Autonomic Dysfunction

Excerpt

The autonomic nervous system (ANS) is a subcomponent of the peripheral nervous system (PNS) that regulates involuntary physiologic processes, including blood pressure, heart rate, respiration, digestion, and sexual arousal. It comprises sympathetic, parasympathetic, and enteric nervous systems, which are three anatomically distinct divisions. The sympathetic nervous system (SNS), as well as the parasympathetic nervous system (PNS), contain afferent fibers that provide sensory input and efferent fibers that provide motor output to the central nervous system (CNS). The SNS and PNS motor pathways incorporate a two-neuron series: a pre-ganglionic neuron with a cell body in the CNS and a post-ganglionic neuron with a cell body in the periphery that innervates target tissues. The enteric nervous system (ENS) is a large, web-like structure capable of functioning independently of the remainder of the nervous system. It is chiefly responsible for regulating digestive processes and contains over a hundred million neurons of over fifteen morphologies, greater than the sum of all other peripheral ganglia.

The autonomic nervous system (ANS) includes all regions implicated in controlling “autonomic,” unconscious, and involuntary functions in total body homeostasis. In general, the full range of physiologic functions are ultimately necessary for human survival and allow us to interact with the external environment in a wide range of conditions. Together with the slow-acting, long-lasting effects of the endocrine system, the ANS exerts its fast-acting, short-lived effects on the following functions (among others):

1. Perfusion of the whole body through regulation of heart rate and blood pressure

2. Homoeothermic role through sweating control and shivering,

3. Processing of nutrients through control and coordination of different parts of the gut and glands,

4. Urinary motility, and

5. Pupil movement, focusing, and lacrimation.

Table 1. Autonomic nervous system functions

Dysfunction of one or more subdivisions of the ANS, when accompanying other diseases, is linked to a worse prognosis of the latter. In some circumstances or when severe, dysfunction of ANS itself results in symptoms and disability, which may, in turn, prompt treatment.