Neurology Flashcards
(33 cards)
1
Q
Neural Development
A
- Notochord induces overlying ectoderm to differentiate into neuroectoderm & form the neural plate
- Neural plate gives rise to neural tube & neural crest cells
- Notochord becomes nucleus pulposus of the intervertebral disc in adults
- Alar plate (dorsal): sensory -same orientation
- Basal plate (ventral): motor as spinal cord
2
Q
Regional Specification of Developing Brain
A
Forebrain - Telencephalon -cerebral hem./lat. vent.
- Diencephalon - thalmus, 3rd ventricle
Midbrain - Mesencephalon-midbrain/aqueduct
Hindbrain - Metencephalon pons (upper part of 4th)
cerebellum
- Myelencephalon medulla (lower part of
4th ventricle)
3
Q
Neural Tube Defects
A
- neuropores fail to fuze (4th week), persistent connection b/w amniotic cavity & spinal canal
- Associated with low folic acid intake before conception & during pregnancy
- Elevated alpha-fetoprotein in amniotic fluid & maternal serum
- inc. AChE in amniotic fluid is a helpful confirmatory test (fetal AAChE in CSF transudates across defect into the amniotic fluid)
4
Q
Spina Bifida Occulta
A
- Failure of bony spinal canal to close, but no structural herniation
- usually seen at lower vertebral levels
- Dura is intact
- Associated with tuft of hair or skin dimple at level or bony defect
5
Q
Meningocele
A
-Meninges (but not the spinal cord) herniate through spinal canal defect
6
Q
Meningomyelocele
A
-Meninges & spinal cord herniate through spinal canal defect
7
Q
Anecephaly
A
Forebrain Anomalies
- Malformation of anterior neural tube resulting in no forebrain, open calvarium “frog-like appearance”
- Clinical findings: inc. AFP; polyhydramnios (no swallowing center in brain)
- Associated with maternal diabetes (type I)
- Maternal folate supplementation dec. risk
8
Q
Holoprosencephaly
A
Forebrain Anomalies
- Failure of left & right hemispheres to separate; usually occurs during weeks 5-6
- Complex multifactorial etiology that may be related to mutations in sonic hedgehog signaling pathways
- Moderate form has cleft lip/palate, most severe form results in cyclopia
9
Q
Chiari II (Arnold-Chiari Malformation)
A
Posterior Fossa Malformations
- Significant cerebellar tonsillar & vermian herniation through foramen magnum with adueductal stenosis & hydrocephalus
- Often presents with thoraco-lumbar myelomeningocele & paralysis below the defect
10
Q
Dandy-Walker
A
Posterior Fossa Malformations
- Agenesis of verebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged posterior fossa)
- Associated with hydrocephalus & spina bifida
11
Q
Syringomyelia
A
- Cystic enlargement of central canal of spinal cord
- Crossing fibers of spinothalmic tract are typically damaged first
- Results in a “cape-like” bilateral loss of pain & temperature sensation in upper extremities (fine touch sensation is preserved)
- Syrinx = tube, as in syringe
- Associated with Chiari I malformatio (> 3-5mm cerebellar tonsillar ectopia)
- Most common at C8-T1
12
Q
Tongue Development
A
- 1st branchial arch forms anterior 2/3 (thus sensation via CN V3, taste via CN VII)
- 3rd & 4th arches form posterior 1/3 (thus sensation & taste mainly via CN IX, extreme posterior via CNX)
- Motor innervation is via CN XII
- Muscles of the tongue are derived from occipital myotomes
Taste: CN VII, IX, X (solitary nucleus)
Pain: CN V3, IX, X
Motor: CN XII
13
Q
CNS/PNS Origins
A
- Neuroectoderm - CNS neurons; ependymal cells (inner lining of ventricles, make CSF), oligodendroglia; astroctes
- Neural crest - PNS neurons, Schwann cells
- Mesoderm - Microglia (like Macrophages, originate from Mesoderm)
14
Q
Neurons
A
- Signal-transmitting cells of the nervous system
- Permanent cells-do not divide into adulthood (and, as a general rule, have no progenitor stem cell population)
- Signal-relaying cells with dendrites (receive input), cell bodies, & axons (send output)
- Cell bodies and dendrites can be stained via teh Nissl substance (stains RER). RER is not present in the axon
- If an axon is injured, it undergoes Wallerian degeneration-degeneration distal to the injury & axonal retraction proximally; allows for potential regeneration of axon (if in PNS)
15
Q
Astrocytes
A
- Physical support, repair, K+ metabolism, removal of excess neurotransmitter, maintenance of blood-brain barrier
- Reactive gliosis in response to injury
- Astrocyte marker-GFAP
16
Q
Microglia
A
- CNS phagocytes, mesodermal origin, not readily discernible in Nissl stains, have small irregular nuclei & relatively little cytoplasm
- Scavenger cells of the CNS, respond to tissue damage by differentiating into large phagocytic cells
- HIV-infected microglia fuse to form multinucleated giant cells in the CNS
17
Q
Myelin
A
- inc. conduction velocity of signals transmitted down axons
- Results in saltatory conduction of action potential b/w nodes of Ranvier, where there are high conc. of Na+ channels
- CNS-oligodendrocytes
- PNS-Schwann cells
- Wraps & insulates axons, inc. space constant & inc. conduction velocity
18
Q
Oligodendroglia
A
- Each myelinates multiple CNS axons (up to 50 each).
