early brain development neuro

What is gastrulation?

An invagination of cells that occur in the very early embryo, which results in the embryo forming 3 germ layers of cells

What are the 3 germ cell layers in a developing embryo?

ectoderm, mesoderm, endoderm

Which germ cell layer becomes part of

the nervous system?

ectoderm

Ectoderm

outer layer, which becomes mostly brain and skin

Mesoderm

middle layer, which becomes mostly muscle, blood, bone, and cartilage

Endoderm

inner layer, which becomes mostly lung, gut, and liver

What is the notochord?

A cylinder that forms at the midline during gastrulation from mesodermal cells. It is transient structure that disappears after development

What are the neural plate and neural tube?

Neural plate-forms when the notochord sends molecular signals to the overlying ectoder, causing it to differentiate into neuroectodermal precursor cells

Neural tube- forms front the neural plate folding inward

Which forms from which neural plate and neural tube?

neural tube forms from the neural plate

What is this

process called when neural tube forms from neural plate?

neuraltion

Where are the floorplate and roofplate?

Roofplate located in the dorsal neural tube

Floorplate located in the ventral neural tube

What is the neural crest?

A subpopulation ofprecursor cells in the lateral neural plate that migrate away from the tube. These migrating cells become precursors to the autonomicganglia, enteric neurons, and neurosecretory cells of the adrenal gland

What divisions of the adult brain develop from the prosencephalon?

cerebrum, thalamus and hypothalamus

What divisions of the adult brain develop from the mesencephalon?

midbrain

What divisions of the adult brain develop from the rhombencephalon?

cerebellum and pons and medulla

These 3 are divisions (prosencephalon, mesencephalon, rhombencephalon) of what embryonic structure?

neural tube

When is neurogenesis (and glial genesis) complete by? Before or after birth?

Completed by well before birth

What two cell types can neural stem cells generate?

New stem cells or neuroblasts

During the neural stem cell cycle, what two surfaces of the neural tube does the cell

body move between?

Between ventricular surface (inner surface of the neural tube) and pial surface (outer surface of the neural tube)

At which surface does DNA replication occur?

pial

At which surface

does mitosis occur?

ventricular

What are the products of symmetrical vs. asymmetrical division? Can each go on

Indefinitely?

Symmetrical- 2 neural stem cells. Each stem cell can undergo indefiintie symmetrical divisions

Asymmetrical- 1 neuroblast (or glial cell) and 1 progenitor cell. Can undergo only a few more asymmetrical divisions

What kind of cell signaling leads a stem cell to undergo asymmetrical vs. symmetrical

Division?

Cell surface-sssociated signaling

What is a neuroblast?

an immature neuron

How do neuroblasts get to the pial surface of the neural tube?

Most neuroblasts that become cortical projection neurons migrate toward the pial surface. This migration is guided by radial glial processes. Radial glia are now thought to be the neural stem cells that create the neuroblasts.

When do stem cells take up nucleotides from the extracellular medium?

Only when they are replicating.

How could

uptake of radioactive nucleotides be used to birthdate a neuron?

Uptake of radioactive nucleotides, such as radioactive thymidine, can be used to birthdate a neuron through the following mechanism:

1. Radioactive thymidine is injected into developing neural tissue and is only taken up by neural stem cells undergoing division.

2. Symmetrical division dilutes the amount of radioactive thymidine across the progeny.

3. Asymmetrical division generates a neuroblast, and since this cell is post-mitotic (meaning it stops dividing), it retains a high concentration of radioactive thymidine.

4. This high concentration effectively "labels" the neurons that were "born" at the time of injection, allowing researchers to determine their birthdate.