DOCSLIB.ORG

Digital Neuroanatomy

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Digital Neuroanatomy DIGITAL NEUROANATOMY LM NEUROHISTOLOGY George R. Leichnetz, Ph.D. Professor, Department of Anatomy & Neurobiology Virginia Commonwealth University 2004 Press the Å and Æ keys on your keyboard to navigate through this lecture There are three morphological types of neurons in the nervous system: unipolar, bipolar, and multipolar. While all three types can be found in the PNS, the CNS only contains multipolar neurons. CNS multipolar neurons vary greatly in morphology: eg. spinal cord motor neurons, pyramidal cells of cerebral cortex, Purkinje cells of cerebellar cortex. The supportive cells of the CNS are neuroglia: astrocytes, oligodendrocytes, and microglia. Oligodendrocytes myelinate CNS axons, while Schwann cells myelinate PNS axons. Protoplasmic astrocytes predominate in CNS gray matter, while fibrous astrocytes predominate in CNS white matter. The ventral horn of the spinal cord Lumbar Spinal Cord contains multipolar motor neurons. Dorsal White Horn Matter Gray Matter Ventral Kluver- Horn Barrera Stain (LFB & CV) Cell bodies of motor neurons Dendrite Gray Matter Dendrite Perineuronal H & E oligodendrocyte Stain Nucleus, nucleolus Abundant Nissl substance Dorsal root Dorsal root ganglion Ventral root Gray Matter: contains White Matter: cell bodies of neurons contains x-sections of myelinated axons Multipolar motor neurons Silver Stain of the ventral horn Large multipolar motor neurons of the spinal cord ventral horn: see nucleus, nucleolus, abundant Nissl substance, multiple tapering processes (dendrites). The axon hillock (origin of axon from cell body) lacks Nissl. Nucleus Axon hillock dendrites Nucleolus Nissl substance (RER) Kluver-Barrera Stain (Luxol Fast Blue and Cresyl Violet) Thoracic Spinal Cord The nucleus dorsalis of Clarke, located in the base of the dorsal horn of the thoracic spinal cord, contains multipolar neurons whose nucleus is eccentric and Nissl around the periphery of the cell body (as if it were chromatolytic). Nucleus dorsalis H & E of Clarke Stain Lateral horn Oligodendrocytes Intermediolateral Cell Lateral horn Column (Lateral Horn) Thoracic Spinal Cord contains multipolar preganglionic sympathetic neurons. Oligodendrocyte nucleus Protoplasmic astrocyte nucleus The cerebral cortex (gray matter on the surface of the cerebrum) contains multipolar pyramidal neurons. Subcortical white matter Cerebral cortex Oligodendrocyte nucleus Protoplasmic Lamina III astrocyte nucleus pyramidal neurons Pyramidal neurons of the cerebral cortex. The neuroglia of the cortex are protoplasmic astrocytes (euchromatic) and perineuronal and juxtavascular oligodendrocytes (heterochromatic, small dense spheroidal nuclei) Apical dendrite Pyramidal neurons Apical dendrite Perineuronal oligodendrocyte nucleus Basal Protoplasmic astrocyte nucleus dendrites Axon Perineuronal oligodendrocyte nucleus The cerebellar cortex contains multipolar Purkinje neurons. Molecular layer Cerebellum Purkinje cell layer Cell body of Granular layer Purkinje cell Primary dendrite Abundant dendritic spines on dendrites Dendrites Cell body of Purkinje H & E Axon Cerebellar Cortex neuron The spinal cord white matter contains myelinated tracts, abundant fibrous astrocytes and interfascicular oligodendrocytes. Cross-sections of myelinated axons Dural sac (dura mater) Dorsal Column Lateral column Ventral column H & E Stain Thoracic Spinal Cord Fibrous astrocyte Interfascicular nucleus oligodendrocyte nucleus The spinal cord white matter is divided into columns: dorsal, lateral and ventral columns. Each contains ascending and descending tracts of myelinated axons. Interfascicular oligodendrocytes myelinate more than 50 axons. Dorsal column Lateral column Ventral column Silver Stain The white matter columns (or funiculi) of the spinal cord contain myelinated axons (black dots). The lighter area (donut) around each axon cylinder was occupied by myelin. Groups of axons (tracts) ascend or descend See cross sections of axons (black dots) in the white matter. surrounded by myelin sheath (donut). The white matter under the cerebral cortex (subcortical white matter) contains myelinated axons going to and from the cortex, and contains abundant fibrous astrocytes and interfascicular oligodendrocytes. Subcortical white matter Interfascicular oligodendrocyte nuclei Fibrous astrocyte nucleus The neuroglia of the cerebral cortex are predominantly protoplasmic astrocytes and perineuronal oligodendrocytes. The “perineuronal” oligodendrocytes myelinate the first segment of the neuron closest to the cell body. Pyramidal neurons Protoplasmic astrocyte nuclei Perineuronal oligodendrocyte nuclei Pyramidal neurons In the PNS, dorsal root ganglia contain sensory unipolar neurons surrounded by supportive elements, the satellite cells. Dorsal root ganglion The larger cell bodies are somatic sensory; smaller are visceral sensory Within the dorsal root ganglion, there (Pseudo-) unipolar are satellite cells and neuron cell bodies fibroblast nuclei between the unipolar neurons. (Fibroblasts are associated with connective tissue in the ganglion.) Spheroidal cell Satellite cell nuclei Nucleus, nucleolus bodies with central nucleus H & E The single process Stain divides into a peripheral process that goes to sensory receptor in skin or muscle and central Single “pole” process that goes of neuron thru dorsal root into Fibroblast the CNS. nuclei In the PNS, bipolar neurons Organ of Corti in are found in special sensory cochlea contains hair ganglia, like the cochlear cell receptors for hearing (spiral) ganglion in the cochlea of the inner ear. Spiral (Cochlear) ganglion The bipolar neurons send one process to the hair cell receptor and the central process into the auditory nerve (CN. VIII) to CNS, which travels centrally into the brain. Bipolar neurons in the vestibular ganglion typically have an ovoid cell body. Its central and peripheral processes extend from the ends of the cell body. The peripheral process goes to hair cells in the vestibular end organs. The central process goes to the vestibular complex in the brainstem. The retina contains bipolar neurons. The rods and cones are specialized receptors on the peripheral processes of neurons that have their bipolar cell bodies in the outer nuclear layer of the retina. Pigmented epithelium Rods Rods Cone Cone Cell bodies of bipolar neurons of the rods and cones Protoplasmic astrocytes, located in gray matter (seen here in cerebral cortex), have a bushy appearance. Protoplasmic astrocyte Apical Protoplasmic Pyramidal dendrite astrocytes neuron Basal dendrites Axon Pyramidal neurons Fibrous astrocytes (seen here in subcortical white matter) have long willowy processes and are less highly branched than protoplasmic astrocytes. Astrocytes send processes to capillaries Fibrous astrocytes Capillary Fibrous astrocytes in the subcortical white matter, stained with a special silver stain, show long processes to capillaries which end in perivascular end feet. Fibrous astrocyte Capillary Capillary Capillary Capillary In the PNS, peripheral nerves are surrounded with epineurium. Fascicles within the nerve are surrounded with perineurium, and individual fibers are surrounded with endoneurium. This connective tissue is produced by fibroblasts. The myelin sheath around each axon is produced by Schwann cells. Thus the nuclei seen within peripheral nerves belong to fibroblasts and Schwann cells. Perineurium Pale violet axons are surrounded by space (donut) of myelin sheath Epineurium Endoneurium Perineurium Schwann cell nuclei are plump, euchromatic; fibroblast nuclei are cigar-shaped.
