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NESC 3670: Genes, Brain & Behaviour > Lec 8: Brain Development (The Early Years) > Flashcards

Lec 8: Brain Development (The Early Years) Flashcards

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1
Q

what were the consequences of the atomic bomb (Hiroshima)?

A

cranium size of children were smaller as a consequence of this bomb (because of radiation)

  • inc in amount of seizures
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2
Q

brains are shaped by the interaction between ____ and _____

A

genetics & experience

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3
Q

3 types of development that are highly interrelated?

A

social
emotional
cognitive

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4
Q

is brain architecture and skills built in top-down or bottom-up sequence?

A

bottom-up

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5
Q

brain plasticity and ability to change behaviour INC/DEC over time?

A

decrease

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6
Q

what are the 3 core concepts of development?

A

1) brain architecture is established early in life and supports lifelong learning, behaviour and health
2) stable, caring relationships and “serve and return” interaction shape brain architecture
3) toxic stress in the early years of life can derail healthy development

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7
Q

what is the timespan for development of the CNS??

A

3 weeks –> 20 years

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8
Q

at what week gestation does the CNS begin to form?

A

3 weeks gestation

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9
Q

what is the first neural element that begins to develop in the ‘early beginnings’?

A

the neural tube

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10
Q

compare the weight of the brain at birth VS 1 year

A

birth= 350g

1 year= 1000g

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11
Q

4 steps/processes in the growth and development of neurons

A
  • proliferation (production of new cells)
  • migration (move towards final destination)
  • differentiation (form axons and dendrites)
  • myelination (addition of insulating sheath)

–> inc in methylation

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12
Q

name the 4 stages of development

A

prenatal
infancy
childhood
adolescence

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13
Q

when is the prenatal phase?? what occurs during this phase?

A

conception–> birth

  • rapid physical growth
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14
Q

what is the infancy stage?? what occurs during this phase?

A

birth –> 2 years

  • motor development
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15
Q

what is the childhood stage?? what occurs during this phase?

A

2-12 years

  • abstract reasoning
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16
Q

what is the adolescence stage?? what occurs during this phase?

A

13-25 years

  • identity creation
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17
Q

what is the main ‘highlight’ after the adolescence stage?

A

development of ‘judgement’

  • risk taking behaviour is high in 20-25 year olds
  • directly related to the maturation of the Prefrontal Cortex
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18
Q

what is Piaget’s Object Permanence task?

A
  • infant sees toy, investigator places barrier in front of toy
  • infants younger than 9mo fail to reach for hidden toy
  • up to 4 years old, do not remember anything, no good connection between prefrontal cortex and hippocampus
  • tasks that require a response to a stimulus that is no longer present depend on the prefrontal cortex (slow to mature)
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19
Q

what occurs during the prenatal phase of development?

A
  • ovum + sperm = zygote
  • once zygote implants in uterus= embryo (composed of germinal layers of cells from which various organs derive later)
  • weak 8 –> birth = fetus
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20
Q

prenatal brain development is primarily ____

A

structural

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21
Q

when does cell creation and movement occur in prenatal development?

A

during first 5 months

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22
Q

what are the 5 phases of brain development?

A

1) neural plate induction
2) neural proliferation
3) migration and aggregation
4) axon growth & synapse formation
5) cell death and synapse rearrangement

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23
Q

embryonic stage of development includes the process of ____

A

organogenesis

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24
Q

what is organogenesis?

A

transformation from embryo to a body structure including defined organs

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25
Q

what forms on day 16 (gestation), and what is its function?

A

primitive streak

  • provides axis which other structures can organize
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26
Q

what is formed on day 21?

A

neural groove

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27
Q

name the 3 germinal layers of the embryo

A

ectoderm
mesoderm
endoderm

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28
Q

the process of ____ in embryos forms the NS and vertebral column

A

neurulation

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29
Q

the process of neurulation in embryos generates a dorsal rod shaped structures termed a _____

A

notochord

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30
Q

the notochord is generated from what structure?

A

primitive streak

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31
Q

the notochord serves as a ______ ____, which is later replaced by the ___ _____

A

serves as a primitive skeleton

later replaced by the vertebral column

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32
Q

the NS develops from the _____ (layer) which is located above/below the notochord?

