03.09.09(b): Spinal Cord & Spinal Nerves, part I

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03.09.09(b): Spinal Cord & Spinal Nerves, part I

  1. 1. Attribution: Department of Neurology, 2009License: Unless otherwise noted, this material is made available under the terms of theCreative Commons Attribution–Non-commercial–Share Alike 3.0 License:http://creativecommons.org/licenses/by-nc-sa/3.0/We have reviewed this material in accordance with U.S. Copyright Law and have tried to maximize your ability to use,share, and adapt it. The citation key on the following slide provides information about how you may share and adapt thismaterial.Copyright holders of content included in this material should contact open.michigan@umich.edu with any questions,corrections, or clarification regarding the use of content.For more information about how to cite these materials visit http://open.umich.edu/education/about/terms-of-use.Any medical information in this material is intended to inform and educate and is not a tool for self-diagnosis or areplacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. Please speak to yourphysician if you have questions about your medical condition.Viewer discretion is advised: Some medical content is graphic and may not be suitable for all viewers.
  2. 2. Citation Key for more information see: http://open.umich.edu/wiki/CitationPolicyUse + Share + Adapt { Content the copyright holder, author, or law permits you to use, share and adapt. } Public Domain – Government: Works that are produced by the U.S. Government. (USC 17 § 105) Public Domain – Expired: Works that are no longer protected due to an expired copyright term. Public Domain – Self Dedicated: Works that a copyright holder has dedicated to the public domain. Creative Commons – Zero Waiver Creative Commons – Attribution License Creative Commons – Attribution Share Alike License Creative Commons – Attribution Noncommercial License Creative Commons – Attribution Noncommercial Share Alike License GNU – Free Documentation LicenseMake Your Own Assessment { Content Open.Michigan believes can be used, shared, and adapted because it is ineligible for copyright. } Public Domain – Ineligible: Works that are ineligible for copyright protection in the U.S. (USC 17 § 102(b)) *laws in your jurisdiction may differ { Content Open.Michigan has used under a Fair Use determination. } Fair Use: Use of works that is determined to be Fair consistent with the U.S. Copyright Act. (USC 17 § 107) *laws in your jurisdiction may differ Our determination DOES NOT mean that all uses of this 3rd-party content are Fair Uses and we DO NOT guarantee that your use of the content is Fair. To use this content you should do your own independent analysis to determine whether or not your use will be Fair.
  3. 3. Spinal Cord and Spinal Nerves UCSF, School of Medicine M1 CNS Head and Neck March 3, 2009
  4. 4. Lecture Outline•  Spinal Cord Function•  Development•  Gross Anatomy –  Regions Cervical, Thoracic, Lumbar, Sacral –  Meninges•  Spinal Nerves•  Gray Matter•  White Matter•  Reflexes•  Blood Supply
  5. 5. Important Terms•  Dermatome •  Lamina of Rexed•  Motor Unit •  White Rami Communicantes•  Receptive Field •  Gray Rami Communicantes•  Column •  Afferent•  Fasciculus •  Efferent•  Lower Motor Neuron •  Dorsal Horn•  Rootlets (Dorsal and •  Ventral Horn Ventral) •  Dorsal Root Ganglia•  Roots (Dorsal and Ventral) •  Sympathetic Ganglia•  Somatic•  Visceral
  6. 6. Spinal Cord Essential Functions•  Receives sensory input –  Somatic and Visceral•  Contains motor neurons•  Direct (local) connections of motor and sensory information: Reflexes•  Carries motor information from brain to muscles –  Somatic and Visceral
  7. 7. REMINDER •  Afferent Arrives•  Information arriving to the CNS in general, a nucleus within the CNS or a neuron •  Efferent Exits•  Information leaving the CNS in general a, a nucleus within the CNS or neuron