Load more

Recommended publications
  • Specification of Optic Nerve Oligodendrocyte Precursors by Retinal Ganglion Cell Axons
    The Journal of Neuroscience, July 19, 2006 • 26(29):7619–7628 • 7619 Cellular/Molecular Specification of Optic Nerve Oligodendrocyte Precursors by Retinal Ganglion Cell Axons Limin Gao and Robert H. Miller Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio 44106 Cell fate commitment in the developing CNS frequently depends on localized cell–cell interactions. In the avian visual system the optic nerve oligodendrocytes are derived from founder cells located at the floor of the third ventricle. Here we show that the induction of these founder cells is directly dependent on signaling from the retinal ganglion cell (RGC) axons. The appearance of oligodendrocyte precursor cells (OPCs) correlates with the projection of RGC axons, and early eye removal dramatically reduces the number of OPCs. In vitro signaling from retinal neurites induces OPCs in responsive tissue. Retinal axon induction of OPCs is dependent on sonic hedgehog (Shh) andneuregulinsignaling,andtheinhibitionofeithersignalreducesOPCinductioninvivoandinvitro.ThedependenceofOPCsonretinal axonal cues appears to be a common phenomenon, because ocular retardation (orJ) mice lacking optic nerve have dramatically reduced OPCs in the midline of the third ventricle. Key words: oligodendrocyte precursors; optic nerve; axon induction; sonic hedgehog; neuregulin; retinal ganglion cells Introduction contributes to the specification of ventral midline cells (Dale et al., During development the oligodendrocytes, the myelinating cells 1997); however, OPCs arise later
    [Show full text]
  • Early Neuronal Processes Interact with Glia to Establish a Scaffold For
    bioRxiv preprint doi: https://doi.org/10.1101/754416; this version posted August 31, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Early neuronal processes interact with glia to establish a scaffold for orderly innervation of the cochlea Running Title: Glia and early cochlear wiring N. R. Druckenbrod1, E. B. Hale, O. O. Olukoya, W. E. Shatzer, and L.V. Goodrich* Department of Neurobiology, Harvard Medical School, Boston, MA, 02115 1Current address: Decibel Therapeutics, Boston, Ma, 02215 *correspondence should be addressed to [email protected] Keywords: neuron-glia interactions, axon guidance, spiral ganglion neuron, cochlea Authors’ contributions: This study was conceived of and designed by NRD and LVG. NRD, EBH, OOO, and WES performed experiments and analyzed results. LVG analyzed results and wrote the manuscript. bioRxiv preprint doi: https://doi.org/10.1101/754416; this version posted August 31, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Summary: Although the basic principles of axon guidance are well established, it remains unclear how axons navigate with high fidelity through the complex cellular terrains that are encountered in vivo. To learn more about the cellular strategies underlying axon guidance in vivo, we analyzed the developing cochlea, where spiral ganglion neurons extend processes through a heterogeneous cellular environment to form tonotopically ordered connections with hair cells.
    [Show full text]
  • Basal Ganglia & Cerebellum
    1/2/2019 This power point is made available as an educational resource or study aid for your use only. This presentation may not be duplicated for others and should not be redistributed or posted anywhere on the internet or on any personal websites. Your use of this resource is with the acknowledgment and acceptance of those restrictions. Basal Ganglia & Cerebellum – a quick overview MHD-Neuroanatomy – Neuroscience Block Gregory Gruener, MD, MBA, MHPE Vice Dean for Education, SSOM Professor, Department of Neurology LUHS a member of Trinity Health Outcomes you want to accomplish Basal ganglia review Define and identify the major divisions of the basal ganglia List the major basal ganglia functional loops and roles List the components of the basal ganglia functional “circuitry” and associated neurotransmitters Describe the direct and indirect motor pathways and relevance/role of the substantia nigra compacta 1 1/2/2019 Basal Ganglia Terminology Striatum Caudate nucleus Nucleus accumbens Putamen Globus pallidus (pallidum) internal segment (GPi) external segment (GPe) Subthalamic nucleus Substantia nigra compact part (SNc) reticular part (SNr) Basal ganglia “circuitry” • BG have no major outputs to LMNs – Influence LMNs via the cerebral cortex • Input to striatum from cortex is excitatory – Glutamate is the neurotransmitter • Principal output from BG is via GPi + SNr – Output to thalamus, GABA is the neurotransmitter • Thalamocortical projections are excitatory – Concerned with motor “intention” • Balance of excitatory & inhibitory inputs to striatum, determine whether thalamus is suppressed BG circuits are parallel loops • Motor loop – Concerned with learned movements • Cognitive loop – Concerned with motor “intention” • Limbic loop – Emotional aspects of movements • Oculomotor loop – Concerned with voluntary saccades (fast eye-movements) 2 1/2/2019 Basal ganglia “circuitry” Cortex Striatum Thalamus GPi + SNr Nolte.
