Set #3 (Lecture 11 and Textbook PGs 128-149 Study Guide)

What does neurodevelopment describe?

Neurodevelopment describes the formation and continued development of the nervous system from early embryonic stages through later life.

Is brain development finished at birth?

No. Neurodevelopment continues through birth and after birth.

What do white areas on developmental brain MRI images represent?

Areas containing axons covered in myelin.

What do gray areas on developmental brain MRI images represent?

Gray areas represent areas containing neuronal cell bodies.

How much white matter is present at about 2 weeks of development?

Very little white matter is present at about 2 weeks.

How does white matter change by about 1 year of age?

White matter becomes much more abundant and becomes concentrated toward the inside of the brain.

Where is gray matter concentrated by about 1 year of age?

Gray matter containing cell bodies is concentrated more toward the outside of the brain.

How does the brain's white matter appear by about 2 years of age?

It is much more developed and complex, making the brain look more like an adult brain.

When does a large amount of myelination occur?

A large amount of myelination occurs during the first year of life.

What myelinated structure can be clearly seen around 329 days?

Myelinated fibers crossing through the corpus callosum can be clearly seen around 329 days.

What two types of sections can be used to view developmental brain images?

Developmental brain images can be viewed in horizontal and coronal sections.

How does gray matter change around birth?

Gray matter increases greatly around birth.

How does white matter change as the brain develops?

White matter steadily increases and is still increasing at age 20.

How can cortical thickness and surface area change during development?

Cortical thickness and surface area can plateau or decrease during development.

What does the long developmental course of white matter demonstrate?

The long developmental course of white matter demonstrates that neurodevelopment continues well beyond birth.

When does gastrulation occur?

Gastrulation occurs between days 13 and 19.

How do cells move during gastrulation?

Cells move toward the midline and then forward along the midline during gastrulation.

What three primitive cell layers are produced by gastrulation?

Gastrulation produces the endoderm, mesoderm, and ectoderm.

Which primitive cell layer gives rise to the nervous system?

The ectoderm, which is the outer primitive cell layer, gives rise to the nervous system.

What does the thickening ectoderm become?

The thickening ectoderm becomes the neural plate.

How does the neural groove form?

Uneven rates of cell division create the neural groove.

What does the neural groove become in the developing embryo?

The neural groove becomes the midline of the embryo.

What are neural ridges?

Neural ridges are ridges of ectoderm that bulge on both sides of the embryonic midline.

How does the neural tube form?

The tops of the neural ridges come together to form the neural tube.

What does the inside of the neural tube eventually form?

The inside of the neural tube forms the cerebral ventricles, central canal of the spinal cord, and connecting passages.

What three major brain subdivisions can be identified by about day 24?

The forebrain, midbrain, and hindbrain can be identified by about day 24.

Which structures are included within the developing forebrain?

The developing forebrain includes the telencephalon and diencephalon.

What five brain divisions develop from the early neural tube?

The myelencephalon, metencephalon, mesencephalon, diencephalon, and telencephalon develop from the early neural tube.

What is located inside the developing neural tube?

A fluid-filled space is located inside the developing neural tube.

What are radial glia?

Radial glia are developing glial cells that span the neural tube and provide tracks for migrating cells.

How do radial glia contribute to brain development?

Radial glia provide tracks that developing neurons can use to travel toward appropriate brain locations.

Which major brain region matures first?

The brainstem matures first.

In what general direction does brain maturation progress?

Brain maturation generally progresses from the brainstem toward higher brain areas.

Which brain structures develop synapses before higher brain structures?

Brainstem structures develop synapses before higher brain structures.

When do cerebral cortical areas develop relative to brainstem areas?

Cerebral cortical areas develop later than brainstem areas.

Why is early brainstem development important for survival?

The brainstem controls immediately essential functions such as breathing, heart rate, and swallowing.

Which brain regions generally develop first?

Lower and more posterior brain regions generally develop before higher brain regions.

Which functional systems come online first, motor systems or sensory systems?

Motor systems come online before sensory systems.

What survival example illustrates why motor systems develop before sensory systems?

The ability of prey to move away from danger illustrates the immediate survival value of early motor development.

What are projection neurons?

Projection neurons are relatively large neurons that connect different brain structures over long distances.

Why are projection neurons called projection neurons?

Projection neurons project axons from one brain region to another brain region.

What are interneurons?

Interneurons are relatively small neurons that make local connections within a brain structure.

What is another name for interneurons based on neuronal size?

Interneurons can also be called microneurons.

Which neurons develop first, projection neurons or interneurons?

Projection neurons develop before interneurons.

Why do projection neurons develop before interneurons?

Early projection-neuron development establishes long-distance communication and coordination between brain regions.

What develops after long-distance projection-neuron connections are established?

Local circuitry formed by interneurons develops after long-distance connections are established.

What are the four major developmental processes emphasized for building the brain?

The four processes are proliferation, migration, differentiation, and cell death through apoptosis.

What does neuronal proliferation mean?

Neuronal proliferation means producing large numbers of neurons.

About how many neurons are present in the human brain?

The human brain contains about 86 billion neurons.

What simplified number of neurons can be used to illustrate the scale of proliferation?

A simplified estimate of 10¹¹ neurons can illustrate the scale of neuronal proliferation.

About how many neurons per minute would need to be produced using the simplified gestational calculation?

Approximately 3.9 × 10⁵ neurons per minute would need to be produced.

