Transcript Slide 1
Parasympathetic NS (craniosacral) Preganglionic neurons………………………. Cranial outflow…. - occulomotor (III) - facial (VII) - glossopharyngeal (IX) - vagus (X) Sacral outflow…..2nd, 3rd and 4th sacral segments Post ganglionic neurons …. terminal ganglia 1 The parasympathetic division often produces antagonistic effects to sympathetic division through the release of acetylcholine from its post ganglionic fibers 2 Functions of Parasympathetic Nervous System 1- Head & Neck: Occulomotor Nerve (3rd cranial nerve): → Pupil constriction (miosis) → increase power of lens necessary for near vision Facial nerve (7th cranial nerve): A- Secretomotor & vasodilator to the submandibular & sublingual salivary glands B- secretion of lacrimal & nasal glands. Glossopharynqeal nerve (9th cranial nerve): Secretomotor & vasodilator to parotid gland. Functions of Parasympathetic Nervous System Thorax & Abdomen are supplied by Vagus nerve (10th cranial nerve ) 2- Thorax: Heart: → Inhibition of all atrial properties (NO vagal supply to ventricles) → Decrease coronary flow & 02 consumption Lungs: → Bronchial constriction → Dilatation of pulmonary blood vessels → Increase bronchial secretion. Functions of Parasympathetic Nervous System (3) Abdomen: GIT: → Motor to esophagus, stomach, small intestine, proximal part of large intestine → Inhibitory to sphincters → Secretory to glands of stomach, small intestine, liver, pancreas Gall bladder: → Motor to wall → Inhibitory to sphincters i.e. Evacuation of gall bladder. Functions of Parasympathetic Nervous System (4) Pelvis: sacral outflow a) Defecation ++ b) Micturition: ++ c) MaIe genitalia: → Erection → Secretory to seminal vesicle & prostate 7 Parasympathetic Response "Rest and Digest" Sympathetic Response "Fight or Flight" Heart Decreased heart rate Cardiac output decreases Increased rate and strength of contraction Cardiac output increases Lung Bronchioles Constriction Dilation Liver Glycogen No effect Glycogen breakdown Blood glucose increases Fat Tissue No effect Breakdown of fat Blood fatty acids increase Basal Metabolism No effect Increases ~ 2X Stomach Increased secretion of HCl & digestive enzymes Increased motility Decreased secretion Decreased motility Intestine Increased secretion of HCl & digestive enzymes Increased motility Decreased secretion Decreased motility Urinary bladder Relaxes sphincter Detrusor muscle contracts Urination promoted Constricts sphincter Relaxes detrusor Urination inhibited Rectum Relaxes sphincter Contracts wall muscles Defecation promoted Constricts sphincter Relaxes wall muscles Defecation inhibited Eye Pupils constrict Adjusts for near vision Pupils dilate Adjusts for far vision Male Sex Organs Promotes erection Promotes ejaculation Organ 8 Chemical transmitters in autonomic nervous system • Acetylcholine • Noradrenaline (Norepinephrine) 9 Acetylcholine Sites of release of acetylcholine • • • • All preganglionic autonomic fibers (sympathetic ¶ sympathetic ) preganglionic sympathetic fibers to suprarenal medulla All postganglionic para sympathetic fibers postganglionic sympathetic fibers to sweet glands and blood vessels of skeletal muscle ( VD) Removal of acetylcholine It is split into acetate & choline by acetylcholine esterase True acetylcholine esterase → cholinergic nerve endings Pseudo acetylcholine esterase → in plasma 10 11 Cholinergic receptors Nicotinic receptors -autonomic ganglia -skeletal muscles ( motor end plate) -suprarenal medulla Muscarinic receptors -viscera supplied by postganglionic para sympathetic fibers -sweet glands and blood vessels of skeletal ( sympathetic cholinergic fibers) muscle 12 Nor adrenaline (Norepinephrine) Sites of release of Noradrenaline All postganglionic sympathetic fibers except fibers to sweet glands and blood vessels of skeletal muscle Fate of Noradrenaline 1. Re-uptake into the adrenergic nerve endings 2. Diffusion away into the body fluids & plasma 3. Destruction by • MAO ( monoamin oxidase) • COMT ( catechol-O –methyl transferase) 14 Adrenergic receptors Alpha receptors Alpha 1 and alpha 2 Alpha 1 →Excitatory ( intracellular Ca++ ) • Vasoconstriction • Contraction of sphincter of GIT, dilator pupillea , spleniccapsule, seminal vesicles and vas deferens Alpha 2 → inhibitory to intestinal wall ( c-AMP) Beta receptors Beta 1 → excitatory, heart & metabolic action Bate 2 → inhibitory,smooth muscles of bronchi, urinary bladder, intestine, VD of skeletal muscle ( c-AMP) 15