CVS - S3 - L1 PDF

Semester Three Session 3 – Lecture 1 https://youtu.be/CNF5eCngEbE Professor Dr. Ihsan M. Ajeena Consultant of Clinical Neurophysiology  Objectives of the lecture B...

Semester Three Session 3 – Lecture 1 https://youtu.be/CNF5eCngEbE Professor Dr. Ihsan M. Ajeena Consultant of Clinical Neurophysiology  Objectives of the lecture By the end of this lecture you should fulfill the following objectives: 1. Realized organisation of the autonomic nervous system (ANS) 2. Specify transmitters and receptors in the ANS 3. Summarize functions of the ANS (list different organs and state, in brief, the effect of ANS upon them) The Autonomic Nervous System (ANS) Regulate many physiologic functions This regulation is largely outside voluntary control Mainly controls: – Smooth muscle (vascular and visceral) – Exocrine (gland) secretion – Heart contraction (frequency and force) Two divisions: Two cells (periph. nerves): – Sympathetic – Preganglionic – Parasympathetic – Postganglionic  ANS organisation Sympathetic Parasympathetic 1973  Soma location Two neurones arranged in series Central Peripheral Target cell Nervous system Nervous system Preganglionic Postganglionic neurone neurone Only one exception... In the adrenal gland pre- and post-ganglionic neurones Preganglionic Postganglionic Target tissue Post- Preganglionic ganglionic Target tissue Neurotransmitters  ANS Neurotransmitters Preganglionic neurones of both divisions release acetylcholine (Ach) Preganglionic Postganglionic ACh ACh acts on nicotinic receptors on the postganglionic (ion channel) Postganglionic neurotransmitters Preganglionic Postganglionic Target tissue sympathetic neurones are usually adrenergic releasing noradrenaline (NA) Sweat glands (other than that at the palm and sole) Pilloerector muscles parasympathetic neurones are usually cholinergic releasing ACh Muscarinic recceptors on target tissue  Neurotransmitters in the sympathetic nervous system nicotinic ACh receptors adrenergic receptors Preganglionic Postganglionic Target tissue acetylcholine (ACh) noradrenaline (NA) (norepinephrine)  Chromaffin cells of adrenal medulla are dealt with as specialised postganglionic sympathetic neurones nicotinic ACh receptors Preganglionic Sympathetic chromaffin cell adrenaline (epinephrine) acetylcholine (ACh) adrenal chromaffin cells release adrenaline which circulates in the blood stream  Neurotransmitters in the parasympathetic nervous system nicotinic ACh receptors muscarinic ACh receptors Preganglionic Postganglionic effector cell Acetylcholine (ACh) Receptors  Receptors on target tissue for sympathetic nervous system noradrenaline (NA) and adrenaline NA and adrenaline act on adrenoreceptors. These are G protein-coupled receptors (not integral ion channel) Types and subtypes of adrenoreceptors – α-adrenoreceptors (1 & 2) – β-adrenoreceptors (1 & 2) Different tissues can have different receptor subtypes: – Result in different actions and response – Selectivity of drug action (see your Membranes & Receptors module) Receptors on target tissue for parasympathetic nervous system parasympathetic postganglionic neurones release Ach as a neurotransmitter Ach acts at muscarinic receptors on the target cells (what is the receptor type at the NMJ ?) G protein-coupled receptors (M1, M2 & M3) no integral ion channel  General Functions in brief … The tone of the automatic nervous systems : The sympathetic and parasympathetic NS are : continually. only low frequency stimulation is required for full activation.  Sympathetic drive to different tissues is independently regulated Ex. sympathetic activity to the heart can be increased without increasing activity to GIT on other occasions (fight or flight) there can be a more co-ordinated sympathetic response (generalized response) Summary  Remember … What does the autonomic nervous system do? regulates physiological functions the parasympathetic and sympathetic divisions both innervate a tissue and they often have opposite effects on the same organ they work together to maintain balance  Examples of ANS control ORGAN Sympathetic effect receptor Parasympathetic receptor effect pupil of Dilatation α1 Contraction (M3) eye (contracts radial muscle) (contracts sphincter muscle) airways of Relax β2 contract (M3) lungs heart increase rate & β1 decrease rate (M2) force of contraction sweat localised secretion α1 no effect glands (ex. palms) Generalised secretion M3 Search for the effect of the ANS on the rest of body organs and tissues… Supportive slide Organ Effect of symp. stimulation Effect of parasy. stimulation Eye - pupil Dilated Constricted - ciliary muscle Slight relaxation (far vision) Contracted (near vision) Glands - adrenal Secretion of ep. and norep. - - salivary Blood vessel constriction & sec. of thick viscous secretion (a) Blood vessel dilatation and sec. of thin copious sec. - gastric Inhibition (a2) Stimulation - pancreatic Decrease insulin sec. (a2) Increase insulin sec. - lacrimal - Stimulation - sweat Copious watery sec. (c), Sweating of palm & sole (a1) - - apocrine Thick odoriferous sec (c) - Bd.Vs - abd. & skin Constricted (a) Little (face blush area) or none - muscle Dilated (c+b2), constricted (a) Little or none - blood pre. Increase blood pressure None or decrease blood pre. Heart - muscle Increase rate and force (b) Slow rate & decrease force - coronary As Dilated (b2), constricted (a) Dilated Lungs - bronchi Dilated (b2), mucus sec. (a1) Constricted - blood Vs Dilated (b2), constricted (a1) - Gut - wall peristalsis & tone (b) Increase - sphincter Increase tone (a) Decrease on strong stimulation only On most of the times Liver Glucose release Slight glycogen synthesis G. blad. & bile duct Relaxed Contracted Kidney Renin secretion (B1) - Urinary Blad-detrusor Slight relaxation Contracted - trigone Contraction Relaxed Reproductive sys. Male: Ejaculation (a1) Erection Female: uterus contraction (a1) Variable, depending on hormones present uterus relaxation (B2) Blood coagulation & [glu.] & [lipid] - Basal metabolism Increased up to 100% - Mental activity Increased - Skeletal muscle glycogenolysis & strength (B2) - Fat cells Lipolysis -