- In Nissel stains, they appear as small nuclei with dark chromatin & little cytoplasm
- Predominant type of glial cell in white matter
- These cells are destroyed in multiple sclerosis
- Looks like fried eggs on H&E staining
19
Q
Schwann Cells
A
- Each myelinates only 1 PNS axon
- also promote axonal regeneration, derived from neural crest
- Inc. conduction velocity via saltatory conduction b/w nodes of Ranvier, where there are high conc. of Na+ channels
- These cells are destroyed in Guillain-Barre syndrome
- Acoustic neuroma: type of schwannoma
- Typically located in internal acoustic meatus (CN VIII)
20
Q
Free Nerve Ending
A
- C-slow, unmyelinated fibers
- A(delta)-fast, myelinated fibers
- Location: all skin, epidermis, some viscera
- Senses: pain & temperature
21
Q
Meissner’s Corpuscles
A
-Large, myelinated fibers, adapt quickly
Location: Glabrous (hairless) skin
Senses: Dynamic, fine/light touch; position sense
22
Q
Pacinian Corpuscles
A
-Large, myelinated fibers
Location: Deep skin layers, ligaments, & joints
Senses: vibration, pressure
23
Q
Merkel’s Discs
A
-Large, myelinated fibers, adapt slowly
Location: Hair follicles
Senses: Pressure, deep static touch (shape, edges), position sense
24
Q
Peripheral Nerve
A
- Endoneurium-invests single nerve fiber layers (inflammatory infiltrate in Guillain-Barre)
- Perineurium (permeabiligy barrier) - surrounds a fascicle of nerve fibers. Must be rejoined in microsurgery for limb reattachment
- Epineurium-dense connective tissue that surrounds entire nerve (fascicles & blood vessels)
endo = inner peri = around epi = outer
25
Neurotransmitters: NE
Change in Disease: inc. in anxiety, dec. in depression
| Locations of Synthesis: Locus ceruleus (pons)
26
Neurotransmitters: Dopamine
Change in Disease: inc. in schizophrenia, dec. in Parkinson's, dec. in depression
Locations of Synthesis: ventral tegmentum & SNc (midbrain)
27
Neurotransmitters: 5-HT
Change in Disease: dec. in anxiety, dec. in depression
Locations of Synthesis: Raphe nucleus (pons)
28
Neurotransmitters: ACh
Change in Disease: dec. in Alzheimer's; dec. in Huntington's, inc. in REM
Locations of Synthesis: Basal nucleus of Menert
29
Neurotransmitters: GABA
Change in Disease: dec. in anxiety; dec. in Huntington's
Locations of Synthesis: Nucleus accumbens
30
Locus Ceruleus
-stress & panic
31
Nucleus accumbens & septal nucleus
-reward center, pleasure, addiction, fear
32
Blood-Brain Barrier
- Prevents circulating blood substances from reaching the CSF/CNS. Formed by 3 structures:
1) tight junctions b/w nonfenestrated capillary endothelial cells
2) basement membranes
3) astrocyte foot processes
- glucose & aa cross slowly by carrier-mediated transport mechanisms
- nonpolar/lipid-soluble substances cross rapidly via diffusion
- a few specialized brain regions with fenestrated capillaries & no blood-brain barrier allow molecules in the blood to affect brain function (area postrema-vomiting after chemo-OVLT-osmotic sensing) or neurosecretory products to enter circulation (neurohypophysis-ADH release)
- infarction and/or neoplasm destroys endothelial cell tight junction leads to vasogenic edema
- Hypothalamic imputs & outputs permeate the BBB
- helps prevent bacteria infection from spreading into the CNS, also restricts drug delivery to the brain
33
Barriers other than the BBB?
- blood-testis barrier
| - maternal-fetal blood barrier of placenta
