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Part 1 book “High – Yield neuroanatomy” has contents: Gross structure of the brain, development of the nervous system, neurohistology, blood supply, meninges, ventricles, and cerebrospinal fluid, meninges, ventricles, and cerebrospinal fluid, brainstem, autonomic nervous system, cranial nerves.
Thank you for purchasing this e-book To receive special offers and news about our latest products, sign up below Sign Up Or visit LWW.com TM FIFTH EDITION Neuroanatomy TM FIFTH EDITION Neuroanatomy Douglas J Gould, PhD Professor and Vice Chair Department of Biomedical Sciences William Beaumont School of Medicine Oakland University Rochester, Michigan Jennifer K Brueckner-Collins, PhD Professor and Vice Chair Department of Anatomical Sciences and Neurobiology University of Louisville School of Medicine Louisville, Kentucky Author of First-Fourth Editions: James D Fix, PhD (1931–2010) Acquisitions Editor: Crystal Taylor Product Development Editor: Stephanie Roulias Director of Medical Marketing: Lisa Zoks Production Project Manager: Bridgett Dougherty Design Coordinator: Teresa Mallon Manufacturing Coordinator: Margie Orzech Prepress Vendor: Aptara, Inc Fifth edition Copyright © 2016 Wolters Kluwer Copyright © 2009 Wolters Kluwer Health / Lippincott Williams & Wilkins Copyright © 2005 Lippincott Williams & Wilkins, a Wolters Kluwer business Copyright © 2000 by Lippincott Williams & Wilkins Copyright © 1995 by Lippincott-Raven Publishers All rights reserved This book is protected by copyright No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews Materials appearing in this book prepared by individuals as part of their official duties as U.S government employees are not covered by the above-mentioned copyright To request permission, please contact Wolters Kluwer at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email at permissions@lww.com, or via our website at lww.com (products and services) Printed in China 978-1-4511-9343-5 Library of Congress Cataloging-in-Publication Data available upon request This work is provided “as is,” and the publisher disclaims any and all warranties, express or implied, including any warranties as to accuracy, comprehensiveness, or currency of the content of this work This work is no substitute for individual patient assessment based upon healthcare professionals’ examination of each patient and consideration of, among other things, age, weight, gender, current or prior medical conditions, medication history, laboratory data and other factors unique to the patient. The publisher does not provide medical advice or guidance and this work is merely a reference tool. Healthcare professionals, and not the publisher, are solely responsible for the use of this work including all medical judgments and for any resulting diagnosis and treatments. Given continuous, rapid advances in medical science and health information, independent professional verification of medical diagnoses, indications, appropriate pharmaceutical selections and dosages, and treatment options should be made and healthcare professionals should consult a variety of sources When prescribing medication, healthcare professionals are advised to consult the product information sheet (the manufacturer’s package insert) accompanying each drug to verify, among other things, conditions of use, warnings and side effects and identify any changes in dosage schedule or contraindications, particularly if the medication to be administered is new, infrequently used or has a narrow therapeutic range To the maximum extent permitted under applicable law, no responsibility is assumed by the publisher for any injury and/or damage to persons or property, as a matter of products liability, negligence law or otherwise, or from any reference to or use by any person of this work LWW.com I dedicate this work to my beloved wife, Marie Your strength, courage, and love are the engine that moves our family forward and provides the foundation for our girls to grow into proud, strong women I love you Thank you Douglas J Gould I dedicate my contributions to this book to my son, Lincoln You are the light of my life and you make each and every day meaningful and fun! You have already taught me a lifetime of lessons about love, life, and the