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aNeuro Exam I- Lindsey's > Embryology II > Flashcards

Embryology II Flashcards

1
Q

In the cerebral cortex, the first neurons to become postmitotic migrate to form a new region known as the _____.

A

preplate (PP)

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2
Q
  1. Define radial, tangential and chain migration and identify what class of neurons undergoes radial migration, tangential migration, and chain migration.
A
  • radial = majority of migration; clusters of cells; ride radial glia
  • tangential = dispersion throughout tissue; paths are inhibitory GABA-containing cells
  • chain = neurons from subventricular zone to the olfactory bulb; no glial cells; move in chains in rostral migratory stream
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3
Q

When the plane of cleavage is parallel to the ventricular surface, ______. This is called asymmetrical division.

A

one of the daughter cells remains attached but the other does not

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4
Q
  1. Provide examples of long‐range and short‐range axon guidance molecules and identify which are attractive or repulsive.
A
  • long range = diffusion
  • short range = direct contact
  • attractive = netrins (long range); cadherins, CAMs, collagin, laminin, fibronectin, and proteoglycans (short range)
  • repulsive = semaphorins, netrins (long range); semaphorins, ephrins, tenascin (short range)
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5
Q

How many neurons are in the human CNS? Glial cells?

A

1011; 1012

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6
Q

While _____, the nucleus is located most deep.

A

cellular division occurs (M phase, mitosis)

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7
Q

While _____, the nucleus is located most superficially.

A

DNA is being synthesized (S phase)

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8
Q
  1. Define and describe what are neurotrophins and the roles they play in neuronal development.
A

neutrophins = induce differentiations, formations of processes can either attract or repel the growth cone over long distances (diffusible) or short distances (contact dependent)

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9
Q
  1. Describe the role that radial glia play in neuronal migration.
A

Radial glia extend from the ventricle to the surface and serve as guides during neuronal migration. They are like a scaffold.

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10
Q
  1. Identify which brain regions are areas of secondary neurogenesis.
A
  • Cerebellum (external granule layer)
  • Olfactory system (subventricular zone)
  • hippocampus (dentate gyrus)
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11
Q

When a progenitor cell in the ventricular zone divides, the plane of cleavage can be either _____ or ______.

A

perpendicular or parallel

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12
Q

The neuroectoderm rounds up and forms the ____.

A

neural tube

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13
Q

When the plane of cleavage is ______ to the ventricular surface, both daughter cells remain attached to the ventricular surface and the cells _____ in the cell cycle.

A

remain

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14
Q
  1. For both the cerebral cortex and retina, describe where the first‐born cells are found with respect to the ventricular zone.
A
  • cerebral cortex= first born medial and later born to periphery (inside-out)
  • retina = ganglion cells born first and photoreceptors last (outside-in)
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15
Q
  1. Compare and contrast “apoptosis” with “necrosis.”
A
  • apoptosis = programmed cell death; cell shrinks and is eventually cleared by macrophages
  • necrosis = accidental cell death; cell contents spill
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16
Q

What happens to the subplate neurons?

A

most die after their pioneering roles play out

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17
Q

In the cerebral cortex, specialized glia called ______ extend from the ventricle to the surface and are used as guides during migration.

A

radial glia

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18
Q
  1. Define synapse elimination and discuss when and where it occurs.
A

synapse elimination = removal of excess nerve contacts ex: muscles are innervated by multiple motor neurons during development/early postnatal life, but this is then reduced by retraction of some individual motor neurons

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19
Q

Neurons migrate into the cortical plate using ______ as a scaffold.

A

radial glia

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20
Q

Once a cell _____, it leaves the ventricular zone.

A

leaves the mitotic cycle

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21
Q

When does the majority of neurogenesis occur?

