Embryology of the Central Nervous System

By Neda Brinster

What is the structure of the Central Nervous System?

The central nervous system contains two main structures: the central and peripheral nervous systems. The Central Nervous system controls the brain and spinal cord, while the Peripheral Nervous System controls the cranial and spinal nerves, ganglia, plexuses, and sensory receptors.

What are the stages of development?

Early Stage:

The nervous system begins to form in the 3rd week of development, with the growth of a primitive streak, a band of cells that form along the axis of a developing egg. Cells migrate down the axis to form three layers: the nervous system is derived from the ectoderm layer.

• Endoderm --> Innermost layer

• Mesoderm --> Middle layer

• Ectoderm --> Outermost layer

Neurulation:

The development of the neural tube occurs during neurulation. During this process, a neural plate forms and fuses into the neural tube, which will later differentiate between the brain and the spinal cord, which make up the central nervous system. In the third week, the notochord, a structure that signals cues to the developing embryo, begins to develop. The notochord forms growth factors, stimulating the formation of the neural plate. The neural plate that fuses into the neural tube forms from a thickened area of cells.

Later development:

During the fifth week of development, swelling appears at the upper end of the neural tube. Three vesicles first appear that later develop into five secondary vesicles. Neurons move throughout the brain, developing into axons and dendrites, forming synapses. After birth, the central nervous system development continues for years, where new synapses and connections form, which increase through childhood and adulthood. In adulthood, only synapses and pathways continue to develop.

Citations:

“Development of the Central Nervous System.” TeachMeAnatomy, https://teachmeanatomy.info/the-basics/embryology/central-nervous-system/.

General Embyology, director. YouTube, YouTube, 3 Oct. 2014, https://www.youtube.com/watch?v=lGLexQR9xGs.

Neurochallenged, director. YouTube, YouTube, 18 Oct. 2015, https://www.youtube.com/watch?v=Fir-v6EoZNE.

“Neurotransmitters: What They Are, Functions & Types.” Cleveland Clinic, https://my.clevelandclinic.org/health/articles/22513-neurotransmitters.