importance of play in the short 1/2 months that we have had together and I am eternally grateful to you for that I hope that we will have the blessed opportunity to share many more years learning from and loving each other I love you to the moon and back, my sweet bunny Jennifer K Brueckner-Collins PREFACE Based on your feedback on previous editions of this text, the fifth edition has been reorganized and updated significantly in order to provide an accurate and quick review of important clinical aspects of neuroanatomy for the future physician New features include the replacement of the “key concepts” with more focused “objectives” for each chapter, driving the content, order, and level of detail The chapters have been reordered and recombined to group “like” topic more closely A new Gross Structure chapter has been incorporated to lay the foundation for understanding the sectional anatomy in the Atlas chapter The fourth edition’s Thalamus and Hypothalamus chapters are now integrated in the fifth edition as a new Diencephalon chapter; the previous Spinal cord, Spinal cord tracts, and Spinal cord lesions chapters are combined in a centralized Spinal Cord chapter; and the former Brainstem and Brainstem lesions chapters are united in a new Brainstem chapter Terminology updates have been included to ensure consistency with Terminologica Anatomica We would appreciate receiving your comments and/or suggestions concerning High-Yield™ Neuroanatomy Fifth Edition especially after you have taken the USMLE Step examination Your suggestions will find their way into the sixth edition You may contact us at djgould@oakland.edu or jkbrue02@louisville.edu vii CONTENTS Preface vii GROSS STRUCTURE OF THE BRAIN I Divisions of the Brain DEVELOPMENT OF THE NERVOUS SYSTEM I II III IV V VI VII VIII IX NEUROHISTOLOGY I II III IV V VI VII VIII IX X XI XII XIII 13 17 Neurons 17 Nissl Substance 17 Axonal Transport 17 Anterograde (Wallerian) Degeneration Chromatolysis 18 Regeneration of Nerve Cells 18 Neuroglia 19 The Blood–Brain Barrier 19 The Blood–CSF Barrier 19 Pigments and Inclusions 20 Classification of Nerve Fibers 21 Tumors of the CNS and PNS 21 Cutaneous Receptors 23 BLOOD SUPPLY I II III IV V viii The Neural Tube 10 The Neural Crest 10 The Cranial Neuropore 12 The Caudal Neuropore 12 Microglia 12 Myelination 12 The Optic Nerve and Chiasma 12 The Hypophysis (pituitary gland) 12 Congenital Malformations of the CNS 18 25 The Spinal Cord and Caudal Brainstem 25 The Internal Carotid System 25 The Vertebrobasilar System 27 The Blood Supply of the Internal Capsule 28 Veins of the Brain 28 10 58 Chapter C Unilateral muscle atrophy and absent quadriceps (L3) and ankle jerk (S1) reflex activity D Unremarkable incontinence and sexual function E Gradual and unilateral onset VII Conus Medullaris Syndrome (Cord Segments S3 to C0) usually results from an intramedullary tumor (e.g., ependymoma) It is characterized by: A Pain, usually bilateral and not severe B Sensory distribution in a bilateral saddle-shaped area C Unremarkable muscle changes; normal quadriceps and ankle jerk reflexes D Severely impaired incontinence and sexual function E Sudden and bilateral onset CHAPTER Brainstem Objectives Identify the brainstem nuclei associated with the cranial nerves and be able to locate them on a brainstem cross section Identify the cranial nerves where they connect to the brainstem Describe the reticular formation—connections, functions, and structure Describe the result of occlusion of the anterior spinal artery and the posterior inferior cerebellar artery, include all brainstem nuclei and pathways affected Describe medial longitudinal fasciculus syndrome and Weber syndrome I Introduction The brainstem includes the medulla, pons, and midbrain It extends from the pyramidal decussation inferiorly to the posterior commissure superiorly The brainstem receives its blood supply from the vertebrobasilar system It gives rise to CNs III to X and XII (Figures 7-1 and 7-2) II Cross Section Through the Caudal Medulla (Figure 7-3) Pyramid (corticospinal fibers) Nucleus gracilis and nucleus cuneatus—give rise to arcuate fibers that cross the midline to form the medial lemniscus Anterior and posterior spinocerebellar tracts Inferior olivary nucleus Accessory cuneate nucleus III Cross Section Through