Autonomic Nervous System - University of Plymouth PDF

Autonomic Nervous System  Learning outcome Explain the key functions of the sympathetic and parasympathetic nervous system, including with reference to key synapses, ganglia and adrenergic receptors. Why do we have an autonomic nervous system? ...

Autonomic Nervous System  Learning outcome Explain the key functions of the sympathetic and parasympathetic nervous system, including with reference to key synapses, ganglia and adrenergic receptors. Why do we have an autonomic nervous system?  Key concept on the course: Recognise the function of physiological variation as a means of adaptation and that consistent features across a population typically signify a strong physiological function Credit: Ernsberger & Rohrer, Nature (2024) Can you describe the branches of the automimic nervus system and how its relationship to the rest the nervous system?  Peripheral nerves contain a variety of nerve cells (a.k.a nerve fibres) Motor (efferent) Sensory The(afferent) autonomic The autonomic (a.k.a nervous system has visceral) nerve fibres relatively few innervate our sensory fibres, and (involuntary) organs. these are not These can either be frequently sympathetic or stimulated. parasympathetic These nerve fibres are neither The somatic nerves sympathetic nor innervate skeletal parasympathetic, but (voluntary) muscle general visceral afferents  Neurons of the central nervous system regulate the effects of the autonomic nervous system Brain Brain Stem Spinal Cord Autonomic Ganglia Target organ Sympathetic Parasympathetic  Between the central nervous system and a target organ there will be one synapse at a ganglion Central Nervous system Parasympathetic Parasympathetic Target postganglionic fibres ACh M 1, M 2, M3, release acetylcholine Nicotinic acetylcholine receptors M4, M5 Preganglionic fibre Postganglionic fibre Most Sympathetic Sympathetic ACh Target postganglionic fibres  1,  2 or 1, Nicotinic acetylcholine release 2,3 receptors noradrenaline Acetylcholine is the transmitter at ALL autonomic ganglia Main exceptions: ACh sweat glands, skeletal muscle blood vessels NO: Erectile tissue Adrenal medulla The sympathetic nervous system has Synapses are closer to the target a craniocaudal outflow organ Fibres from Target organs cranial nerves Target organs III,VII, IX, X Pelvic splanchnic nerves The sympathetic nervous system travels via rami communicantes By Mysid (original by Tristanb) - Vectorized in CorelDraw by Mysid on an existing image at en-wiki by Tristanb., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1420508 The sympathetic nervous system has Synapses are further from the target a thoracolumbar outflow (T1-L2/3) organ Target organs Target organs Pre-vertebral ganglion Some preganglionic neurons will innervate the adrenal medulla. This will cause chromaffin cells to release adrenaline Paravertebral ganglia In a little more detail….  The sympathetic ganglia Motor fibres run through the anterior spinal nerves and via the white rami communicantes toward a ganglion 2 There are four main fates of the preganglionic neurone: 1 4 1. Form a synapse and continue along the spinal nerve via the grey rami Pre-vertebral communicantes ganglion 2. Ascend to form a synapse (and often return via the grey rami – not shown) 3 3. Ascend to form a synapse (and often return via the grey rami – not shown) Paravertebral 4. Move through the ganglion ganglion to a prevertebral ganglion Hall: Guyton and Hall Textbook of Medical Physiology, Parasympathetic Sympathetic nervous system nervous system Target organs Target organs  *The autonomic nervous system carries some limited sensory information from the internal organs By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See "Book" section below)Bartleby.com: Gray's Anatomy, Plate 799This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: vectorization (CorelDraw). The original can be viewed here: Gray799.png:. Modifications made by Mysid., Public Domain, https://commons.wikimedia.org/w/index.php?curid=1421005  What are some effects of the sympathetic nervous system being activated? What are some effects of the parasympathetic nervous system being activated? Think throughout the entire body Think back to what you have seen on the course so far…. Sympathetic nervous system  Eyes CNS Neurology Dilates pupils (mydriaisis) via Increased alertness/stress contraction of the radial muscles of the iris Lungs Vascular System Relaxation of bronchial smooth Net effects is and increase muscle peripheral vasoconstriction leading to an increase in systemic vascular Heart resistance (SVR) Increased contractility (positive inotrope) Metabolic Increased heart rate (positive Increases blood sugar via a number chronotrope) of mechanisms including Increased cardiac conduction