Neurodevelopment Quiz

Neurodevelopment

• The adult brain contains approximately 80 billion neurons, 15 times more than the global human population.
• During early embryonic development, neurons are generated at a rate of 250,000 per minute.
• Almost all brain structures are present at birth.
• Brain growth reaches roughly 80% of its adult size by age 2.
• A single neuron typically interacts with an average of 15,000 other cells.

Stages of Neurodevelopment

• Neurogenesis (Mitosis): Stem cells in the neural tube divide through mitosis to create more progenitor cells (early in development; symmetrical cell division). Later progenitor cells divide asymmetrically creating one progenitor cell and one neuron/glial cell. This process is most prominent during weeks 8-16 of development.

• Neural Migration: Newly formed neurons from the ventricular zone are guided to their correct location by radial glial cells. A wave-like process, with earlier migrating neurons setting the position for later migrations. Brain region development relies on precise spatial relationships among neurons. This is heavy during weeks 8-16 and then slows until around 25 weeks after conception.

• Neural Differentiation: Immature neurons, once in their proper positions, mature into specific neuron types. This differentiation process leads to the distinctive layers of the cerebral cortex.

• Synaptogenesis: Overproduction of synapses. Begins around 17 weeks post-conception and mostly occurs after birth. This period is characterized by synapse redundancy.

• Apoptosis (Cell Death): Neurons whose axons do not find their targets undergo programmed cell death (apoptosis) which is genetically driven -different from necrosis. This process occurs from around 16 weeks post-conception, to after birth.

• Synapse Rearrangement: Synaptic connections are reorganized and refined, leading to more precise and efficient neuronal circuits. This process extends from approximately 26 weeks after conception until after birth or even into adolescence.

• Myelination: Oligodendrocytes produce myelin which coats axons. Myelination plays a crucial role in facilitating efficient nerve impulse transmission. It starts in the visual system before birth and extends to other sensory systems. Sensory systems are myelinated earlier than motor systems. All white matter tracts are myelinated by 2 years.

Time Course of Neurodevelopment

• The images show how neurodevelopment is a protracted process that continues after birth.

• The stages occur during specific time periods. This is helpful in understanding what may harm a developing fetus.

Summary of Critical Period Stages

• The stages of early brain development are influenced by critical periods. The first 2 weeks of embryonic development, critical periods for creating systems, and for the sensory systems following these critical periods.
• Critical periods are related to neural activity and their relationships, as well as synaptic and/or dendritic connections and arborisations, during specific time periods.

Test your knowledge on the stages and facts of neurodevelopment. Learn about the number of neurons, their generation rate, and the growth of the brain during early development. This quiz covers key concepts from neurogenesis to neural migration.