the Mid-Medulla (Figure 7-4) Hypoglossal nucleus Dorsal motor nucleus of the vagus—preganglionic parasympathetic cell bodies that send fibers into CN X Solitary nucleus—special sense nucleus Medial longitudinal fasciculus—yolks together cranial nerve nuclei from opposite sides of the brainstem Tectospinal tract—fibers descending from the midbrain colliculi to lower motor neurons of the cervical spinal cord 59 Optic nerve Optic chiasm Anterior perforated substance Infundibulum Mamillary bodies Cerebral peduncle Optic tract Posterior perforated substance Midbrain Oculomotor nerve Trochlear nerve Trigeminal nerve Pons Pons Abducent nerve Facial nerve and nervus intermedius Vestibulocochlear nerve Glossopharyngeal nerve Medulla Vagus nerve Hypoglossal nerve Spinal accessory nerve Anterior root C1 Figure 7-1 The anterior or ventral surface of the brainstem and the attached cranial nerves Superior colliculus Midbrain Inferior colliculus Superior cerebellar peduncle Middle cerebellar peduncle CN V Pons CN VII CN VIII Medulla Area postrema Tuberculum cuneatus Tuberculum gracilis Figure 7-2 The posterior or dorsal surface of the brainstem 60 Brainstem Nucleus gracilis Medial longitutinal fasciculus Nucleus cuneatus Accessory cuneate nucleus Spinal tract (CN V) Central canal Spinal nucleus (CN V) Fibers of CN X Reticular formation Nucleus ambiguus Posterior spinocerebellar tract Spinothalamic tracts Anterior spinocerebellar tract Inferior olivary nucleus Pyramid Decussation of medial lemniscus Figure 7-3 Caudal medulla Nucleus ambiguus—lower motor neuron nucleus that sends fibers into CNs IX and X Medial lemniscus Inferior cerebellar peduncle IV Cross Section Through the Rostral Medulla (Figure 7-5) Hypoglossal nucleus Dorsal motor nucleus of CN X Fourth ventricle Medial vestibular nucleus Inferior vestibular nucleus Solitary nucleus Medial longitudinal fasciculus Inferior cerebellar peduncle Tectospinal tract Spinal nucleus and tract of CN V Reticular formation Lateral spinothalamic tract Nucleus ambiguus Inferior olivary nucleus Medial lemniscus Pyramid Figure 7-4 Mid-medulla 61 62 Chapter Fourth ventricle Medial longitudinal fasciculus Solitary nucleus and tract Inferior vestibular nucleus Tectospinal tract Inferior cerebellar peduncle Spinal nucleus and tract of CN V Dorsal and ventral cochlear nuclei Spinothalamic tracts Medial lemniscus Inferior olivary nucleus Pyramid Figure 7-5 Rostral medulla Spinothalamic tracts (spinal lemniscus) Spinal nucleus and tract of trigeminal nerve Inferior cerebellar peduncle—contains olivocerebellar, cuneocerebellar, and posterior spinocerebellar tracts V Cross Section Through the Caudal Pons (Figure 7-6) has a posterior tegmentum and an anterior base Fourth ventricle Genu of facial nerve Inferior cerebellar peduncle MLF The pons Abducens nucleus of CN VI Facial colliculus Vestibular nuclei (lateral and superior) Spinal nucleus and tract Solitary nucleus and tract Middle cerebellar peduncle Spinothalamic tracts Facial motor nucleus Transverse pontine fibers and deep pontine nuclei Central tegmental tract Medial lemniscus Trapezoid body Figure 7-6 Caudal pons Corticonuclear and corticospinal tracts Brainstem 10 11 VI 63 Medial longitudinal fasciculus (MLF) Abducent nucleus of CN VI (underlies facial colliculus) Genu (internal) of CN VII (underlies facial nerve; facial colliculus) Medial lemniscus Corticospinal and corticonuclear tracts (in the base of the pons) Facial motor nucleus (CN VII) Spinal nucleus and tract of trigeminal nerve (CN V) Spinothalamic tracts (spinal lemniscus) Vestibular nuclei of CN VIII Inferior and middle cerebellar peduncle Central tegmental tract—fiber pathway traversing the reticular formation Cross Section Through the Mid-Pons (Figure 7-7) Raphe nuclei Deep pontine nuclei and transverse pontine fibers Superior cerebellar peduncle—main cerebellar outflow pathway, also contains decussating anterior spinocerebellar fibers VII Cross Section Through the Rostral Pons (Figure 7-8) Mesencephalic nucleus—unconscious proprioception for the head Locus ceruleus—source of norepinephrine for the brain Cerebral aqueduct—connects the third and fourth ventricles Periaqueductal gray—involved in pain modulation, source of serotonin Superior cerebellar peduncle Fourth ventricle MLF M Raphe nuclei S Middle