PSYC*2410 Chpater 9: Development of the Nervous System Flashcards
(173 cards)
1
Q
What are the three things that cells of the developing nervous system must do?
A
- Differentiate
- Travel and align themselves to form structures
- Establish appropriate functional relations with other cells
2
Q
What are the five stages of early neural development?
A
- Induction of the neural plate
- Neural proliferation
- Migration and aggregation
- Axon growth and synapse formation
- Neuron death and synapse rearrangement
3
Q
What are totipotent cells?
A
Cells that can develop into any type of body cell
4
Q
T or F: A fertilized egg is pluripotent.
A
False. It’s totipotent.
5
Q
What are pluripotent cells?
A
Cells that can develop into many, but not all, classes of body cells
6
Q
When do cells become pluripotent?
A
After the totipotent cells have divided
7
Q
What are multipotent cells?
A
Cells that can can only develop into different cells of one type
8
Q
What are unipotent cells?
A
Cells that can develop into only one type of cell
9
Q
Which type of cell has an almost unlimited capacity for self renewal and the ability to develop into many types of cells?
A
Stem cells
10
Q
Which three types of cells created during early development are considered embryonic stem cells?
A
- Totipotent
- Pluripotemt
- Multipotent
11
Q
What two properties of stem cells play a critical role in nervous system development?
A
- They have an almost unlimited capacity for self-renewal if maintained in an appropriate cell culture
- They have the ability to develop into many different kinds of cells
12
Q
What is the mechanism by which stem cells divide?
A
Asymmetric cell division
13
Q
What is asymmetric cell division?
A
Cell division that produces two daughter cells with different characteristics
14
Q
What are the two products of stem cell division?
A
- One daughter cell that remains a stem cell
- One daughter cell that develops into a more specific cell type
15
Q
When does the neural plate become recognizable?
A
Three weeks after conception
16
Q
What is the first major stage of neurodevelopment in all vertebrates?
A
The development of the neural plate
17
Q
What is the neural plate, and where is it located?
A
A small patch of ectodermal tissue on the dorsal surface of the vertebrate embryo
18
Q
What are the three layers of embryonic cells?
A
- The ectoderm
- The mesoderm
- The endoderm
19
Q
Which layer of embryonic cells releases the chemicals that induce the development of the neural plate?
A
The mesoderm layer
20
Q
What would happen if tissue was taken from the dorsal mesoderm of one embryo and implanted beneath the ventral ectoderm of another embryo?
A
It would induce the development of an extra neural plate on the ventral surface of the host
21
Q
What is the tube formed in vertebrate embryos that eventually develops into the central nervous system?
A
The neural tube
22
Q
What occurs to the neural plate before fusing to form the neural tube?
A
It folds to form the neural groove
23
Q
During which week of embryological development does the neural tube form?
A
The third or fourth week
24
Q
What does the inside of the neural tube eventually become?
A
The cerebral ventricles and spinal canal
25
About 40 days after conception, what is visible at the anterior end of the neural tube?
Three swellings
26
What is neural proliferation?
The rapid increase in the number of neurons following the formation of the neural tube
27
T or F: Proliferation occurs simultaneously and equally in all parts of the neural tube.
False
28
Where does most cell division in the neural tube occur?
The ventricular zone and subventricular zone
29
In terms of early neural development, what is the ventricle?
The fluid-filled centre of the neural tube
30
What is the ventricular zone?
The region adjacent to the ventricle in the developing neural tube
31
What is the subventricular zone?
The region adjacent to the ventricular zone
32
The pattern of proliferation is controlled in part by chemical signals from which two organizer areas in the neural tube?
- The floor plate
- The roof plate
33
Which organizer area in the neural tube runs along the midline of the ventral surface of the tube?
The floor plate
34
Which organizer area in the neural tube runs along the midline of the dorsal surface of the tube?
The roof plate
35
What are radial glial cells?
