Unit 2 - Chapter 4 Reading Flashcards
The embryo consists of three layers of cells, which are:
- endoderm
- mesoderm
- ectoderm
the outermost cellular layer of the developing embryo, giving rise to the skin and the nervous system.
ectoderm
List the 6 stages of cellular processes needed for brain development.
- neurogenesis
- cell migration
- cell differentiation
- synaptogenesis
- neuronal cell death
- synapse rearrangement
The beginning of the central nervous system occurs when the tops of the neural groove come together to form the —————.
neural tube
the frontal division of the neural tube, which in the mature vertebrate contains the cerebral hemispheres, the thalamus, and the hypothalamus
forebrain
the middle division of the brain
midbrain
the rear division of the brain, which in the mature vertebrate, contains the cerebellum, pons, and medulla
hindbrain
the earliest stage in a developing animal; humans are considered to be ———– until 8-10 weeks after conception
embryo
a developing individual after the embryo stage; humans are considered to be ——– from 10 weeks after fertilization until birth
fetus
What is neurogenesis?
the mitotic division of nonneuronal cells to produce neurons
What is cell migration?
the massive movements of nerve cells or their precursors to establish distinct nerve cell populations (nuclei in the CNS, layers of cerebral cortex, etc.)
What is cell differentiation?
the refining of cells into distinctive types of neurons or glial cells
What is synaptogenesis?
the establishment of synaptic connections as axons and dendrites grow
What is neuronal cell death?
the selective death of many nerve cells
What is synapse rearrangement?
the loss of some synapses and the development of others, to refine synaptic connections, which extends throughout our lifespan
Compared to humans, chimps brain development after birth is ————–.
modest; humans seem to have much more brain development that occurs after birth
The protracted brain development post-birth results in a much ———- brain relative to body size, in humans than other apes or Old World monkeys.
larger
The production of neurons is called ————-.
neurogenesis
the mitotic division of nonneuronal cells to produce neurons
what is the process by which cells divide?
mitosis
process of division of somatic cells that involves duplication of DNA
another word for the ventricular zone
ependymal layer
a region lining the cerebral ventricals from which new glial cells are born throughout life, via mitosis
ventricular zone
What is it alled when cells move over relatively long distances to fill out the brain?
cell migration
the movement of cells from site of origin to final location
the turning off of specific genes; the process by which a cell makes an mRNA transcript of a particular gene
gene expression
process of —————————— enables cells to acquire the distinctive appearance and functions of neurons characteristic of their particular regions
cell differentiation
the establishment of synaptic connections as axons and dendrites grow
synaptogenesis
the hallmark of vertebrate devlepment cells sort themselves out via ———————
cell-cell interactions
the general process during development in which one cell affects the differentiation of other, usually neighboring, cells
cell-cell interactions
What is an important consequence of the cell-cell interactions’ impact on brain development?
if cells that have not yet differentiated extensively can be obtained and placed in a certain brain region, they can differentiate in an appropriate way and become properly integrated
stem cells
cells that are undifferentiated and therefore can take on the fate of any cell that a donor organism can produce
True or False: At birth, mammals have already produced most of the neurons they will every have.
True
4.1
What causes postnatal brain growth?
- size of neurons
- branching of dendrites
- eleboration of synapses
- increase in myelin
- addition of glial cells
4.1
Define adult neurogenesis.
generation of new neurons in adulthood (especially in the dentate gyrus of the hippocampal formation)
4.1
True or False:
Research in animals shows that the birth of and/or survival of new neurons is enhanced by factors like exercise, environmental enrichment, and training.
True
4.1
True or False:
Cell death is bad for brain development.
False; cell death is a crucial phase of brain development
4.1
What is another word for cell death?
apoptosis
4.1
True or False:
In some regions of the brain and spinal cord, most of the young nerve cells die during prenatal development.
True
4.1
Genes that are expressed only when a cell undergoes apoptosis.
death genes
4.1
a target-derived chemical that induces innervating neurons to survive
neurotrophic factors; “feed” the neurons to help them survive
4.1
Stages of competition for neurotrophic factors
- Different neurotrophic factors are produced by different target cell groups
- Innervating neurons take up particular neurotrophic factors and transport them to their cell bodies
- Upon reaching the cell body, neurotropic factors regulate the expression of various genes, affecting the development of the neuron
- Early in development, neurons that manage to gather sufficient amounts of the appropriate neurotrophic factor survive. Neurons that gather insufficient trophic factor die.
