Spinal Cord & Meninges

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Author:
mnm2186
ID:
30695
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Spinal Cord & Meninges
Updated:
2010-08-21 16:36:11
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Anatomy
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Exam 2
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  1. Spinal cord has ____ segments and ______ enlargements
    • 31 segments
    • 2 enlargements
  2. Spinal enlargements
    • Receive sensory (afferent) information from limbs
    • Send motor (efferent) axons to the limbs

    • Cervical = upper limb
    • Lumbosacral = lower limb
  3. Termination of adult spinal cord
    L1 / L2
  4. Termination of dural (thecal) sac
    S2 (PSIS)

    End of arachnoid
  5. Distal attachment of spinal cord
    Attached to coccyx via filum terminale
  6. Layers of filum terminale
    • Internal filum = pia mater
    • External flium = dura mater
  7. Origins of spinal ganglion
    Neural crest

    (PNS!)
  8. Ventral Root
    • Motor / Efferent
    • Anterior
  9. Dorsal Root
    • Sensory / Afferent
    • Posterior
  10. Spinal ganglia contain ______
    Sensory neurons

    (DRG's)
  11. Dermatome
    Area of skin innervated by a single spinal segment
  12. Myotomes
    Mass of muscle innervated by a particular spinal cord segment

    • Myotomes include portions of several muscles
    • Many muscles contain portions fo more than one myotome
  13. Radiculopathy
    • Injury to spinal nerve
    • - Affects dermatome innervated by segment from which nerve arises
    • - Causes muscle weakness (not paralysis)

    Myotome contributes to more than one muscle!
  14. Neuropathy
    • Injury to peripheral nerves
    • - Affects multiple adjacent dermatomes
    • - Causes muscle paralysis
  15. Lower Motor Neurons
    • - Anterior horn of spinal cord
    • - Axons innervate skeletal muscle (form motor part of peripheral nerves)
    • - "final common pathway" = receive information from brain (UMN)
  16. Upper Motor Neurons
    • - Higher centers of brain (e.g. motor cortex)
    • - Cross in pyramidal decussation (i.e. medulla)
    • - Axons excite / inhibit lower motor neurons
  17. Anterior Horn Somatotopy
    • Gray Matter
    • Medial LMNs = proximal muscles
    • Lateral LMN's = distal muscles

    • Dorsal LMN's = flexors
    • Ventral LMN's = extensors
  18. Spinal cord directional landmark
    Anterior fissure = ventral
  19. Somatic Reflexes:
    Afferent Component
    • Afferent component
    • - 1o sensory / afferent neurons (Ia) in DRG
    • - Peripheral axons carry info from receptors in skin / muscles / tendons / joints
    • - Central axons carry info into spinal cord via dorsal roots
  20. Somatic Reflexes:
    Efferent Component
    • Efferent component
    • - Spinal LMN's (efferent) in anterior horn
    • - Cholinergic

    • α motor neurons -> extrafusal fibers
    • - generate muscle force
    • γ motor neurons -> intrafusal fibers
    • - regulate tension on muscle spindle
  21. Motor Unit
    One α motor neurons + extrafusal fibers = motor unit

    • Large motor unit -> large muscles w/ coarse movements
    • Small motor unit -> small muscles w/ fine movements
  22. Muscle Spindle
    • Proprioceptor (length)
    • γ motor neuron
    • 1o (Ia) afferent neuron
    • 2o (II) afferent neuron
  23. Golgi Tendon Organ
    • Proprioceptor (force)
    • GTO (Ib) afferent neuron
  24. Lateral Corticospinal Tract
    • - Arises from UMN in motor cortex
    • - 85-90% axons descend / cross in pyramidal decussation (caudal medulla)
    • - Innervates LMNs (which innervate limbs)
    • - Trunk muscles tend not to cross

    Clinically most important descending tract
  25. Somatosensory Systems
    Primary sensory cortex = postcentral gyrus (BA 3,1,2)

    • Two major sensory (ascending) pathways
    • Dorsal columns (lemniscal system)
    • - discriminative touch / proprioception / vibration
    • - crosses in medulla

    • Anterolateral (spinothalamic) system
    • - crude touch / pain / temperature
    • - crosses in spinal cord
  26. Meninges
    • - Periosteum
    • - Epidural space
    • - Dura mater
    • - Subdural space (potential space)
    • - Arachnoid mater
    • - CSF
    • - Pia mater (tightly adherent to cord)
  27. Denticulate ligaments
    • - Formed by pia mater
    • - Suspends spinal cord
  28. Pachymeninx
    • Dura Mater
    • - Derived from mesenchyme
    • - Dense CT
    • - longitudinal collagen fibers w/ circular elastic fibers
  29. Leptomeninx
    • Arachnoid / Pia Mater
    • - Derived from neural crest
    • - Contains blood vessels

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