DOCSLIB.ORG

Compartmental Distribution of Ventral Striatal Neurons Projecting to the Mesencephalon in the Rat

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

The Journal of Neuroscience, June 1992, 72(6): 2079-2103 Compartmental Distribution of Ventral Striatal Neurons Projecting to the Mesencephalon in the Rat Henk W. Berendse,a Henk J. Groenewegen, and Anthony H. M. Lohman Department of Anatomy and Embryology, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands The ventral striatum is characterized by an intricate neu- turn. The other component can, by way of the pars reticulata rochemical compartmentation that is reflected in the distri- of the substantia nigra, participate in nigrothalamic and ni- bution of most of its afferent fiber systems. In the present grotectal output pathways of the basal ganglia. study, the compartmental relationships of ventral striatal neurons projecting to the mesencephalon were studied by In spite of their long-standing exclusive associationwith motor combining tract tracing with the immunohistochemical lo- functions, the basal ganglia are now considered as a group of calization of leu-enkephalin. Injections of the retrograde interconnected nuclei that are involved in the processing of tracer cholera toxin subunit B were placed at various sites information related to many aspectsof behavior, ranging from in the ventral mesencephalon. The anterograde tracer fha- motor acts to complex emotional and motivational influences. seolus vu/garis leucoagglutinin was injected in single com- The underlying anatomical substratehas only recently been elu- partments in the rostrolateral part of the nucleus accumbens. cidated by demonstrating a parallel organizational principle The projections from the ventral striatum to the dopaminer- within basal ganglia connections (Heimer and Wilson, 1975; gic cell groups in the ventral mesencephalon and those to Alexander et al., 1986, 1990; Nauta, 1986). Information from the substantia nigra pars reticulata originate from distinct functionally diverse parts of the cerebral cortex is channeled subpopulations of ventral striatal neurons that respect neu- through different parts of the basal ganglia and thalamus back rochemically defined compartmental boundaries. In the to the cortex, thus forming a number of parallel cortico-striato- “shell” of the nucleus accumbens, neurons that project to pallido-thalamo-cortical circuits that may each be involved in the dopaminergic cell groups are located outside areas of different aspects of behavior. The importance of this organi- high cell density and weak enkephalin immunoreactivity zational principle is underscoredby the parallel arrangement of (ENK-IR). Rostrolaterally in the “core” of the nucleus ac- the projections from the midline and intralaminar thalamic nu- cumbens, neurons inside large areas of strong ENK-IR sur- clei and the amygdala to both the striatum and the prefrontal rounding the anterior commissure project to the dorsomedial cortex (Berendseand Groenewegen, 1990, 1991; Groenewegen part of the substantia nigra pars reticulata, whereas neurons et al., 1990b). outside these areas innervate the ventral tegmental area An important issue in basal ganglia research is whether and and/or the medial part of the substantia nigra pars compacta. where integration takes place in this systemof segregatedcircuits By contrast, more caudally in the dorsal part of the nucleus in order to produce coherent behavior. Local interactions may accumbens and in the ventral part of the caudate-putamen, occur at the level of the striatum through overlapping inputs. the relationships are reversed: neurons in- or outside small Widespread integration may take place through the projections patches of strong ENK-IR project respectively to the pars from the ventral striatum to the dopaminergic cell groups in the compacta or the pars reticulata of the substantia nigra. Since mesencephalon(Nauta et al., 1978; Somogyi et al., 1981; Nauta the thalamic and cortical afferents of the ventral striatum are and Domesick, 1984) which seemto defy the parallel arrange- compartmentally ordered as well, the present results imply ment of basal ganglia connections. By way of projections to the that through the ventral striatal compartments information substantia nigra pars compacta, the ventral tegmental area, and from disparate combinations of cortical and thalamic sources the retrorubral field, containing the A9, A 10, and A8 dopamin- may be conveyed to distinct mesencephalic targets. The ergic cell groups, respectively (Dahlstriim and Fuxe, 1964; component of the ventral striatomesencephalic system Bjiirklund and Lindvall, 1984) the ventral striatum appearsto reaching the dopaminergic cell groups Al 0, A9, and A8 may be in a position to influence the dopaminergic input to virtually modulate the dopaminergic input to virtually the entire stria- the entire striatum (Fallon and Moore, 1978; Bjiirklund and Lindvall, 1984; Gerfen et al., 1987) and, consequently, the in- formation processingin each of the parallel cortico-striato-pal- Received June 7, 1991; revised Dec. 30, 1991; accepted Jan. 6, 1992. lidofugal pathways. Whether the ventral striatal projections to We thank Dr. Pieter Voorn for helpful discussions, Mrs. Yvonne Galis-de Graaf for technical assistance, Mr. Dirk de Jong for his photographical skills, and Ms. the dorsomedial part of the substantia nigra pars reticulata Loes van Zanten for secretarial support. This work was supported by NW0 Pro- (Swansonand Cowan, 1975; Conrad and Pfaff, 1976; Nauta et gram Grant 900-550-093. Correspondence should be addressed to Henk J. Groenewegen, M.D., Ph.D., al., 1978; Troiano and Siegel, 1978) originate from the same Department of Anatomy and Embryology, Vrije Universiteit, Van der Boechorst- neurons remains to be established. straat 7, 1081 BT Amsterdam, The Netherlands. Superimposedupon the topographical organization of its con- = Present address: Neurology Unit, University of Rochester, Monroe Com- munity Hospital, 435 East Henrietta Road, Rochester, NY 14620. nections, the striatum is characterized by a heterogeneousdis- Copyright 0 1992 Society for Neuroscience 0270-6474/92/122079-25$05.00/O tribution of many neurotransmitters,neuromodulators, and their 2080 Berendse et al. * Ventral Striatomesencephalic Projections receptors. In the dorsal striatum, two neurochemically distinct more detailed features of the neurochemical compartmentation compartments, the patch or striosomal compartment and the of the ventral striatum (Voom et al., 1989). matrix compartment, have been identified (Graybiel and Rags- In order to label the ventral striatal neurons projecting to the dale, 1978; Graybiel et al., 1981; Gerfen, 1984; Gerfen et al., different mesencephalic targets, retrograde tracer injections were 1985; for reviews, see Graybiel, 1984,199O). Virtually all striatal made in the different parts of the dorsomedial substantia nigra, afferent and efferent systems observe the boundaries of these in the ventral tegmental area, and in the retrorubral field. Ad- neurochemical compartments (e.g., Herkenham and Pert, 198 1; ditional injections were placed in the peribrachial region to iden- Ragsdale and Graybiel, 198 1, 1990; Gerfen, 1984, 1985, 1989; tify the neuronal population projecting to more caudal parts of Donoghue and Herkenham, 1986; Jimtnez-Castellanos and the midbrain. The opioid peptide enkephalin (ENK), visualized Graybiel, 1987, 1989; Gimknez-Amaya and Graybiel, 1990; for immunohistochemically, was used as a marker for the ventral reviews, see Graybiel, 1984, 1990). The differential connections striatal compartments (Berendse et al., 1988; Voorn et al., 1989; of the patch/striosome and matrix compartments with the sub- Berendse and Groenewegen, 1990). A preliminary set of exper- stantia nigra and associated dopaminergic cell groups constitute iments, using fluorogold and diamidine yellow as retrograde the most striking example of the compartmental ordering. The tracers, provided us with the first indications of differential com- efferents of the striatal patches or striosomes preferentially reach partmental origins of the ventral striatomesencephalic projec- the pars compacta of the substantia nigra, whereas the matrix tions (Groenewegen et al., 1989). The retrograde tracer cholera projects mainly to the pars reticulata (Gerfen, 1984, 1985; Ger- toxin subunit B (CTb) proved to be more sensitive and produced fen et al., 1985; JimCnez-Castellanos and Graybiel, 1989). The a more extensive filling of the dendritic trees of the rather small projection from the patch or striosomal compartment to the striatal projection neurons. Therefore, the present account is pars compacta is reciprocated by a projection from particular based on CTb experiments only. The analysis of a limited num- subgroups of dopaminergic neurons, which in the rat reside in ber of PHA-L injections in the nucleus accumbens and the ven- the ventral tier of the pars compacta or in the ventrolateral part tral part of the caudate-putamen was necessary to supplement of the pars reticulata, and in the cat in the densocellular portion the data obtained by means of retrograde tracing. of the pars compacta (Gerfen et al., 1985, 1987; Jimknez-Cas- tellanos and Graybiel, 1987; see also Feigenbaum-Langer and Materials and Methods Graybiel, 1989). Neurons in the dorsal strata of the pars com- In the present study, 32 female Wistar rats (Harlan/CPB, Zeist, The pacta, in the ventral tegmental area, and in the retrorubral area Netherlands) weighing 180-220 gm were used. Following anesthesia with an intramuscular injection of a mixture (4:3) of ketamine and 2- project to the striatal matrix compartment. The striatal
Recommended publications
  • Auditory and Vestibular Systems Objective • to Learn the Functional

