Embryology of the Nervous System

  1. What is the critical period for development of the CNS?
    Weeks 3-16
  2. When during gestation is the nervous system sensitive to teratogens?
    Almost all of gestation
  3. Neurulation is the process of…
    Forming the neural tube
  4. Gastrulation occurs during which week of gestation?
    Week 3
  5. Gastrulation begins with the appearance of the ______________________
    Primitive streak
  6. During gastrulation, cells of the epiblast migrate towards the ____________________. What happens once it gets there?
    • Primitive streak
    • Cells of the epiblast
  7. All three germ layers are derived from ____________________
  8. Where is the notochord found?
    Between ectoderm and endoderm
  9. The notochord gives rise to the __________________
    Nucleus propulsus
  10. The ___________________ gives rise to the nucleus propulsus
  11. How is the neural plate derived?
    The ectoderm overlying the notochord thickens into the neural plate
  12. The dorsal view of the trilaminar embryo shows the ____________________ superiorly
    Neural plate
  13. _________________ is the name of the process of folding that results in a closed tube of neuroectoderm
  14. What is neurulation?
    Process of folding that results in a closed tube of neuroectoderm
  15. What happens 16-18 days post-fertilization?
    Formation of neural plate
  16. When in gestation does formation of neural plate occur?
  17. What happens 19-20 days post-fertilization?
    Neural folds elevate
  18. When in gestation does neural folds elevate?
    19-20 days
  19. What happens 21-24 days post-fertilization?
    Fusion of neural folds
  20. When in gestation does fusion of neural folds?
    21-24 days
  21. What happens 25 days post-fertilization?
    Cranial neuropore closes
  22. When in gestation does cranial neuropore close?
    25 days
  23. What happens 27 days post-fertilization?
    Caudal neuropore closes
  24. When in gestation does caudal neuropore close?
    27 days
  25. The closure of the neural tube begins at the level of the __________________
    First five somites
  26. Neurulation commences as the neural plate begins to crease and the…
    Lateral lips of the neural tube (neural folds) begin to approximate each other
  27. What causes anencephaly?
    Failure of the cranial neuropore to close
  28. What is the most common neural tube defect?
    Spina bifida
  29. What is spina bifida?
    A cleft in the vertebral column with a corresponding skin defect and possible exposure of the spinal cord
  30. Spina bifida is most commonly seen in which region of the back?
  31. What causes spina bifida?
    Failure of the caudal neuropore to close
  32. What is the most common form of spina bifida?
    Spina bifida occulta
  33. What is the difference between spina bifida vs spina bifida occulta?
    Spina bifida occulta has a cleft in vertebral column but without skin and neural structure defects
  34. What is meningocele?
    • Severe form of spina bifida
    • Sac containing the meninges pushes through the vertebral column defect
  35. What is meningomyelocele?
    • Severe form of spina bifida
    • Sac contains meninges and neural tissue
  36. Which form of spina bifida has tissues and nerves exposed and is more prone to infection?
  37. Which form of spina bifida is known as complete spina bifida?
  38. In this variation of spina bifida, the cleft may extend through the entire spine from the cervical region to the sacrum
