brain, spinal cord, and nerve disorders
Effects of Aging on the Nervous System
 Overview of the Peripheral Nervous System 
As people age, peripheral nerves may conduct impulses more slowly and release of neurotransmitters is impaired, resulting in decreased sensation, slower reflexes, and often some clumsiness. Nerve conduction can slow because the myelin sheaths around nerves degenerate. Myelin sheaths are layers of tissue that insulate nerves and speed conduction of impulses (see figure). Degeneration also occurs because as people age, blood flow decreases, nearby bones overgrow and put pressure on the nerves, or both. Age-related changes in function can become more noticeable when the nerves are injured by something else (for example, by Diabetes Mellitus (DM) ). The peripheral nervous system’s response to injury is reduced. When the axon of a peripheral nerve is damaged in younger people, the nerve is able to repair itself as long as its cell body, located in or near the spinal cord, is undamaged. This self-repair process occurs more slowly and incompletely in older people, making older people more vulnerable to injury and disease. 