    Auditory and Vestibular Systems Objective • to Learn the Functional

    Auditory and Vestibular Systems Objective • To learn the functional organization of the auditory and vestibular systems • To understand how one can use changes in auditory function following injury to localize the site of a lesion • To begin to learn the vestibular pathways, as a prelude to studying motor pathways controlling balance in a later lab. Ch 7 Key Figs: 7-1; 7-2; 7-4; 7-5 Clinical Case #2 Hearing loss and dizziness; CC4-1 Self evaluation • Be able to identify all structures listed in key terms and describe briefly their principal functions • Use neuroanatomy on the web to test your understanding ************************************************************************************** List of media F-5 Vestibular efferent connections The first order neurons of the vestibular system are bipolar cells whose cell bodies are located in the vestibular ganglion in the internal ear (NTA Fig. 7-3). The distal processes of these cells contact the receptor hair cells located within the ampulae of the semicircular canals and the utricle and saccule. The central processes of the bipolar cells constitute the vestibular portion of the vestibulocochlear (VIIIth cranial) nerve. Most of these primary vestibular afferents enter the ipsilateral brain stem inferior to the inferior cerebellar peduncle to terminate in the vestibular nuclear complex, which is located in the medulla and caudal pons. The vestibular nuclear complex (NTA Figs, 7-2, 7-3), which lies in the floor of the fourth ventricle, contains four nuclei: 1) the superior vestibular nucleus; 2) the inferior vestibular nucleus; 3) the lateral vestibular nucleus; and 4) the medial vestibular nucleus. Vestibular nuclei give rise to secondary fibers that project to the cerebellum, certain motor cranial nerve nuclei, the reticular formation, all spinal levels, and the thalamus.
  • Medial Lemniscal and Spinal Projections to the Macaque Thalamus

    Medial Lemniscal and Spinal Projections to the Macaque Thalamus

    The Journal of Neuroscience, May 1994, 14(5): 2485-2502 Medial Lemniscal and Spinal Projections to the Macaque Thalamus: An Electron Microscopic Study of Differing GABAergic Circuitry Serving Thalamic Somatosensory Mechanisms Henry J. Ralston III and Diane Daly Ralston Department of Anatomy, W. M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, California, 94143-0452 The synaptic relationships formed by medial lemniscal (ML) jority of these spinal afferents suggests that the transmis- or spinothalamic tract (STT) axon terminals with neurons of sion of noxious information is probably not subject to GA- the somatosensory ventroposterolateral thalamic nucleus of BAergic modulation by thalamic interneurons, in contrast to the macaque monkey have been examined quantitatively by the GABAergic processing of non-noxious information car- electron microscopy. ML and STT axons were labeled by the ried by the ML afferents. The differences in the GABAergic anterograde axon transport of WGA-HRP following injection circuits of the thalamus that mediate ML and STT afferent of the tracer into the contralateral dorsal column nuclei, or information are believed to underlie differential somatosen- the dorsal horn of the spinal cord, respectively. Thalamic sory processing in the forebrain. We suggest that changes tissue was histochemically reacted for the presence of HRP. in thalamic GABAergic dendritic appendages and GABA re- Serial thin sections were stained with a gold-labeled anti- ceptors following CNS injury may play a role in the genesis body to GABA, to determine which neuronal elements ex- of some central pain states. hibited GABA immunoreactivity (GABA-ir). Serially sec- [Key words: thalamus, somatosensory, monkey, GABA, tioned thalamic structures were recorded in electron medial lemniscus, spinothalamic tract, inhibition, interneu- micrographs and reconstructed in three dimensions by com- ron, pain] puter.
  • 05 Trigeminal System 2013.Pdf