  8. 8. The Nervous System consists of:1. Central Nervous System (CNS)2. Peripheral Nervous System (PNS)CENTRAL NERVOUS SYSTEM (CNS) BRAIN: Forebrain Telencephalon Diencephalon Brain Stem Midbrain Pons Medulla Cerebellum SPINAL CORD (5 regions): Cervical Thoracic Lumbar Sacral Coccygeal Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  9. 9. Spinal Cord DevelopmentG.M. Shepard, Neurobiology, 3rd Edition Fig. 9.3
  10. 10. Spinal Cord DevelopmentDorsal = PosteriorVentral = Anterior Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 9-1
  11. 11. Spinal Cord A. OUTER LAYER = White Matter ; (tracts of axons & their myelin) 1. Ascending Sensory (Afferent) Tracts 2. Descending Motor (Efferent) Tracts B. Inner Layer - Gray Matter, rich in neuronal cell bodies and dendrites Source Undetermined Dorsal White Gray Dorsal Root VentralGray’s Anatomy Ganglia
  12. 12. Source Undetermined, See also Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed
  13. 13. The Spinal Cord and Spinal Nerves Dorsal Median Sulcus Gray Matter White Matter Spinal Segment Rootlets of the Dorsal Root Gray’s Anatomy Ventral View
  14. 14. SPINAL NERVES:31 pairs (left and right) innervate the neck, trunk and limbs from 5 regions of the spinal cord: 8 pairs of cervical nerves innervate the neck and arms Image of spinal nerves removed 12 pairs of thoracic nerves innervate the thorax 5 pairs of lumbar nerves and 5 pairs of sacral nerves and 1 pair of coccygeal nerves collectively innervate the abdomen, pelvis,and legs
  15. 15. Spinal nerves pass through the vertebral column (intervertebral foramen) The first (C1) emerges between the first vertebrae and the base of the skull. C8 emerges from intervertebral foramen between C7 and T1. Other spinal nerves emerge from intervertebral foramen below the vertebrae of the same number. The vertebral column grows longer than the spinal cord; therefore, these vertebrae become located several segments below the entrance/exit ofGray’s Anatomy the spinal nerve from the spinal cord.
  16. 16. Sensory Neuron Motor Neuron Dorsal Root GanglionSpinal Cord Ventral Horn UCSF School of Medicine University of Medicine and Dentistry of New Jersey
  17. 17. Spinal Cord and Spinal Nerve Dorsal Root Dorsal Root Ganglion Dorsal Funiculus Dorsal Dorsal Primary Horn Ramus Lateral Horn Ventral Primary Ramus SKIN Lateral Ventral Funiculus Gray Horn Ramus Ventral Root White Ventral Ramus FuniculusSpinal Cord Paravertebral T3 Ganglion SKELETAL Thoracic MUSCLE Visceral Nerve Source Undetermined
  18. 18. A “dermatome” = an area of skin innervated by one segment of the spinal cord (in other words, by one pair of spinal nerves). Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 18-4
  19. 19. Receptive Fields and Motor Units Receptive Field = area of skin innervated by one DRG neuron Motor Unit = total number of skeletal muscle fibers innervated by one motor neuron Dorsal Root Ganglion (DRG) Cell Dorsal Horn somatic afferent free nerve fiber endings interneuron SKIN (pain and temperature receptors) Ventral Ventral Horn Root somatic efferent fiberVentral Horn Cell receptive (VHC) field motor unit Motor end plates SKELETAL MUSCLE Source Undetermined
  20. 20. Dermatomes of Adjacent Spinal Cord Segments Overlap Overlapping distribution of spinal nerves inSpinal Cord the skin the dermatome Segments Dorsal Root map Ganglia T2 T2 T3 T3 T4 T4 Source Undetermined Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 6-1
  21. 21. Four Functional Components of the Spinal Nerve: Somatic Afferent Somatic (body wall) Afferent (sensory) Somatic Efferent 2 X2 = 4 Visceral (viscera) Efferent (motor) Visceral Afferent Visceral Efferent Somatic Afferent & Visceral Afferent DRG cells Spinal Nerve Visceral Efferent Neuron (preganglionic) Somatic Afferent nerve endings in receptors of skin, muscles and joints SomaticEfferent Neuron Visceral Visceral Efferent Efferent Neurons endings (postganglionic) on sweat glands, arrector pili mm., HEART SKELETAL and smooth muscle MUSCLE in blood vessels Visceral Afferent endings Source Undetermined
  22. 22. Gray Matter
  23. 23. Motor Neuron Spinal Cord Ventral Horn 3 Types of Motor neurons Alpha Motor Neurons (somatic) Innervate skeletal muscle Gamma Motor Neurons Innervate intrafusal muscle fibers Preganglionic Sympathetic Neurons (visceral)UCSF, School of Medicine
