Ch. 4

Question 1

Ectoderm

Answer 1

The outer cellular layer of the developing embryo, giving rise to the skin and the nervous system

Question 2

At a week, what does the human embryo show?

Answer 2

three distinct cell layers which are the beginnings of all the tissues of the body.

Question 3

Neural Tube

Answer 3

An embryonic structure with subdivisions that correspond to the future brain and spinal cord. Cells in the neural crest will migrate to form the peripheral nervous system

Question 4

At the anterior part of the neural tube in an embryo, what three subdivisions become apparent?

Answer 4

corresponding to the future forebrain (cortical regions, thalamus, and hypothalamus), midbrain, and hindbrain (cerebellum, pons, and medulla)

Question 5

Forebrain

Answer 5

The front division of the neural tube and brain, which in a mature vertebrate contains the cerebral hemispheres, the thalamus, and the hypothalamus

Question 6

When does a developing human move from being called an embryo to a fetus?

Answer 6

It is called an embryo during the first 10 weeks after fertilization and a fetus thereafter

Question 7

Embryo

Answer 7

earliest stage in a developing animal

Question 8

fetus

Answer 8

A developing individual after the embryo stage

Question 9

What are the six distinct stages of development for the nervous system?

Answer 9

1. neurogenesis- the mitotic division of nonneuronal cells to produce neurons
2. Cell migration- the massive movement of nerve cells or their precursors to establish distinct nerve cell populations (nuclei in the CNS, layers of the cerebral cortex, and so on)
3. Cell differentiation- the refining of cells into distinctive types of neurons or glial cells
4. Synaptogenesis- the establishment of synaptic connections as axons and dendrites grow
5. Neuronal cell death- the selective death of many nerve cells that begins well before birth
6. Synapse rearrangement- the loss of some synapses and the development of others, to refine synaptic connections, which extends throughout our lifespan

Question 10

Neurogenesis

Answer 10

The mitotic division of nonneuronal cells to produce neurons

Question 11

Mitosis

Answer 11

The process of division of somatic cells that involves duplication of DNA

Question 12

Where does mitosis occur for neurons?

Answer 12

The Ventricular Zone– inside the neural tube

Question 13

Cell Migration

Answer 13

The movement of cells from site of origin to final location

Question 14

Once cells reach their destination after mitosis in the ventricular zone, what happens?

Answer 14

alter their gene expression

Question 15

Gene Expression

Answer 15

The process by which a cell makes an mRNA transcript of a particular gene; the turning on or off of specific genes

Question 16

Cell Differentiation

Answer 16

The development stage in which cells acquire distinctive characteristics, such as those of neurons, as a result of expressing particular genes

Question 17

After the cells take on the characteristics of neurons, what happens?

Answer 17

they begin making synaptic connections with one another

Question 18

Synaptogenesis

Answer 18

The establishment of synaptic connections as axons and dendrites grow

Question 19

Cell-Cell Interactions

Answer 19

The general process during development in which one cell affects the differentiation of other, usually neighboring, cells

Question 20

Stem Cells

Answer 20

A cell that is undifferentiated and therefore can take on the fate of any cell that a donor organism can produce

Question 21

The postnatal increase of human brain weight is due to what?

Answer 21

growth in the size of neurons, branching of dendrites, elaboration of synapses, increase in myelin, and addition of glial cells

Question 22

Adult Neurogenesis

Answer 22

The creation of new neurons in the brain of an adult

Question 23

Cell Death

Answer 23

Also called apoptosis. The developmental process during which “surplus” cells die

Question 24

Neurotrophic Factors

Answer 24

A target-derived chemical that acts as if it “feeds” certain neurons to help them survive.

Question 25

Synapse Rearrangement

Answer 25

The loss of some synapses and the development of others

Question 26

Fragile X Syndrome

Answer 26

A condition that is a frequent cause of inherited intellectual disability and is produced by a fragile site on the X chromosomes that seems prone to breaking because the DNA there is unstable. Results in too many synapses

Question 27

Intellectual Disability

Answer 27

A disability characterized by significant limitations in intellectual functioning and adaptive behavior

Question 28

Amblyopia

Answer 28

Reduced visual acuity of one eye that is not caused by optical or retinal impairments

Question 29

Binocular Deprivation

Answer 29

Depriving both eyes of form vision, as by sealing the eyelids

Question 30

In order to achieve normal vision in adulthood, what has to happen in childhood?

Answer 30

realignment of the eyes (if the child was born with misalignment in the eyes)

Question 31

What happens to the structure in the visual cortical neurons as a result of binocular deprivation?

