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What is an undifferentiated zygote?
a single cell that is a combination of your parents that divides many times to make up our body
Specification of genes meaning
Genes turn on and off, and are specified for different areas of the brain
Do genes turn back on after they've been turned off?
Some do, but others turn on during development and never turn back on again
Blastula
An unspecified ball of cells
What do identical twins come from?
From breaking off of the blastula
When does the ectoderm form?
14-18 days after fertilization
ectoderm, mesoderm, endoderm
Neural tube -- 18 days
Neural plate forms (skin or nervous system)
Neural tube -- 21 days
Neural groove forms
Neural tube -- 22 days
Neural groove is closing to form the neural tube --> neural tube ventricle
Neural tube -- 23 days
Anterior neural folds close to form brain --> neural tube is fully formed
Neural tube -- 24 days
Brain and spinal cord are fully developed and contain the neural tube, developing forebrain, and developing heart
The neural tube is part of what nervous system?
The CNS
The neural crest is part of what nervous system?
The PNS
Neural Crest
A band of cells along the border where the neural tube pinches off from the ectoderm (found above the tube)
What happens to the human embryo at 7 weeks?
The brain forms via cell division and contracting cells form the heart
T/F: All vertebrates have a brain and spinal cord
True
How do vertebrates differ between early and late development?
In early development, all vertebrates look the same but in later development, all vertebrates look different
Stages of neural development
Proliferation
Migration
Differentiation
Pruning and Cell Death
Myelination
Proliferation
Cell division
Where does proliferation occur?
In the neural tube
Migration
Neuroblasts; when cells are done dividing, they move out of the tube and to the outside of the central canal, creating a bump and eventually becoming neurons
Differentiation
Forming axons and dendrites, and making synapses --> ultimately forms the neuron
Axon Terminals
Branches at the end of the axon that make many synapses
Neurotrophic Factors
Proteins responsible for growth and survival of neurons during development and maintaining adult neurons
Growth Cone
Growing tip of axon or dendrite that forms appropriate synaptic connections
Target cells secrete ___
Neurotrophic factors
Explain what the growing axon does
Axon makes a synapse and gives off neurotransmitters that target cells interact with to get neurotrophic factors
There is a series of attraction between the growing tip of the axon and what?
The rest of the growing nervous system
CAM Cell Adhesion Molecules
Proteins that allow cells to recognize each other and contribute to proper cell differentiation and development
Forms proper chemical attractions or repulsions from what it needs
Examples of neurotrophic factors
NGF --> nerve growth factor
BDNF --> brain derived neurotrophic factor
Pruning and Cell Death
Apoptosis, where you injure the cell by draining its blood supply or set off its genetic program for killing it
What stage does pruning and cell death overlap with?
Differentiation
What is apoptosis? When does it occur?
A genetic program for cell death due to too little neurotrophic factor; occurs around birth in the cortex
___x as many neurons are generated in the spinal cord than will stay
2x
Pruning
Even when new synapses are being made, unnecessary and unused connections are being removed
Do neurons get replaced/regenerated?
No; once they divide, they'll never divide again
Myelination
Wrapping of glial cells around the axon to speed up chemical transmission
When does myelination occur?
Mainly after pruning and cell death is finished
Why does myelin stop/end?
In order for synapses to be made
Schwann Cells
Form myelin in the PNS
Oligodendroglia
Form myelin in the CNS
What 2 stages of neural development are babies already born with?
Proliferation and migration
Which stage of neural development starts prenatally, but differentiates after birth?
Differentiation
What is the first kind of synapse to occur in development?
Spinal synapses
Maturation of spinal cord
Spinal cord --> subcortex ----> cortex
Brain weight increases from birth to 12 years old by ____x
3.5x
At what size is the brain pretty much at adult size
12 years old; connections are not yet fully formed though
Proliferation: cerebellum (how long does it continue for?)
Continues for 2 years
Proliferation: olfactory bulb
Continues for life; highest proliferation during 1st year
Proliferation: dentate gyrus of hippocampus
Continues for life; highest proliferation during 1st year
When does most differentiation occur?
Before birth
Less than ___% of brain cell proliferation occurs from the cerebellum, olfactory bulb, and dentate gyrus of hippocampus
0.5%
T/F: Exposure to many substances (toxins) during development can have permanent effects on the brain
True
When are these permanent effects greater?
During early childhood, as opposed to later in childhood or adulthood
Toxins vs Toxicants
Toxins = occuring in nature
Reptiles, insects, plants and microorganisms
Toxicants = human made
alcohol, lead, pesticides, BPA, phthalates, most drugs
T/F: Most toxins get through the placental barrier
True
How do areas of the cerebral cortex develop?
They develop at different times
Development: Sensory
Highest after birth; babies don't see find detail nor have great acuity --> we're born with neurons but not connections
Development: Motor/Language
Middle stage of development
Development: Higher Cognition
Last stage of development; continues throughout childhood and into adolescence
Dendritic Growth
Mature neurons generally can't divide, but new dendrites can grow --> newborns to 2 years gradually increase in dendritic connections
___ are pre-wired from birth
Axons
Binocular Vision
Vision using two eyes with overlapping fields of view, allowing good depth perception
What happens if your right eye is blurry?
Your left eye takes over more of the cortex because the right eye doesn't see fine detail
What happens when axons compete for synaptic space?
Growth of axons and pruning both occur
You will always have a weaker eye if not corrected by ___ months of age
18 months
Amblyopia
Eyes out of alignment --> the dominant eye takes over; AKA lazy eye
Glutamate
The most common excitatory neurotransmitter in the CNS
2 types of glutamate receptors
AMPA and NDMA
AMPA
Ionotropic glutamate receptor that ALWAYS opens and leads to an EPSP
NDMA
Ionotropic glutamate receptor that only opens via membrane depolarization to create an EPSP
Synaptic Strengthening
Synapses that work together to strengthen each other
Binocular Neurons
Wiring of visual cortex --> using both eyes
Left eye: Axon releases glutamate repeatedly -->
AMPA receptor --> much Na+ enters
NMDA receptor --> Na+ and Ca++ enter from depolarization
Right eye: Axon releases glutamate repeatedly -->
AMPA receptor --> Much Na+ enters
Does the right eye or the left eye have not many AMPA receptors?
The left eye
Steps in NMDA coincidence detection
Several AMPA receptors in close proximity used simultaneously results in increased depolarization
NMDA opens and lets Ca++ into the dendrite
Ca++ starts a chemical cascade that results in more AMPA receptors being put into the membrane
This results in a stronger synapse
Enriched Condition (EC)
Also called complex environment. A condition in which laboratory rodents are group-housed with a wide variety of stimulus objects.
Does proliferation occur after birth?
No
What is the cerebral cortex during the first year after birth?
The visual cortex
What is the cerebral cortex through adolescence?
The prefrontal cortex
Prefrontal Cortex
Involved with executive functions, decision-making, etc.
When does the prefrontal cortex develop?
Mid 20s
What kind of milk do babies need for growth? Why?
Fatty milk to help myelinate axons and increase connections
Who develops frontal grey matter earlier, males or females?
Females
When does frontal grey matter peak?
During adolescence
Note 
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