L4 - Embryology

Question 1

Neural induction

Answer 1

Assigning neural potential to a region of early embryo

Question 2

Neuralation

Answer 2

Forming the rudimentary NS (neural tube)

Question 3

Neurogenesis

Answer 3

Production of neurons and glia from precursor cells

Question 4

What determines epidermal fate? What blocks it?

Answer 4

Epidermal fate is determined by local bone morphogenetic protein (BMP) signalling.

Signals from “organizer” region underneath epidermis layer (Noggin, Chordin) block the BMP signal inducing neural fate.

*Chick embryo, the organiser is aka Hensen’s node, in human embryo - the node

Question 5

Human embryonic development

Answer 5

1) 2 cell stage
2) 4 cell stage
3) Blastula -hollow sphere of cells
4) Blastocyst -differentiation of cells has occurred
5) Implantation
6) Embryo gastrulation- the single-layered blastula is reorganized into a trilaminar (“three-layered”- ectoderm, mesoderm, and endoderm)
7) Neurula - First appearance of NS

Question 6

Neural tube zips up uni or bidirectionally?

Answer 6

Bidirectionally

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Question 7

Formation of neural tube (neurulation)

Answer 7

Transformation of neural plate into neural tube - Elevation of neural folds, neural folds fuse in dorsal midline, neural tube pinched off from epidermis

Question 8

What do neural crest give rise to?

Answer 8

Peripheral and enteric NS ganglia, melanocytes, schwann cells, cartilage and bone (face, jaw), cells in adrenal medulla

Question 9

Overlying ectoderm induces roof plate that secretes

Answer 9

Dorzalizing morphogens (BMPs, Fibroblastic Growth Factors, Wnts)

Question 10

Underlying notochord induces floor plate that secretes

Answer 10

Ventralizing morphogen (sonic hedgehog)

Question 11

The brain vesicles/neural tube initially consist of a single or multi layer of neuroepithelial cells?

Answer 11

Single

Appears multi-layered because the nucles and cell body move to different positions along the apical-basal axis with different phases of cell cycle

Question 12

Symmetric divisions give rise to two identical or different daughter cells? What about asymmetric divisions?

Answer 12

Identical, different

Question 13

The order of cortical layer formation is “inside out”. What does this mean?

Answer 13

The deepest cellular layers are assembled first and those closest to the surface last.

Question 14

Where are cortical interneurons produced?

Answer 14

In the basal forebrain (MGE - Medial ganglionic eminence)

Question 15

Olfactory bulb neuroblasts migrate along ____

Answer 15

The rostral migratory stream

Question 16

Cerebellar granule cell precursors migrate from ___

Answer 16

Rhombic lip

Question 17

Neurogenesis preceed gliogenesis

Answer 17

Production of neurons and glia is controlled by separate transcriptional programs, each blocks the other

Question 18

80% of neurons in cortex are

Answer 18

Pyramidal neurons - excitatory long range projection neurons

Question 19

20% of neurons in cortex are

Answer 19

Interneurons - locally projecting inhibitory neurons that modulate cortical excitatory output

Question 20

Growth cones are made from ___ which carry out what sort of functions?

Answer 20

Actin filaments - regulate shape and directed growth of growth cone

Microtubules - provide structural support to axon shaft and are essential for axon extension

Question 21

Filopodia (On growth cone)

Answer 21

Thin, actin-rich plasma-membrane protrusions that function as antennae for cells to probe their environment

Question 22

Critical period where sensory input from left and right eyes rearranges developing circuits into occular dominance columns is within _ weeks

Answer 22

At 6 weeks, occular dominance columns look normal.