cerebellar peduncle Sensory (S) and motor (M) nuclei of CN V Medial lemniscus Transverse pontine fibers Central tegmental tract Deep pontine nuclei Corticonuclear and corticospinal tracts Figure 7-7 Mid-pons 64 Chapter Superior medullary velum Trochlear nerve (CN IV) Mesencephalic nucleus Cerebral aqueduct Periaqueductal gray Superior cerebellar peduncle Locus ceruleus MLF Central tegmental tract Medial lemniscus Middle cerebellar peduncle Raphe nucleus Deep pontine nuclei Corticonuclear and corticospinal tracts Figure 7-8 Rostral pons VIII Cross Section Through the Caudal Midbrain (Figure 7-9) The midbrain has a posterior tectum, an intermediate tegmentum, and a base The cerebral aqueduct lies between the tectum and the tegmentum Medial lemniscus Inferior colliculus—auditory relay nucleus Trochlear nucleus—lower motor neuron nucleus that innervates the superior oblique Cerebral aqueduct Crus cerebri (basis pedunculi cerebri or cerebral peduncle)—composed of descending fibers IX Cross Section Through the Rostral Medulla (Figure 7-10) Superior colliculus—visual relay nucleus Oculomotor nucleus—lower motor neuron nucleus that innervates the majority of the extraocular musculature Red nucleus—part of the primitive motor system, involved in coordination Ventral tegmental area—source of dopamine, involved in the reward system Spinothalamic and trigeminothalamic tracts Medial lemniscus X Corticonuclear Fibers project bilaterally to all motor cranial nerve nuclei except the facial nucleus The division of the facial nerve nucleus that innervates the upper face (the orbicularis oculi and above) receives bilateral corticonuclear input The division of the facial nerve nucleus that innervates the lower face receives only contralateral corticonuclear input Brainstem 65 Lesions of the Brainstem I Lesions of the Medulla (Figure 7-6) A Medial Medullary Syndrome (Anterior Spinal Artery Syndrome) Affected structures include the following: Corticospinal tract (medullary pyramid) Lesions result in contralateral spastic hemiparesis; Medial lemniscus Lesions result in contralateral loss of tactile and vibration sensation from the trunk and extremities; Hypoglossal nucleus and its intra-axial fibers Lesions result in ipsilateral flaccid hemiparalysis of the tongue When protruded, the tongue points to the side of the lesion (i.e., the weak side) See Figure 9.8 B Lateral Medullary (Wallenberg; Posterior Inferior Cerebellar Artery [PICA]) Syndrome is characterized by dissociated sensory loss Affected structures include the following: Vestibular nuclei Lesions result in nystagmus, nausea, vomiting, and vertigo; Inferior cerebellar peduncle Lesions result in ipsilateral cerebellar signs (e.g., dystaxia, dysmetria [past pointing], and dysdiadochokinesia); Nucleus ambiguus Lesions result in ipsilateral laryngeal, pharyngeal, and palatal hemiparalysis (i.e., loss of the gag reflex [efferent limb], dysarthria, dysphagia, and dysphonia [hoarseness]); Glossopharyngeal nerve roots Lesions result in loss of the gag reflex (afferent limb); Vagal nerve roots Lesions result in the same deficits as seen in lesions involving the nucleus ambiguus; Spinothalamic tracts (spinal lemniscus) Lesions result in contralateral loss of pain and temperature sensation; Spinal trigeminal nucleus and tract Lesions result in ipsilateral loss of pain and temperature sensation from the face (facial hemianesthesia); Descending sympathetic tract Lesions result in ipsilateral Horner syndrome (i.e., ptosis, miosis, hemianhidrosis, and apparent enophthalmos) II Lesions of the Pons (Figure 7-7A) A Medial Inferior Pontine Syndrome results from occlusion of the paramedian branches of the basilar artery Affected structures include the following: Corticospinal tract Lesions result in contralateral spastic hemiparesis Medial lemniscus Lesions result in contralateral loss of tactile sensation from the trunk and extremities Abducent nerve roots Lesions result in ipsilateral lateral rectus paralysis B Lateral Inferior Pontine Syndrome (anterior inferior cerebellar artery syndrome; Figure 7-7B) Affected structures include the following: Facial nucleus and intra-axial nerve fibers Lesions result in: a Ipsilateral facial paralysis; b Ipsilateral loss of taste from the anterior two-thirds of the tongue; c Ipsilateral loss of