    05 Trigeminal System 2013.Pdf

    Dental Neuroanatomy Thursday February 7th, 2013 David A. Morton, Ph.D. 5. THE TRIGEMINAL SYSTEM Somatic Sensation of the Face and Head Objectives 1. Outline the two pathways for facial sensation from the head. 2. Contrast facial sensation from the head and somatic sensation from the body. In what ways are they similar? Different? Try drawing this on the Haines atlas diagram at the end of the lecture. 3. Diagram the corneal reflex: the afferent and efferent limbs as well as nuclei involved in the brainstem. 4. If a person does not blink, how would you determine if the problem were in the sensory (afferent) limb, motor (efferent) limb, or brainstem interconnections for the corneal reflex? 5. Explain how a single, small medullary vascular lesion could abolish pain and temperature from the face on the right side and pain and temperature from the body on the left side. What vessel is most likely occluded? Introduction – The trigeminal system for the face and oral cavity is organized in a manner similar to the spinal cord. It has the equivalent of both the DCML pathway and the ALS pathway. The two trigeminal pathways will converge in the thalamus. The most confusing thing is that one of them descends before crossing and the other crosses immediately. Peripheral Receptors and Sensation Structures served by trigeminal system. 1. Cornea 2. Mucocutaneous tissues around mouth and nostrils. 3. Oral and nasal mucosae 4. Paranasal sinuses 5. Tongue (anterior two thirds) 6. Teeth and gums 7. Dura of anterior and middle cranial fossae 8. Skin of face to the vertex except angle of jaw 9.
  • White Matter Anatomy: What the Radiologist Needs to Know

    White Matter Anatomy: What the Radiologist Needs to Know

    White Matter Anatomy What the Radiologist Needs to Know Victor Wycoco, MBBS, FRANZCRa, Manohar Shroff, MD, DABR, FRCPCa,*, Sniya Sudhakar, MBBS, DNB, MDb, Wayne Lee, MSca KEYWORDS Diffusion tensor imaging (DTI) White matter tracts Projection fibers Association Fibers Commissural fibers KEY POINTS Diffusion tensor imaging (DTI) has emerged as an excellent tool for in vivo demonstration of white matter microstructure and has revolutionized our understanding of the same. Information on normal connectivity and relations of different white matter networks and their role in different disease conditions is still evolving. Evidence is mounting on causal relations of abnormal white matter microstructure and connectivity in a wide range of pediatric neurocognitive and white matter diseases. Hence there is a pressing need for every neuroradiologist to acquire a strong basic knowledge of white matter anatomy and to make an effort to apply this knowledge in routine reporting. INTRODUCTION (Fig. 1). However, the use of specific DTI sequences provides far more detailed and clini- DTI has allowed in vivo demonstration of axonal cally useful information. architecture and connectivity. This technique has set the stage for numerous studies on normal and abnormal connectivity and their role in devel- DIFFUSION TENSOR IMAGING: THE BASICS opmental and acquired disorders. Referencing established white matter anatomy, DTI atlases, Using appropriate magnetic field gradients, and neuroanatomical descriptions, this article diffusion-weighted sequences can be used to summarizes the major white matter anatomy and detect the motion of the water molecules to and related structures relevant to the clinical neurora- from cells. This free movement of the water mole- diologist in daily practice.
  • The Dorsal Column Nuclei Neuroanatomy Reveals a Complex Sensorimotor Integration and Distribution Hub

    The Dorsal Column Nuclei Neuroanatomy Reveals a Complex Sensorimotor Integration and Distribution Hub