  24. 24. Five Spinal Cord Regions And Two Enlargements The absolute amount of white cervical matter decreases cervical from cervical enlargement to coccygeal segments. thoracic The amount of gray matterConus Medullaris is greater in theat L1-L2 enlargementsvertebral level L2 than the upperin the adult cervical and lumbo-sacral lumbar thoracic regions.Cauda Equina enlargementfrom L2into the sacralcanal sacral coccygeal Source Undetermined
  25. 25. Source Undetermined
  26. 26. GeneralGSA (general sensoryafferent) – receive Organization of thesomatic sensory input Spinal Cord GVA (general visceral afferent)– receive visceral sensory input (restricted distribution) GVE (general visceral efferent) (autonomics) – motor to viscera; secretomotor to organs and motor smooth muscle. (restricted distribution)GSE (general somaticefferent) – motor to somatic(striated) muscles Source Undetermined
  27. 27. The Spinal Cord Gray Matter Nuclear Groups Rexed’s Laminae Substantia Posteromarginal Gelatinosa (SG) Nucleus (PM) I PM Nucleus Proprius II SG (NP) Nucleus Dorsalis III - V NP (of Clarke) (ND) II V, VI SVGSecondary Visceral I VII ND, IML IV III Gray (SVG) VIII interneuron pool VIntermediolateral IX VHC VICell Column (IML) X interneuron pool X VII VIII IX (VHC) Ventral Horn Cells motor neurons Source Undetermined
  28. 28. The Spinal Cord Gray Matter Nuclear Groups Rexed’s LaminaePain and Temperature PM SG I PMFine touch and II SGProprioception ND NP III - V NP II V, VI SVGVisceral SVG I VII ND, IMLSensation IV III VIII interneuron pool V IX VHC Visceral IML VI X interneuron pool Motor X VII VIII IX VHC Somatic Motor to distal limb mm. to proximal limb mm. to axial mm. Source Undetermined
  29. 29. Somatotopic Organization of the Spinal Cord Medial Dorsal Lateral Distal Proximal Ventral
  30. 30. Spinal CordLongitudinal Organizationof the gray matterNuclei (laminae) of thegray matter are actually For example,longitudinal columns of cells. the substantia gelatinosa (receiving pain andEach column is a temperature input)structurally and extends throughout thefunctionally defined length of the cord.population of neurons. Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  31. 31. Spinal CordLongitudinal Organizationof the gray matter A second example is the column of ventral horn cells that innervate axial muscles at all levels of the vertebral column. This cell column forms the medial part of the ventral horn. Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  32. 32. Spinal CordLongitudinal Organizationof the gray matter In the enlargements, neurons innervating the limb muscles form a lateral cell column in the ventral horn. This is a discontinuous column of cells. These added cells in the enlargements make the ventral horn much larger than the ventral horn of the thoracic cord. Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  33. 33. Phrenic NucleusAccessory NucleusVHC - lateral columnsVHC - medial columnIML & SVG - visceralNucleus dorsalisSubstantia Gelatinosa cervical thoracic lumbar sacral Co C7 T4 L4 Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  34. 34. Nucleus or Column Spinal Level Function Dorsal HornPosteromarginal nucleus All levels All three nuclei receive primary sensorySubstantia gelatinosa information. The first two appearPrincipal sensory nucleus to modulate this information,(Nucleus proprius) whereas the principal sensory nucleus is associated more with transmission to higher centers and with reflex connections.Dorsal nucleus of Clarke C8-L3 Nucleus of origin of the dorsal(nucleus dorsalis) spinocerebellar tract Ventral HornSpinal accessory nucleus C1-C5 Lower motor neurons of trapezius and sternocleidomastoid musclesPhrenic nucleus C3-C5 Lower motor neurons of the diaphragmIntermediolateral nucleus T1-L3 Nucleus of origin of sympathetic preganglionic fibers S2-S4 Nucleus of origin of sacral parasympathetic preganglionic fibersMedial motor column All levels Lower motor neurons that innervate the trunkLateral motor column C5-T1 Lower motor neurons that innervate the L1 -S3 limbs
