1 / 17

Chapter 19 Viscerosensory Pathways

Chapter 19 Viscerosensory Pathways. MP. Thibeault-Eybalin, R4 Academic Half-Day March 25 th , 2009. Outline. In parallel to somatosensory system conveying info from external environment, viscerosensory system conveys info about internal environment

noma
Download Presentation

Chapter 19 Viscerosensory Pathways

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 19Viscerosensory Pathways MP. Thibeault-Eybalin, R4 Academic Half-Day March 25th, 2009

  2. Outline • In parallel to somatosensory system conveying info from external environment, viscerosensory system conveys info about internal environment • Viscerosensory receptors, fibers, ascending sympathetic and parasympathetic pathways • Examples of reflexes based on above

  3. Viscerosensory receptors 2 types • Nociceptors • Free nerve endings of Aδ and C fibers located in heart, respiratory, GI and GU tracts • Project to Lamina 1 and 5 in dorsal horn • Mediate visceral pain, e.g. angina pectoris • Physiologic receptors • Mechanoreceptors • Rapidly adapting, e.g. cough • Slowly adapting, e.g. full stomach or urinary bladder • Baroreceptors, e.g. baroreflex • Chemoreceptors, e.g. in carotid and aortic bodies • Osmoreceptors, e.g. osmolarity and ADH production • Internal thermal receptors, e.g. core temperature in hypothalamus

  4. Classification of viscerosensory receptors and their respective stimuli

  5. Baroreceptor • Chemoreceptor

  6. Viscerosensory fibers • A.K.A. General visceral afferents • Travel with general visceral efferents in • Sympathetic nerves • e.g. splanchnic and cardiac nerves • Efferents>afferents • Mainly info from nociceptors • Parasympathetic nerves • e.g. vagus and pelvic nerves • Afferents>efferents • Mainly info from physiologic receptors

  7. Ascending sympathetic pathways • Mainly nociceptive info from thoracic and abdominal viscera via splanchnic and cardiac nerves • Cell bodies are in DRG T1 to L2 • Synapse onto 2nd order neurons • Afferent • In lamina 1 and 5, cross through anterior white commissure to project to ALS contralaterally, about 2 sensory levels higher → VPL of thalamus → inferolateral post-central gyrus (parietal opeculum) and insular cortex • In lamina 7 and 8 to project to spinoreticular tracts bilaterally • periaqueductal gray → dorsal longitudinal fasciculus • mesencephalic reticular formation → mammillary peduncle and medial forebrain bundle • ultimately to hypothalamus and intralaminar thalamic nuclei • Efferent • In intermediolateral column at same level → anterior horn → pre-ganglionic sympathetic efferent • Large receptive fields in brain, poorly localizing

  8. 1st order visceral afferent 2nd order visceral afferent Visceral efferent

  9. → dorsal longitudinal fasciculus → mammillary peduncle and medial forebrain bundle

  10. Referred pain • Noxious stimuli originating from visceral organs are perceived as arising from somatic tissues (skin, bone, muscle, etc.) • Whose afferents enter the spinal cord at the same level • Due to collateral synapses between visceral and somatic afferents in dorsal horn • Example: Angina pectoris • Pain referred to retrosternal area and left ± right arms, neck, jaw, TMJ

  11. Classic patterns of referred pain

  12. Angina pectoris Sympathetic trunk

  13. Ascending parasympathetic pathways (cranial and sacral) • Cranial • Only CN 9 and 10 have significant parasympathetic afferents • CN 9 • Chemoreceptors from carotid bodies • Baroreceptors from carotid sinus wall • Nociceptors from oropharynx (afferent limb for gag reflex) • CN 10 • Chemoreceptors and baroreceptors in aortic arch • Physiologic receptors from thoracic and abdominal viscera above splenic flexure of colon • Both enter skull through jugular foramen • Cells bodies located in INFERIOR ganglia of CN 9 and 10 • Superior ganglia contain cell bodies of somatic afferents • Synapse onto 2nd order neuron in solitary nucleus • Mediate vasopressor and vasodepressor responses

  14. Dual role of solitary nucleus in baroreflex Reticular formation Hypothalamus

  15. Ascending parasympathetic pathways • Sacral • Parasympathetic afferents from S2-3-4 travel through pelvic nerves, then spinal nerves • Relay info on bowel and bladder distension • Via ALS and spinoreticular fibers • To VPL of thalamus, reticular formation, and hypothalamus • Spinal and supraspinal autonomic reflexes

  16. Summary points • Viscerosensory afferents • Sympathetic • Mostly nociceptors • Referred pain due to collaterals with somatosensory afferents • Parasympathetic • Mostly physiologic receptors • Bowel, bladder, baroreflex • Information goes to reticular formation, periaqueductal gray, VPL and intralaminar nuclei of thalamus, hypothalamus, and cortex • Brief chapter but essential to neurophysiology

More Related