A

ectoderm

above the notochord

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33
Q

explain the basic steps of neurulation

A
  • neural folds form from neural plate
  • folds fuse
  • neural tube forms
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34
Q

NS development proceeds from the generation of the neural ___ to neural ____, which eventually develop into the neural ____

A

neural plate

neural folds

neural tube

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35
Q

___ days after conception the embryo begins to implant in the uterine wall
(induction of neural plate)

A

18 days

  • this becomes the patch of tissues on the dorsal surface of the embryo that will become the NS
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36
Q

thickening of the ____ germ layer leads to the development of the neural_____

A

ectoderm

neural plate

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37
Q

when does the neural groove begin to develop?

A

20 days

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38
Q

during the induction of the neural plate, what occurs at 22 days?

A

neural groove closes along the length of the embryo making the neural tube

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39
Q

during the induction of the neural plate, what occurs a few days after day 22 and neural tube production?

A

brain subdivides into the:

  • forebrain
  • midbrain
  • hindbrain
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40
Q

what structure(s) are included in the forebrain

A

telencephalon

diencephalon

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41
Q

what structure(s) are included in the midbrain?

A

mesencephalon

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42
Q

what structure(s) are included in the hindbrain?

A

rhomencephalon

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43
Q

what does proliferation mean?

A

generation of new cells

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44
Q

____ cels are the stem cells of the NS

A

neuroepithelial cells

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45
Q

what occurs during the 2nd step of brain developmentL neural proliferation

A

neuroepithelial cells of the ectoderm proliferate

  • 3 swellings at the anterior end in humans become forebrain, midbrain, hindbrain
  • after mitosis, “daughter” cells become “fixed” post mitotic
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46
Q

where does mitosis/proliferation occur????

A

ventricular zone

  • rate can be 250 000/min
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47
Q

what occurs during the 3rd phase of brain development: migration

A

slow movement to the right place

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48
Q

describe the characteristics of migrating neurons

A
  • immature
  • lacking dendrites
  • only a soma and immature axon
  • undifferentiated at start of migration
49
Q

differentiation begins as ……

A

neurons migrate

  • they develop NT making ability and AP (as they migrate)
50
Q

(migration) neuroepithelial cells of the ventricular zone give rise to ___ ____cells that further differentiated into ____ or ____ cells

A

radial glial cells

neurons or glial cells (e.g. astrocytes)

51
Q

function of radial glial cells?

A

act as guide wires for migration of neurons

  • scaffolding structures
52
Q

what is the process of aggregation (following migration)

A

cells that are done migrating align themselves with other cells and form structures

  • later neuroepithelial cells= present at top
  • earlier neuroepithelial cells= at the bottom
  • brain develops inside-out
53
Q

describe the relationship between methylation in the cell and dietary methionine

A

inc methylation in the cell from dietary methionine

  • high methionine and high choline in diet of pregnant women= to continue methylation
  • low methylation= spina bifida & cleft lips
54
Q

closure of the neural tube and action of neural crest cells from neural folds is dependent on….

A

methylation machinery

55
Q

brain regions (forebrain, midbrain, hindbrain) further divide and contain

A

fluid filled region= ventricle, aqueduct or canal

56
Q

where do the 2 major bends/flexures occur?

A

midbrain and cervical

57
Q

name the 3 primary brain vesicles

A

prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

58
Q

name the 5 secondary brain vesicles & which primary vesicles they are derived from

A

prosencephalon

1) telencephalon
2) diencephalon

mesencephalon
3) mesencephalon

rhombencephalon

4) metencephalon
5) myelencephalon

59
Q

which adult brain structures & ventricles are derived from the secondary brain vesicles?

A

1) telencephalon: cerebrum/cerebral hemispheres (cortex, white matter, basal nuclei)
- lateral ventricles

2) diencephalon: diencephalon (thalamus, hypothalamus, epithalamus)
- third ventricle

3) mesencephalon: brainstem- midbrain
- cerebral aqueduct

4) metencephalon: brainstem-
pons
- 4th ventricle

5) myelencephalon: braintem-
medulla oblongata
- 4th ventricle

60
Q

what are gyri?

A

elevated ridges

entire surface

(BUMPS)

61
Q

what are sulci?

A

groove separating gyri

shallow groove

62
Q

what are fissures?