lacrimation and reduced salivation; d Loss of the efferent limb of the corneal blink and stapedial reflexes (hyperacusis) Cochlear nuclei and intra-axial nerve fibers Lesions result in ipsilateral deafness; Vestibular nuclei and intra-axial nerve fibers Lesions result in nystagmus, nausea, vomiting, and vertigo; 66 Chapter Spinal nucleus and tract of the trigeminal nerve Lesions result in ipsilateral loss of pain and temperature sensation from the face (facial hemianesthesia); Middle and inferior cerebellar peduncles Lesions result in ipsilateral limb and gait dystaxia; Spinothalamic tracts (spinal lemniscus) Lesions result in contralateral loss of pain and temperature sensation from the trunk and extremities; Descending sympathetic tract Lesions result in ipsilateral Horner syndrome C MLF Syndrome (Internuclear Ophthalmoplegia) (Figure 7-7C) interrupts fibers from the contralateral abducent nucleus that project through the MLF to the ipsilateral medial rectus subnucleus of CN III It causes medial rectus palsy on attempted lateral conjugate gaze and nystagmus in the abducting eye Convergence remains intact This syndrome is often seen in patients with multiple sclerosis D Facial Colliculus Syndrome usually results from a pontine glioma or a vascular accident The internal genu of CN VII and the abducent nucleus underlie the facial colliculus Lesions of the internal genu of the facial nerve cause: a Ipsilateral facial paralysis; b Ipsilateral loss of the corneal blink reflex (efferent limb) Lesions of the abducent nucleus cause: a Lateral rectus paralysis (medial strabismus); b Horizontal diplopia III Lesions of the Midbrain (Figure 7-8) A Posterior Midbrain (Parinaud) Syndrome (see Figure 7-8A) is often the result of a pinealoma or germinoma of the pineal region Affected structures include the following: Superior colliculus and pretectal area Lesions cause paralysis of upward and downward gaze, pupillary disturbances, and absence of convergence; Cerebral aqueduct Compression causes noncommunicating hydrocephalus B Paramedian Midbrain (Benedikt) Syndrome (see Figure 7-8B) Affected structures include the following: Oculomotor nerve roots (intra-axial fibers) Lesions cause complete ipsilateral oculomotor paralysis Eye abduction and depression is caused by the intact lateral rectus (CN VI) and superior oblique (CN IV) Ptosis (paralysis of the levator palpebrae superioris) and fixation and dilation of the ipsilateral pupil (complete internal ophthalmoplegia) also occur; Dentatothalamic fibers Lesions cause contralateral cerebellar dystaxia with intention tremor; Medial lemniscus Lesions result in contralateral loss of tactile sensation from the trunk and extremities C Medial Midbrain (Weber) Syndrome (see Figure 7-8C) Affected structures and resul- tant deficits include the following: Oculomotor nerve roots (intra-axial fibers) Lesions cause complete ipsilateral oculomotor paralysis Eye abduction and depression are caused by intact lateral rectus (CN VI) and superior oblique (CN IV) Ptosis, fixation, and dilation of the ipsilateral pupil also occur; Corticospinal tracts Lesions result in contralateral spastic hemiparesis; Corticonuclear fibers Lesions cause contralateral weakness of the lower face (CN VII), tongue (CN XII), and palate (CN X) The upper face division of the facial nucleus receives bilateral corticonuclear input The uvula and pharyngeal wall are pulled toward the normal side (CN X), and the protruded tongue points to the weak side Brainstem IV 67 Acoustic Neuroma (Schwannoma) (Figure 7-9) is a benign tumor of Schwann cells that affects the vestibulocochlear nerve (CN VIII) It accounts for 8% of all intracranial tumors It is a posterior fossa tumor near the internal auditory meatus and cerebellopontine angle The neuroma often compresses the facial nerve (CN VII), which accompanies CN VIII in the cerebellopontine angle and internal auditory meatus It may impinge on the pons and affect the spinal trigeminal tract (CN V) Schwannomas occur twice as often in women as in men Affected structures and resultant deficits include the following: A Cochlear Division of CN VIII Damage results in tinnitus and unilateral nerve deafness; B Vestibular Division of CN VIII Damage results in vertigo, nystagmus, nausea, vomiting, and unsteadiness of gait; C Facial