Chapter 7: Life-Span Development of the Brain and Behavior Flashcards
Initial development occurs in the…
zygote and embryo
How many cell layers does the embryo develop?
3
Ectoderm
The outer cell layer = The NS
How long after implantation is development shown?
18-24 days
What is stage 1 of NS development?
Neurogenesis
What is stage 2 of NS development?
Cell Migration
What is stage 3 of NS development?
Differentiation
What is stage 4 of NS development?
Synaptogenesis
What is stage 5 of NS development?
Neuronal Cell Death
What is stage 6 of NS development?
Synapse Rearrangement
Neurogenesis
The cells on the inner side of the neural tube divide to create the ventricular zone.
Ventricular Zone
Cells from which all neurons and gila cells are derived
What is a cells birthdate?
The point at which they stop dividing.
What determines what kind of cell is born?
Intrinsic and Extrinsic factors (cell to cell interactions)
Intrinsic Factors of Neurogenesis
Genetic determination of a cell’s fate
Extrinsic Factors of Neurogenesis
Cells interact with each other to determine fate
Which type of factor makes it harder to predict a cell’s fate?
Extrinsic
Vertebrate Neuron Development
More focused on extrinsic factors and much less hardwired.
Invertebrate Development
More dependent on intrinsic factors
Vertebrates are born with…
Most of the neurons they will ever have.
Cell Migration
Neurons move from their original location to a new destination in the developing brain.
When is cell migration done in primates?
By birth
In what animal does cell migration occur after birth?
Rats
What is cell migration dependent on?
CAMS = Cell Adhesion Molecules
What do CAMS help guide in adulthood?
Axon cuts
Cell Differentiation
The development of intrinsic self organization.
Cell Autonomous
Genes determine cellular fate
Regulation
Adaptions of cells occur in response to early injuries.
Stem Cells
Cells are placed into a new environment and develop appropriately.
Synaptogenesis
The growth of neuronal processes (axons and dendrites)
Where do axons and dendrites have growth cones?
Their ends
What is axon growth guided by?
Chemicals
- Chemoattractants
- Chemorepellants
Apoptosis
Neuronal cell death
Where does cell death occur?
Throughout the entire body.
Apoptotic Process
- There is an influx of Ca2+ ions outside the cell, and an internal storage agent releases Ca2+ ions inside the cell.
- High levels of Ca2+ enter the mitochondria, and the Diablo Protein is released inside the cell.
- The Diablo Protein binds to IAP’s so they can no longer pass block the caspases (enzymes related to apoptosis).
- A small waterfall of caspases destroy the various proteins and DNA of the cell, making it incapable of survival.
- The family of Bcl-2 proteins can inhibit apoptosis by blocking the release of Diablo from the mitochondria.
Diablo Protein
A protein in the mitochondria that promotes apoptosis.
What helps keeps cells alive?
Cell to cell interactions
How do synaptic targets play a role in cell survival?
The synaptic targets provide neurotrophic factors. The cells that get enough survive.
Nerve Growth Factor
Target organs provide proteins that prevent cells from dying.
Synaptic Rearrangement
Many of the early synapses are retracted and new ones are added.
Model of The Role of Neurotrophic Factors
- Cells that take up enough neurotrophic factors live
- Those cells compete for various neurotrophic factors and the synapses can re-arrange
- Can be dependent on experiences that modulate synaptic activity
Where do muscle cells receive input from in early development?
Several motor neurons
Where do muscle cells receive input from in later development?
One singular motor neuron
Glial Cell Development
Continuously occurs but is stronger after birth for many animals.
When does myelination primarily occur?
After birth
What is myelination important for?
Neural transmission or coordinated control
Genotype
Genetic makeup of an organism
What type of factor is genotype?
Intrinsic
Phenotype
The sum of all your physical characteristics
What does your phenotype result from?
The interaction of genotype with enviorment/experience
What is responsible for neural development in invertebrates?
Genotype
What is responsible for development in vertebrates?
Neurotrophic Factors (combination)
Behavioral Teratology
Investigate how maternal environment for fetus influences NS development
Hypoxia at birth
Disabilities and increased risk of schizophrenia.
What happens when there is a lack of food during the prenatal period?
Increased risk of schizophrenia.
Teratogen
Exogenous agent that may harm development (not just in the NS)
What are examples of drugs that have teratogenic effects?
Thalidomide and Accutane
Trisomy 21 / Down Syndrome
Variability in behavioral effects
- Mild to serious cognitive impairment
What do most people with down syndrome develop?
Alzheimers disease
How many people show symptoms of Alzheimers before 50?
10-25%
Fagile X Syndrome
More than 200 trinucleotide repeats in the x chromosome, causing the x chromosome to break
Is fragile x more common in males or females?
Males
What impact does Fragile X Syndrome have?
Mild to severe cognitive impairments.
What does Fragile X syndrome demonstrate?
Genes/DNA are not passed on faithfully.
Phenylketonuria (PKU)
Presence if phenylketones in the urine.
What is the effect of PKU?
Intellectual disability resulting from buildup in the brain.
How do you lower the chance of getting PKU?
Reduce your consumption of foods containing phenylalanine.
How do you study individual genes?
Transgenic and Knockout organisms
Knockout (KO) mice
A gene has been selectively inactivated
Transgenic mice
A gene has been introduced (transgene)
What is the problem with KO and transgenic organism testing?
The alteration is ALWAYS present.
Conditional Systems
The trans-gene or KO system is present in the DNA, but not active.
What is required for the conditional systems to work?
The presence/absence of an antibiotic.
Epigenetics
Studying the regulation of gene expression
Methylation
Reduces gene expression of DNA that has been methylated (adding a methyl group).
Lazy Eye
Born with one eye turned inward/outward
- not aligned properly
What happens if the lazy eye is not treated by 7/8?
Will never develop good acute vision in that eye, even if the eyes are aligned later.
Amblyopia
Eye is normal and retina is normal, but the person cannot see clearly through the eye.
Sensitive period of Development
A time where a child is especially receptive to certain skills/knowledge areas.
Binocular Deprivation
The loss of dendritic spines and synapses in the visual cortex (animals)
What happens if binocular deprivation is not fixed?
Blindness
Hubel and Wiesel
Won a Nobel Prize for understanding the effects of ocular deprivation and development of the visual cortex.
What maps the visual field?
The visual cortex
What eye do cortical cells respond to?
Both eyes
Ocular Dominance
Degree to which a visual cortical cell responds to light in one eye vs the other
What happens when one eye is closed for a long period of time?
The cortical cells that were once responding to the closed eye begin to only respond to the eye that is open (even if the closed eye is open again).
When do many psychiatric disorders develop?
The end of adolescence.
What does the hippocampal volume relate to?
Memory decline
Alzheimers
- Characterized by memory loss and followed by personality changes
What is the most common form of dementia?
Alzheimers
Amyloid Plaques
Extracellular accumulations of beta-amyloid.
- Moves from the hippocampus, to the limbic system, and eventually frontal cortex.
Neurofibrillary Tangles
Tangles of protein tau inside the neurons
What happens during the loss of basal forebrain nuclei?
ACh neurons decreases (where they are located)
What do amyloid plaques lead to?
Tau tangles
Alzheimers Hypothesis
- Amyloid precursor protein releases the beta-amyloid extracellularly is removed.
- Beta-amyloid forms clumps (plaques). Plaques accumulate on axons and dendrites = impaired function
- The plaques also accumulate inside the cell which form neurofibrillary tangles.
- Basal forebrain neurons cease the production of acetylcholine-> dementia
Apoptosis -> loss of basal forebrain produced acetylcholine -> dementia