A

deeper grooves

63
Q

describe how the cerebral hemispheres are forced to grow

A

due to space restrictions, grow posteriorly over rest of brain, envelop it

  • grow into horseshoe shape
  • continued growth causes creases, folds, wrinkles
64
Q

what is grey matter?

A

neuronal cell bodies
- brown when fixed

  • dendrites and axon terminals of neurons
  • where all synapses are
65
Q

what is white matter?

A

neuronal axons coated with electrical insulation= myelin

connecting different parts of grey matter to each other

66
Q

what occurs during the 4th stage of brain development: axon growth/synaptogenesis?

A
  • once migration is complete and structures have formed (aggregation), axons/dendrites begin to grow to their “mature” size/shape
  • axons (with growth cones on end) and dendrites form a synapse with other neurons/tissue
  • growth cones and chemo-attractants are critical for this (e.g. NCF)
67
Q

name the 2 types of cells in CNS

A

neurons

glial cells (~10:1)

68
Q

the formation of new synapses is called???

A

synaptogenesis

69
Q

most neurons are formed halfway through gestation and have no synaptic connections, what forms these synaptic connections?

A

experience and interaction with environment

70
Q

during what time frame does synaptogenesis occur?

A

through to the 2nd year of life

71
Q

what % of dendritic growth occurs after birth?

A

83%

72
Q

what is a synaptic cleft?

A

space between neurons at nerve synapse across which a nerve impulse is transmitted by a NT

73
Q

what are dendrites?

A

receive messages from other cells

74
Q

what are axons terminals?

A

passes on messages to other cells

75
Q

what is a Node of Ranvier?

A

separate Schwann cells (glial) which are formed around axon to form axon sheath

76
Q

after birth, development is ….

A

refinement of neuronal connections

maturity of neurons

increasing complexity of dendrite interconnections

77
Q

what % of neurons made will die after migration??

A

40-75%

  • death is normal and necessary, important to strengthen connections
78
Q

why do neurons typically die?

A

due to failure to compete for chemicals provided by targets

79
Q

what are neurotrophins?

A

family of proteins (e.g. NGF, BDNF)

80
Q

3 functions of neurotrophins

A
  • promote growth/survival
  • guide axons
  • stimulate synaptogenesis
81
Q

axons not exposed to neurotrophins after making connections undergo ___

A

apoptosis

  • preprogrammed mechanism of cell death
82
Q

describe ‘use it or lose it’ (neural darwinism)

A
  • neurons and synapses must get hooked together properly to develop specific skills and abilities in humans
  • during infancy and early childhood, developing cortex overproduces synapses (2X as needed)
  • overproduction leads to competition for survival of fittest synapses (competition for neurotrophin, NGF)
  • after maturity, apoptoci mechanisms become dormant
  • neurons no longer need neurotrophins for survival
  • neurotrophins inc the branching on axons and dendrites throughout life
83
Q

when does synaptogenesis and pruning occur?

A
  • in cortex, synapses begin to form after neuronal migration (23 weeks prenatal)
  • most synapses form after birth (form randomly)
  • flourish, and selectively prune by levels of NT (up to 100 000 synapses pruned per second)
84
Q

what are the 2 types of synapse development?

A

1) experience-expectant development

2) experience-dependent development

85
Q

what is experience-expectant development?

A
  • overproduces synapses, prune with experience
  • ‘experiences leads to LESS’
  • tied to critical/sensitive periods
  • organizes brain to process info, behaviours EXPECTED for humans (sensory processes, parental attachment, eye-hand coordination, language capacity)
86
Q

pruning leads to more/less cells?

A

LESS

87
Q

what is experience-dependent development?

A
  • new synapses formed, maybe some pruning
  • ‘experience leads to MORE’
  • continues throughout life
  • codes experiences/learning that is person-specific (particular language, specific knowledge, memories, skills)
88
Q

result of enriched housing in INFANT rats

A
  • enrichment REDUCED synapse density
  • facilitated pruning of excess synapses in experience-expectant development

prune > gain
(synaptic gain is less, when dec synapse density)

89
Q

result of enriched housing in ADULT rats

A
  • enrichment INCREASED synapse density
  • facilitate growth of new synapses in experience-dependent development

Gain > prune
(more gain of synapse density, compared to loss of pruning)

90
Q

experience influences pruning and growth of new synapses in ____ ___ manner

A

age dependent ***

  • has to do with # of structures formed (e.g. in regions of cortex)
91
Q

what occurs during synapse rearrangement?

