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Transcript
M555 Medical Neuroscience Lab 2: The Spinal Cord OBJECTIVES 1. Recognize cervical, thoracic, lumbar and sacral levels of the spinal cord. 2. Be able to name and locate major structures in the spinal cord. 3. Recognize major nuclei and tracts in the spinal cord. 4. Know basic spinal cord anatomy in order to localize lesions in the spinal cord and to know the outcomes resulting from spinal cord lesions. NOTES 1. Spinal cord slides will be available in lab for several weeks. January 11th and 13th, the open lab on January 20th and during the first Brain Stem Lab on January 25th and 27th. 2. Digital images of spinal cord sections can also be accessed on line: medsci.indiana.edu/m555/index.html SPINAL CORD STRUCTURES Gross Anatomy Spend a few minutes looking at a spibnal cord to see these structures: spinal cord enlargements (cervical and lumbar) conus medullaris cauda equina spinal nerves dorsal roots dorsal root ganglions ventral roots brain Cervical Nerves enlargement dorsal columns gracile fasciculus cuneate fasciculus Three Questions What might explain the Cervical and Lumbar enlargements compared to the narrower Thoracic cord? Why are the lower Lumbar and Sacral Spinal Nerves (in the Cauda Equina) so long ? Why is it an over-simplification to say that each spinal level has one dorsal and one ventral root on each side of the cord? spinal cord Thoracic Nerves Lumbar Nerves Sacral Nerves enlargement conus medularis cauda equina Compare the size amd the relative amounts of gray and white matter at the four levels of the spinal cord so that you can identify the spinal level( cervical, thoracic, lumbar or sacral) when shown a cross-section of the cord. Here are cross-sections several cervical, thoracic and lumbar levels, along with one sacral leve, that allow comparisons of the four major levels of th espinal cord.l cervical 3 thoracic 10 cervical 5 cervical 8 lumbar 2 lumbar 5 thoracic 5 sacral 4 Nolte, figure 10-6 How do the absolute sizes (particularly the widths) of the spinal sections change from level to level? How do the relative amount of gray matter to white matter of the spinal sections change from level to level? What might explain these differences? At what levels can a lateral horn of the spinal gray matter be seen? (see the Microscopic Anatomy section for more information on the Lateral Horn) Microscopic Anatomy central canal gray matter dorsal horn substantia gelatinosa dorsolateral tract (Lissauer’s Fasciculus) intermediolateral gray column (thoracic and upper lumbar levels) nicknamed “the lateral horn” location of the Dorsal Nucleus of Clarke (thoracic and upper lumbar levels) ventral (anterior) horn large motor neurons in the ventral gray matter white matter dorsal median sulcus dorsal funiculus dorsal columns gracile fasciculus (all levels of spinal cord) cunate fasciculus (above thoracic 5) lateral funiculus and ventral funiculus location of corticospinal tract location of anterolateral system (a major pain and temperature pathway) anterior (ventral) white commissure LARGE Multipolar Neurons in the Anterior Horn location: one or more locations in anterior (ventral) horn of spinal cord gray matter present at all spinal cord levels, but ... particularly numerous at the level of the cervical and lumbar enlargements significance: innervate skeletal muscles axons of these cells form the ONLY link between the CNS and skeletal muscle cells also known as: Somatic Motor Neurons Alpha Motor Neurons Lower Motor Neurons Central Canal location: in the center of the spinal gray matter significance: vestige of the hollow core of the neural tube note: inner surface lined by ependymal cells (like all surfaces that border a ventricular space in the brain) digital images may be found at medsci.indiana.edu/m555/index.html Anterior White Commissure (AWC) commissure: a term for a bundle of axons that cross the midline of the CNS location: just anterior (ventral) to the Central Canal of the spinal cord significance: axons of spinal cord neurons that carry pain and temperature information pass through the AWC cervical spinal cord low thoracic level thoracic spinal cord Dorsal Columns (DCs) location: dorsal (posterior) white mater of the spinal cord significance: axons of primary sensory neurons that carry fine touch, low thoracic level proprioceptive and vibration sense up to the lower medulla form the DCs composition: two “columns” of axons on each side GRACILE FASCICULUS (more medial) at all levels of the spinal cord CUNEATE FASCICULUS (more lateral) at levels of the spinal cord above Thoracic 5 fasciculus: a term for axons gathered together in a bundle Dorsal Nucleus of Clarke (“Clarke’s Nucleus”) location: in the medial gray matter at the base of the dorsal horn of spinal levels Thoracic 1 – Lumbar 3 significance: contains cell bodies of neurons whose axons form the posterior spinocerebellar tract an important source of input to the cerebellum low thoracic level Lateral Horn of Spinal Cord Gray Matter more formally known as the Intermediolateral Column location: lateral margin of gray matter at spinal levels Thoracic 1 – Lumbar 3 the Lateral Horn and Clarke’s Nucleus are located at the same spinal levels, but they have nothing to do with one another significance: contains the cell bodies of preganglionic sympathetic neurons Dorsolateral Fasciculus (DF) Lissauer’s Tract location: tip of dorsal horn at all spinal levels significance: entrance point for thin-diameter sensory axons, including “pain and temperature fibers” these axons may run up or down in DF several spinal levels before terminating on neurons in the dorsal horn fasciculus: a term for axons gathered together in a bundle cervical spinal cord cervical spinal cord Substantia Gelatinosa location: posterior part of dorsal horn gray matter at all levels low thoracic level of the spinal cordlow thoracic level significance: incomming pain and temperature information crosses synapses here note: clearer appearance - gelatinous name