  35. 35. INTERMISSION•  10 minute visceral afferent/efferent break
  36. 36. White Matter
  37. 37. The White Matter of the Spinal Cord is composed of: •  ascending tracts (fibers relaying sensory information from the spinal nerves to the brain) •  descending tracts (fibers from the brain that terminate in each segment to influence motor function and sensory transmission) •  fiber bundles with both ascending and descending fibers, carrying information for intersegmental coordination White matter decreases from the cervical to the sacral segments of the cord. All tracts have a topographic organization. Not all tracts are present at all levels of the cordHaines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  38. 38. REFLEXES This is one of the types of “localprocessing” that occurs in the spinal cord without influence from higher centers.
  39. 39. A Polysynaptic Spinal Reflex ArcReceptor - in skin, muscle, joint or visceraAfferent (sensory) fiber - process of a pseudounipolar cell in the dorsal root ganglionInterneuron in Spinal Cord - (distinguishes polysynaptic from monosynaptic reflex)Efferent (motor) fiber - axon of cell in the ventral or lateral hornEffector - muscle (striated or smooth) or glandAfferent Arrives Efferent Exits
  40. 40. Spinal Reflex Arc Dorsal Root Dorsal Root Ganglion Cell free nerve Dorsal endings Horn somatic afferent (pain and interneuron fiber temperature receptors) Ventral Ventral Horn Root somatic efferent fiber Ventral Horn Cellor Alpha Motor Neuron SKIN Motor end plates SKELETAL MUSCLE Source Undetermined
  41. 41. = Lissauer’s tract The Flexor Reflex •  contraction of flexor muscles in response to pain and •  inhibition of antagonistsPain fibers (afferents) are small diameter, lightly myelinated, slowly-conducting fibers PolysynapticBranching axons of the afferents spread activation to flexor VHCs in adjacent spinal segments Result is recruitment of all flexors of the limb (and inhibition of the extensors) receptor: free nerve endings in skin Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  42. 42. Flexor Reflex The Crossed Extension Reflex Elicited by the afferents of the Flexor Reflex Interneurons send axons to the contralateral ventral horn Activate: excitatory interneurons to Ventral Horn Cells that innervate extensors inhibitory interneurons to VHCs that innervate flexors Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  43. 43. Christina T3, Wikipedia Source Undetermined
  44. 44. DRG cell Autogenic Inhibition •  relaxation of a muscle in response to relatively high tension on the tendon VHC •  a relatively rapid and a discrete response receptor Golgi tendon Leg Extensor organ MusclesHaines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002
  45. 45. extrafusal muscle The Muscle Spindle fibers Muscle spindle afferents respond to stretch afferent Muscle on the membrane nerve fibers Muscle Spindle Sbmehta (Wikipedia) Source Undetermined contractile ends of the intrafusal muscle fibers muscle spindleGamma motorneuron axon a small connective tissuecontrols capsule containing “intrafusal” muscle fiberscontractionof theintrafusal fiber
  46. 46. The Brain Controls the Muscle Spindle’s Responsiveness The muscle spindle is stretched Muscle spindle afferents by lengthening of the muscle. respond to stretch Muscle on the membrane The firing of the afferent fibers in response depends upon the tension on the central part of the intrafusal Muscle Spindle fibers. Contraction of the intrafusal fibers (via gamma motor neuron firing) sets the tension on the central region of the intrafusal fiber. Sbmehta (Wikipedia) This control is governed by input to the gamma motor neurons from the brain.Gamma motorneuron axon contractile ends of thecontrols intrafusal muscle fiberscontractionof theintrafusal fiber
  47. 47. Alpha Motor Neurons Integrate Input from the Brain with Input from the Muscles, Tendons and Joints Gamma Motor Neurons are controlled by the Brain Source Undetermined“Alpha-gamma coactivation” from the brain (“descending fibers”) keeps the muscle spindle sensitive to changes in length and the rate of change.