A
  • release and uptake of neurotrophic factors
  • neurons receiving insufficient neurotrophic factor die
  • axonal processes compete for limited neurotrophic factor
92
Q

what are active synapses?

A

receive enough neurotrophic factor to remain stable

93
Q

what are inactive synapses?

A

receive too little neurotrophic factor to remain stable

94
Q

what is the process of myelination?

A
  • glial cells (formed by oligodendrocytes in CNS and Schwann cells in PNS) wrap themselves around axons
  • inc speed of AP conduction down axon
95
Q

when does myelination occur?

A
  • begin at birth
  • rapidly inc to 2 years
  • continue to inc slowly to 30 years old
96
Q

glial cells in CNS are formed by

A

oligodendrocytes

97
Q

glial cells in PNS are formed by

A

schwann cells

98
Q

what is the function of myelin?

A
  • in adults, dendritic growht and synapse refinement are coated with myelin
  • serves as an electrical insulation
99
Q

myelination slows/speeds the travel of impulses and makes travel more/less efficient?

A

speeds up

more efficient

100
Q

correlation between myelination and breastfeeding?

A
  • myelin composed of 15% cholesterol, 20% protein

- myelin content and speeds of electrical signals INC with breasfeeding

101
Q

SUMMARY: name the 8 phases of embryonic and fetal development at a cellular level **

A

1) mitosis/proliferation
2) migration
3) differentiation
4) aggregation
5) synaptogenesis
6) neuron death
7) synapse re-arrangement
8) myelination

102
Q

postnatal growth is a consequence of … (3)

A

1) synaptogenesis
2) inc dendritic branches
3) myelination (prefrontal cortex continues into adolescence)

103
Q

overproduction of synapses may underlie the greater ____ of the young brain

A

plasticity

  • young brain more able to recover function after injury, as compared to older brain
104
Q

name the 3 structures that compose the forebrain

A
  • cerebrum (cortex)
  • thalamus
  • hypothalamus
    (part of limbic system)
105
Q

name the 2 structures that compose the midbrain

A

tectum & tegmentum

106
Q

name the 3 main structures that compose the hind brain

A
  • cerebellum
  • pons
  • medulla
107
Q

what structures are referred to as the brainstem?

A

midbrain, pons, medulla

108
Q

the frontal lobe is responsible for

A
  • self-regulation
  • problem solving
  • goal setting
  • social cognition
  • judgement, decisions, planning, creativity
109
Q

occipital lobe is responsible for

A

vision and perception

  • processes visual input that is sent to the brain from retinas
110
Q

the parietal lobe is responsible for

A

sensory motor perception

spatial abilities

  • main sensory inputs from skin (touch, temp, pain receptors) relay through thalamus to parietal lobe
111
Q

the temporal lobe is responsible for

A

hearing
language
memory
social-emotional function

112
Q

brainstem is important for which 4 basic functions?

A
  • HR
  • breathing
  • sleeping
  • eating

(“survival”)

113
Q

limbic system is responsible for….

A

emotion

114
Q

cerebellum is responsible for…

A

movement

115
Q

what are the frontal lobes executive functions?

A 
governing emotions
judgement
planning 
organizing 
problem solving 
impulse inhibition 
abstraction 
analysis/synthesis
self-awareness
self-concept 
identity
spirituality
116
Q

maturation occurs from ___ to ___ of the brain

A

back to front

117
Q

early development of back of brain and later development of front of brain leads to… (in adolescents)

A
  • preference for physical activity
  • less than optimal planning and judgement
  • more risky, impulsive behaviours
  • minimal consideration of negative consequences
118
Q

describe frontal lobe development

A
  • very sensitive to early experience
  • long process beginning prenatally, continue until early adulthood
  • altered by range of positive and negative experiences (e.g. parent-infant interactions, drugs, stress)
119
Q

describe neuroplasticity in adults

  • where is neurogenesis?
A
  • mature brain changes and adapts

- neurogenesis (birth of new neurons) seen only in olfactory bulb and hippocampus of adult mammals

NESC 3670: Genes, Brain & Behaviour (12 decks)

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