A

before birth

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22
Q
  1. Describe when myelination occurs.
A
  • begins during embryonic stages
  • first present in periphery
  • CNS = spinal cord @ end of 1st trimester, brain by end of 3rd trimester, cortical tracts after birth
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23
Q
  1. Contrast migration of neural crest cells to radial migration in the cerebral cortex.
A
  • neural crest cell migration = from top of the dorsal neural tube throughout the body
  • dorsal stream migration or ventral stream migration
  • laminin and fibronectin involved radial migration = inside-out pattern
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24
Q

What region of the hippocampus develops postnatally?

A

dentate gyrus

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25
Q

Proliferating cells are found in the _____.

A

ventricular zones

26
Q
  1. Describe factors/mechanisms that determine when a cell stops dividing and begins differentiating.
A
  • Keep dividing= stay attached to ventricular surface; signaling factors inhibit division
  • Stop dividing and differentiate = detach from vent. surface; signaling factors keep it dividing
27
Q

What region of the olfactory system develops postnatally?

A

the subventricular zone

28
Q
  1. Describe the changes in nuclear position that occur during the cell cycle of neuronal precursors.
A
  • nucleus superficial (near pial surface) = S phase (DNA replication)
  • nucleus deep (near ventricular surface) = M phase (mitosis)
  • nucleus intermediate = G1, G2 (gap)
29
Q
  1. Describe methods used to study neurogenesis.
A

Use radiolabeled nucleotides to track replication and cell division

30
Q
  1. Identify factors that influence the ability of axons to regenerate.
A
  1. ability to grow
  2. presence of growth factors (FGF, neutrophins)
  3. presence of molecules/receptors that inhibit growth (Nogo)
31
Q
  1. Describe genes that play a role in neuronal migration in the cerebral cortex and which stages of migration they affect.
A
  • Reeler = inside-out pattern of cortical organization; mutant = inversion *** step 1 (onset) and step 3 (stopping)
  • filaminA gene (FLNA) = actin binding crosslinking protein; mutations cause periventricular heterotopia (PH) *** step 1 (onset)
  • LIS1 = helps migration towards cortical plate; mutation = smooth brain surface, lack of layer specificity bc the neurons derail from radial glia at the wrong times ***step 2 (migration)
  • doublecortin (DCX) = helps migration towards cortical plate by regulating the microtubular cytoskeleton; mutation = double cortex syndrome *** step 2 (migration)
  • Dab1, Vldlr, Apoer2 = termination of migration and getting off radial glia ***step 3 (stopping)
32
Q

While cellular division occurs (M phase, mitosis), the nucleus is located _______.

A

most deep

33
Q
  1. Define and describe 3 stages of neuronal migration in the cerebral cortex.
A
  1. onset of migration = post-mitotic cell leaves the ventricular zone by riding the radial glia (FLNA mutation –> PH)
  2. ongoing migration = ride the radial glia to approp. destination (LIS1, DCX mutations –> don’t make it to cortical plane)
  3. migration stop = terminate migration and get off radial glia (Reeler, Dab1, Vldlr, Apoer2 mutations–> layering/patterning problems)
34
Q
  1. Describe neural crest cells and the neuronal populations they give rise to.
A
  • arise from boundary btw the neuroectoderm and the epidermis
  • give rise to the PNS, pigment cells, and cartilage
35
Q

What region of the cerebellum develops postnatally?

A

the external granule layer

36
Q
  1. Describe what is known about neurogenesis in the adult brain and discuss key questions for future research.
A
  • Neurogenesis occurs in the adult brain in the dentate gyrus and the subventricular zone of the hippocampus and olfactory bulb
  • Cell death also occurs
  • Total neuron # remains about constant
37
Q

What is a secondary zone of neurogenesis?

A

a hot spot of postnatal neurogenesis

38
Q

When the plane of cleavage is perpendicular to the ventricular surface, both daughter cells ______ to the ventricular surface and the cells remain in the cell cycle.

A

remain attached

39
Q

When the plane of cleavage is ______ to the ventricular surface, both daughter cells remain attached to the ventricular surface and the cells remain in the cell cycle.

