صدق هللا العظيم‬ ‫البقرة‪ :‬من اآلية ‪32‬‬ Autonomic Nervous System BY Dr /Ahmed Abdalfattah Professor of Medical Physiology Tanta University...

‫بسم هللا الرحمن الرحيم‬ ‫قالوا سبحانك ال علم لنا إال ما علمتنا‬ ‫إنك أنت العليم الحكيم‬ ‫صدق هللا العظيم‬ ‫البقرة‪ :‬من اآلية ‪32‬‬ Autonomic Nervous System BY Dr /Ahmed Abdalfattah Professor of Medical Physiology Tanta University  The peripheral nervous system ⚫The cranial nerves: 12 pairs of cranial nerves which connect the brain stem with different parts of the body. ⚫The spinal nerves: 31 pairs of spinal nerves  Divisions of the ANS ⚫ The sympathetic nervous system: arise from the lateral horn cells of all thoracic and upper 3 lumbar segments (Thoraco-Lumbar outflow) ⚫ The parasympathetic nervous system: Crainio-sacral outflow) ⚫ 3rd Occulo motor ⚫ 7th Facial ⚫ 9th Glossopharyngeal ⚫ 10th Vagus  The ANS has 2 subdivisions : sympathetic and parasympathetic 10/31/2024 10  Division of autonomic nerve system sympathetic – fight or flight parasympathetic – rest or digest enteric system  Overview of the Autonomic Nervous System Differences between Sympathetic & Parasympathetic Location of Preganglionic Cell Bodies Sympathetic Parasympathetic Thoracolumbar Craniosacral T1 – L2/L3 levels Brain: CN III, VII, IX, X of the spinal cord Spinal cord: S2 – S4  AUTONOMIC GANGLIA ⚫ Definition - They are collection of nerve cells outside the central nervous system  The autonomic nervous system pathways: The autonomic division consists of two efferent neurons in series Fig. 11-4 Tasrget tissue : effector Effector 10/31/2024 14  Overview of the Autonomic Nervous System Differences between Sympathetic & Parasympathetic Relative Lengths of Neurons Sympathetic CNS ganglion target short preganglionic long postganglionic neuron neuron Parasympathetic ganglion target CNS long preganglionic short postganglionic neuron neuron  Types of Autonomic Ganglia According to their situation the autonomic ganglia are classified into: - Lateral - Collateral- - Terminal  The Lateral (Vertebral OR Paravertebral) ganglia - Forming 2 chains, each has 23 ganglia connected together by nerve fibers. In the cervical region there are only (3) ganglia i.e. superior, middle and the inferior cervical sympathetic ganglia. - The inferior cervical ganglion may join with the first one or two thoracic ganglia to form the satellite ganglion. - Below the inferior cervical ganglia there is regularly a ganglion for each segment of thoracic (12), lumbar (4) and sacral regions (4), but at the coccygeal region there is only one ganglion.  Collateral ganglia - Fibres that supply the abdominal and pelvic viscera, leave the sympathetic trunk as pregnanglionic fibres to form the greater and lesser splanchnic nerves that relay in collateral ganglia situated near the abdominal aorta at the origin of the big arterial branches of the aorta and are named (coeliac, superior mesenteric, renal and hypogastric ganglia).  Terminal ganglia The sacral autonomic outflow, that belongs to the parasympathetic, pass in the pelvic visceral nerve and relays in terminal ganglia as well as the cranial parasympathetic fibres. i.e. the sympathetic mostly relay in lateral ganglia but some relay in collateral, while the Parasympathetic relay mainly in the terminal ganglia but some relay in collateral one Types of the autonomic ganglia  Sympathetic System: Postganglionic Cell Bodies 1. Paravertebral ganglia Located along sides of vertebrae United by preganglionics into Sympathetic Trunk Preganglionic neurons are thoracolumbar (T1–L2/L3) Paravertebral but postganglionic neurons are cervical to coccyx ganglia Some preganglionics ascend or descend in trunk sympathetic trunk (chain) synapse at same level Prevertebral ganglia celiac ganglion sup. mesent. g. inf. mesent. g. ascend to descend to synapse at synapse at aorta higher level lower level Moore’s COA6 2010 Structure of spinal nerves: Somatic pathways dorsal root dorsal dorsal root ganglion ramus spinal dorsal nerve somatic horn sensory nerve CNS (GSA) inter- neuron ventral ventral somatic horn ramus motor nerve gray ramus (GSE) ventral root communicans white ramus communicans Mixed Spinal sympathetic Nerve ganglion Structure of spinal nerves: Sympathetic pathways dorsal ramus intermediolateral gray column spinal nerve ventral ramus gray ramus communicans white ramus communicans sympathetic ganglion  Functions of Autonomic Ganglia I- They act as distributing centers:The pre-ganglionic fibers are relatively few in number and arise from limited regions of the C.N.S. By the aid of the ganglia the activity of a preganglionic fiber can activate larger number of postganglionic fibers and produce a wide spread activity all over the body e.g. one sympathetic preganglionic fiber can activate 32 fibers of postganglionic, i.e. 1:32 ratio while in the case of parasympathetic the ratio is 1:2 i.e. parasympathetic activity is much limited than the sympathetic, SINCE geneeralized ara sympathetic functions are undesirable and may be fetal.  II - Unidirectional conduction: Impulses travel in one direction from the preganglionic fibers to the postganglionic and not in the reverse direction.  III - One relay The autonomic efferent relay only once in the autonomic ganglia whereas it may pass through other autonomic ganglion but without relay Methods of Determination of the site of relay a) Section of ventral root is followed by degeneration of the corresponding preganglionic fibres. If degeneration extended after ganglia this means that these fibres pass without relay in this ganglia. b)Langltey,s Nicotine test: When we apply nicotine in large dose locally to the ganglion it causes paralysis to the fibre that relay in autonomic ganglia but not affect the non relaying fibres.  IV- The chemical transmitter :In all autonomic ganglia is acetylcholine (nicotine- like action). V - Delay of transmission : conduction in the autonomic ganglia takes longer time VI - Conduction : is obligatory Impulses must pass from the preganglionic fibre through the ganglion to the postganglionic fibre  Overview of the Autonomic Nervous System Differences between Sympathetic & Parasympathetic Neurotransmitters Sympathetic NE (ACh at sweat glands), ACh, + + / -, α & ß receptors All preganglionics release acetylcholine (ACh) & are excitatory (+) Symp. postgangl. — norepinephrine (NE) & are excitatory (+) or inhibitory (-) Parasymp. postgangl. — ACh & are excitatory (+) or inhibitory (-) Excitation or inhibition is a receptor-dependent & receptor-mediated response Parasympathetic ACh, + Potential for pharmacologic ACh, + / - muscarinic receptors modulation of autonomic responses Thank you