Cells that exist in the neural tube during the period of neural migration
36
The stem cells created in the developing neural tube are virtually always what type of cell?
Radial glial cells
37
Where do the cell bodies of radial glial cells lie?
In the ventricular or subventricular zones
38
Which type of cell migration occurs along radial glial cells?
Radial migration
39
What type of cell division do radial glial cells undergo?
Asymmetric cell division
40
T or F: During early neural development, cells only begin to migrate once they are fully mature.
False. During migration, cells are still immature and lack the processes of mature neurons
41
What are the two major factors that govern migration in the developing neural tube?
- Time
- Location
42
What are the two types of cell migration in the developing neural tube?
- Radial
- Tangential
43
In which type of migration do cells in the developing neural tube move from the ventricular zone in a straight line outward toward the outer wall of the tube?
Radial migration
44
In which type of migration do cells in the developing neural tube move in a direction parallel to the tube's walls?
Tangential migration
45
What are the two mechanisms for neural migration?
- Somal translocation
- Radial-glia-mediated migration
46
How do neural cells migrate via somal translocation?
An extension/process extends from the body of the undeveloped neuron and is guided by chemical signals and once a suitable environment is found, the cell body moves along the process
47
Which type of neural migration allows cells to migrate either radially or tangentially?
Somal translocation
48
How doe neural cells travel via radial-glia-mediated migration?
The undeveloped neurons use the processes extending from each radial-glia cell as a rope to pull themselves along
49
Which type of neural migration allows cells to only migrate radially?
Radial-glia-mediated migration
50
T or F: The patterns of proliferation and migration are different depending on the area of the developing cortex.
True
51
Which structure is situated just dorsal to the neural tube?
The neural crest
52
Where do the cells that form the neural crest come from?
They break off the neural tube as it's being formed
53
What do neural crest cells develop into?
The neurons and glial cells of the peripheral nervous system and other cell types in the body
54
What is aggregation?
The process in which neurons align during the development of the nervous system to form its structures
55
Aggregation is thought to be mediated by what three non-exclusive mechanisms?
- Cell-adhesion molecules
- Gap junctions
- Interactions between glial cells and neurons
56
What are cell-adhesion molecules?
Molecules on the surface of cells that are able to recognize and adhere to molecules on other cells
57
What are gap junctions?
Points of communication between adjacent cells
58
What are the narrow tubes that bridge gap junctions?
Connexions
59
What occurs after neurons have migrated to their appropriate positions and aggregated into neural structures?
Axons and dendrites begin to grow from them
60
What are the amoeba-like structures at the tip of each growing axon and dendrite that guide growth to the appropriate target?
Growth cones
61
T or F: Most growth cones reach their correct target.
True
62
What are the fingerlike cytoplasmic extensions that extend and retract from growth cones?
Filopodia
63
What are retinal ganglion cells?
Retinal neurons whose axons leave the eyeball and form the optic nerve
64
What is the main destination of retinal ganglion cells in non-mammalian vertebrates?
The optic tectum
65
What is the mammalian equivalent of the optic tectum?
The superior colliculus
66
In Roger Sperry's study, what evidence supported the conclusion that, after the optic nerves were cut and the eyeballs rotated, each retinal ganglion cell grew back to the same point of the optic tectum where it was originally connected ?
Frogs whose eyes had been rotated, but whose optic nerves had not been cut, responded the same as the frogs whose eyes were rotated after their optic nerves were cut
67
What is the chemoaffintiy hypothesis of axonal development?
The hypothesis that each postsynaptic surface in the nervous system releases a specific chemical label that attracts the growing axons to their correct targets
68
What does the chemoaffinity hypothesis fail to account for?
The discovery that some growing axons follow the same circuitous route to reach their target rather than growing directly to it
69
What is different about the revised version of the chemoaffinity hypothesis?
Growth cones are influenced by a series of chemical and physical signals along the route, rather than just being drawn in by a single attractant
70
What are pioneer growth cones?
