The central nervous system consists of the brain and spinal cord. The brain has several major parts: the cerebrum, the cerebellum, and the brainstem. A part called the "midbrain" bridges the area between the brainstem and cerebrum. Following is a brief description of each of these parts, and their function.

The cerebrum is the part of the brain responsible for memory, learning, language, and the voluntary initiation of motor movements. The cerebellum coordinates movement and balance.

The brainstem is a stalk like structure that is connected to the spinal cord at the base of the skull. The brainstem contains brain cells, or neurons, that relay information from the sense organs and regulate automatic functions such as breathing.

The spinal cord is a cable of neurons beginning at the medulla oblongata, and extending down the back, enclosed by and protected by the vertebral column, or backbone. Neurons in the spinal cord send a process called the axon out of the spinal cord. Together, axons leaving the spinal cord traveling to a specific muscle constitute what is called a "motor nerve."

The spinal cord and brain start to form early in development (around 3 weeks) and start as a flat plate of cells. The cells along the edges of the plate divide rapidly and begin to form elevations on either side of the plate. Eventually, these elevations join in the middle. What is formed is a tube, similar to the cardboard tube found in the middle of a roll of paper towels. At the upper, or head end, of the tube, three bulges form. These bulges are called the "primary brain vesicles." Each bulge develops into a part of the brain. The first, or most forward bulge, develops to form the cerebrum. The middle bulge doesn't change much, and forms the midbrain. The last, or tailmost bulge, forms the cerebellum and brainstem. The brain stem is a stalk like structure that is connected to the spinal cord at the base of the skull. The brain stem contains neurons that relay information from the sense organs. Many neurons that regulate automatic functions, such as balance, blood pressure, breathing, and heartbeat, are also in the brain stem. The spinal cord develops from cells dividing and multiplying around the neural tube itself. The spinal cord is a cable of neurons that extends from the neck down through the backbone. The backbone surrounds and protects the spinal cord.

Spina bifida is a spinal defect that is present at birth caused by incomplete fusion of the neural plate. In spina bifida myelomeningocele, several vertebrae do not develop completely and cannot enclose the spinal cord. A section of the cord sticks out of the resulting gap in the spine. This section of the cord remains undeveloped, as do nerves that connect it to the lower part of the body. About 8,000 babies with the defect are born yearly in the United States. New methods of surgery are allowing doctors to operate on the baby before it is born thus closing the opening before birth. With proper medical treatment including physical therapy, many victims can lead independent, productive lives. Stories about children born with spina bifida can be found on the web, including "Simon's Story" at http://www.waisman.wisc.edu/~rowley/sb-kids/st-simon.htm