Physiology and Pathophysiology of the Autonomic Nervous System

Control of the function of the sympathetic, parasympathetic, and enteric nervous system functions depends on complex interactions at all levels of the neuraxis. Peripheral sympathetic outputs are critical for maintenance of blood pressure, thermoregulation, and response to stress. Parasympathetic reflexes control lacrimation, salivation, pupil response to light, beat-to-beat control of the heart rate, gastrointestinal motility, micturition, and erectile function. The insular cortex, anterior and midcingulate cortex, and amygdala generate autonomic responses to behaviorally relevant stimuli. Several nuclei of the hypothalamus generate coordinated patterns of autonomic responses to internal or social stressors. Several brainstem nuclei participate in integrated control of autonomic function in relationship to respiration and the sleep-wake cycle. Disorders affecting the central or peripheral autonomic pathways, or both, manifest with autonomic failure (including orthostatic hypotension, anhidrosis, gastrointestinal dysmotility, and neurogenic bladder or erectile dysfunction) or autonomic hyperactivity, primary hypertension, tachycardia, and hyperhidrosis.