The first growth cones to travel along a particular route in the developing nervous system
71
How are pioneer growth cones believed to follow the correct trail?
By interacting with guidance molecules along the route
72
What is fasciculation?
The tendency of developing axons to grow along the paths established by preceding axons
73
Which hypothesis was proposed as an explanation for accurate axonal growth, involving topographic mapping in the developing brain rather than by point-by-point chemoaffinity?
The topographic gradient hypothesis
74
What is a topographic map?
The ordered projection of a sensory surface or effector system to one or more structures of the CNS
75
What is the key point of the topographic gradient hypothesis?
Growing axons are guided to their destination by two intersecting signal gradients
76
What are the two intersecting signal gradients that guide growing axons to their destination?
- The anterior-posterior gradient
- The medial-lateral gradient
77
When half the retina is destroyed and the optic nerve is cut, how are the retinal ganglion cells from the remaining half of the retina projected when they grow back?
Systematically over the entire optic tectum
78
When half the optic tectum is destroyed and the optic nerve is cut, how are the retinal ganglion cells from the remaining retina projected when they grow back?
Systematically over the remaining half of the optic tectum
79
What is synaptogenesis?
The formation of new synapses
80
T or F: Spontaneous neurotransmitter release is harmful for synapse formation?
False, it's important
81
T or F: Cell surfaces have shown to interact prior to synapse formation.
True
82
Synaptogenesis depends on the presence of what type of cell?
Glial cells
83
What do early theories suggest as the reason for why astrocytes promote synaptogenesis?
Astrocytes supply the cholesterol needed during synapse formation
84
What is current research on synaptogenesis focused on?
Determining chemical signals that must be exchanged between presynaptic and postsynaptic neurons for a synapse to be created
85
What is a complication faced when studying synaptogenesis?
The promiscuity displayed by developing neurons
86
What is meant when describing developing neurons as promiscuous?
Any type of neuron will form synapses with other types of neurons, then when it doesn't function appropriately, it is eliminated
87
T or F: About 50% more neurons than needed are produced.
True
88
T or F: Large-scale neuron death only occurs in the prefrontal cortex during adolescence.
False, waves of large-scale neuron death occur in various parts of the brain throughout development
89
What is necrosis?
Passive cell death
90
What is active cell death called?
Apoptosis
91
Is cell death during development typically active or passive?
Active
92
T or F: Apoptosis is safer than necrosis.
True
93
T or F: Some developing neurons appear to be genetically programmed for an early death.
True
94
What two observations indicate that some developing neurons seem to die because they fail to obtain life-preserving chemicals from their targets?
- Grafting an extra target structure (ex. An extra limb) to an embryo before synaptogenesis reduces the death of neurons growing into that area
- Destroying some of the neurons growing into an area before cell death increases the survival rate of remaining neurons
95
What is the most prominent class of chemical supplied to developing neurons by their targets that promote their survival?
Neurotrophins
96
What were the first two neurotrophins discovered?
- Nerve growth factor (NGF)
- Brain-derived neurotrophic factor (BDNF)
97
What are three things that neurotrphins do?
- Promote the growth and survival of neurons
- Function as axon guidance molecules
- Stimulate synaptogenesis
98
T or F: Cell death results in a massive rearrangement of synaptic connections.
True
99
During the period of cell death, which neurons are particularly likely to die?
Neurons that have established incorrect connections
100
As neurons die, what fills the space they leave vacant on postsynaptic membranes?
The sprouting axon terminals of surviving neurons
101
T or F: Microglia play a role in synapse rearrangement.
True
102
During the synapse rearrangement, the output of each neuron is focused on a smaller of postsynaptic cells. This leads to what?
An increase in the selectivity of transmission
103
What part of the human brain to reaches full maturity last?
The prefrontal cortex
104
What is the prenatal period?
The period of development before birth
105
What is the postnatal period?