    [Show full text]
  • Imaging of the Confused Patient: Toxic Metabolic Disorders Dara G
    Imaging of the Confused Patient: Toxic Metabolic Disorders Dara G. Jamieson, M.D. Weill Cornell Medicine, New York, NY The patient who presents with either acute or subacute confusion, in the absence of a clearly defined speech disorder and focality on neurological examination that would indicate an underlying mass lesion, needs to be evaluated for a multitude of neurological conditions. Many of the conditions that produce the recent onset of alteration in mental status, that ranges from mild confusion to florid delirium, may be due to infectious or inflammatory conditions that warrant acute intervention such as antimicrobial drugs, steroids or plasma exchange. However, some patients with recent onset of confusion have an underlying toxic-metabolic disorders indicating a specific diagnosis with need for appropriate treatment. The clinical presentations of some patients may indicate the diagnosis (e.g. hypoglycemia, chronic alcoholism) while the imaging patterns must be recognized to make the diagnosis in other patients. Toxic-metabolic disorders constitute a group of diseases and syndromes with diverse causes and clinical presentations. Many toxic-metabolic disorders have no specific neuroimaging correlates, either at early clinical stages or when florid symptoms develop. However, some toxic-metabolic disorders have characteristic abnormalities on neuroimaging, as certain areas of the central nervous system appear particularly vulnerable to specific toxins and metabolic perturbations. Areas of particular vulnerability in the brain include: 1) areas of high-oxygen demand (e.g. basal ganglia, cerebellum, hippocampus), 2) the cerebral white matter and 3) the mid-brain. Brain areas of high-oxygen demand are particularly vulnerable to toxins that interfere with cellular respiratory metabolism.
    [Show full text]
  • Neuron Numbers Increase in the Human Amygdala from Birth to Adulthood, but Not in Autism
    Neuron numbers increase in the human amygdala from birth to adulthood, but not in autism Thomas A. Avinoa, Nicole Bargera, Martha V. Vargasa, Erin L. Carlsona, David G. Amarala,b,c, Melissa D. Baumana,b, and Cynthia M. Schumanna,1 aDepartment of Psychiatry and Behavioral Sciences, UC Davis MIND Institute, School of Medicine, University of California, Davis, Sacramento, CA 95817; bCalifornia National Primate Research Center, University of California, Davis, CA 95616; and cCenter for Neuroscience, University of California, Davis, CA 95618 Edited by Joseph E. LeDoux, New York University, New York, NY, and approved March 1, 2018 (received for review February 12, 2018) Remarkably little is known about the postnatal cellular develop- process, however, may also make the amygdala more susceptible ment of the human amygdala. It plays a central role in mediating to developmental or environmental insults. emotional behavior and has an unusually protracted development ASD is characterized by impairments in social communication well into adulthood, increasing in size by 40% from youth to combined with restricted interests and behaviors. Alterations in adulthood. Variation from this typical neurodevelopmental trajec- amygdala growth can be detected as early as 2 y of age (23–26) tory could have profound implications on normal emotional devel- and persist into late childhood (5, 27). The severity of the indi- vidual’s social and communicative symptoms positively correlates opment. We report the results of a stereological analysis of the – number of neurons in amygdala nuclei of 52 human brains ranging with amygdala enlargement, suggesting a potential structure from 2 to 48 years of age [24 neurotypical and 28 autism spectrum function relationship (23).
