Central control of the autonomic nervous system John Morris Hypothalamus as an integrative centre regulating the ANS Involved in homeostasis stress responses anticipatory responses Sympathetic and para are output systems Sympathetic: fight or flight Para: rest and digest Visceral afferents Enteric nervous system 2-neuron output systems preganglionic postganglionic Sympathetic system ganglia Ganglionic synapse allows divergence Divergence greater in than in para
Sympathetic Para Enteric nervous system: intrinsic system of neurons coordinating the activity of the gut wall Myenteric plexus motility; Submucosal plexus - secretion Para (vagus) nerve Mesentery Sympathetic perivascular nerve External longitudinal muscle External circular muscle Submucosal plexus Myenteric plexus ganglion Subepithelial plexus Muscularis mucosa No para to limbs Submucosa Villus Serosa Pain from viscera: referred pain Note: some evidence for ascending projections via the dorsal column system; see Matthews PJ, Aziz Q (2005): Postgrad Med J : 81:448-455 Functional Abdominal Pain Pain from viscera: referred pain S2 cortex insula, cingulate cortex PAG reticular formation Receptors: TRPV1 acid, heat Mechanical -? degenerin Chemical P2X (ATP) Bradykinin PGE2 Anterolateral column NB Bad representation of course of ascending fibres Nociceptive afferents from viscera synapse on the same polymodal neurons in the main sensory nucleus of the dorsal horn as do some of the Aβ fibres from skin mechanoceptors. Projection via anterolateral column. Hence poor localisation of referred pain.
Referred pain Levels at which visceral afferents synapse in the spinal cord Pain is poorly localised, central/symmetical e.g. Heart T1-T5 central chest Appendix (mid-gut) T10 umbilical Autonomic nerves in thorax Sympathetic chain and vagus thoracic chain thoracic splanchnic (preganglionic) nerves vagus nerve cardiac & pulmonary plexuses oesophageal plexus Sympathetic nerves Head and neck superior cervical ganglion Sympathetic supply to upper limb From: T2-T5 segments of cord, Via: subclavian artery; brachial plexus middle cervical ganglion Pathology: Raynaud s disease inferior cervical ganglion
Sympathetic supply to lower limb From: T10-L2 segments Via: Iliac/femoral artery femoral, sciatic nerves Abdomen and pelvis thoracic splanchnic renal lumbar vagus nerves Pathology: lumbar sympathectomy as a treatment in peripheral vascular disease affecting the lower limbs presacral pelvic para Cranial para ganglia and distribution VII IX III ciliary sphenopalatine Para innervation via cranial nerves Cranial nerve Ganglion Supplies Oculomotor (III) Ciliary Globe of eye Pupil sphincter, ciliary otic Facial (VII) Sphenopalatine Hard palate and above Nose, lacrimal gland Facial (VII) Submandibular Floor of mouth Submandibular, sublingual glands (vagus nerve; X) Glossopharyngeal (IX) Otic Parotid gland submandibular Vagus (X) Local ganglia Foregut & midgut derivatives
CONTROL CENTRES IN THE CNS Pivotal role of the nucleus of solitary tract Spinal cord: Medulla: Pons: Cerebellum: Hypothalamus: Amygdala: Cerebral cortex sacral pelvic viscera; hind-gut thoracic cardiovascular; fore/mid gut C8/T1 control of pupil cardiac, respiratory, salivation, swallowing/vomiting micturition motion sickness anterior para; posterior emotional responses vascular, bladder, temperature RECEPTORS Cholinergic (N1 nicotinic ion channel somatic NS) N2 nicotinic ion channel symp, parasymp ganglia; adrenal medulla M1, 3, 5 muscarinic Gαq; PLC M2, 4 muscarinic Gαi,o; AdCycl e.g. heart bradycardia; presyn muscle vasodil. Adrenergic α1 (NA>A) Gαq; PLC predominate on blood vessels α2 (NA>A) Gαi; AdCycl predominate on presynaptic terminals β1 (A>NA) Gαs; AdCycl e.g. heart on SAN, muscle; JGA β2 (A>NA) Gαs; AdCycl e.g. bronchial, coron art smooth muscle, liver β3 (A>NA) Gαs; AdCycl e.g. fat cells, vasodilate salivary gland 5-HT ATP P2 purinoceptors Ca channel NO e.g. TNG in angina, sildenafil (Viagra) in erectile dysfunction; pulmonary oedema. Peptides: VIP, opioid peptides, somatostatin; substance P, CGRP in visceral afferents Autonomic control of the end organs/systems Eye and eyelid Head in general Heart and blood vessels Thermoregulation Digestive system Urinary tract Reproductive tract Sleep Emotional expression
Autonomic innervation Heart Note that many cardiac & vagal branches arise in the neck and descend to the cardiac plexuses Reflects position of embryonic development β1 β2 vagus M2 Note the large number of nerves (, vagus, phrenic) crossing the arch of the aorta Autonomic nerves in abdomen and pelvis Supply: kidneys: α1 to renal art β1 to JGA adrenals: β2 to vessels N2 to medulla G-I tract α1 to arteries M secretion NANC motility, sphincters lower limbs α1 to vessels lumbar chain sacral chain coeliac superior mesenteric inferior mesenteric presacral nerves to pelvic plexus Autonomic innervation of the bladder Next week Stress: Integrated action of Autonomic nervous system and Endocrine system