The period of development after birth
106
What are three major technical advances that have allowed the examination of prenatal human neural tissue?
- The development of three-dimensional brain organoids in culture
- The ability to image the brains of prenatal humans
- The characterization of cell-level transcriptomes
107
What is functional connectivity?
The correlated activity between different brain regions over time
108
What is a transcriptome?
A catalogue of all proteins transcribed in a particular cell
109
How much does the human brain change in volume between birth and adulthood?
It doubles
110
T or F: The size increase in the human between birth and adulthood is caused by the development of additional neurons.
False
111
What are the three kinds of growth that cause an increase in postnatal brain size?
- Synaptogenesis
- Axon myelination
- Increased branching of dendrites
112
T or F: Synaptogenesis occurs at the same rate across cortical regions.
False
113
When do the primary visual and auditory cortices achieve maximum synapse density?
The seventh or eighth postnatal month
114
When is maximum synapse density in the prefrontal cortex reached?
During the second postnatal year
115
What does myelination of various brain areas roughly parallel?
The function development of those areas
116
An increase in the speed of axonal conduction is the result of what?
Myelination
116
Myelination of ________ areas occurs in the first few months after birth, followed shortly thereafter by myelination of ________ areas.
Sensory, Motor
117
T or F: Myelination of the prefrontal cortex stops around age 13.
False, myelination of the prefrontal cortex continues into adulthood
118
T or F: Myelination is an ongoing process that changes with experience throughout one's lifespan.
True
119
T or F: In general, the pattern of dendritic branching in the cortex duplicates the inside-out pattern of neural migration.
True
120
T or F: Dendritic spines can change their shapes in response to experience and current environment very quickly.
True
121
What occurs once maximum synaptic density and gray matter volume have been achieved?
There are periods of decline
122
In what order does cortical thinning typically occur in the brain areas?
- First occurs in the primary sensory and motor areas
- Progresses to secondary areas
- Culminates in association areas
123
Are adult levels of gray matter more or less than infant levels?
Less than infant levels
124
What is a proteome?
A catalogue of the proteins in different cell types
125
The development of which brain area develops over the same as human cognitive development?
The prefrontal cortex
126
What are the four cognitive functions linked to the prefrontal cortex?
- Working memory
- Planning and carrying out sequences of actions
- Inhibiting inappropriate responses
- Following rules for social behaviour
127
What is perseveration?
The tendency to continue making a formerly correct response that is currently incorrect
128
During which age range do children tend to make perseveration errors?
7-12 months
129
What causes perseveration errors?
A lag in prefrontal cortex development
130
When does the number of synapses in the prefrontal cortex reach its maximum?
The second postnatal year
131
What is an important feature of the effects of experience on development?
They are time-dependent
132
What is the difference between a critical period and a sensitive period?
- Critical period: A period during development in which an experience must occur to influence subsequent development
- Sensitive period: A period during development in which an experience will have a greater effect on development, but that same experience will still have an effect if it occurs outside the interval
133
Early research on the effects of experience on brain development focused on which two general manipulations of experience?
- Sensory deprivation
- Sensory enrichment
134
What were the consequences of rearing rats in the dark from birth?
They had fewer synapses and dendritic spines in their primary visual cortex and as adults had deficits in depth and pattern vision
135
What happened when human babies with cataracts in both eyes had it removed between 1 and 6 weeks after birth?
Some aspects of vision quickly improved, but some visual deficits persisted into adulthood
136
T or F: Rats raised in enriched environments had a thicker cortex, and more dendritic spines and axons per neuron than rats alone in empty cages.
True
137
What happens to ocular dominance columns if one eye is blindfolded for just a few days during the first few months of life?
The width of the columns from the deprived eye decreased and the width of the columns in the non-deprived eye increased
138
Are the effects of monocular deprivation on ocular dominance columns an example of critical periods or sensitive periods?
