Chapter 8 - Brain Development

Question 1

ontogenetic development

Answer 1

the development of the individual human from a sperms and egg cell. the development of the nervous system and behavior go hand in hand. after fertilization, the following distinction can be made:
- zygote: from conception
- embryo: from week 2
- fetus: from week 8-9
- baby: from birth

Question 2

congenital traits

Answer 2

consists of genetic traits plus prenatal and perinatal environmental influences. prenatal is before birth, perinatal is during birth and postnatal is after birth. congenital is not necessarily genetic.

Question 3

spina bifida

Answer 3

a birth defect caused by the neural tube not closing sufficiently, in which the spine and spinal cord are not formed properly. can be prevented by taking folic acid while pregnant

Question 4

15th day after fertilization

Answer 4

the emerging embryo resembles a fried egg: a structure formed by several sheets of cells with an elevated spot in the middle called the embryonic disk

Question 5

23rd day of fertilization

Answer 5

anterior neural folds close to form the brain. if it does not happen properly, it leads to anencephaly, which is a series of severe abnormalities in the brain that are fatal once the baby is born. the rest of the tube gradually develops into the spinal cord

Question 6

25th day of fertilization

Answer 6

forebrain, midbrain, and hindbrain are visible.

Question 7

7-9 months

Answer 7

the gyri and sulci are formed 7 months after conception. at 9 month, the brain has the overall shape of an adult brain, but its cells are different

Question 8

neural stem cells

Answer 8

neural stem cells in the neural tube have an extensive capacity for self-renewal. in adult humans, neural stem cells line the ventricles, forming the sub-ventricular zone

Question 9

functions of stem cells

Answer 9

in addition to self-renewal, neural stem cells have the function of giving rise to progenitor cells (pre-cursor cells), which can also divide. these cells produce neuroblast and glioblast cells, which cannot divide

Question 10

neurotrophic factors

Answer 10

chemicals that can turn on (express) certain genes that instruct the cell to develop in a specific way

Question 11

gene methylation

Answer 11

a chemical process that turns off specific genes

Question 12

summarized

Answer 12

• when a stem cell divides, it produces two stem cells: one dies and the other divides again (this is a cycle)
• stem cells develop into precursor cells, which can also divide
• progenitor cells produce non-dividing cells, neuroblasts and glioblasts
• neuroblasts develop into specialised neurons, and glioblasts develop into specilized glial cells

Question 13

7 stages of brain development

Answer 13

1. cell birth (neurogenesis)
2. cell migration
3. cell differentiation
4. neural maturation
5. synaptogenesis
6. apoptosis and synaptic pruning
7. myelination

Question 14

1. cell birth (neurogenesis)

Answer 14

this is the formation of nerve cells from stem cells that happen in the neural tube, up to about 25 weeks after conception. all neurons are produced except hippocampus, in which neurogenesis continues throughout lifetime.

Question 15

2. cell migration

Answer 15

from the neural tube, the cells travel to the right place, which goes from the inside to the outside. cells know where to go because of redial glial cells, which guide them from subventricular zone to the cortical surface

Question 15

3. cell differentiation

Answer 15

the brain relies on a general-purpose neuron that matures into a specific cell type in a specific location when exposed to local environmental chemicals. this happens when the cells reach their destination. then chemicals in the environment determine what type of specialised cell they should become by turning on certain genes

Question 16

4. neural maturation (from week 20)

Answer 16

neurons begin to develop by growing dendrites and then axons. dendrites grow, and axons look for targets on which to form a synapse. the development of dendrites starts with the creation of branches (dendritic aborization) and ends with the growth of dendritic spines.

Question 17

growth cones

Answer 17

tips of a growing axon

Question 18

filopodia

Answer 18

‘fingers’ that extend from growth cones, which are guided by signals from neurotropic chemicals

Question 19

autism spectrum disorder (ASD)

Answer 19

people who are on the autism spectrum disorder may have a broad range of symptoms that can be severe or mild, including impaired social interaction, a narrow range of interest, and poorly developed language and communication.

Question 20

5. synaptogenesis

Answer 20

formation of synapses. starts around 5 months after conception. after birth, synaptogenesis accelerates, creating many new synapses.

Question 21

6. apoptosis and synaptic pruning

Answer 21

first there is an overproduction of neurons, and then unnecessary cells die (apoptosis). the synapses on the remaining neurons are either included in a functional network and reach adulthood, or they are eliminated through synaptic pruning.

Question 22

apoptosis

Answer 22

pre-programmed cell death due to dependence on neurotrophic factors

Question 23

7. myelination

Answer 23

the formation of myelin around axons. increased connectivity in the default network is related to higher intelligence. this continues till adulthood. myelination is an index of cerebral maturation. white matter increases, gray matter decreases, but not in language areas, where it increases

Question 24

birth to 18-24 months (piagets stages of cognitive development)

Answer 24

stage 1: sensorimotor
experiencing the world through senses and actions
- object permanence
- stranger anxiety

Question 25

about 2-6 years (piagets stages of cognitive development)

Answer 25

stage 2: pre-operational
represents things with words and images but lacks logical reasoning
- pretend play
- egocentrism
- language development

Question 26

about 7-11 years (piagets stages of cognitive development)

Answer 26

stage 3: concrete operational
thinks logically about concrete events: grasps concrete analogies and performs arithmetical operations
- conversation
- mathematical transformations

Question 27

about 12+ years

Answer 27

stage 4: formal operational
reasons abstractly
- abstract logic
- potential for mature moral reasoning

Question 28

neural (cortical) plasticity

Answer 28

brain is a flexible organ, connections are not fixed

Question 29

role of the environment

Answer 29

an enriched environment leads to the formation of more synapses

Question 30

testosterone

Answer 30

testosterone is an androgen (male sex hormone), when it is present, it leads to a male; when it is not present, it leads to a female.

Question 31

estrogens

Answer 31

female sex hormones and involved in menstrual cycles and pregnancy

Question 32

chemoaffinity hypothesis

Answer 32

states that specific molecules in different cells in various midbrain regions give each cell a distinctive chemical identity