  48. 48. Visceral Spinal Reflex Arc Visceral Afferent Neuron (DRG cell) Interneuron in Secondary Visceral Gray Visceral EfferentVisceral Efferent endings Neuron Visceral Efferent on sweat glands,(Preganglionic) Neurons arrector pili mm.,in Lateral Horn (Postganglionic) and smooth muscle in paravertebral in blood vessels ganglion HEART Source Undetermined
  49. 49. Blood Supply to the Spinal Cord Ventral Spinal Dorsal Spinal and andVentral Radicular Dorsal Radicular Arteries Arteries Image of Netter’s spinal arteries removedVentral and Dorsal spinalbranches off the vertebralarteries descend the spinal cordand are supplemented by spinalradicular branches of thesegmental arteries.
  50. 50. BLOOD SUPPLY OF SPINAL CORDHaines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 8-25
  51. 51. Blood Supply to the Spinal CordManter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 27
  52. 52. Blood Supply to the Spinal Cord Dorsal Columns: Fine Touch & ProprioceptionLateral Corticospinal Tract:Voluntary Movement Lateral Spinothalamic Tract: Pain and Temperature Modified From Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 6-1
  53. 53. Additional Source Information for more information see: http://open.umich.edu/wiki/CitationPolicySlide 3: UCSF, School of Medicine http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/cell_structure.htmSlide 8: Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002)Slide 9: G.M. Shepard, Neurobiology, 3rd Edition Fig. 9.3Slide 10: Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 9-1Slide 11: Gray’s Anatomy; Source UndeterminedSlide 12: Source Undetermined, See also Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th edSlide 13: Gray’s AnatomySlide 15: Gray’s AnatomySlide 16: UCSF School of Medicine, http://missinglink.ucsf.edu/lm/lDS_101_histo_resource/cell_structure.htm; University of Medicine and Dentistry of New JerseySlide 17: Source UndeterminedSlide 18: Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 18-4Slide 19: Source UndeterminedSlide 20: Source Undetermined; Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 6-1Slide 21: Source UndeterminedSlide 23: UCSF, School of Medicine, http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/cell_structure.htmSlide 24: Source UndeterminedSlide 26: Source UndeterminedSlide 27: Source UndeterminedSlide 28: Source UndeterminedSlide 29: Elsevier. Haines, Fundamental Neuroscience for Basic and Clinical Applications 3e.Slide 30: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 31: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 32: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 33: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 37: Elsevier. Haines, Fundamental Neuroscience for Basic and Clinical Applications 3e.Slide 38: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 41: Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 9-6Slide 42: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 43: Haines, Fundamental Neuroscience, 2nd ed.,Churchill-Livingstone, 2002Slide 44: Source Undetermined; Christina T3, Wikipedia, CC:BY:SA, http://creativecommons.org/licenses/by-sa/3.0/Slide 45: Haines, Fundamental Neuroscience, 2nd ed., Churchill-Livingstone, 2002)
  54. 54. Slide 46: CC:BY: Sbmehta (Wikipedia) http://creativecommons.org/licenses/by/2.5/; Source UndeterminedSlide 47: CC:BY: Sbmehta (Wikipedia) http://creativecommons.org/licenses/by/2.5/Slide 48: Source UndeterminedSlide 49: Source UndeterminedSlide 51: Haines, Fundamental Neuroscience for Basic and Clinical Applications, 3rd edition, 2005, Fig. 8-25Slide 52: Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 6-1Slide 53: Modified From Manter and Gatzs Essentials of Clinical Neuroanatomy and Neurophysiology, 8th ed, Fig. 6-1

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