  39. How do you prevent neural tube defects?
    Folic acid
  40. The forebrain is aka ___________________
  41. The midbrain is aka ___________________
  42. The hindbrain is aka __________________
  43. Where is the cephalic flexure located?
  44. Where is the cervical flexure located?
    Inferior border of the rhombencephalon
  45. What encephalons make up the prosencephalon?
    • Telencephalon
    • Diencephalon
  46. What encephalons make up the mesencephalon?
  47. What encephalons make up the rhombencephalon?
    • Metencephalon
    • Myelencephalon
  48. What structures make up the diencephalon?
    Thalamus and hypothalamus
  49. Thalamus and hypothalamus make up the _______________________
  50. What structures make up the telencephalon?
    Cerebral hemispheres
  51. Cerebral hemispheres make up the ______________________
  52. What structures make up the mesencephalon?
  53. Midbrain makes up the _______________________
  54. What structures make up the metencephalon?
    Pons and cerebellum
  55. Pons and cerebellum make up the ______________________
  56. What structures make up the myelencephalon?
  57. Medulla makes up the ___________________
  58. All the encephalons appear during which week of gestation?
    Week 5
  59. Neural tube is aka _______________________
  60. Neural tube will become the ________________________
    Spinal cord
  61. At what month of gestation does the brain develop sulci and gyri?
    30 weeks/6 months
  62. When during gestation do ventricles start to form?
    Week 5
  63. What is hydrocephalus?
    Accumulation of CSF
  64. Why does accumulation of CSF cause hydrocephalus?
    Skull bones are not fused so it expands
  65. What is the first evidence of eye formation in the embryo?
    Appearance of the optic nerve
  66. The future lens will develop from the ____________________
    Lens vesicle
  67. The optic cup is connected to the brain by the _____________________
    Optic stalk
  68. The inferior part of the optic vesicle invaginates creating the ______________________
    Choroid fissure
  69. What are the layers of the eye?
    • Neural retina
    • Inner layer
  70. __________________ is the part of the retina that contains the photoreceptors
    Neural retina
  71. Most congenital eye defects involve what part of the eye?
    Inferior aspect of the eye
  72. Choroid fissure fuses during which week?
    Week 7
  73. What is coloboma? What is it caused by?
    • Gap on inferior portion of the iris
    • Portions of the choroid fissure remain open
  74. What are the three layers of the neural tube from innermost to outermost?
    • Ventricular layer
    • Mantle layer
    • Marginal layer
  75. When the neural tube closes, it produces primitive nerve cells called ____________________
  76. Neuroblasts develop from the ____________________ layer of the neural tube then they migrate into the __________________ layer
    • Ventricular
    • Mantle
  77. The ___________________ of the neural tube contains nerve fibers emerging from the neuroblasts in the mantle layer
    Marginal layer
  78. The white matter of the spinal cord is made up of which neural tube layer?
    Marginal layer
  79. The gray matter of the spinal cord is made up of which neural tube layer?
    Mantle layer
  80. What is the sulcus limitans?
    Separates grey matter (mantle layer) into ventral and dorsal
  81. What separates grey matter (mantle layer) into ventral dorsal?
    Sulcus limitans
  82. Dorsal root of spinal cord comes from the ________________
    Alar plate
  83. Ventral root of spinal cord comes from the _________________
    Basal plate
  84. What happens in week 8 in the spinal cord?
    Vertebral column grows faster than spinal cord resulting in conus medullaris
  85. Where do you insert needle for lumbar puncture?
    After conus medullaris
  86. The conus medullaris ends at ___________ in newborns and at ____________ in adults
    • L3
    • L1
  87. The PNS largely develops from _________________ cells
    Neural crest
  88. During _________________, folds of neuroectoderm approximate each other in the midline
  89. Neural crest cells are derived from _________________ that are initially at a zone between the neural plate and surface ectoderm
    Ectodermal cells
  90. How does the PNS develop from the neural crest?
    • Folds of neuroectoderm approximate each other
    • Neural crest cells detach from the neural tube and migrates to regions around the body
  91. What are neurocristopathies?
    Pathologies that arise from defects in the tissues that contain cells of the neural crest
  92. What is the genetics behind DiGeorge’s syndrome?
    Deletion on chromosome 22
  93. DiGeorge’s syndrome is a type of ____________________
  94. What PNS structures are developed from the neural crest? (6)
    • Dorsal root ganglia
    • Sympathetic postganglionics
    • Parasympathetic postganglionics
    • Cranial nerve sensory ganglia
    • Adrenal medulla
    • Schwann cells
  95. _________________ is formed from clusters of neural crest cells located along future spinal cord and they grow processes that extend into the alar plate. These processes will become fibers that will convey __________________ information into the CNS
    • Dorsal root ganglia
    • Afferent
  96. Nerve fibers in the dorsal root are formed from the ____________________
    Neural crest
  97. Since some visceral afferent neurons and somatic afferent neurons use the same DRG, some information can be confused, such as pain in the arm during an MI. What can this cause?
    Referred pain
  98. Sympathetic fibers travel to the heart from which spinal level?
  99. Nerve fibers in the ventral root are formed from the ____________________
    Neural tube
  100. Preganglionic sympathetics are found at which spinal level?
  101. Postganglionic parasympathetics are found at which spinal level?
  102. Which cranial nerves have sensory ganglia derived from the neural crest?
    • V: trigeminal
    • VII: facial
    • VIII: vestibulocochlear
    • IX: glossopharyngeal
    • X: vagus
  103. True or false. Preganglionic neurons are neural crest cell derived.
    False! They are derived from neural tube
  104. True or false. Postganglionic neurons are neural crest cell derived.
  105. Which ganglia make up the paravertebral ganglia?
    Sympathetic trunk ganglia
  106. Which ganglia make up the prevertebral ganglia?
    • Celiac ganglion
    • Superior mesenteric ganglion
  107. Are the paravertebral and prevertebral ganglia sympathetic or parasympathetic?
  108. Which ganglia make up the intrinsic ganglia?
    Ganglia in target organ
  109. Which ganglia make up the head/neck ganglia?
    • Ciliary ganglion
    • Otic ganglion
    • Pterygopalatine ganglion
    • Submandibular ganglion
  110. Neural crest cells migrate in what direction? Because of this, what is the last region they colonize?
    • Proximodistally
    • Rectum
  111. What causes Hirschprung’s disease?
    Failure of neural crest cell migration to the distal gut tube
  112. What would a biopsy show in a patient with Hirschsprung’s disease?
    Absence of ganglia in the lower colon
  113. How is Hirschprung’s disease usually treated?
    Surgical resection of part of the bowel lacking ganglia
Card Set
Embryology of the Nervous System