Nerve (CN VII) Damage results in facial weakness and loss of the corneal blink reflex (efferent limb); D Spinal Tract of Trigeminal Nerve (CN V) Damage results in paresthesia, anesthesia of the ipsilateral face, and loss of the corneal blink reflex (afferent limb) NEUROFIBROMATOSIS TYPE This disorder often occurs with bilateral acoustic neuromas V Jugular Foramen Syndrome usually results from a posterior fossa tumor (e.g., glomus jugulare tumor, the most common inner ear tumor) that compresses CNs IX, X, and XI Affected structures and resultant deficits include the following: A Glossopharyngeal Nerve (CN IX) Damage results in: Ipsilateral loss of the gag reflex; Ipsilateral loss of pain, temperature, and taste in the tongue Tectum Cerebral aqueduct Lateral lemniscus Trigeminal thalamic fibers Spinothalamic fibers Inferior colliculus Periaqueductal gray Trochlear nucleus Medial lemniscus Cerebral peduncle Crus cerebri Superior cerebellar peduncle Tegmentum (reticular formation) Figure 7-9 Caudal midbrain Substantia nigra 68 Chapter B Vagal Nerve (CN X) Damage results in: Ipsilateral paralysis of the soft palate and larynx; Ipsilateral loss of the gag reflex C Accessory Nerve (CN XI) Damage results in: Paralysis of sternocleidomastoid, which results in the inability to turn the head to the opposite side; Paralysis of trapezius, which causes shoulder droop and inability to shrug the shoulder VI “Locked-in” Syndrome is a lesion of the base of the pons as the result of infarction, trauma, tumor, or demyelination The corticospinal and corticonuclear tracts are affected bilaterally The oculomotor and trochlear nerves are not injured Patients are conscious and may communicate through vertical eye movements VII Central Pontine Myelinolysis is a lesion of the base of the pons that affects the corticospinal and corticonuclear tracts More than 75% of cases are associated with alcoholism or rapid correction of hyponatremia Symptoms include spastic quadriparesis, pseudobulbar palsy, and mental changes This condition may become the locked-in syndrome VIII “Top of the Basilar” Syndrome results from embolic occlusion of the rostral basilar artery Neurologic signs include optic ataxia and psychic paralysis of fixation of gaze (Balint syndrome), ectopic pupils, somnolence, and cortical blindness, with or without visual anosognosia (Anton syndrome) IX Subclavian Steal Syndrome (Figure 7-10) results from thrombosis of the left subclavian artery proximal to the vertebral artery Blood is shunted in the left vertebral artery and into the left subclavian artery Clinical signs include transient weakness and claudication of the left upper limb on exercise and vertebrobasilar insufficiency (i.e., vertigo, dizziness) X The Cerebellopontine Angle is the junction of the medulla, pons, and cerebellum CNs VII and VIII are found there Five brain tumors, including a cyst, are often located in the cerebellopontine angle cistern Remember the acronym SAME: schwannoma (75%), arachnoid cyst (1%), meningioma (10%), and ependymoma (1%) and epidermoid (5%) The percentages refer to cerebellopontine angle tumors Brainstem Tectum Cerebral aqueduct Tegmentum (reticular formation) 69 Superior colliculus Periaqueductal gray Oculomotor nucleus Medial lemniscus Spinothalamic and trigeminothalamic tracts Substantia nigra Pars compacta Red nucleus Cerebral peduncle Occipito, parieto, temporopontine fibers Corticospinal fibers Corticonuclear fibers Crus cerebri Frontopontine fibers CN III Ventral tegmental area Figure 7-10 Rostral midbrain CASE 7-1 For several weeks, a 60-year-old hypertensive, diabetic man has experienced sudden dizziness, facial pain, double vision, and difficulty in walking He is also having problems in swallowing and speaking What is the most likely diagnosis? Relevant Physical Exam Findings ● ● ● ● Decreased temperature and pain sense below the left T-4 level Horner syndrome on the right side Decreased position sensation in the right fingers and toes Ataxia and mild weakness in the right limbs Relevant Lab Finding ● An infarct involving the right lateral part of the lower medulla and the cerebellum seen on brain magnetic resonance image Diagnosis ● Wallenberg’s syndrome is an infarction involving the lateral or medial branches of the posterior inferior cerebellar artery CHAPTER