Sensitive periods
139
In general, what is the result of attaching the inputs of one sensory system to cortex that would normally develop into another system?
The cortex would develop many characteristics typical of the newly attached system
140
T or F: Early music training expands the area of the auditory cortex that responds to complex musical tones.
True
141
What is neurogenesis?
The growth of new neurons
142
T or F: Neurogenesis does not occur in adults.
False
143
In most nonhuman adult mammals, substantial neurogenesis seems to be restricted to which two areas?
- The subventricular zone
- The hippocampus
144
T or F: In human adults, neurogenesis has been observed in the striatum and hippocampus, but not the subventricular zone.
True
145
Prior to the early 1980s, what was believed to happen to neurons after early brain development?
After early brain development, neurons continually die throughout life, and once lost, are never replaced
146
Where are new neurons continually generated?
The subventricular zone
147
What two things may reduce or delay memory problems?
- Enriching one's environment
- Engaging in regular exercise
148
What did Freund et al., find had an even greater influence on adult hippocampal neurogenesis than physical activity?
Exploration
149
What do adult-generated olfactory bulb and striatal neurons become?
Internerons
150
Most research on the function of adult-generated neurons has focused on which brain region?
The hippocampus
151
Adult hippocampal neurogenesis is said to be important in what four psychological and cognitive capacities?
- Memory functioning and forgetting
- Pattern separation
- Mood and anxiety regulation
- The flexibility to adapt to complex environments
152
T or F: Experience in adulthood can lead to reorganization of sensory and motor cortical maps.
True
153
Adult musicians who play string instruments with their left hand have an enlarged hand-representation in which cortex?
The right somatosensory cortex
154
What is the most prevalent neurodevelopmental disorder?
Autism spectrum disorder (ASD)
155
T or F: ASD is almost always apparent before the age of 3 and typically does not increase in severity after that.
True
156
What are the two core symptoms of ASD?
- Reduced capacity for social interaction and communication
- Restricted and repetitive patterns of behaviour, interests, or activities
157
What are savants?
Individuals with developmental disabilities who display amazing and specific cognitive or artistic abilities
158
Savant-like abilities can emerge in otherwise healthy individuals following damage or transient inactivation to which brain area?
The left anterior temporal lobe
159
What seems to be the best predictor of ASD?
Transcription-related errors in the brain cells
160
Did the fusiform face area of adolescents with ASD display more or less activation than typical in response to faces?
Less
161
How did fusiform face area activation differ between adolescents with ASD and adults with ASD in response to faces?
Adults did not show lower activation than typical, but adolescence did
162
Some evidence suggests that decreased synaptic pruning by glial cells during development, which in turn leads to larger than typical cerebral volumes during the first year of life, is implicated in which neurodevelopmental disorder?
Autism spectrum disorder
163
Which neurodevelopmental disorder is characterized by intellectual disability, but preserved language and social skills?
Williams syndrome
164
What are three cognitive strengths in individuals with Williams syndrome?
- Remarkable language skills considering their low IQs
- They are often musically gifted
- Near-typical ability to recognize faces
165
What are four cognitive deficits in individuals with Williams syndrome?
- Severe attentional problems
- Poor spatial abilities
- Poor space-related speech
- Unable to draw objects
166
What is something that people with Williams syndrome show an excessive interest in?
Human faces
167
T or F: Those with Williams syndrome have difficulty perceiving negative facial emotions.
True
168
What do several of the health problems associated with Williams syndrome involve?
The heart
169
95% of individuals with Williams syndrome are missing the gene involved in elastin production on one of the two copies of which chromosome?
Chromosome 7
170
T or F: Williams syndrome is associated with a general thinning of the cortex and underlying white matter.
True
171
Individuals with Williams syndrome show the greatest cortical thinning in which two areas?
- The boundary of the parietal and occipital lobes
- The orbitofrontal cortex
172
Where do individuals with Williams syndrome often have a thicker cortex?
The superior temporal gyrus