    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 8 November 2019 doi:10.20944/preprints201911.0084.v1 The Dorsal Column Nuclei Neuroanatomy Reveals A Complex Sensorimotor Integration and Distribution Hub Alastair J Loutit1,2, Richard M Vickery1, and Jason R Potas1,2 * 1School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, 2052, Australia 2The Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, 2601, Australia * Correspondence: Dr Jason R Potas [email protected] Number of words (excluding references, abstract and abbreviations): 14,490 Number of figures: 6 Number of Tables: 1 Number of supplementary figures: 0 Keywords: brainstem sensory nuclei; somatosensation; secondary afferents; posterior column Abstract The dorsal column nuclei (DCN) are organised by both somatotopy and modality, and have a diverse range of afferent inputs and projection targets. The functional organisation and connectivity of the DCN implicate them in a variety of sensorimotor functions, beyond their commonly accepted role in processing and transmitting somatosensory information to the thalamus, yet this is largely underappreciated in the literature. In this review, we examine the morphology, organisation, and connectivity of the DCN and their associated nuclei, to improve understanding of their sensorimotor functions. First, we briefly discuss the receptors, afferent fibres, and pathways involved in conveying tactile and proprioceptive information to the DCN. Next, we review the modality and somatotopic arrangements of the constituents of the dorsal column nuclei complex (DCN-complex), which includes the gracile, cuneate, external cuneate, X, and Z nuclei, and Bischoff’s nucleus. Finally, we examine and discuss the functional implications of the myriad of DCN-complex projection targets throughout the midbrain, and hindbrain, in addition to their modulatory inputs from the cortex.
  • Pain-Relieving Mechanisms in Neuromodulation 10

    Pain-Relieving Mechanisms in Neuromodulation 10

    Pain-Relieving Mechanisms in Neuromodulation 10 Vikram Sengupta, Sascha Qian, Ned Urbiztondo, and Nameer Haider Introduction painful disease state being treated. Although clinical evi- dence will be provided, more exhaustive summaries of the Since its inception more than 50 years ago, the forms and clinical data will be reserved for later chapters in Part VI, applications of modern neuromodulation have undergone each of which is dedicated to the clinical aspects of a particu- tremendous expansion. The International Neuromodulation lar form of neuromodulation. Society defines neuromodulation as “the alteration of nerve activity through targeted delivery of a stimulus, such as elec- trical stimulation or chemical agents, to specific neurological Background and Historical Perspective sites in the body,” most commonly to reduce pain or improve neurologic function. All forms of neuromodulation are The earliest documented use of electrical current for the reversible. Neurostimulation is the most common form of treatment of pain was around 63 AD, when the Mesopotamian neuromodulation technology used today, and it refers to the physician, Scribonius Largus, discovered that shocks deliv- use of electrical or electromagnetic stimuli upon target tis- ered by the electrical torpedo fish could relieve bodily aches sues to elicit a therapeutic response. Although the focus of and pains. In the eleventh century, the Islamic philosopher this chapter will be on neurostimulation, other non-electrical Avicenna used cranial shocks delivered by the electric catfish therapies, such as intrathecal drug delivery systems, may fall to treat epilepsy. In the 1600s, the natural philosopher, into the category of neuromodulation. William Gilbert, reported using the magnetic lodestone to On August 10, 2017, the CDC recommended that the opi- treat headaches and psychiatric illness.
  • Essential Neuromodulation This Page Intentionally Left Blank Essential Neuromodulation

    Essential Neuromodulation This Page Intentionally Left Blank Essential Neuromodulation

    Essential Neuromodulation This page intentionally left blank Essential Neuromodulation Jeffrey E. Arle Director, Functional Neurosurgery and Research, Department of Neurosurgery Lahey Clinic Burlington, MA Associate Professor of Neurosurgery Tufts University School of Medicine, Boston, MA Jay L. Shils Director of Intraoperative Monitoring, Dept of Neurosurgery Lahey Clinic Burlington, MA AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Academic Press is an Imprint of Elsevier Academic Press is an imprint of Elsevier 32 Jamestown Road, London NW1 7BY, UK 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA 525 B Street, Suite 1800, San Diego, CA 92101-4495, USA First edition 2011 Copyright © 2011 Elsevier Inc. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier's Science & Technology Rights Department in Oxford, UK: phone ( + 44) (0) 1865 843830; fax ( +44) (0) 1865 853333; email: [email protected]. Alternatively, visit the Science and Technology Books website at www.elsevierdirect.com/rights for further information Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of
  • The Sensory Axis