Autonomic Nervous System Objectives List the functions of the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS), using Table 8.1 as a reference Describe the location(s) of the pre- and postganglionic cell bodies of the sympathetic and parasympathetic divisions of the ANS Trace the pathways that pre- and postganglionic fibers take to reach their destinations I Introduction The autonomic nervous system (ANS) is a general visceral efferent motor system that controls and regulates smooth muscle, cardiac muscle, and glands A The ANS consists of a two-neuron chain from the CNS to the effector: a pre- and postganglionic neuron B Autonomic Output is generally reflexive and is influenced rostrally by the hypothalamus C The ANS has three divisions: Sympathetic (Figure 8-1) ● Prepares the body for action—fight or flight ● Uses a lot of energy, as it upregulates function in a nonspecific way ● Preganglionic cell bodies in the spinal cord between T1 and L2, form the intermediolateral cell column of the lateral horn ● Postganglionic cell bodies are found in the sympathetic chain—primarily for innervation of the body wall (i.e., erector pili, blood vessels, and sweat glands) or in prevertebral ganglia for innervation of the gut Parasympathetic (Figure 8-2) ● Responsible for resting state of the body—rest and digest ● Conserves energy, functions more specifically because of the short postganglionic fibers (i.e., it can activate targets with more specificity) ● Preganglionic cell bodies in the brainstem—associated with CNs III, VII, IX, and X, and the sacral spinal cord S2-S4 ● Postganglionic cell bodies are found in the ciliary, otic, pterygopalatine, or submandibular ganglia for the head—all postganglionic parasympathetic fibers in the head run in branches of CN V to reach their targets, and in the walls of the target organ for the body Enteric The enteric nervous system is composed of the intramural ganglia of the gastrointestinal tract, submucosal plexus, and myenteric plexus 70 Autonomic Nervous System 71 Eye: superior tarsal muscle Lacrimal gland Dilator pupillae Submandibular and sublingual glands Superior cervical ganglion Parotid gland Heart To blood vessels, arrector pili, and sweat glands T1 Bronchial tree Celiac plexus Superior mesenteric plexus Stomach Small intestine Suprarenal medulla Large intestine Inferior mesenteric plexus L2 Ductus deferens Sympathetic trunk Figure 8-1 The sympathetic (thoracolumbar) innervation of the autonomic nervous system II Cranial Nerves (CN) With Parasympathetic Components include the following: A CN III—preganglionic cell bodies in the accessory oculomotor (Edinger–Westphal) nucleus; postganglionic cell bodies in the ciliary ganglion 72 Chapter Ciliary ganglion Midbrain Accessory occulomotor nucleus CN III Pons Superior salivatory nucleus Pterygopalatine ganglion Submandibular ganglion CN VII Inferior salivatory nucleus Medulla Dorsal motor nucleus of the vagus CN IX Otic ganglion CN X Sphincter pupillae and ciliaris Lacrimal and nasal glands Submandibular and sublingual glands Parotid gland Heart Bronchial tree Stomach Small intestine Large intestine S-2 S-3 Urinary bladder S-4 Pelvic splanchnic nerves Genital erectile tissue Figure 8-2 The parasympathetic (craniosacral) innervation of the autonomic nervous system B CN VII—preganglionic cell bodies in the superior salivatory nucleus; postganglionic cell bodies in the pterygopalatine and submandibular ganglia C CN IX—preganglionic cell bodies in the inferior salivatory nucleus; postganglionic cell bodies in the otic ganglion D CN X—preganglionic cell bodies in the dorsal motor nucleus of the vagus; postganglionic cell bodies in intramural ganglia ... Pathway 10 0 Hearing Defects 10 2 Auditory Tests 10 2 VESTIBULAR SYSTEM I II III IV 14 10 0 11 6 Introduction 11 6 Major Components 11 6 The Papez Circuit 11 6 Clinical Correlations 11 8 BASAL NUCLEI AND EXTRAPYRAMIDAL... Reflex Pathway 11 1 The Pupillary Dilation Pathway 11 1 The Near Reflex and Accommodation Pathway 11 2 Cortical and Subcortical Centers for Ocular Motility 11 3 Clinical Correlation 11 4 LIMBIC SYSTEM... 13 17 Neurons 17 Nissl Substance 17 Axonal Transport 17 Anterograde (Wallerian) Degeneration Chromatolysis 18 Regeneration of Nerve Cells 18 Neuroglia 19 The Blood–Brain Barrier 19 The Blood–CSF