The nervous system has two distinct parts. The central nervous system comprises the brain and spinal cord. The peripheral nervous system is the network of nerves that connects the brain and spinal cord to the rest of the body. The brain coordinates the ability to move, touch, smell, hear, and see. It allows us to think, decide, and control our actions. The brain is in close and constant communication with the entire nervous system.

The disorders associated with the nervous system are some of the most frightening problems we face. It is difficult for us to consider memory loss, dementia, and Alzheimer's disease. Stroke is always a worry. And problems with the sense organs – such as cataracts, macular degeneration, and hearing loss – are worrisome to us as we grow older.

Diet and lifestyle do make a difference. A diet low in B vitamins may affect our "brain health." There are also links between nervous disorders such as Alzheimer's and Parkinson's diseases and our increasingly toxic environment.