The nervous system is organized into two parts – the central nervous system and the peripheral nervous system. The central nervous system is made of the brain and the spinal cord. The brain is divided into three parts – Forebrain, Midbrain, and Hindbrain. The Forebrain develops into two parts – the telencephalon which consists of the cerebrum or the cerebral hemispheres and includes cerebral cortex, white matter, and basal nuclei; and diencephalon which consists of thalamus, hypothalamus, and epithalamus. The Midbrain develops through mesencephalon into a part of the brainstem. The Hindbrain develops through two parts, the metencephalon, and myelencephalon. The metencephalon eventually develops into pons (part of the brainstem) and cerebellum. The myelencephalon derives into medulla oblongata, which is also part of the brain stem.
Spinal cord
The spinal cord which is about 45 cm in length, starts from the brain stems and stretches to the lowest end of the backbone. It comprises a nerve bundle and is protected by a series of vertebrae which are divided into five regions – cervical, thoracic, lumbar, sacral, and coccygeal.
The spinal cord itself spans only about two-thirds of the vertebral column, but the rest of the space is filled with nerve fibers of spinal roots. Both the spinal cord and the brain contain fluid-filled spaces or cavities called cerebrospinal fluid (CSF) which contains nutrients, hormones, and the white blood cells. Additionally, the cerebrospinal fluid acts as the shock absorber cushioning the brain and provides a direct link across the blood-brain barrier for exchanging nutrients and other essential biomolecules.
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