Why does the simplified neuron-production calculation underestimate the developmental challenge?

The neural tube and other necessary structures must form before large-scale neuronal production and migration can occur.

Approximately how much gestational time is lost while early neural structures form?

Roughly one month is required to establish early neural structures before later neuronal production.

What is neurogenesis?

Neurogenesis is continued cell division that produces cells, many of which become neurons.

What shape do dividing cells take before cell division?

Dividing cells become squat and round before cell division.

What happens to dividing cells after cell division?

They extend (lengthen) again.

Can neurogenesis occur after birth?

Yes. New neurons can be formed throughout life.

When are the vast majority of neurons produced?

The vast majority of neurons are produced before birth.

What developmental processes follow neurogenesis?

Migration, differentiation, connectivity, and other developmental processes follow neurogenesis.

What is neuronal migration?

Neuronal migration is the movement of newly formed neurons toward permanent locations in the developing nervous system.

Where are many developing neurons initially produced?

Many developing neurons are produced near the inner fluid-filled portion of the neural tube.

Where are dividing neural cells concentrated in the neural tube?

Dividing neural cells are concentrated around the inner fluid-filled region of the neural tube.

What must newly formed neurons do after proliferation?

Newly formed neurons must migrate away from their birth locations toward permanent locations.

What can migrating neurons eventually form?

Migrating neurons can form groups of cells that develop into particular brain regions.

Is neuronal migration limited to movement directly outward from the neural tube?

No. Neurons can migrate in many directions and can follow complicated routes.

Can developing neurons migrate across the brain's midline?

Yes. Developing neurons can cross the midline and establish permanent locations on the opposite side.

What can developing neurons gain while traveling toward final destinations?

Developing neurons can gain experiences and information that influence later neuronal organization and function.

What can happen when migrating neurons meet near the midline?

Migrating neurons can exchange information that helps establish later communication partners.

What does complex neuronal migration demonstrate about the developmental journey?

The developmental journey can contribute to the final organization and connectivity of neurons.

What does cortical mean?

Cortical means relating to the cerebral cortex.

What does histogenesis mean?

Histogenesis means the formation or development of tissue and cells.

What is cortical histogenesis?

Cortical histogenesis is the developmental process that produces the cerebral cortex and the cerebral cortex's six-layer organization.

Do all cortical areas have identical layer characteristics?

No. Different cortical areas can have different thicknesses of particular cortical layers.

What cortical-layer differences can occur between Brodmann areas?

Some cortical areas can have a particularly thick layer 5, while other cortical areas can have a particularly thick layer 6.

What role do radial glia have in cortical histogenesis?

Radial glia extend outward and provide tracks that young neurons use to migrate toward their cortical locations.

Where do the earliest cortical neurons stop during cortical development?

The earliest cortical neurons stop in deeper cortical locations.

What route do later-born cortical neurons take relative to earlier-born neurons?

Later-born cortical neurons migrate past earlier-born neurons and stop in more superficial cortical locations.

Where are the oldest cortical cells located?

The oldest cortical cells are located deeper in the cortex, closer to the ventricles.

Where are the youngest cortical cells located?

The youngest cortical cells occupy more superficial cortical regions.

What does SVZ stand for?

SVZ stands for subventricular zone.

Where is the subventricular zone located?

The subventricular zone is located near the ventricular region.

What two factors help determine a cortical neuron's eventual location?

The timing of neuronal birth and the spatial conditions during migration help determine cortical location.

How does neuronal migration contribute to cortical column formation?

Migrating neurons interact with neurons in different layers and help create organized columns across the six cortical layers.

What must deeper cortical neurons do to transmit information out of the cortex?

Deeper cortical neurons send axons downward and out of the cerebral cortex.

How have superficial cortical neurons interacted with deeper cortical neurons during development?

Superficial cortical neurons passed and interacted with deeper cortical neurons during migration.

What is a cortical functional unit?

A cortical functional unit is an organized column of cells spanning cortical layers that coordinates information.

What can a cortical functional unit do with information?

A cortical functional unit can coordinate information within a column and send information to appropriate brain locations.

How can the cerebral cortex be conceptualized organizationally?

The cerebral cortex can be conceptualized as a series of column-like functional units.

Does greater cortical complexity require adding more than six cortical layers?

No. The cerebral cortex retains six layers.

How does the cerebral cortex increase complexity without adding cortical layers?

The cerebral cortex increases complexity by creating more functional units that can communicate with one another.

What anatomical features increase cortical surface area?

Gyri and sulci increase cortical surface area.

Why is increased cortical surface area important?

Increased cortical surface area creates more room for columns of cortical functional units.

What type of organization characterizes cortical function?

Cortical function has a modular organization based on many functional units.

What types of cues influence cortical proliferation and migration?

Spatial and temporal cues influence cortical proliferation and migration.

How can migrating cortical neurons influence one another?

Migrating cortical neurons can interact with or effectively tag other cells, helping define later brain organization.

What is neuronal differentiation?

Neuronal differentiation is the process through which a neuron becomes the specialized type of neuron required for a particular function.

What develops during neuronal differentiation?

Neurons develop their dendrites, cell-body shapes, and connections.

What structure usually begins growing first during neuronal differentiation?

The axon usually begins growing before the dendrites.

What structure is located at the growing end of a developing neuronal process?

A growth cone is located at the growing end of a developing neuronal process.

What does a growth cone help a developing axon accomplish?

A growth cone helps a developing axon find an appropriate destination.