Chapter 7 Flashcards

β-amyloid
A protein that accumulates in senile plaques in Alzheimer’s disease.
β-secretase
An enzyme that cleaves amyloid precursor protein, forming β-amyloid, which can lead to Alzheimer’s disease. See also presenilin.
adult neurogenesis
The creation of new neurons in the brain of an adult.
Alzheimer’s disease
A form of dementia that may appear in middle age but is more frequent among the aged.
amblyopia
Reduced visual acuity that is not caused by optical or retinal impairments.
amyloid precursor protein (APP)
A protein that, when cleaved by several enzymes, produces β-amyloid. Buildup of β-amyloid is thought to cause Alzheimer’s disease.
anterograde degeneration
Also called Wallerian degeneration. The loss of the distal portion of an axon resulting from injury to the axon. See Box 7.1. Compare retrograde degeneration.
apolipoprotein E (ApoE)
A protein that may help break down amyloid. Individuals carrying the ApoE4 allele are more likely to develop Alzheimer’s disease.
apoptosis
See cell death.
Asperger’s syndrome
Sometimes called high-functioning autism. A syndrome characterized by difficulties in social cognitive processing; usually accompanied by strong language skills.
autism
A disorder arising during childhood, characterized by social withdrawal and perseverative behavior.
Bcl-2
A family of proteins that regulate apoptosis.
behavioral teratology
The study of impairments in behavior that are produced by embryonic or fetal exposure to toxic substances.
binocular deprivation
Depriving both eyes of form vision, as by sealing the eyelids. Compare monocular deprivation.
caspases
A family of proteins that regulate cell death (apoptosis).
cell adhesion molecule (CAM)
A protein found on the surface of a cell that guides cell migration and/or axonal pathfinding.
cell death
Also called apoptosis. The developmental process during which “surplus” cells die. See Figure 7.3.
cell differentiation
The developmental stage in which cells acquire distinctive characteristics, such as those of neurons, as the result of expressing particular genes. See Figure 7.3.
cell migration
The movement of cells from site of origin to final location. See Figure 7.3.
cell-autonomous
Referring to cell processes that are directed by the cell itself rather than being under the influence of other cells.
cell–cell interactions
The general process during development in which one cell affects the differentiation of other, usually neighboring, cells.
chemoattractants
Compounds that attract particular classes of growth cones. Compare chemorepellents.
chemorepellents
Compounds that repel particular classes of growth cones. Compare chemoattractants.
clones
Asexually produced organisms that are genetically identical.
death gene
A gene that is expressed only when a cell becomes committed to natural cell death (apoptosis). See Figure 7.11.
dementia
Drastic failure of cognitive ability, including memory failure and loss of orientation.
Diablo
A protein released by mitochondria, in response to high calcium levels, that activates apoptosis.
Down syndrome
Intellectual disability that is associated with an extra copy of chromosome 21.
ectoderm
The outer cellular layer of the developing fetus. The ectoderm gives rise to the skin and the nervous system.
embryo
The earliest stage in a developing animal. Humans are considered to be embryos until 8–10 weeks after conception.
epigenetics
The study of factors that affect gene expression without making any changes in the nucleotide sequence of the genes themselves.
expression
In the context of genetics, the process by which a cell makes an mRNA transcript of a particular gene.
fetal alcohol syndrome (FAS)
A disorder, including intellectual disability and characteristic facial anomalies, that affects children exposed to too much alcohol (through maternal ingestion) during fetal development.
fetus
A developing individual after the embryo stage. Humans are considered to be fetuses from 10 weeks after fertilization until birth.
filopodia (sing. filopodium)
Very fine, tubular outgrowths from the growth cone. See Figure 7.8.
forebrain
Also called prosencephalon. The anterior division of the brain, containing the cerebral hemispheres, the thalamus, and the hypothalamus. See Figure 2.14.
fragile X syndrome
A condition that is 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.
genotype
Also called genome. All the genetic information that one specific individual has inherited. Compare phenotype.
growth cone
The growing tip of an axon or a dendrite. See Figure 7.8.