glycogenolysis Faster relaxation (positive lusitrope) Increases potassium uptake by cells Haematological Increased platelets/clotting factors Urinary and Reproductive Relaxes bladder and uterus Gastrointestinal Initiates ejaculation Inhibits peristalsis and secretion (inc. saliva) Urinary MSK Constricts internal urethral sphincter Tremor Parasympathetic nervous system  Eyes CNS Neurology Wakefulness, learning, attention Dilates pupils via contraction of the radial muscles of the iris Lungs Vascular System Constriction of bronchial smooth Net effects is and increase muscle peripheral vasoconstriction leading to an increase in systemic vascular Heart resistance (SVR) Decreased heart rate (Negative Metabolic chronotrope) Increases glycogen storage Reproductive Gastrointestinal Promotes peristalsis and secretion Promotes erection (inc. clitoris) (inc. saliva) Urinary Relaxes internal urethral sphincter What parts of the body release adrenaline and noradrenaline? How are they produced and removed? How do they exert their effects?  Catecholamines Catechol Catecholamines contain a Catechol backbone Catecholamine s  Catecholamines are derived from tyrosine Tyrosine hydroxylase is the rate limiting step in synthesis and is inhibited by noradrenaline Dopamine is a precursor to the formation of adrenaline/noradrenaline Dopamine β-hydroxylase and other enzymes are dependent on the function of the adrenal cortex Adrenaline is made from the methylation of noradrenaline by PNMT Ritter: Rang & Dale's Pharmacology, 9th Edition Adrenal Cortex Adrenaline/ Adrenal Medulla Epinephrine Noradrenalin e/ Norepinephri ne Catecholamines are peptide hormones and bind to adrenergic receptors on the cell surface  Noradrenaline is stored in granules in the sympathetic These can then stimulate Ca 2 trimeric nerve terminus and is released + upon calcium influx following G- protein coupled receptors arrival of an action potential found in the target organ α2 Sympathetic receptor nerve terminus α1 β1 Β2 receptor receptor receptor Phospholipase Adenylate Adenylate C cyclase cyclase Phospahtid IP3 ATP cAMP ATP cAMP yl -inostol PKC PKA *Beta 3 not PKA Target covered today  Adrenaline (and small quantities of noradrenaline) can be released into the blood stream from chromaffin cells in the adrenal medulla α1 β1 Β2 receptor receptor receptor Phospholipase Adenylate Adenylate C cyclase cyclase Phospahtid IP3 ATP cAMP ATP cAMP yl -inostol PKC PKA PKA Target Adrenergic receptors are not uniformly distributed  Alpha 2 (α2) Ca2 adrenoreceptors + α2 receptor Vascular System Some vasoconstrictive effects Metabolic Increases blood sugar via a number of mechanisms including glycogenolysis Gastrointestinal Reduced GI motility  Beta 1 (β1) adrenoreceptors Heart Increased contractility (positive inotrope) Increased heart rate (positive chronotrope) Increased cardiac conduction Faster relaxation (positive lusitrope) Renal Increased renin release  Beta 2 (β2) adrenoreceptors Lungs Relaxation of bronchial smooth muscle Vascular system Mild relaxation of vessels, typically those that supply muscle Metabolic Raises blood glucose Increases potassium uptake by cells MSK Tremor Urinary and Reproductive Relaxes bladder and uterus Nor are Acetyl cholerine receptors  Eyes CNS Neurology Relaxation Dilates pupils via contraction of the radial muscles of the iris Lungs Vascular System Constriction of bronchial smooth Net effects is and increase muscle peripheral vasoconstriction leading to an increase in systemic vascular Heart resistance (SVR) Decreased heart rate (Negative Metabolic chronotrope) Increases glycogen storage Reproductive Gastrointestinal Promotes peristalsis and secretion Promotes erection (inc. clitoris) (inc. saliva) Urinary MSK Relaxes internal urethral sphincter Tremor Removal and degradation  Ca2 Noradrenaline is primarily + removed by reuptake into the nerve terminus Sympathetic nerve terminus α1 β1 Β2 receptor receptor receptor Phospholipase Adenylate Adenylate C cyclase cyclase Phospahtid IP3 ATP cAMP ATP cAMP yl -inostol PKC PKA PKA Target  Inside the cell the noradrenaline is then quickly taken up into vesicles by the type 2 vesicular monoamine transporters (VMAT-2) and recycled By doing this up to 90% of the noradrenaline is recycled Noradrenaline can be taken up by the Norepinephrine Transporter (NET)  Adrenaline is primarily removed in the peripheral circulation and metabolized. The main sites for this are the liver and kidney. Adrenaline can also be taken up by NET transporters at nerve terminals Target  Cholin e Acetyl Co-A Choline recycled Acetyl choline Acetyl choline esterase (Ach) Acetyl choline receptors  Learning outcome Explain the key functions of the sympathetic and parasympathetic nervous system, including with reference to key synapses, ganglia and adrenergic receptors.