Chapter 7- Development process

genotype

genes for traits contained within an individual

Phenotype

Physical characteristics

• results as an interaction between genotype and environment

• Ex. I have blue eyes

Pre-Nueral development

• Initial development occurs in the zygote and embryo

• fertilized egg develops in 3 layers

  • Ectoderm

  • Mesoderm (muscles, heart, red blood cells)

  • Endoderm (lung, pancreas, glands)

Ecoderm

Outer layer of egg development, formed during gestation, eventually becomes the nervous system/skin

transcription factors

Proteins that bind DNA and switch genes on/off

• Establish body parts/specifc tissue and cell types

Segmenetation

the body’s process of establishing specific parts during genstation

Hox genes

TFs which tell each body segment what to become

Development of the brain

• Human CNS forms at 2 weeks

• Dorsal surface thickens and forms a neural tube that surrounds a fluid-filled cavity

  • Anterior to the neural tube becomes the hindbrain, midbrain, and forebrain

  • rest becomes the spinal cord

Stages of neural development

1. nuergenesis

2. cell migration

3. differentation

4. synatogenesis

5. neuronal cell death

6. synaptic rearrangement

Nuerogenesis

Cells undergo cell division in the ventricular zone; this is the creation of neurons

• People are generally born with all the neurons that will ever need

• SOME REGIONS THIS STILL OCCURS

  • Olfactory bulb

  • granule neurons (hippocampal formation)

Ventricular zone (VZ)

tissue layer that lines ventricular system; general center for creating nuerons

Cell Migration

the movement of newly formed nuerons/glia to their environmental location; 2 types

• most cell migration finished by birth

• failure = Lissencephaly (“smooth brain”)

Radial migration

occurs on scaffolding cells (radial glia) from the ventricle towards the outer surface

Tangental migration

movement parallel to the brain’s surface

Cell differentaition

process of cells adapting their phenotype appropriate for the particular brain region; axons grow first, then dendrites

Neural Cell Adhesion Molecules (NCAMs)

Proteins on the outer surface of cells that guide cells and grow axons to their targets

Growth cones

tips of the growth axons that act as a “steering apparatus” for the axons; contain Filopodia

Filopodia

detects chemicals and guides growth for growth cones

Chemoattractants/Chemorepellants

Chemical signals that attract/repel growth cones to guide neurons to their correct locations

• When guidance fails, corpus callosum fails to form correctly

Synaptogenesis

formation of synaptic connections between neurons during brain development

• occurs throughout life, not prenatally exclusive

• slows down in later years

Cell death/cell suvival (yes this is a step)

the pruning/keeping of cells after/while diffrentation and synaptogenesis occurs

apoptosis

“programmed” mechanism for implementing cell death

• ex. Finger webbing

necrosis

cell death from injury/damange

• Ex. whippets, dementia

Neurotrophins

regulates development and matinence of the vertabrae

Nerve Growth Factor (NGF)

Neurotrophins secreted in target organs in the peripheral nervous system; these are types of proteins

• Neurotrophin for the peripheral nervous system

Brain-derived neurotrophic factor (BDNF)

A nuerotrophin secreated by target neurons in the neocortex and hippocampus

Synaptic rearrangement

The process where earlier formed synapses are eliminated while others are added; rewiring, NOT killing the wires

• if this fucks up we have issues, like a lazy eye

Gliagenesis

the birth/creation of glia cells, occurs throughout prenatal development and is concurrent with neurogenesis

• this still occurs after birth and for the rest of your life

myelination

Mainly occurs after birth; increases AP conduction velocity, the creation of the myelin sheath