| What is the number one cause of death during the first year of life?
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Birth defects
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| What are the three major stages of development and when do they happen?
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1. Zygotic: 0-14 days
2. Embryotic: 14 days to 8 weeks
3. Fetal: 8 weeks to 36 weeks
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| When are most neurons produced?
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Prenatally
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| How much does the brain weigh at birth?
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350g
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| When does a majority of myelination occur?
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Postnatally
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| What are the five stages of neurodevelopment?
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1. Neurulation
2. Proliferation
3. Migration
4. Differentiation
5. Synaptogenesis
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| What is the neural tube the precursor for?
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The neurons and glial cells of the CNS.
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| What is the PNS the made from?
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Neural crest cells
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| What day in development does the blastocyst form?
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Day 5
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| What part of the blastula becomes the embryo proper?
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The ICM
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| What does the placenta form from?
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Trophoectoderm
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| What day does the ICM delaminate?
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Day 5
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| What part of the ICM becomes the embryo proper?
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The epiblast
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| What part of the ICM becomes the yolk sack?
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The hypoblast
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| What is the aggregation medially where the cells dive down in the epiblast?
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Primitive streak or groove
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| What end of the epiblast does the primitive groove begin at?
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The cranial end (Hensen's node)
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| What is the notochord derived from?
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Axial mesoderm
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| What is the importance of the notochord in regard to neurodevelopment?
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It induces the formation of the neural plate from the ectoderm.
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| What day does the neural plate form?
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Day 18-19
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| Which end of the neural plate is wider and what will it give rise to?
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The cranial end is wider and it will give rise to the brain.
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| What does the caudal portion of the neural plate give rise to?
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Spinal cord
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| During primary neurulation, how does cell morphology change?
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Cells take on a more pseudostratified character.
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| What is the area in the middle of the folding during neurulation called? What is it between? When does it form?
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1. Neural groove
2. Neural folds
3. 18-19
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| When does closure of the neural tube occur? What area of the tube closes first?
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1. Week 4
2. The midline
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| Where is the primary hinge joint in neurulation?
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The midline
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| During wedging, how does a cell change its shape?
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It widens at the basolateral end while narrowing at the apical end.
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| Where do secondary hinge joints occur in neurulation?
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Dorsolaterally
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| At what level does the neural tube start fusing?
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The level of the 4th somite
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| Which neuropores fuse first, last?
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1. Rostral
2. Caudal
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| What are the two phases of neurulation in higher vertabrates? What is developed in each stage?
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1. Primary - brain
2. Secondary - formation of caudal structures
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| What causes the phenomenon of segmentation?
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The change in cell to cell adhesion properties. Most likely tight junctions.
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| First segmentation produces what three vesicles?
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1. Prosencephalon
2. Mesencephalon
3. Rhombocephalon
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| What causes the actual differentiation in segement size? How is this achieved?
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Different pressures of CSF cause by transient blockages.
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| Where does the cephalic flexure occur?
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Between the prosencephalon and the mesencephalon.
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| Where does the cervical flexure occur?
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Between the hindbrain and the spinal cord
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| What does the prosencephalon divide into?
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The telencephalon and the diencephalon.
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| What does the rhombocephalon divide into?
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The metencephalon and the myencephalon.
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| The forebrain gives rise to which ventricles?
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1 2 and 3
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| The midbrain gives rise to which part of the ventricular system?
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The cerebral aqueduct
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| The hindbrain gives rise to which ventricle?
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The 4th ventricle
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| Dorsal alar plates have what function and what are they separated by?
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Sensory functions and the roof plate
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| The ventral basilar plates have what function and what are they separated by?
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Motor function and the floor plate
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| What is the furrow between the basilar and alar plates called?
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The sulcus limitans
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| What neurons in the PNS are not of neural crest origin(3)?
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1. Cranial sensory neurons
2. Motor neurons which have their cell bodies in the CNS
3. Preganglionic autonomic neurons
|
|
What is the name given to cells that lie just outside the neural plate?
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Placodal ectoderm cells
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| Cranial neural crest cells are from what level up and what are some of the things that they give rise to?
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5th somite and up; skeletal elements of the branchial arches and periocular structures
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| Truncal neural crest cells are from what level down?
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The 6th somite down.
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| What are neural crest cells highly prone to?
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Mutations and tumors.
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| What is the most common neurological defect seen at birth?
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Neural tube defects
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| What is a result of the caudal neuropore (5) not closing upon birth?
