Introduction to the Central Nervous System

Abstract

The brain and spinal cord form the central nervous system. The brain is the part of the central nervous system that is housed in the cranium/skull. It consists of the brain stem, diencephalon, cerebellum, and cerebrum. At the foramen magnum, the highest cervical segment of the spinal cord is continuous with the lowest level of the medulla of the brain stem. The spinal nerves from the sacral, lumbar, thoracic, and cervical levels of the spinal cord form the lower part of the peripheral nervous system and record general sensations of pain, temperature touch, and pressure. The 12 cranial nerves attached to the brain form the upper part of the peripheral nervous system and record general sensations of pain, temperature touch, and pressure, but in addition we now find the presence of the special senses of smell, vision, hearing, balance, and taste. The blood supply to the brain originates from the first major arterial branches from the heart insuring that over 20% of the entire supply of oxygenated blood flows directly into the brain.