- Because the amount of neurotrophic factor matches the number of target cells, this process results in a rouch matching of the size of the target and the number of innervating neurons.
- Later in development, axonal processes also compete for neurotrophic factors. Active synapses compete more successfully than inactive synapses.
- Because experience can modulate synaptic activity, different experiences can result in the maintenance of different patterns of synaptic connectivity
4.1
Another word for synapse rearrangement
synaptic remodeling
Synapse rearrangement takes place after cell death
4.2
the loss of some synapses and development of others; a refinement of synaptic connections that is often seen in development
Synapse rearrangement (aka synaptic remodeling)
4.2
the layer of gray matter on the surface of the cortex gets ———— throughout development as synapses are retracted
thinner
4.2
the ——————— does not finish maturation until adolescence and is usually important in —————-
prefrontal; inhibiting behavior
4.2
What is one factor that determines which synapses are kept and which are lost?
we don’t know all factors, but one factor is neural activity
4.2
what is the most frequent cause of intellectual disability
fragile X syndrome
4.2
Define fragile X syndrome.
a frequent cause of inherited intellectual disability produced by a fragile site on the X chromosome that seems prone to breaking because the DNA there is unstable
4.2
a disability characterized by significant limitations in intellectual functioning and adaptive behavior
intellectual disability
4.2
Which syndrome indicates that a loss of synapses helps the brain function better?
Fragile X Syndrome
4.2
Cortical neurons from brains of people with Fragile X Syndrome possess a(n) ————— of small, immature dendritic spines.
excess
4.2
reduced visual acuity of one eye that is not caused by optical or retinal impairments
amblyopia
4.2
depriving both eyes of form vision, as by sealing the eyelids
binocular deprivation
4.2
————- produces structual changes in visual cortical neurons: a loss of dendritic spines and a reduction in synapses
binocular deprivation
4.2
period during development in which an organizsm can be permanently altered by a particular experience or treatment (e.g., visual experience is crucial for proper development of vision, especially at a certain time)
senstive period (aka critical period)
4.2
what is monocular deprivation
depriving one eye of light
4.2
———– produces profound structural and functional changes in thalamus and visual cortex and permanently impairs vision in deprived eye
monocular deprivation
4.2
a graph that portrays the strength of response of a brain neuron to stimuli presented either to the left or right eye
ocular dominance histogram
4.2
a synapse that is strengthened when it successfully drives the postsynaptic cell
Hebbian synapses
(aka - synapses that grow stronger/weaker depending on effectiveness in driving target cells)
4.2
Early visual experience is known to be especially crucial for learning to perceive ———-
faces
bc infants w cataracts in first 6mo impaired in recognizing faces at 9yr
4.2
we can consider genes to be ———— factors, that is, factors that originate within the developing cell itself
intrinsic
4.3
——- is fixed at birth, but ——– changes throughout life.
genotype; phenotype
4.3
all genetic information that one specific individual has inherited
genotype (aka genome)
this is the sum of all of a person’s “intrinsic” factors
4.3
the sum of an individual’s physical characteristics - including anatomical, physiological, and behavioral - at one particular time
phenotype
4.3
when is your genotype determined
at the moment of fertilization; your genotype remains the same throughout your life
4.3
when is your phenotype determined
your phenotype changes constantly, as it is determined by the interaction of genotype and extrinsic factors, including experience
4.3
True or False:
Individuals with identical genotypes will have identical phenotypes, as well.
False; since people with identical genotypes don’t have the exact same environmental influences, they will not have identical phenotypes
4.3
a heritable disorder of protein metabolism that at one time resulted in many people with intellectual disability
phenylketonuria (PKU)
4.3
What is the basic defect in PKU?
absence of an enzyme necessary to metabolize phenylalanine, an amino acid present in many foods
as result, the brain is damaged by a buildup of phenylalanine, which becomes toxic
4.3
The discovery of PKU marked the first time that ———————.
an inherited error of metabolism was associated with intellecutal disability
4.3
Why are the effects of PKU not as common today?
