Final answer:
The process of myelination begins prenatally and continues into adolescence and adulthood, with the spinal cord beginning myelination during the later stages of fetal development and the brain becoming more efficient during adolescence.
Step-by-step explanation:
The process of myelination begins prenatally and continues into adolescence and adulthood. This developmental stage links to changes in the brain's structure, including areas like the spinal cord which starts to be myelinated during the later stages of fetal development, around developmental weeks 21-30. Myelination is crucial for efficient nervous system functioning and is carried out by glial cells, such as Schwann cells and oligodendrocytes. This process significantly accelerates during adolescence, contributing to the brain becoming more efficient and functional, and coinciding with major cognitive developments.
It's important to note that this complex process doesn't fully complete until adolescence. The frontal lobes, specifically, continue to mature and become fully developed by the age of 25 years old. Understanding the timeline of myelination is essential for comprehending how the brain evolves from infancy through adulthood and the corresponding cognitive and physical maturation that occurs.