Lecture 2 - BS3580

What is corticogenesis?

The cellular process of brain development involving the formation and migration of neurons.

What is the primary function of the cerebral cortex?

Involved in processing and cognition, including motor areas, sensory areas, and emotional behavior.

What are radial glial cells?

Cells in the ventricular zone that remain attached to both apical and basal surfaces and guide migrating neurons.

What term describes the process of neuron formation in the brain during development?

Neurogenesis.

How do axonal growth cones navigate to their target cells?

By responding to guidance cues in their environment, using filopodia to search for attractive signals.

What is synaptogenesis?

The formation of synapses between neurons.

What happens to neurons that do not receive neurotrophic factors?

They undergo apoptosis (programmed cell death).

Describe the 'inside-out' pattern of corticogenesis.

Neurons born in the deeper layers of the cortex migrate to form more superficial (outer) layers.

What are the two mechanisms of cell movement in corticogenesis?

Somal translocation and radial-glia directed locomotion.

What cell types does the neuroepithelium generate during brain development?

Neurons, glial cells, and other neural stem cells.

What are the stages of brain development as listed in the lecture?

1. Cell birth, 2. Cell migration, 3. Cell differentiation, 4. Cell maturation, 5. Synaptogenesis, 6. Cell death and pruning, 7. Myelogenesis.

What role do neurotrophic factors play in neuronal survival?

They support neuron survival; without them, neurons may die through apoptosis.

What visualizes the dynamic changes in brain structure as it develops?

The different gestational age stages, highlighting the morphology of the brain.

What is the role of diffusible chemotropic cues in neuronal migration?

They guide migrating neurons by attracting or repelling them.

Describe the role of growth cones in axonal growth.

Growth cones extend processes to navigate and find the correct path for axon extension.

Timeline for brain development

3 weeks: Initial formation of the spinal cord and midbrain, establishing foundational structures for nervous system development.

7 weeks: Development of hindbrain, midbrain, and forebrain structures, setting the stage for differentiated brain functions.

11 weeks: Major brain structures become visible, indicating progression toward functional maturity.

At birth: Established morphology is achieved through folding and growth processes, leading to the complex architecture of the human brain.

Cerebrum

Cerebrum: Largest component of the brain, involved in higher-order functions including thought, action, and emotion.

Basal ganglia

Basal ganglia: Plays a key role in movement regulation and coordination.

Diencephalon

Diencephalon: Integrates sensory information and regulates autonomic functions.

Midbrain

Associated with vision, hearing, motor control, and alertness.

Cerebellum

Essential for coordination, precision, and accurate timing of movements.

Brainstem

Brainstem: Maintains basic life functions such as respiration and heart rate.

Spinal cord

Spinal cord: Acts as the main pathway for transmitting information between the brain and body.

Cerebral cortex components and functions

Gray matter: Responsible for processing information, cognition, emotional behavior, and memory through complex networks of neurons.

White matter: Facilitates signal transmission between different areas of gray matter, consisting of myelinated axons that improve the speed of communication.

What are the stages of brain development?

Neurogenesis: The birth of neurons and glial cells; crucial for forming the foundational cellular architecture.

Cell Migration: Cells migrate to designated areas, guided by molecular signals, to establish their functional locations.

Cell Differentiation: Non-specific progenitor cells become specialized neuron types based on intrinsic and extrinsic factors.

Cell Maturation: Development of dendrites and axons, critical for establishing synaptic connections.

Synaptogenesis: Formation of synapses, where neurons connect and communicate, influencing network properties.

Cell Death and Synaptic Pruning: Regulated elimination of surplus neurons and synapses, optimizing connectivity for efficient processing.

Myelogenesis: Formation of myelin sheaths around axons, enhancing signal conducting speed and improving neural communication.

How does adult neurogenesis occur? Includes two key areas.

Involves the formation of mature neurons from neural stem cells within restricted brain regions, critical for restructuring neural circuits.

Key areas include:

Subgranular zone of the hippocampus: Integral for memory formation and navigation.

          Subventricular zone (SVZ): Sends migrating cells to olfactory bulbs, essential for repair and regeneration within the nervous system.

What are two key mechanisms in cortical development?

Cellular Changes: Neuroepithelium, originating from the ventricular zone (VZ), transforms, migrates, and differentiates to build the cerebral cortex's layered structure.

Radial Glial Cells: Serve as scaffolding for migrating neuroblasts and help maintain their orientation by forming attachments to both apical and basal surfaces of the developing cortex.

Describe the key parts of the process of axon migration and pathfinding

Neurons are polarized, exhibiting a single axon along with multiple dendrites for effective communication.

Growth Cones: Specialized structures at the axon tip that extend outwards; filopodia within growth cones dynamically explore the environment for guidance cues.

Directional Growth: Driven by actin polymerization, growth cones respond to extracellular signals that influence attraction or repulsion to guide axon trajectory toward target regions.

Cellular Mechanisms: Local RNA and protein synthesis within growth cones governs growth direction, enabling fine-tuned responses to environmental cues.

Synapse Formation: Initiated when axonal filopodia contact dendrites, inducing the assembly of presynaptic and postsynaptic structures critical for functional synapses.

What is apoptosis and synaptic pruning?

Apoptosis is the programmed cell death that eliminates unnecessary or damaged cells during development. Neurons typically undergo apoptosis unless supported by neurotrophic factors (e.g., nerve growth factor), which provide survival signals and promote healthy synaptic connections.

Synaptic Pruning: Involves the selective elimination of less active synapses; this process is crucial for refining neural circuits and optimizing brain function during development.

How can we study synaptic mechanisms in invertebrates

The Giant Fiber System in Drosophila: A model system utilized to investigate rapid neural responses via large identifiable neurons, providing insights into basic principles of neuronal function.

Modeling: Incorporates electrical and chemical synapse dynamics, underlining their roles in rapid action potential propagation, which is foundational for understanding neural circuit responsiveness.