It functions as part of the network for the communication of messages sent from the brain to the rest of the body and to receive messages from the body needing to be sent to the brain. The information is transmitted in the form of electrical impulses that travel along a nerve pathway jumping from nerve cell to nerve cell. Improper balance of neurochemicals affects timing, and can result in some physical or mental dysfunction. Researchers have suggested that depression may be related to improper serotonin levels and dopamine may play a role in Parkinson's Disease. The Aging Nervous System Brain weight and volume declines as a result of aging .
Controversy remains as to the cause.
Some researchers suggest there is a loss in the total number of neurons. Others attribute the change to a shrinkage in the size of existing neurons. It has also been suggested that the brain at any age has a surplus of cells beyond what is needed for normal function, therefore the loss with aging may not matter. This adaptive feature is referred to as plasticity . Dysfunction results when cell loss impairs a vital function and other cells are not able to compensate.