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Flashcards in Lecture - development Deck (31)
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1
Q

Embryos consist of three layers of tissue

A

ectoderm (outermost), mesoderm (middle), and endoderm (innermost).

2
Q

phases of development

A

induction of the neural plate; neural proliferation; migration and aggregation; axon growth and synapse formation; and neuron death and synapse rearrangement.

3
Q

induction of the neural plate

A

A patch of tissue on the ectoderm becomes the neural plate. This transformation is induced by chemical signals from the mesoderm. Visible three weeks after conception.

4
Q

embryonic stem cells

A

neural plate cells. have unlimited capacity for self renewal. can become any type of mature cell.

5
Q

totipotent

A

earliest cells have the ability to become any type of body cell

6
Q

Multipotent

A

with development, neural plate cells are limited to becoming one of the range of mature nervous system cells

7
Q

neural crest

A

A structure dorsal to the neural tube and formed from neural tube cells. Develops into the cells of the peripheral nervous system.

8
Q

neural proliferation

A

Neural plate folds to form the neural groove, which then fuses to form the neural tube. The neural tube will become the cerebral ventricles and central canal in the spinal cord. Neural tube cells proliferate forming three swellings: forebrain, midbrain, and hindbrain.

9
Q

neural migration

A

Once cells have been created through cell division in the ventricular zone of the neural tube, they migrate to their final destinations to form nuclei and cortical layers. Migrating cells are immature, lacking axons and dendrites.

10
Q

cortical layers form in an

A

“inside out pattern.” layer 6 forms first, then 5, 4, etc.

11
Q

two types of neural tube migration

A

radial migration and tangential migration. most cells engage in both types.

12
Q

radial migration

A

usually by moving along radial glial cells

13
Q

two methods of migration

A

somal - caterpillar-like

glial-mediated migration - – cell moves along a radial glial network

14
Q

neural aggregation

A

After migration, cells align themselves with others cells and form nuclei.

15
Q

neural differentiation

A

Neurons take their adult morphology

16
Q

myelination

A

In humans, starts in spinal cord and continues toward forebrain

17
Q

growth cone

A

At the growing tip of each axon, the growth cone

extends and retracts filopodia as if exploring to find its way

18
Q
  1. blueprint hypothesis (for target finding and synapse info)
A

pre-formed pathways and tunnels.

  • Pioneer growth cones, guidepost cells, fasciculation.
  • Role of cell-adhesion molecules (CAM).
  • Evidence against: Cells transplanted to other places still find correct targets.
19
Q
  1. chemoaffinity hypothesis (for target finding and synapse info)
A

Connections are

highly specific. Sperry’s eye rotation experiment.

20
Q

topographic gradient hypothesis

A

sheets of developing neurons are often charcterized by two intersecting chemical gradients, which can define the localization of each neuron.

21
Q
  1. fine-tuning of connections by spontaneous and experience-evoked neural activity (for target finding and synapse info)
A
  • The Hebb postulate: Neurons that fire together, wire together.
  • N-methyl-D-aspartate receptors (NMDA receptors) detect correlated activity between pre- and post-synaptic neurons
22
Q

overproduction

A

during development many neurons die.

23
Q

apoptosis

A

active, programmed cell death

24
Q

necrosis

A

passive cell death.

25
Q

Neurons die due to failure to

A

compete for neurotrohic factors provided by targets (e.g., NGF, nerve growth factor). the more targets, the fewer cell deaths. destroying some cells increases survival rate of remaining cells.

26
Q

synapse rearrangemnet

A

a diffuse pattern of synaptic contact is characteristic of early stages of devleopment. a more focused pattern of synaptic contact is present after synapse rearrangment.

27
Q

More than 200 genetic mutations

A

associated with mental retardation

28
Q

Developing brain is more vulnerable than the mature brain to

A

malnutrition, toxic chemicals and infections.

29
Q

Hypothyroidism

A

induces mental retardation in infants.

30
Q

fetal alcohol syndrome

A

Dendrites tend to be short, with few branches

31
Q

rett syndrome

A

Anomaly of brain development with mental retardation affecting mainly girls older than 1-2 years. Associated with lack of dendritic development.