Hebbian synapse
A synapse that is strengthened when it successfully drives the postsynaptic cell.
hindbrain
Also called rhombencephalon. The rear division of the brain, which, in the mature vertebrate, contains the cerebellum, pons, and medulla. See Figure 2.14.
hypoxia
A transient lack of oxygen.
in vitro
Literally, “in glass” (in Latin). Usually, in a laboratory dish; outside the body.
induction
The process by which one set of cells influences the fate of neighboring cells, usually by secreting a chemical factor that changes gene expression in the target cells.
inhibitors of apoptosis proteins (IAPs)
A family of proteins that inhibit caspases and thereby stave off apoptosis.
intellectual disability
A disability characterized by significant limitations in intellectual functioning and adaptive behavior.
knockout organism
An individual in which a particular gene has been disabled by an experimenter. See Box 7.3.
methylation
A chemical modification of DNA that does not affect the nucleotide sequence of a gene but makes that gene less likely to be expressed.
midbrain
Also called mesencephalon. The middle division of the brain. See Figure 2.14.
mitosis
The process of division of somatic cells that involves duplication of DNA.
monocular deprivation
Depriving one eye of light. Compare binocular deprivation.
multiple sclerosis
Literally, “many scars”; a disorder characterized by widespread degeneration of myelin.
mutation
A change in the nucleotide sequence of a gene as a result of unfaithful replication.
myelination
The process of myelin formation. See Figures 2.7, 7.16.
nerve growth factor (NGF)
A substance that markedly affects the growth of neurons in spinal ganglia and in the ganglia of the sympathetic nervous system. See Figure 7.12.
neural groove
In the developing embryo, the groove between the neural folds. See Figure 7.1.
neural tube
An embryonic structure with subdivisions that correspond to the future forebrain, midbrain, and hindbrain. The cavity of this tube will include the cerebral ventricles and the passages that connect them. See Figure 7.1.
neurofibrillary tangle
An abnormal whorl of neurofilaments within nerve cells. Neurofibrillary tangles are especially apparent in people suffering from dementia. See Figure 7.26.
neurogenesis
The mitotic division of nonneuronal cells to produce neurons. See Figures 7.2, 7.3.
neurotrophic factor
A target-derived chemical that acts as if it “feeds” certain neurons to help them survive. See also trophic factor.
neurotrophin
A chemical that prevents neurons from dying.
notochord
A midline structure arising early in the embryonic development of vertebrates. See Figure 7.1.
ocular dominance histogram
A graph that portrays the strength of response of a brain neuron to stimuli presented to either the left eye or the right eye. Ocular dominance histograms are used to determine the effects of manipulating visual experience. See Figure 7.23.
perseverate
To continue to show a behavior repeatedly.
phenotype
The sum of an individual’s physical characteristics at one particular time. Compare genotype.
phenylketonuria (PKU)
An inherited disorder of protein metabolism in which the absence of an enzyme leads to a toxic buildup of certain compounds, causing intellectual disability.
presenilin
An enzyme that cleaves amyloid precursor protein, forming β-amyloid, which can lead to Alzheimer’s disease. See also β-secretase.
process outgrowth
The extensive growth of axons and dendrites.
radial glial cells
Glial cells that form early in development, spanning the width of the emerging cerebral hemispheres, and guide migrating neurons. See Figure 7.5.
regulation
An adaptive response to early injury, as when developing individual cells compensate for missing or injured cells.
senile dementia
A neurological disorder of the aged that is characterized by progressive behavioral deterioration, including personality change and profound intellectual decline. It includes, but is not limited to, Alzheimer’s disease.
senile plaques
Also called amyloid plaques. Senile plaques are small areas of the brain that have abnormal cellular and chemical patterns. Senile plaques correlate with senile dementia. See Figure 7.28.
sensitive period
The period during development in which an organism can be permanently altered by a particular experience or treatment.
stem cell
A cell that is undifferentiated and therefore can take on the fate of any cell that a donor organism can produce.
synapse rearrangement
Also called synaptic remodeling. The loss of some synapses and the development of others; a refinement of synaptic connections that is often seen in development. See Figure 7.15.
synaptogenesis
The establishment of synaptic connections as axons and dendrites grow. See Figure 7.8.
Tau
1. A protein associated with neurofibrillary tangles in Alzheimer’s disease. 2. A mutation (tau) in hamsters that causes a shorter circadian period in free-running conditions.
transgenic
Referring to an animal in which a new or altered gene has been deliberately introduced into the genome. See Box 7.3.
trinucleotide repeat
Repetition of the same three nucleotides within a gene, which can lead to dysfunction, as in the cases of Huntington’s disease and fragile X syndrome.
ventricular zone
Also called ependymal layer. A region lining the cerebral ventricles that displays mitosis, providing neurons early in development and glial cells throughout life. See Figure 7.5.
zygote
The fertilized egg.
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