Answer 31

loss of dendritic spines and a reduction in synapses. After several weeks during development, the animal will be blind

Question 32

Sensitive Period

Answer 32

Also called critical period. The period during development in which an organism can be permanently altered by a particular experience or treatment

Question 33

Monocular Deprivation

Answer 33

Depriving one eye of light during the developmental sensitive period

Question 34

What are the effects of monocular deprivation during developmental sensitive period?

Answer 34

produces profound structural and functional changes in the thalamus and visual cortex and permanently impairs vision in the deprived eye

Question 35

Ocular Dominance Histogram

Answer 35

A graph that portrays the strength of response of a brain neuron to stimuli presented to either the left eye or the right eye

Question 36

Hebbian Synapses

Answer 36

A synapse that is strengthened when it successfully drives the postsynaptic cell. These cells grow stronger at the expense of ineffective synapses. Other definition: synapses that grow stronger or weaker depending on their effectiveness in driving their target cell

Question 37

How do genes influence the form, arrangements, and connections of the developing brain?

Answer 37

Genes direct the production of every protein the cell can make. An individual who has inherited an altered gene will make an altered protein, which will affect every cell that uses that protein.

Question 38

Genotype

Answer 38

All the genetic information that one specific individual has inherited

Question 39

Phenotype

Answer 39

The sum of an individual's anatomical, physiological, and behavioral characteristics

Question 40

How are genotypes and phenotypes different?

Answer 40

Your genotype was determined at the moment of fertilization and remains the same throughout your life. However, the phenotype changes constantly, as you grow up and grow old. Phenotype is determined by the interaction of genotype and extrinsic factors, including experience

Question 41

Phenylketonuria (PKU)

Answer 41

An inherited disorder in which the absence of an enzyme leads to a toxic buildup of phenylalanine metabolites (amino acid present in many foods), causing intellectual disability

Question 42

How can PKU be prevented?

Answer 42

reducing phenylalanine in the diet

Question 43

Why is interaction of genes and the environment important in PKU?

Answer 43

the dysfunctional gene causes intellectual disability only in the presence of dietary phenylalanine. Reducing phenylalanine consumption reduces or prevents this effect of the gene

Question 44

Clones

Answer 44

Asexually produced organisms that are genetically identical

Question 45

What is found in the behavior and temperament of clones?

Answer 45

Genetically identical clones show as much variation in behavior and temperament as do normal siblings

Question 46

Epigenetics

Answer 46

The study of factors that affect gene expression without making any changes in the nucleotide sequence of the genes themselves

Question 47

What does it mean when a cell has expressed a gene?

Answer 47

When the cell uses a particular gene to make a particular protein

Question 48

What results in the variation of brain development?

Answer 48

The same protein is produced in gene expression, but the amount of protein can vary considerably, which leads to variation in brain development

Question 49

Methylation

Answer 49

A chemical modification of DNA that does not affect the nucleotide sequence of a gene but makes that gene less likely to be expressed

Question 50

How can mothering affect gene expression in rodents?

Answer 50

Rodent pups provided with inattentive mothers, or subjected to interruptions in maternal care, secrete more glucocorticoids in response to stress as adults. poor maternal care produces this heightened stress hormone response by inducing methylation of the glucocorticoid receptor gene in the brain, making the pups hyperresponsive to stress for the rest of their lives

Question 51

Starting at age 40, what happens to the brain?

Answer 51

Human brain volume steadily declines

Question 52

Memory impairment correlates with what during aging?

Answer 52

hippocampal shrinkage

Question 53

Alzheimer's Disease

Answer 53

A form of dementia that may appear in middle age but is more frequent among the aged

Question 54

Dementia

Answer 54

Drastic failure of cognitive ability, including memory failure and disorientation

Question 55

What reduces the risk of alzheimer's disease?

Answer 55

remaining physically and mentally active

Question 56

What happens in the brain that correlates with alzheimer's?

Answer 56

-cortical atrophy (shrinkage) in the frontal, temporal, and parietal areas -reduction of metabolism in posterior parietal cortex and some portions of the temporal lobe -amyloid plaques appear in the cortex, hippocampus, and associated limbic system sites. Plaques are formed by the buildup of substance called beta-amyloid -Neurofibrillary tangles -lose of neurons in the basal forebrain, which make the transmitter acetylcholine (ACh)

Question 57

Amyloid Plaques

Answer 57

A small area of the brain that has abnormal cellular and chemical patterns

Question 58

Beta-amyloid

Answer 58

A protein that accumulates in amyloid plaques in Alzheimer's disease

Question 59

Neurofibrillary Tangles

Answer 59

An abnormal whorl of neurofilaments that from a tangled array inside the cell