MODULE SUPPLEMENT: NEUROLOGICAL SYSTEM
The Peripheral Nervous System

So far the focus has been mainly on the central nervous system although what is seen--the functional changes--also usually involve participation of the peripheral nervous system (PNS), which in turn is composed of both the somatic and the autonomic systems.

However, while we see clinical indicators suggesting changes in the PNS, little is written specifically about changes that occur in the PNS with age in isolation of other systems, and these will be discussed in other modules. For example, changes in the neural innervation of muscles and the cardiovascular system are extremely important to how these systems function in older adults. And changes in receptors can influence sensory function. As in the CNS, many of the changes in the neurons of the PNS may be location specific, selective, and even species specific (Cowen, 1993). Thus cell loss may only affect a relative minority of nerve groups unless there are superimposed disease processes (e.g. like diabetes). In addition, many drugs and treatments used for other purposes influence somatic and autonomic nervous system function, and many clinical measures used to assess ANS function are rather insensitive to subtle changes. This complicates any study.

There are, however, a few general points that are important to highlight here as a background to the other modules. Consider the clinical vignette that follows.