Neurology Flashcards – First Aid for the USMLE STEP 1

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  • what happens in neural development between day 18 and day 21?
    neural plate + notochord --> neural crest --> neural tube and neural crest cells
  • notochord induces overlying ectoderm to differentiate into what?
    neuroectoderm and form the neural plate
  • neural plate gives rise to what?
    the neural tube and neural crest cells
  • notochord becomes what in adults?
    nucleus pulposus of the intervertebral disc
  • what are the name and function of the dorsal part of the neural tube?
    Alar plate: sensory
  • what are the name and function of the ventral part of the neural tube?
    Basal plate: motor
  • what are the three primary vesicles of the developing brain?
    1. Forebrain (prosencephalon) 2. Midbrain (mesencephalon) 3. Hindbrain (rhombencephalon)
  • what are the five secondary vesicles of the developing brain?
    1. telencephalon 2. Diencephalon 3. Mesencephalon 4. Metencephalon 5. Myelencephalon
  • the Forebrain (prosencephalon) gives rise to which secondary vesicles?
    1. Telencephalon 2. Diencephalon
  • the Midbrain (mesencephalon) gives rise to which secondary vesicles?
    1. Mesencephalon
  • the Hindbrain (rhombencephalon) gives rise to which secondary vesicles?
    1. Metencephalon 2. Myelencephalon
  • the walls of the telencephalon give rise to what?
    cerebral hemispheres
  • the cavities of the telencephalon give rise to what?
    lateral ventricles
  • the walls of the diencephalon give rise to what?
    thalamus
  • the cavities of the diencephalon give rise to what?
    third ventricle
  • the walls of the mesencephalon give rise to what?
    midbrain
  • the cavities of the mesencephalon give rise to what?
    aqueduct
  • the walls of the metencephalon give rise to what?
    Pons and Cerebellum
  • the cavities of the metencephalon give rise to what?
    upper part of fourth ventricle
  • the walls of the myelencephalon give rise to what?
    medulla
  • the cavities of the myelencephalon give rise to what?
    lower part of the fourth ventricle
  • what happens in neural tube defect?
    neuropores fail to fuse (4th week) --> persistent connection between amniotic cavity and spinal canal
  • neural tube defects are associated with what?
    low folic acid intake before conception and during pregnancy
  • what are the lab levels in neural tube defect?
    1. (increase) AFP in amniotic fluid and maternal serum 2. (increase) AChE in amniotic fluid is a helpful confirmatory test
  • why is it that AChE can be measured in NTD?
    fetal AChE in CSF transudates across defect into the amniotic fluid
  • what is spina bifida occulta?
    "failure of bony canal to close, but no structural herniation"
  • spina bifida occulta is usually seen where?
    lower vertebral levels
  • status of dura in spina bifida occulta?
    intact
  • spina bifida occulta is associated with what?
    tuft of hair or skin dimple at level of bony defect
  • what is meningocele?
    meninges (but not the spinal cord) herniate through spinal canal defect
  • what is meningomyelocele?
    meninges and spinal cord herniate through spinal canal defect
  • what are the types of forebrain anomalies?
    anencephaly holoprosencephaly
  • what happens in anencephaly?
    "malformation of anterior neural tube resulting in no forebrain, open calvarium (frog like appearance)"
  • what are the clinical findings in anencephaly?
    "(increase)AFP, polyhydramnios"
  • why is there polyhydramnios in anencephaly?
    no swallowing center in the brain
  • anencephaly is associated with what?
    maternal diabetes type I
  • what decreases the risk of anencephaly?
    folate supplementation
  • what is holoprosencephaly?
    failure of left and right hemispheres to separate
  • when does holoprosencephaly happen?
    usually occurs during weeks 5-6
  • what is the etiology of holoprosencephaly?
    complex multifactorial etiology that may be related to mutations in sonic hedgehog signaling pathway
  • what is the spectrum of severity of holoprosencephaly?
    "moderate form has celf lip/palate, most severe form results in cyclopia"
  • what are the posterior fossa malformations?
    Chiari II (Arnold-Chiari malformation) Dandy Walker
  • what is an Arnold Chiari malformation?
    Significant cerebellar tonsillar and vermian herniation through foramen magnum with aqueductal stenosis and hydrocephalus
  • Chiari II (Arnold-Chiari) malformation often presents with what?
    thoraco-lumbar myelomeningocele and paralysis below the defect
  • what is a Dandy-Walker malformation?
    Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged posterior fossa)
  • Dandy Walker malformation is associated with what?
    hydrocephalus and spina bifida
  • what is syringomyelia?
    cystic enlargement of central canal of spinal cord
  • which fibers of spinal cord are damaged first in syringomyelia?
    crossing fibers of spinothalamic tract
  • syringomyelia results in what?
    cape like bilateral loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved)
  • syringomyelia is associated with what?
    Chiari I malformation
  • what is Chiari I malformation?
    >3-5mm cerebellar tonsillar ectopia
  • where is syringomyelia most common?
    C8-T1
  • which embryonic structures form the tongue?
    1st branchial arch forms anterior 2/3 3rd and 4th branchial arches form posterior 1/3
  • muscles of the tongue are derived from what?
    occipital myotomes
  • which nerves carry taste?
    "CN VII, IX, X (solitary nucleus)"
  • which nerves carry tongue pain?
    "CN V3 (ant 2/3), IX, X"
  • which nerve is responsible for motor function of tongue?
    CN-XII
  • neuroectoderm gives rise to which neural tissue?
    CNS neurons ependymal cells oligodendroglia astrocytes
  • neural crest gives rise to which neural tissue?
    PNS neurons schwann cells
  • mesoderm gives rise to which neural tissue?
    Microglia
  • which are the signal transmitting cells of the nervous system?
    neurons
  • how often do neurons divide?
    "permanent cells- do not divide in adulthood (and, as a general rule, have no progenitor stem cell population)"
  • what are neurons?
    "signal relaying cells with dendrites (receive input), cell bodies, and axons (send output)"
  • cell bodies and dendrites of neurons can be stained how?
    via the Nissl substance (stains RER)
  • why doesn't Nissl stain the axon?
    RER is not present in the axon
  • what happens if an axon is injured?
    undergoes Wallerian degeneration- degeneration distal to the injury and axonal retraction proximally
  • what are the functions of astrocytes?
    "Physical support repair K+ metabolism removal of excess neurotransmitter, maintenance of blood-brain barrier"
  • how do astrocytes respond to injury?
    reactive gliosis
  • what is the astrocyte marker?
    GFAP
  • what are microglia?
    CNS phagocytes Scavenger cells of CNS
  • what is the germ layer origin of microglia?
    mesoderm
  • how do microglia stain with Nissl?
    not readily discernable in Nissl stains
  • what is the function of microglia?
    respond to tissue damage by differentiating into large phagocytic cells
  • what happens to microglia in HIV?
    HIV-infected microglia fuse to form multinucleated giant cells in the CNS
  • what is the function of myelin?
    Wraps and insulates axons: (increase) space constant and (increase) conduction velocity
  • the function of myelin results in what action?
    "saltatory conduction of action potentials between nodes of Ranvier, where there are high concentrations of Na + channels"
  • what makes myelin in the CNS?
    oligodendrocytes
  • what makes myelin in the PNS?
    Schwann cells
  • Each oligodendrocyte myelinates how many CNS axons?
    multiple (up to 50 each)
  • how do oligodendroglia appear in Nissl stain?
    much smaller nuclei with dark chromatin and little cytoplasm
  • what is the predominant type of glial cell in white matter?
    oligodendrocyte
  • oligodendroglia are destroyed in which disease?
    MS
  • how do oligodendroglia look in H&E stain?
    like fried eggs
  • each Schwann cell myelinates how many PNS axons?
    only 1
  • Schwann cells also promote what?
    axonal regeneration
  • Scwhann cells are derived from what?
    Neural crest
  • Schwann cells are destroyed in which disease?
    Guillan-Barre syndrome
  • what is Acoustic neuroma?
    type of Schwannoma typically located in internal acoustic meatus CNVIII
  • what are the 2 types of free nerve endings?
    C Adelta
  • what type of fibers are C fibers?
    "slow, unmyelinated fibers"
  • what type of fibers are Adelta fibers?
    "fast, myelinated fibers"
  • what are the locations of C fibers and Adelta fibers?
    "All skin, epidermis, some viscera"
  • what are the senses carried by C fibers and Adelta fibers?
    Pain and temperature
  • what type of fibers are Meissner's corpuscles?
    "Large, myelinated fibers that adapt quickly"
  • what is the location of Meissner's corpuscles?
    glabrous (hairless) skin
  • what are the senses carried by Meissner's corpuscles?
    "dynamic, fine/light touch; position sense"
  • what type of fibers are Pacinian corpuscles?
    "Large, myelinated fibers"
  • what is the location of Pacinian corpuscles?
    "deep skin layers, ligaments, and joints"
  • what are the senses carried by pacinian fibers?
    vibration pressure
  • what type of fibers are Merkel's discs?
    "Large, myelinated fibers that adapt slowly"
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