    [Show full text]
  • Spinal Nerves, Ganglia, and Nerve Plexus Spinal Nerves
    Chapter 13 Spinal Nerves, Ganglia, and Nerve Plexus Spinal Nerves Posterior Spinous process of vertebra Posterior root Deep muscles of back Posterior ramus Spinal cord Transverse process of vertebra Posterior root ganglion Spinal nerve Anterior ramus Meningeal branch Communicating rami Anterior root Vertebral body Sympathetic ganglion Anterior General Anatomy of Nerves and Ganglia • Spinal cord communicates with the rest of the body by way of spinal nerves • nerve = a cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue – mixed nerves contain both afferent (sensory) and efferent (motor) fibers – composed of thousands of fibers carrying currents in opposite directions Anatomy of a Nerve Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epineurium Perineurium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endoneurium Nerve Rootlets fiber Posterior root Fascicle Posterior root ganglion Anterior Blood root vessels Spinal nerve (b) Copyright by R.G. Kessel and R.H. Kardon, Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, 1979, W.H. Freeman, All rights reserved Blood vessels Fascicle Epineurium Perineurium Unmyelinated nerve fibers Myelinated nerve fibers (a) Endoneurium Myelin General Anatomy of Nerves and Ganglia • nerves of peripheral nervous system are ensheathed in Schwann cells – forms neurilemma and often a myelin sheath around the axon – external to neurilemma, each fiber is surrounded by
    [Show full text]
  • Spinal Cord Organization
    Lecture 4 Spinal Cord Organization The spinal cord . Afferent tract • connects with spinal nerves, through afferent BRAIN neuron & efferent axons in spinal roots; reflex receptor interneuron • communicates with the brain, by means of cell ascending and descending pathways that body form tracts in spinal white matter; and white matter muscle • gives rise to spinal reflexes, pre-determined gray matter Efferent neuron by interneuronal circuits. Spinal Cord Section Gross anatomy of the spinal cord: The spinal cord is a cylinder of CNS. The spinal cord exhibits subtle cervical and lumbar (lumbosacral) enlargements produced by extra neurons in segments that innervate limbs. The region of spinal cord caudal to the lumbar enlargement is conus medullaris. Caudal to this, a terminal filament of (nonfunctional) glial tissue extends into the tail. terminal filament lumbar enlargement conus medullaris cervical enlargement A spinal cord segment = a portion of spinal cord that spinal ganglion gives rise to a pair (right & left) of spinal nerves. Each spinal dorsal nerve is attached to the spinal cord by means of dorsal and spinal ventral roots composed of rootlets. Spinal segments, spinal root (rootlets) nerve roots, and spinal nerves are all identified numerically by th region, e.g., 6 cervical (C6) spinal segment. ventral Sacral and caudal spinal roots (surrounding the conus root medullaris and terminal filament and streaming caudally to (rootlets) reach corresponding intervertebral foramina) collectively constitute the cauda equina. Both the spinal cord (CNS) and spinal roots (PNS) are enveloped by meninges within the vertebral canal. Spinal nerves (which are formed in intervertebral foramina) are covered by connective tissue (epineurium, perineurium, & endoneurium) rather than meninges.
    [Show full text]
  • 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.
    [Show full text]
  • Review of Spinal Cord Basics of Neuroanatomy Brain Meninges
    Review of Spinal Cord with Basics of Neuroanatomy Brain Meninges Prof. D.H. Pauža Parts of Nervous System Review of Spinal Cord with Basics of Neuroanatomy Brain Meninges Prof. D.H. Pauža Neurons and Neuroglia Neuron Human brain contains per 1011-12 (trillions) neurons Body (soma) Perikaryon Nissl substance or Tigroid Dendrites Axon Myelin Terminals Synapses Neuronal types Unipolar, pseudounipolar, bipolar, multipolar Afferent (sensory, centripetal) Efferent (motor, centrifugal, effector) Associate (interneurons) Synapse Presynaptic membrane Postsynaptic membrane, receptors Synaptic cleft Synaptic vesicles, neuromediator Mitochondria In human brain – neurons 1011 (100 trillions) Synapses – 1015 (quadrillions) Neuromediators •Acetylcholine •Noradrenaline •Serotonin •GABA •Endorphin •Encephalin •P substance •Neuronal nitric oxide Adrenergic nerve ending. There are many 50-nm-diameter vesicles (arrow) with dark, electron-dense cores containing norepinephrine. x40,000. Cell Types of Neuroglia Astrocytes - Oligodendrocytes – Ependimocytes - Microglia Astrocytes – a part of hemoencephalic barrier Oligodendrocytes Ependimocytes and microglial cells Microglia represent the endogenous brain defense and immune system, which is responsible for CNS protection against various types of pathogenic factors. After invading the CNS, microglial precursors disseminate relatively homogeneously throughout the neural tissue and acquire a specific phenotype, which clearly distinguish them from their precursors, the blood-derived monocytes. The ´resting´ microglia
    [Show full text]
  • Nucleus Laminaris
    OUP UNCORRECTED PROOF – FIRST-PROOF, 26/03/2010, GLYPH 1 2 2 2 Nucleus Laminaris 3 Yuan Wang Jason Tait Sanchez , and Edwin W Rubel 4 Our ability to detect subtle acoustic cues in noisy environments, like a con- 5 versation in a crowded restaurant, is one benefi t of binaural hearing. Binaural 6 hearing is also essential for sound localization. The ability to localize the 7 source of a sound is dependent on time disparities in the arrival of low- 8 frequency signals between the two ears, referred to as interaural time differ- 9 ence (ITD). In all vertebrates, ITDs are encoded by distinct neural circuits in 10 the central auditory nervous system specialized for the temporal processing 11 of sound at the network, synaptic, and cellular levels. Coding of ITDs is fi rst 12 performed by the medial superior olive (MSO) of mammals and by the 13 nucleus laminaris (NL) in birds and some reptiles. 14 This chapter will focus on the microcircuitry of the chicken NL, which is 15 an excellent example of neural architecture exquisitely tailored for its special- 16 ized function in sound localization. Neurons in NL are coincidence detectors, 17 encoding temporal information of sound arriving at the two ears by respond- 18 ing maximally when resulting action potentials (APs) arrive simultaneously, 19 a unique feature responsible for the coding of ITDs in the microsecond range. 20 We will discuss the important structural and functional specializations of NL 21 that optimize this specialized ability, fundamental for binaural hearing in 22 most birds and mammals.