    The Sensory Axis

    The sensory axis By Gustav Emil Dietrichson Things I’m going to cover and you’re going to understand • The basics • Cutaneous receptors • Dorsal column-medial lemniscus • Spinothalamic tract • The thalamus and the cortex • Pain • Quesons Receptors • Smulus à Conducon change à Generator poten?al • Intereceptors, exteroceptors, proprioceptors, teleceptors Thermoreceptors Chemoreceptors Photoreceptors Mechanoreceptors Nerve fibers • A • B – Preganglionic • C – Pain, temp • Aα – Propriocep?on autonomic ggl • 0,5-2m/s • 70-120m/s • 3-12m/s • Cggl – Postsynap?c • Aβ – Touch sympathe?ch ggl • 5-12m/s • 0,7-2,3m/s • Aγ – Motor • 3-6m/s • Aδ – Pain, temp • 12-30m/s A fibers = Thickest C fibers = Thinnest Cutaneous receptors • Merkel discs • Ruffini endings • Fine touch • Skin stretch • Discriminave touch Apical • Sustained pressure Basal • Meissner corpuscles • Pacinian corpuscles • Texture change • Deep touch • Slow vibraons • Fast vibraons • Both ”Corpuscles” are PHASIC receptors, while the other two are TONIC receptors • *ALL USE Aβ FIBERS Thalamus • What is the Thalamus? • Ventroposterolateral nucleusàBrodmann area 3,1,2 Dorsal column- medial lemniscus • Receives all informaon from • Merkel discs, Meissner corpuscles, Pacinian corpuscles, Ruffini endings • Muscles spindles and Golgi tendon organs • Propriocep?on • Fine touch • Vibraon (Low and high) • Pressure (deep and superficial) • Two touch discriminaon • DRAW! Spinothalamic tract Lateral spinothalamic tract • Anterior spinothalamic • Crude touch • Lateral spinothalamic • Temperature • Pain Everything
  • The Pons Neurological System > Brainstem & Cranial Nerve Anatomy > Brainstem & Cranial Nerve Anatomy

    The Pons Neurological System > Brainstem & Cranial Nerve Anatomy > Brainstem & Cranial Nerve Anatomy

    The Pons Neurological System > Brainstem & Cranial Nerve Anatomy > Brainstem & Cranial Nerve Anatomy THE PONS OVERVIEW Here, we'll learn about the pons. • Start a table. • Denote that, from a clinician's perspective, the pons is, most notably, the neurobiological site of injury that produces locked-in syndrome. • Start a mid-sagittal section. First, draw the different brainstem levels, from superior to inferior: • Midbrain • Pons • Medulla KEY SURROUNDING STRUCTRES Label the anterior/posterior orientational plane of our diagram. • Include the key structures that border the brainstem: • The hyopthalamus, superiorly. • The cerebellum, posteriorly. • The cervical spinal cord, inferiorly. • And the temporal lobe, laterally. • Now, point out the pontine basis, which comprises pontine nuclei and pontocerebellar fiber tracts. • Shade in the CSF and indicate that the 4th ventricle lies at the level of the pons. RADIOGRAPHIC AXIAL SECTION • Before we draw a detailed anatomical section, let's review an axial section in radiographic perspective, which is the 1 / 4 common clinical perspective. • Show its anterior/posterior orientational plane. • Draw the pons. • Demarcate the pontine basis, anteriorly. • In this view, show its representative pontine nuclei. • And show its pontocerebellar fibers, which cross the pons and pass into the middle cerebellar peduncle as an important step in the corticopontocerebellar pathway. Clinical Correlation: central pontine myelinolysis ANATOMIC AXIAL SECTION Now, let's draw an anatomic axial outline of the pons. • Indicate the anterior–posterior axis of our diagram. • Label the left side of the page as nuclei and the right side as tracts. • Then, label the fourth ventricle — the cerebrospinal fluid space of the pons. • Next, distinguish the large basis from the comparatively small tegmentum.
  • Sensory System