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Spina bifida
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| What is the most common neural tube defect?
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Spina bifida
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| What condition is usually associated with spina bifida?
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Hydrocephalus
|
|
Including what in your diet can cut down on the occurance of spina bifida?
|
Folic acid
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| What defect is seen as a result of anterior neuropore (2) closure?
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Anencephaly
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| What defect is described as having part of the brain protruding through the skull?
|
Encephalocele
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| What is a failure of the lobes of the brain to separate?
|
Holoprosencephaly
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| What often is seen with holoprosencephaly?
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Malfortmation of the midline structures of the face.
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| What are the four types of induction?
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1. Binary choice
2. Graded response
3. Relayed signals
4. Reciprocal signaling
|
| Inductive signals that allow the ectoderm to differentiate into neuroectoderm originate where?
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Notochord
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| What portion of the blastopore is the neural inducing region?
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The dorsal lip of the blastopore
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| What chemicals are produced by the neural inducing region to promote neuroectoderm formation
|
1. Noggin
2. Chordin
3. Follistatin
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| How do the chemicals that induce neuroectoderm formation actually do that?
|
They antagonize BMP which is an inhibitor of neuroectoderm formation.
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| What family do BMPs belong to?
|
TGF-B
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| What is the default pathway?
|
Formation of neuronal tissue.
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| What type of cell adhesion proteins do neural plate ectoderm cells express?
|
N-Cadherins and N-Cam
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| How is the dorsal-ventral axis established? What chemical is associated which each direction of the axis?
|
The dorsal epidermis produces of gradient of BMP for dorsal
differentiation. The notochord produces a gradient of Shh for ventral
differentiation.
|
| What mutation is specifically associated with holoprosencephaly?
|
Shh
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| What transcription factor downstream of Shh is also been linked to defects?
|
Glee
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| What set of trascription factors (large group) can also lead to defects?
|
Homeobox (Hox) domain TF
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| What signaling molecules (4) are involved in the production of the anterior/posterior axis?
|
1. Wnt
2. BMP
3. Retinoic acid
4. FGF
|
| When does proliferation of cells with in the neural tube begin? End?
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5 weeks; 7th month postnatally
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| Most neurons are produced between what days prenatally?
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42 and 120
|
| Which form first, neurons or glial cells?
|
Neurons
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| At the peak level of mitosis, what is the rate of formation of neurons?
|
250,000 neurons/minute
|
| Where are the cortical neurons produced?
|
The ventricular zone of the neural tube.
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| What are the two intervals of proliferation and what are their purposes?
|
1. Pre-neurogenic: proliferation of the cells
2. Neurogenic: cells leave and go take their place in the cortex
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| Where do cells form their cell to cell adhesions and undergo synaptogenesis after proliferation?
|
Just below the cortical plate
|
| Why do the cells that are proliferating look like they are pseudostratified?
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They are at different stages of the cell cycle.
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| What are the two different types of cleavage seen during cell proliferation?
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1. Symmetrical 28-42
2. Asymmetrical
|
| When do migrating cells arrive at their final destination?
|
Five months
|
|
What cells make the pathway for migrating neurons?
|
Radial glial cells
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| How would you describe the manner in which the cortex develops?
|
Inside-out manner ie the oldest cortex is the deepest
|
| What is it called when cells migrate to a particular level and then move tangentially?
|
Tangential migration
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| Where can you find neural stem cells in adult life(2)?
|
Hippocampus and the sub-ventricular region of the cortex
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| What is the best studied molecule of migration?
|
Reelin
|
| What two other knock-outs have shown a result of maldevelopment of the cortex?
|
Apoprotein-E and VLDL receptor
|
| What is an example of a LDL receptor that has been shown to cause defects close to holoprosencephaly in knockout models?
|
Megalin
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| When does differentiation and synaptogenesis begin? End?
|
4 or 5 months; 6th month postnatally
|
| What are the two types of cues that cause differentiation?
|
Intrinsic and extrinsic
|
| What exactly does the differentiation process involve?
|
The activation of specific genes for a specific cell type.
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| What molecules allow synaptogenesis?
|
Cell adhesion molecules, neurotrophic factors (BNDF) and neurotransmitters
|
| Are there more neurons produced than needed?
|
Yes
|
| What is apoptosis? What percent of cells undergo apoptosis?
|
A subtractive process; 20-50%
|
| What is responsible for the 3x of brain mass?
|
Increase in the density of synapes and myelination.
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