Laboratory Evaluation of the Autonomic System

Excerpt

The autonomic nervous system (ANS) controls body functions that can proceed independent of volitional activity. The system consists of a somatic afferent pathway, a central nervous system (CNS) integrating complex (brain and spinal cord), and two distinct efferent limbs (sympathetic and parasympathetic) each made up of preganglionic and postganglionic neurones. The viscera are innervated by both sympathetic and parasympathetic fibers, and the ANS controls the activity of the cardiovascular, respiratory, gastrointestinal, and genitourinary systems, and has effects on smooth muscle, blood vessels, and sweat glands, and on the endocrine system. It provides a mechanism that influences the end organs through chemical transmitters: catecholamines at the sympathetic and acetylcholine at the parasympathetic nerve endings. Centrally, acetylcholine, monoamines, and several peptides in the hypothalamus and brainstem may modulate the system.