    Sensory System

    Sensory system. Sándor Katz M.D., Ph.D. Sensory pathways - receptors Sensory pathways (ascending tracts)- Fasciculus gracilis (Goll’s) and cuneatus (Burdach’s) • Both tracts convey fibers for position sense (conscious proprioception) and fine cutaneous sensation (touch, vibration, fine pressure sense, two-point discrimination) =EPICRITIC SENSATION. • The fasciculus gracilis carries fibers only from the lower limbs, while the fasciculus cuneatus carries fibers only from the upper limbs, therefore it is not presented in the spinal cord below the T3-(6) level. Sensory pathways (ascending tracts)- Fasciculus gracilis and cuneatus • Receptors: Meissner’s and Pacinian corpuscles. Muscle spindles and tendon organs for the conscious proprioception. • 1st neuron: pseudounipolar neurons in the dorsal root ganglion. The fibers divide into long ascending and short descending fibers. • The descending fibers give off collateral branches (in the cervical region: Schultze’s comma tract, in the thoracic and lumbar regions: Flechsig’s oval field, in the sacral region: Philippe-Gombault’s trigone) that synapse with posterior or anterior horn’s neurons. (They are involved with intersegmental reflexes). • Many of the long ascending fibers travel ipsilaterally in the posterior funiculi to the gracile and cuneate nuclei (2nd neuron) in the medulla oblongata. Sensory pathways (ascending tracts)- Fasciculus gracilis and cuneatus • The axons (called the internal arcuate fibers) cross in the medulla oblongata and travel as a single bundle (medial lemniscus) to the VPL of thalamus (3rd neuron). • (Many axons from the 2nd neurons in the nucleus cuneatus relay to the cerebellum, traveling through the inferior cerebellar peduncle (called cuneocerebellar tract), carrying muscle joint sense.) • The axons of the third neurons terminate in the primary somatosensory cortex, located in the postcentral gyrus.
  • Lab 3. Pons & Midbrain

    Lab 3. Pons & Midbrain

    Lab 3. Pons & Midbrain Lesion Lessons Lesion 4.1 Anne T. Pasta i) Location ii) Signs/symptoms (Slice of Brain © 993 Univs. of Utah and Washington; E.C. Alvord, Jr., Univ. of Washington) iii) Cause: Lesion 4.2 Colin S. Terase i) Location ii) Signs/symptoms (Slice of Brain © 993 Univs. of Utah and Washington; M.Z. Jones, Michigan St. Univ.) iii) Cause: Medical Neuroscience 4– Pontine Level of the Facial Genu Locate and note the following: Basilar pons – massive ventral structure provides the most obvious change from previous med- ullary levels. Question classic • pontine gray - large nuclear groups in the basilar pons. Is the middle cerebellar peduncle composed – origin of the middle cerebellar peduncle of climbing or mossy • pontocerebellar axons - originate from pontine gray neurons and cross to form the fibers? middle cerebellar peduncle. • corticopontine axons- huge projection that terminates in the basilar pontine gray. • corticospinal tract axons – large bundles of axons surrounded by the basilar pontine gray. – course caudally to form the pyramids in the medulla. Pontine tegmentum • medial lemniscus - has now assumed a “horizontal” position and forms part of the border between the basilar pons and pontine tegmentum. Question classic • central tegmental tract - located just dorsally to the medial lemniscus. What sensory modali- – descends from the midbrain to the inferior olive. ties are carried by the • superior olivary nucleus - pale staining area lateral to the central tegmental tract. medial and lateral – gives rise to the efferent olivocochlear projection to the inner ear. lemnisci? • lateral lemniscus - lateral to the medial lemniscus. – composed of secondary auditory projections from the cochlear nuclei.
  • Download English-US Transcript (PDF)

    Download English-US Transcript (PDF)

    MITOCW | MIT9_14S14_lec10.mp3 The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resources for free. To make a donation or view additional materials from hundreds of MIT courses, visit MIT OpenCourseWare at ocw.mit.edu. PROFESSOR: Can somebody tell me what the homeobox genes are? They're often called Hox genes. What are they code for? Transcription factors. And if you delete certain Hox genes or change their position, you can get abnormalities in the segmentation of the body. Some of that has been done with flies. They can produce a fly, for example, with legs coming out his head or something like that. And it's interesting that of rearrangement on the chromosome that the position of the gene and the sequence of genes on the chromosome, it's always consistent right across the species. As we saw last time this slide of a mouse showing the expression of three different genes. They were doing immunostaining of the antibodies for the proteins of those genes. And here, this is actually not-- it's mesodermal expression. But these genes are expressed in nervous system and other body tissues. But you see each on of them, each of these transcription factors has a rostral limit for its expression, less precise than the caudal side. But now, if you look at the hindbrain, during development at a certain period, you see this pattern appearing. The segmentation is visible in the bulges of the hindbrain. We call them rhombomeres. Mere for for the section or segment.