today, the level of phenylalanine in the blood is measured a few days after birth; by detecting it early, we can prevent later brain impairment by reducing phenylalanine in the diet
knowing a baby is born with PKU doesn’t tell you anything about how the child’s brain will develop unless you also know something about the child’s diet
4.3
when a cell uses a particular gene to make a particular protein, we say the cell has ————– the gene
expressed
4.3
asexually produced organisms that are genetically identical
clones
4.3
the study of factors that affect gene expression without making any changes in the nucleotide sequence of the genes
epigenetics
ex. same protein is created but amount varies –> varying brain dev
4.3
Figure 4.14 Epigenetic Effects on Mouse Behavior
prenatal environment/postnatal mothering can impact behavior of genetically identical male mice
Experiment:
Genetically identical mouse embryos are implanted into the womb of a foster mother of either their own strain (Black6) or a different train (albino Balb strain). After birth, transfer 1/2 the males to be raised by either Black6 or albino Balb female. When males grow up, measure behavior on tests in which the two types of mice normally differ.
Four groups of Black6 mice:
- Group 1: carried and raised by Balb
- Group 2: carried by Balb, raised by Black6
- Group 3: carried by Black6, raised by Balb
- Group 4: carried and raised by Black6
Result:
Males of Black6 strain carried and raised by mothers from albino strain show significant differences in several behaviors:
- Group 1 mice (carried/raised by diff strain) behaved like albino males in many ways – explored less, more anxious, slower at mazes than normal Black6 males.
- Group 2 mice (carried by diff strain, raised by same strain) behaved like albino males in some ways – more anxious and slower at mazes, but explored like normal Black6 males
- Group 3 mice (carried by same strain, raised by diff strain) behaved like normal Black6 males in most ways but they did act slightly more anxious than Black6 males (anxious = feature of albino).
- Group 4 mice (carried/raised by same strain) behaved like normal Black6 males as expected.
Conclusion:
Since various males are genetically identical to one another, their different behaviors must be due to the effect of different prenatal enviornments and postnatal experiences, like the mothering they received, on how those genes are expressed.
4.3
chemical modification of DNA that does not affect the nucelotide sequence of a gene but makes that gene less likely to be expressed
methylation
4.3
Explain how methylation and epigenetics relate in rodent mothers.
Attentive rodent mothers prevent methylation of the stress hormone receptor gene in their pups, so their daughters grow up to be attentive mothers themselves. In this way, maternal care can have epigenetic effects that can be transmitted across generations.
4.3
The methylation mechanism in Figure 4.15 “Early experience imprints genes to affect the stress response in adulthood” may apply to humans because this same gene is also more likely to be methylated in the psotmortem brains of suicide victims than of controls, but only ——————–.
in those victims who were subjected to childhood abuse; suicide victims who did not suffer childhood abuse were no more likely to thave the gene methylated than were controls
4.3
Hippocampal shrinkage during aging is correlated with ————— impairment.
memory
4.4
Alzheimer’s disease is associated with a decline in —————.
cerebral metabolism
4.4
a form of dementia that may appear in middle age but is more frequent among the aged
Alzheimer’s disease
dementia
drastic failure of cognitive ability, including memory failure and disorientation
Extensive use of the brain makes Alzheimer’s ———– likely.
less
Observations of brains of people with Alzheimer’s reveal —————, especially in the ———-, —————, and ————- areas.
cortical shrinkage; frontal; temporal; posterior
a small area of the brain that has abnormal cellular and chemical patterns; correlates with dementia; appear in cortex, hippocampus, and associated limbic system sites
amyloid plaques
a protein that accumulates in amyloid plaques in Alzheimer’s disease
beta-amyloid
abnormal whorl of neurofilaments within neurons that is seen in Alzheimer’s disease
neurofibrillary tangles
the number of neurofibrillary tangles is directly related to the —————- of ———– ————; they are probably a secondary response to amyloid plaques
magnitude of cognitive impairment;
Alzheimer’s causes a gradual loss of neurons in the ———– ————–, which make the transmitter ——————.
basal forebrain; acetylcholine (ACh)
4.4
Describe a new approach for diagnosing or tracking treatments for Alzheimer’s in the future.
At present, the only sure diagnosis is postmortem exam of brain revealing amyloid plaques and neurofibriallary tangles.
Possible approach is to inject PiB dye, which has an affinity for beta-amyloid, then conduct a PET scan to determine how much dye accumulates in brain.
There is good evidence that —————, ————, and ———— can postpone the appearance of Alzheimer’s disease.
physical activity; mental activity; adequate sleep
