Cogs 17 Fall 2026 HW 3

Inner layer of cells that becomes organs and glands

Endoderm

Outer layer of cells that become sthe skin and nervous system

ectodern

The middle layer of cells that becomes bones, muscles, and blood vessels

Mesoderm

Long enclosed chamber that becomes the CNS

Neural tube

Failure of ridges to fuse

Spinal Bifida

Surface of fused ridges that become the PNS

Neural crest

When the ridges fuse, this hollow chamber, the length of the embryo, is formed

Neural Tube

Hardening dorsal surface of embryo

Neural Plate

Undifferentiated ectodermal cells

Stem cells

Inner lining of neural tube, from which neurons will migrate

Ventricular zone

When stem cells divide into one stem cell and one neuron or glial cell

Asymmetrical division

Cells emanating from ventricular zone for neurons to migrate along

radial glia

When stem cells divide into 2 identical, daughter stem cells

Symmetrical Division

Genetic factors that influence differentiation

Cell-autonomous factors

Can be laid down by glia cells to form a chemical trail for migrating neurons to follow

Neurotrophins

Any chemical that promotes the development and functioning of neurons

neurotrophins

environmental conditions taht affect differentiation

induction factors

_____is the earliest form of an axon’s terminal

A Growth Cone

______ are the glial cells that show axons where to go

Guidepost cells

______ detect chemicals released by guidepost cells

Filopodia

Whats it called when Greater positive, chemical feedback from groups of cells is more likely to promote connections, than less such feedback

Cells that fire together, wire together

Forming the critical connections between neurons

Synaptogenesis

In a fetus, the layer with the nervous system and skin is the

Ectoderm

In a fetus, the layer with the bones, muscles, and blood vessels is teh

Mesoderm

In a fetus, the layer with the organs and glands is the

Endoderm

in the first 2 weeks The dorsal ectoderm on the “back” of the worm-embryo thickens and forms the hard…

Neural plate

The rostral end of the neural tube becomes the

brain dividing into forebrain, midbrain, and hindbrain

The caudal end of the neural tube becomes the

spinal cord

the surface of ridges (neural crest) later breaks away from tube to become

ganglia ofANS and peripheral neurons/glia

Teh Hollow center of tube form

the 4 chambers (ventricles) in teh brain and the central canal of the cord

Growth of new cells (neurons and glial cells) occurs primarily prenatally, sometimes in infancy

Proliferation

Ectodermal cells that line the inside of the neural tube

Stem Cells

The inside of the Neural Tube

Ventricular Zone

These cells give rise to neurons by asymmetrical division

Stem cells

at week 7 asymmetrical division starts and lasts about

3 months

some stem cells become

radial glia

neurons migrate by

crawling along radial glial fibers, aided by chemical trails from glial cells or other neurons

cell-autonomous and induction factors decide

what neurons differentiate into

synaptogenesis is

developing junctions between cells

T/F Atoms have axons and dendrites when they migrate

False: after migration axons develop then dendrites

at the end of the elongating axon and has many Filopedia that detect chemicals

Growth Cone

Guidepost cells are

Glia cella that adhere to growing axon and direct it towards the target cell

if tehy do not have guidepost cells, others depend on

chemical trails made by glia cells/ other migrating neurons/axons

Chemicals that attract/repel and promote survival and later axonal branching

Neurotrophins

NGF (nerve growth factor) that attracts and promotes survivial of SNS axons is a

Neurotrophin

in the CNS, BDNF (Brain-derived Neurotrophic Factors) that promotes axon survival and axonal branching is….

neurotrophin

How many extra cells are produced during fetal development

up to 50% more than needed

after development most stem cells…

die by suicide genes

Why do some connections between pre-synaptoc and post-synaptic cells die off

because even if the post-synaptic cell releases the neurotrophins that let pre-synaptic one survive, this is most effective on the active pre-synaptic cells, so only teh most aligned pre/post activity get stronger and survive

after teh oit competed connections die, the remaining ones produce

Collatral sprouts that take over synapses

Why do the same cells in the wrist correlate to teh wrist part of teh rbain

adjacent pre-synaptic cells correlate their bursts of activity so they connect to adjacent targets

WHat causes the increase in the weight of brain after birth

Teh size of cells and amount of axonal and dendritic branching

T/F synaptogenesis is shaped by post-natal experience

True

T/F glia cells stop developing and differentiating afetr birth

False