    [Show full text]
  • Different Projections of the Central Amygdaloid Nucleus Mediate Autonomic and Behavioral Correlates of Conditioned Fear
    The Journal of Neuroscience, July 1988, 8(7): 2517-2529 Different Projections of the Central Amygdaloid Nucleus Mediate Autonomic and Behavioral Correlates of Conditioned Fear Joseph E. LeDoux, Jiro Iwata, Piera Cicchetti, and Donald J. Reis Division of Neurobiology, Cornell University Medical College, New York, New York 10021 The purpose of the present study was to determine whether Iwata et al., 1986a).The critical amygdaloid regionsare located lesions of areas projected to by the central amygdaloid nu- in the dorsal part of this structure, and include the lateral and cleus (ACE) would disrupt the classical conditioning of auto- central nuclei and the amygdalostriatal transition zone (Iwata nomic and/or behavioral emotional responses. The areas et al., 1986a; LeDoux et al., 1986a). Since the major projection studied included 3 projection targets of the ACE: the lateral from the acoustic thalamus terminates in the lateral nucleusand hypothalamic area (LH), midbrain central gray (CG) region, the amygdalostriatal zone (LeDoux et al., 1985), one of these and bed nucleus of the stria terminalis (BNST). Lesions were regionsprobably servesas the sensoryinterface of the amygdala made either electrolytically or by microinjection of ibotenic during conditioning (Cicchetti et al., 1987). In contrast, the acid, which destroys local neurons without interrupting fibers amygdaloid output pathway is likely to involve the central nu- of passage. Two weeks later, the animals were classically cleus, a structure implicated in the expressionof the autonomic
    [Show full text]
  • Gathering at the Nodes
    RESEARCH HIGHLIGHTS GLIA Gathering at the nodes Saltatory conduction — the process by which that are found at the nodes of Ranvier, where action potentials propagate along myelinated they interact with Na+ channels. When the nerves — depends on the fact that voltage- authors either disrupted the localization of gated Na+ channels form clusters at the nodes gliomedin by using a soluble fusion protein of Ranvier, between sections of the myelin that contained the extracellular domain of sheath. New findings from Eshed et al. show neurofascin, or used RNA interference to that Schwann cells produce a protein called suppress the expression of gliomedin, the gliomedin, and that this is responsible for characteristic clustering of Na+ channels at the clustering of these channels. the nodes of Ranvier did not occur. The formation of the nodes of Ranvier is Aggregation of the domain of gliomedin specified by the myelinating cells, not the that binds neurofascin and NrCAM on the axons, and an important component of this surface of purified neurons also caused process in the peripheral nervous system the clustering of neurofascin, Na+ channels is the extension of microvilli by Schwann and other nodal proteins. These findings cells. These microvilli contact the axons at support a model in which gliomedin on the nodes, and it is here that the Schwann References and links Schwann cell microvilli binds to neurofascin ORIGINAL RESEARCH PAPER Eshed, Y. et al. Gliomedin cells express the newly discovered protein and NrCAM on axons, causing them to mediates Schwann cell–axon interaction and the molecular gliomedin. cluster at the nodes of Ranvier, and leading assembly of the nodes of Ranvier.
    [Show full text]