A

perpendicular

40
Q

As postmitotic cells accumulate within the preplate (PP), the PP divides into the ______, ______, _____, and _____.

A

marginal zone (MZ), cortical plate (CP), subplate (SP), and the deep ventricular zone

41
Q

What secretes reelin?

A

Cajal-Retzius cells

42
Q

When the plane of cleavage is ______ to the ventricular surface, one of the daughter cells remains attached but the other does not. This is called asymmetrical division.

A

parallel

43
Q

What happens in the mouse mutant, reeler?

A

the normal inside-out pattern of cortical organization is inverted

44
Q

While DNA is being synthesized (S phase), the nucleus is located _____.

A

most superficially

45
Q

As each precursor progresses through the cell cycle, the position of the _____ changes.

A

nucleus

46
Q

A daughter cell can detach its processes from the ventricular surface and will ______.

A

cease dividing (aka post-mitotic)

47
Q
  1. Describe normal postnatal changes in brain morphology and how Autism Spectrum Disorder (ASD) and Down syndrome affect these normal developmental changes in neuronal morphology.
A
  • normal = low neural connection density but interconnections change and increase rapidly during 1st prenatal year; dendrite spines also thicken
  • ASD = abnormally high increases in brain size, esp of white matter areas, with smaller neuronal cell bodies and less branching
  • Down syndrome = dendritic spines are abnormally thin and short
48
Q
  1. Draw and describe an asymmetric cell division.
A

When the plane of cleavage is parallel to the ventricular surface, one of the daughter cells remains attached but the other does not. The unattached begins differentiating and migrating.

49
Q

What is fund within the intermediate zone (IZ)?

A

neuronal and radial glial processes

50
Q

When the plane of cleavage is parallel to the ventricular surface, one of the daughter cells remains attached but the other does not. This is called _______.

A

asymmetrical division

51
Q
  1. Discuss when and where neurogenesis occurs.
A
  • Most = prior to birth
  • exceptions = cerebellum, olfactory system, hippocampus
52
Q
  1. Define preplate and subplate with respect to neuronal migration.
A
  • preplate = 1st stage of corticogenesis btw pia and ventricular zone; contains the first-born “pioneer” cells (lots of Cajal-Retzius cells)
  • subplate = below the 6 cortical layers
53
Q

What are the 3 distinct stages in neuronal migration?

A
  1. onset of migration
  2. ongoing migration
  3. migration stop
54
Q
  1. Describe two ways in which function of GABA receptors is developmentally regulated.
A
  • Many GABA receptors and subtypes present in developing brain
  • function changes as eq potential for Cl- changes
  • Cl- is elevated during development to have more depolarized value
  • ECl activation leads to depolarization and excitation –> increased sz susceptibility in neonates
55
Q

The nervous system begins as a flat epithelium known as the _____.

A

neuroectoderm

56
Q

Neurons migrate into the _____ using radial glia as a scaffold.

A

cortical plate

57
Q
  1. Describe what is meant by a neuron’s birthdate and discuss whether a neuron’s birthdate influences its differentiation.
A

birthdate = last round of DNA synthesis (S phase); earlier-born neurons are located more medially than their later-born counterparts, which have to travel farther and become more lateral/superficial layers (EXCEPT in the retina)

58
Q

Cells in each of the 3 secondary zones of neurogenesis all have what 3 characteristics in common?

A
  1. arise in a ventricular zone
  2. migrate before exiting the mitotic cycle
  3. proliferate postnatally in non-ventricular zone locations
59
Q
  1. Describe when cell death occurs in the nervous system.
A

About half of original cell population dies due to pattern recognition, brain morphogenesis, and removal of unnecessary neurons and matching populations to targets

60
Q

During the 2 gap phases (G1 and G2), where is the nucleus located?

A

intermediate within the cell

61
Q

Once a cell leaves the mitotic cycle, it _____.

A

also leaves the ventricular zone

aNeuro Exam I- Lindsey's (26 decks)

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